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Sample records for electro-active polymers pvdf

  1. Modeling and Simulation of Viscous Electro-Active Polymers

    PubMed Central

    Vogel, Franziska; Göktepe, Serdar; Steinmann, Paul; Kuhl, Ellen

    2014-01-01

    Electro-active materials are capable of undergoing large deformation when stimulated by an electric field. They can be divided into electronic and ionic electro-active polymers (EAPs) depending on their actuation mechanism based on their composition. We consider electronic EAPs, for which attractive Coulomb forces or local re-orientation of polar groups cause a bulk deformation. Many of these materials exhibit pronounced visco-elastic behavior. Here we show the development and implementation of a constitutive model, which captures the influence of the electric field on the visco-elastic response within a geometrically non-linear finite element framework. The electric field affects not only the equilibrium part of the strain energy function, but also the viscous part. To adopt the familiar additive split of the strain from the small strain setting, we formulate the governing equations in the logarithmic strain space and additively decompose the logarithmic strain into elastic and viscous parts. We show that the incorporation of the electric field in the viscous response significantly alters the relaxation and hysteresis behavior of the model. Our parametric study demonstrates that the model is sensitive to the choice of the electro-viscous coupling parameters. We simulate several actuator structures to illustrate the performance of the method in typical relaxation and creep scenarios. Our model could serve as a design tool for micro-electro-mechanical systems, microfluidic devices, and stimuli-responsive gels such as artificial skin, tactile displays, or artificial muscle. PMID:25267881

  2. Standing wave tube electro active polymer wave energy converter

    NASA Astrophysics Data System (ADS)

    Jean, Philippe; Wattez, Ambroise; Ardoise, Guillaume; Melis, C.; Van Kessel, R.; Fourmon, A.; Barrabino, E.; Heemskerk, J.; Queau, J. P.

    2012-04-01

    Over the past 4 years SBM has developed a revolutionary Wave Energy Converter (WEC): the S3. Floating under the ocean surface, the S3 amplifies pressure waves similarly to a Ruben's tube. Only made of elastomers, the system is entirely flexible, environmentally friendly and silent. Thanks to a multimodal resonant behavior, the S3 is capable of efficiently harvesting wave energy from a wide range of wave periods, naturally smoothing the irregularities of ocean wave amplitudes and periods. In the S3 system, Electro Active Polymer (EAP) generators are distributed along an elastomeric tube over several wave lengths, they convert wave induced deformations directly into electricity. The output is high voltage multiphase Direct Current with low ripple. Unlike other conventional WECs, the S3 requires no maintenance of moving parts. The conception and operating principle will eventually lead to a reduction of both CAPEX and OPEX. By integrating EAP generators into a small scale S3, SBM achieved a world first: direct conversion of wave energy in electricity with a moored flexible submerged EAP WEC in a wave tank test. Through an extensive testing program on large scale EAP generators, SBM identified challenges in scaling up to a utility grid device. French Government supports the consortium consisting of SBM, IFREMER and ECN in their efforts to deploy a full scale prototype at the SEMREV test center in France at the horizon 2014-2015. SBM will be seeking strategic as well as financial partners to unleash the true potentials of the S3 Standing Wave Tube Electro Active Polymer WEC.

  3. Design of electro-active polymer gels as actuator materials

    NASA Astrophysics Data System (ADS)

    Popovic, Suzana

    Smart materials, alternatively called active or adaptive, differ from passive materials in their sensing and activation capability. These materials can sense changes in environment such as: electric field, magnetic field, UV light, pH, temperature. They are capable of responding in numerous ways. Some change their stiffness properties (electro-rheological fluids), other deform (piezos, shape memory alloys, electrostrictive materials) or change optic properties (electrochromic polymers). Polymer gels are one of such materials which can change the shape, volume and even optical properties upon different applied stimuli. Due to their low stiffness property they are capable of having up to 100% of strain in a short time, order of seconds. Their motion resembles the one of biosystems, and they are often seen as possible artificial muscle materials. Despite their delicate nature, appropriate design can make them being used as actuator materials which can form controllable surfaces and mechanical switches. In this study several different groups of polymer gel material were investigated: (a) acrylamide based gels are sensitive to pH and electric field and respond in volume change, (b) polyacrylonitrile (PAN) gel is sensitive to pH and electric field and responds in axial strain and bending, (c) polyvinylalcohol (PVA) gel is sensitive to electric field and responds in axial strain and bending and (d) perfluorinated sulfonic acid membrane, Nafion RTM, is sensitive to electric field and responds in bending. Electro-mechanical and chemo-mechanical behavior of these materials is a function of a variety of phenomena: polymer structure, affinity of polymer to the solvent, charge distribution within material, type of solvent, elasticity of polymer matrix, etc. Modeling of this behavior is a task aimed to identify what is driving mechanism for activation and express it in a quantitative way in terms of deformation of material. In this work behavior of the most promising material as

  4. The Jellyfish: smart electro-active polymers for an autonomous distributed sensing node

    NASA Astrophysics Data System (ADS)

    Blottman, John B.; Richards, Roger T.

    2006-05-01

    The US Navy has recently placed emphasis on deployable, distributed sensors for Force Protection, Anti-Terrorism and Homeland Defense missions. The Naval Undersea Warfare Center has embarked on the development of a self-contained deployable node that is composed of electro-active polymers (EAP) for use in a covert persistent distributed surveillance system. Electro-Active Polymers (EAP) have matured to a level that permits their application in energy harvesting, hydrophones, electro-elastic actuation and electroluminescence. The problem to resolve is combining each of these functions into an autonomous sensing platform. The concept presented here promises an operational life several orders of magnitude beyond what is expected of a Sonobuoy due to energy conservation and harvesting, and at a reasonable cost. The embodiment envisioned is that of a deployed device resembling a jellyfish, made in most part of polymers, with the body encapsulating the necessary electronic processing and communications package and the tentacles of the jellyfish housing the sonar sensors. It will be small, neutrally buoyant, and will survey the water column much in the manner of a Cartesian Diver. By using the Electro-Active Polymers as artificial muscles, the motion of the jellyfish can be finely controlled. An increased range of detection and true node autonomy is achieved through volumetric array beamforming to focus the direction of interrogation and to null-out extraneous ambient noise.

  5. Electro-Active Polymer (EAP) Actuators for Planetary Applications

    NASA Technical Reports Server (NTRS)

    Bar-Cohen, Y.; Leary, S.; Shahinpoor, M.; Harrison, J. O.; Smith, J.

    1999-01-01

    NASA is seeking to reduce the mass, size, consumed power, and cost of the instrumentation used in its future missions. An important element of many instruments and devices is the actuation mechanism and electroactive polymers (EAP) are offering an effective alternative to current actuators. In this study, two families of EAP materials were investigated, including bending ionomers and longitudinal electrostatically driven elastomers. These materials were demonstrated to effectively actuate manipulation devices and their performance is being enhanced in this on-going study. The recent observations are reported in this paper, include the operation of the bending-EAP at conditions that exceed the harsh environment on Mars, and identify the obstacles that its properties and characteristics are posing to using them as actuators. Analysis of the electrical characteristics of the ionomer EAP showed that it is a current driven material rather than voltage driven and the conductivity distribution on the surface of the material greatly influences the bending performance. An accurate equivalent circuit modeling of the ionomer EAP performance is essential for the design of effective drive electronics. The ionomer main limitations are the fact that it needs to be moist continuously and the process of electrolysis that takes place during activation. An effective coating technique using a sprayed polymer was developed extending its operation in air from a few minutes to about four months. The coating technique effectively forms the equivalent of a skin to protect the moisture content of the ionomer. In parallel to the development of the bending EAP, the development of computer control of actuated longitudinal EAP has been pursued. An EAP driven miniature robotic arm was constructed and it is controlled by a MATLAB code to drop and lift the arm and close and open EAP fingers of a 4-finger gripper. Keywords: Miniature Robotics, Electroactive Polymers, Electroactive Actuators, EAP

  6. Postgraduate education on electro-active polymers at Southern Denmark University

    NASA Astrophysics Data System (ADS)

    Jones, Richard W.

    2009-03-01

    A recently introduced elective to the Master's of Science in Mechatronics program at Southern Denmark University, entitled 'Mechatronics: Design and Build' concentrates on some of the interdisciplinary aspects of Mechatronics Engineering. The 'Motion Control of Mechatronic Devices' is the main theme of this elective. Within this 'theme' the modelling, identification and compensation of nonlinear effects such as friction, stiction and hysteresis are considered. One of the most important components of the elective considers 'Smart Materials' and their use for actuation purposes. The theory, modelling and properties of piezoceramics. magneto- and electro- rheological fluids and dielectric electro active polymers (DEAP) are introduced in the 'Smart Materials' component. This paper initially reviews the laboratory experiments that have been developed for the dielectric electro active polymer section of the 'Mechatronics: Design and Build' elective. In lectures the students are introduced to the basic theory and fabrication of tubular actuators, that use DEAP material based on smart compliant electrode technology. In the laboratory the students to (a) carry out a series of experiments to characterise the tubular actuators, and (b) design a closed-loop position controller and test the performance of the controlled actuator for both step changes in desired position and periodic input reference signals. The last part of this contribution reviews some of the DEAP-based demonstration devices that been developed by Danfoss PolyPower A/S using their PolyPowerTM material which utilizes smart compliant electrode technology.

  7. Micro- and nanostructured electro-active polymer actuators as smart muscles for incontinence treatment

    SciTech Connect

    Osmani, Bekim E-mail: tino.toepper@unibas.ch; Töpper, Tino E-mail: tino.toepper@unibas.ch; Weiss, Florian M. E-mail: bert.mueller@unibas.ch; Leung, Vanessa E-mail: bert.mueller@unibas.ch; Müller, Bert E-mail: bert.mueller@unibas.ch

    2015-02-17

    Treatments of severe incontinence are currently based on purely mechanical systems that generally result in revision after three to five years. Our goal is to develop a prototype acting in a natural-analogue manner as artificial muscle, which is based on electro-active polymers. Dielectric actuators have outstanding performances including millisecond response times, mechanical strains of more than 10 % and power to mass densities similar to natural muscles. They basically consist of polymer films sandwiched between two compliant electrodes. The incompressible but elastic polymer film transduces the electrical energy into mechanical work according to the Maxwell pressure. Available polymer films are micrometers thick and voltages as large as kV are necessary to obtain 10 % strain. For medical implants, polymer films should be nanometer thin to realize actuation below 48 V. The metallic electrodes have to be stretchable to follow the strain of 10 % and remain conductive. Recent results on the stress/strain behavior of anisotropic EAP-cantilevers have shown dependencies on metal electrode preparation. We have investigated tunable anisotropic micro- and nanostructures for metallic electrodes. They show a preferred actuation direction with improved stress-strain behavior. The bending of the cantilever has been characterized by the laser beam deflection method. The impact of the electrode on the effective Young's Modulus is measured using an Ultra Nanoindentation Tester with an integrated reference system for soft polymer surfaces. Once ten thousand layers of nanometer-thin EAP actuators are available, devices beyond the envisioned application will flood the market.

  8. Micro- and nanostructured electro-active polymer actuators as smart muscles for incontinence treatment

    NASA Astrophysics Data System (ADS)

    Osmani, Bekim; Töpper, Tino; Deschenaux, Christian; Nohava, Jiri; Weiss, Florian M.; Leung, Vanessa; Müller, Bert

    2015-02-01

    Treatments of severe incontinence are currently based on purely mechanical systems that generally result in revision after three to five years. Our goal is to develop a prototype acting in a natural-analogue manner as artificial muscle, which is based on electro-active polymers. Dielectric actuators have outstanding performances including millisecond response times, mechanical strains of more than 10 % and power to mass densities similar to natural muscles. They basically consist of polymer films sandwiched between two compliant electrodes. The incompressible but elastic polymer film transduces the electrical energy into mechanical work according to the Maxwell pressure. Available polymer films are micrometers thick and voltages as large as kV are necessary to obtain 10 % strain. For medical implants, polymer films should be nanometer thin to realize actuation below 48 V. The metallic electrodes have to be stretchable to follow the strain of 10 % and remain conductive. Recent results on the stress/strain behavior of anisotropic EAP-cantilevers have shown dependencies on metal electrode preparation. We have investigated tunable anisotropic micro- and nanostructures for metallic electrodes. They show a preferred actuation direction with improved stress-strain behavior. The bending of the cantilever has been characterized by the laser beam deflection method. The impact of the electrode on the effective Young's Modulus is measured using an Ultra Nanoindentation Tester with an integrated reference system for soft polymer surfaces. Once ten thousand layers of nanometer-thin EAP actuators are available, devices beyond the envisioned application will flood the market.

  9. Sensing performance of electrically conductive fabrics and dielectric electro active polymers for parachutes

    NASA Astrophysics Data System (ADS)

    Favini, Eric; Niezrecki, Christopher; Manohar, Sanjeev K.; Willis, David; Chen, Julie; Niemi, Eugene; Desabrais, Kenneth; Charette, Christine

    2011-04-01

    This paper quantifies the sensing capabilities of novel smart materials in an effort to improve the performance, better understand the physics, and enhance the safety of parachutes. Based upon a recent review of actuation technologies for parachute applications, it was surmised that the actuators reviewed could not be used to effectively alter the drag or lift (i.e. geometry, porosity, or air vent openings) of a parachute during flight. However, several materials showed potential for sensing applications within a parachute, specifically electrically conductive fabrics and dielectric electro-active polymers. This paper introduces several new conductive fabrics and provides an evaluation of the sensing performance of these smart materials based upon test results using mechanical testing and digital image correlation for comparison.

  10. Electro-active Polymer Actuator Based on Sulfonated Polyimide with Highly Conductive Silver Electrodes Via Self-metallization.

    PubMed

    Song, Jiangxuan; Jeon, Jin-Han; Oh, Il-Kwon; Park, K C

    2011-10-04

    We report here a facile synthesis of high performance electro-active polymer actuator based on a sulfonated polyimide with well-defined silver electrodes via self-metallization. The proposed method greatly reduces fabrication time and cost, and obviates a cation exchange process required in the fabrication of ionic polymer-metal composite actuators. Also, the self-metallized silver electrodes exhibit outstanding metal-polymer adhesion with high conductivity, resulting in substantially larger tip displacements compared with Nafion-based actuators.

  11. Energy harvesting using ionic electro-active polymer thin films with Ag-based electrodes

    NASA Astrophysics Data System (ADS)

    Anand, S. V.; Arvind, K.; Bharath, P.; Mahapatra, D. Roy

    2010-04-01

    In this paper we employ the phenomenon of bending deformation induced transport of cations via the polymer chains in the thickness direction of an electro-active polymer (EAP)-metal composite thin film for mechanical energy harvesting. While EAPs have been applied in the past in actuators and artificial muscles, promising applications of such materials in hydrodynamic and vibratory energy harvesting are reported in this paper. For this, functionalization of EAPs with metal electrodes is the key factor in improving the energy harvesting efficiency. Unlike Pt-based electrodes, Ag-based electrodes have been deposited on an EAP membrane made of Nafion. The developed ionic metal polymer composite (IPMC) membrane is subjected to a dynamic bending load, hydrodynamically, and evaluated for the voltage generated against an external electrical load. An increase of a few orders of magnitude has been observed in the harvested energy density and power density in air, deionized water and in electrolyte solutions with varying concentrations of sodium chloride (NaCl) as compared to Pt-based IPMC performances reported in the published literature. This will have potential applications in hydrodynamic and residual environmental energy harvesting to power sensors and actuators based on micro-and nano-electro-mechanical systems (MEMS and NEMS) for biomedical, aerospace and oceanic applications.

  12. Systematic approach to development of pressure sensors using dielectric electro-active polymer membranes

    NASA Astrophysics Data System (ADS)

    York, A.; Dunn, J.; Seelecke, S.

    2013-09-01

    Dielectric electro-active polymers (DEAPs) have become attractive materials for various actuation and sensing applications due to their high energy and power density, high efficiency, light weight, and fast response speed. However, commercial development has been hindered due to a variety of constraints such as reliability, non-linear behavior, cost of driving electronics, and form factor requirements. This paper presents the systematic development from laboratory concept to commercial readiness of a novel pressure sensing system using a DEAP membrane. The pressure sensing system was designed for in-line pressure measurements for low pressure applications such as health systems monitoring. A first generation sensor was designed, built and tested with a focus on the qualitative capabilities of EAP membranes as sensors. Experimental measurements were conducted that demonstrated the capability of the sensor to output a voltage signal proportional to a changing pressure. Several undesirable characteristics were observed during these initial tests such as strong hysteresis, non-linearity, very limited pressure range, and low fatigue life. A second generation prototype was then designed to remove or compensate for these undesirable characteristics. This prototype was then built and tested. The new design showed an almost complete removal of hysteretic non-linear effects and was capable of operating at 10 × the pressure range of the initial generation. This new design is the framework for a novel DEAP based pressure sensor ready for commercial applications.

  13. Electronics drivers for high voltage dielectric electro active polymer (DEAP) applications

    NASA Astrophysics Data System (ADS)

    Zhang, Zhe; Andersen, Michael A. E.

    2015-04-01

    Dielectric electro active polymer (DEAP) can be used in actuation, sensing and energy harvesting applications, but driving the DEAP based actuators and generators has three main challenges from a power electronics standpoint, i.e. high voltage (around 2.5 kV), nonlinearity, and capacitive behavior. In this paper, electronics divers for heating valves, loud speakers, incremental motors, and energy harvesting are reviewed, studied and developed in accordance with their corresponding specifications. Due to the simplicity and low power capacity (below 10W), the reversible Fly-back converters with both magnetic and piezoelectric transformers are employed for the heating valve and incremental motor application, where only ON/OFF regulation is adopted for energy saving; as for DEAP based energy harvesting, the noisolated Buck/Boost converter is used, due to the system high power capacity (above 100W), but the voltage balancing across the series-connected high voltage IGBTs is a critical issue and accordingly a novel gate driver circuitry is proposed and equipped; due to the requirements of the audio products, such as low distortion and noise, the multi-level Buck converter based Class-D amplifier, because of its high control linearity, is implemented for the loud speaker applications. A synthesis among those converter topologies and control techniques is given; therefore, for those DEAP based applications, their diversity and similarity of electronics drivers, as well as the key technologies employed are analyzed. Therefore a whole picture of how to choose the proper topologies can be revealed. Finally, the design guidelines in order to achieve high efficiency and reliability are discussed.

  14. Evaluation of piezoelectric PVDF polymers for use in space environments.

    SciTech Connect

    Dargaville, Tim Richard; Assink, Roger Alan; Celina, Mathias Christopher; Chaplya, Pavel Mikhail

    2003-07-01

    Thin polymer films have been identified as one of the major enabling technologies for future space-based systems. Potential devices include those based on piezoelectric bimorph polymers that deform when a charge is deposited, for example, from an electron gun. The thin-film and lightweight nature of the polymeric devices will allow them to be launched more readily and deployed to operating conditions once in orbit. Until now little work has been done aimed at investigating the performance of piezoelectric properties of PVDF and its copolymers and the prediction of their long-term stability in low Earth orbit (LEO) environmental conditions. In this paper, the piezoelectric properties of PVDF and the copolymers formed from polymerization of vinylidene fluoride and trifluoroethylene (TrFE) or hexafluoropropylene (HFP) have been studied over a broad temperature range simulating that expected in LEO. The temperatures experienced by unprotected polymers on low altitude spacecraft have previously been reported as ranging from approximately -100 C to +130 C as the polymer/spacecraft passes in and out of the Earth's shadow. To examine the effects of temperature on the piezoelectric properties of poled PVDF, P(VDF-TrFE) and P(VDF-HFP) the d{sub 33} piezoelectric coefficients and electric displacement-electric field (D-E) hysteresis loops were measured up to 160 C for the d{sub 33} measurements and from -80 to +110 C for the D-E loops. The room temperature d{sub 33} coefficient of PVDF homopolymer films, annealed for extended periods at 50, 80 and 125 C, dropped rapidly within a few days of heating, then remained unchanged for periods of up to 300 days. In contrast, the TrFE copolymer exhibited greater thermal stability than the homopolymer, with the d{sub 33} remaining almost unchanged from the pre-annealing value after heating at 50, 80 and 125 C. The HFP copolymer exhibited poor retention of d33 at temperatures above 80 C. For all three polymers short term annealing at 160

  15. Towards a physics-based multiscale modelling of the electro-mechanical coupling in electro-active polymers

    PubMed Central

    Menzel, Andreas; deBotton, Gal

    2016-01-01

    Owing to the increasing number of industrial applications of electro-active polymers (EAPs), there is a growing need for electromechanical models which accurately capture their behaviour. To this end, we compare the predicted behaviour of EAPs undergoing homogeneous deformations according to three electromechanical models. The first model is a phenomenological continuum-based model composed of the mechanical Gent model and a linear relationship between the electric field and the polarization. The electrical and the mechanical responses according to the second model are based on the physical structure of the polymer chain network. The third model incorporates a neo-Hookean mechanical response and a physically motivated microstructurally based long-chains model for the electrical behaviour. In the microstructural-motivated models, the integration from the microscopic to the macroscopic levels is accomplished by the micro-sphere technique. Four types of homogeneous boundary conditions are considered and the behaviours determined according to the three models are compared. For the microstructurally motivated models, these analyses are performed and compared with the widely used phenomenological model for the first time. Some of the aspects revealed in this investigation, such as the dependence of the intensity of the polarization field on the deformation, highlight the need for an in-depth investigation of the relationships between the structure and the behaviours of the EAPs at the microscopic level and their overall macroscopic response. PMID:27118885

  16. Impact of electrode preparation on the bending of asymmetric planar electro-active polymer microstructures

    NASA Astrophysics Data System (ADS)

    Weiss, Florian M.; Töpper, Tino; Osmani, Bekim; Winterhalter, Carla; Müller, Bert

    2014-03-01

    Compliant electrodes of microstructures have been a research topic for many years because of the increasing interest in consumer electronics, robotics, and medical applications. This interest includes electrically activated polymers (EAP), mainly applied in robotics, lens systems, haptics and foreseen in a variety of medical devices. Here, the electrodes consist of metals such as gold, graphite, conductive polymers or certain composites. The common metal electrodes have been magnetron sputtered, thermally evaporated or prepared using ion implantation. In order to compare the functionality of planar metal electrodes in EAP microstructures, we have investigated the mechanical properties of magnetron sputtered and thermally evaporated electrodes taking advantage of cantilever bending of the asymmetric, rectangular microstructures. We demonstrate that the deflection of the sputtered electrodes is up to 39 % larger than that of thermally evaporated nanometer-thin film on a single silicone film. This difference has even more impact on nanometer-thin, multi-stack, low-voltage EAP actuators. The stiffening effect of many metallic electrode layers is expected to be one of the greatest drawbacks in the multi-stack approaches, which will be even more pronounced if the elastomer layer thickness will be in the sub-micrometer range. Additionally, an improvement in voltage and strain resolution is presented, which is as low as 2 V or 5 × 10-5 above 10 V applied.

  17. Studies on Proton Conducting Polymer Electrolytes Based on Pvdf-Pva with NH4NO3

    NASA Astrophysics Data System (ADS)

    Muthuvinayagam, M.; Gopinathan, C.; Rajeswari, N.; Selvasekarapandian, S.; Sanjeeviraja, C.

    2013-07-01

    PVDF-PVA polymer electrolytes with various blend ratios are prepared by solution casting technique with DMF (Merck) as solvent to optimize the blend ratio on the basis of high ionic conductivity. Then, different concentrations of NH4NO3 are doped with the optimized PVDF-PVA blend ratio and polymer blend electrolytes are prepared. The complex formation has been confirmed by XRD and FTIR analysis. The ac impedance studies are performed to evaluate the ionic conductivity of the polymer electrolyte membranes in the range 303-323K and it is found that the temperature dependence of ionic conductivity of the polymer blend electrolytes obey the Arrhenius relation. The maximum ionic conductivity is found to be 5.99×10-4 S/cm with activation energy Ea=0.21 eV for PVDF-PVA-NH4NO3 (80:20:0.4MWt%) polymer electrolyte.

  18. Electric poling-assisted additive manufacturing process for PVDF polymer-based piezoelectric device applications

    NASA Astrophysics Data System (ADS)

    Lee, ChaBum; Tarbutton, Joshua A.

    2014-09-01

    This paper presents a new additive manufacturing (AM) process to directly and continuously print piezoelectric devices from polyvinylidene fluoride (PVDF) polymeric filament rods under a strong electric field. This process, called ‘electric poling-assisted additive manufacturing or EPAM, combines AM and electric poling processes and is able to fabricate free-form shape piezoelectric devices continuously. In this process, the PVDF polymer dipoles remain well-aligned and uniform over a large area in a single design, production and fabrication step. During EPAM process, molten PVDF polymer is simultaneously mechanically stresses in-situ by the leading nozzle and electrically poled by applying high electric field under high temperature. The EPAM system was constructed to directly print piezoelectric structures from PVDF polymeric filament while applying high electric field between nozzle tip and printing bed in AM machine. Piezoelectric devices were successfully fabricated using the EPAM process. The crystalline phase transitions that occurred from the process were identified by using the Fourier transform infrared spectroscope. The results indicate that devices printed under a strong electric field become piezoelectric during the EPAM process and that stronger electric fields result in greater piezoelectricity as marked by the electrical response and the formation of sharper peaks at the polar β crystalline wavenumber of the PVDF polymer. Performing this process in the absence of an electric field does not result in dipole alignment of PVDF polymer. The EPAM process is expected to lead to the widespread use of AM to fabricate a variety of piezoelectric PVDF polymer-based devices for sensing, actuation and energy harvesting applications with simple, low cost, single processing and fabrication step.

  19. A study on the effect of surface topography on the actuation performance of stacked-rolled dielectric electro active polymer actuator

    NASA Astrophysics Data System (ADS)

    Sait, Usha; Muthuswamy, Sreekumar

    2016-05-01

    Dielectric electro active polymer (DEAP) is a suitable actuator material that finds wide applications in the field of robotics and medical areas. This material is highly controllable, flexible, and capable of developing large strain. The influence of geometrical behavior becomes critical when the material is used as miniaturized actuation devices in robotic applications. The present work focuses on the effect of surface topography on the performance of flat (single sheet) and stacked-rolled DEAP actuators. The non-active areas in the form of elliptical spots that affect the performance of the actuator are identified using scanning electron microscope (SEM) and energy dissipated X-ray (EDX) experiments. Performance of DEAP actuation is critically evaluated, compared, and presented with analytical and experimental results.

  20. Study on characteristics of PVDF/nano-clay composite polymer electrolyte using PVP as pore-forming agent

    SciTech Connect

    Dyartanti, Endah R. E-mail: endah-rd@uns.ac.id; Purwanto, Agus; Widiasa, I. Nyoman; Susanto, Heru E-mail: endah-rd@uns.ac.id

    2016-02-08

    Polyvinylidene fluoride (PVDF) based polymer electrolytes have a high dielectric constant, which can assist in greater ionization of lithium salts. The main advantages of PVDF are its durability in long battery operation and its ability to be a good ion conductor. However, the limitation of this polymer is its crystalline molecular structure. Dispersing nano-particles in the polymer matrix may improve the characteristics of the PVDF polymer. This paper aims to investigate the impact of nano-clay addition on the characteristics of PVDF polymer to be used as a polymer electrolyte membrane. In addition, the effect of poly(vinyl pyrrolidone) (PVP) is also investigated. The membrane was prepared by phase separation method whereas the polymer electrolyte membranes was prepared by immersing into 1 M lithium hexafluorophosphate (LiPF{sub 6}) in ethylene carbonate/dimethyl carbonate (EC/DMC) electrolytes for 1 h. The membranes were characterized by scanning electron microscope (SEM), porosity and electrolyte uptake and performance in battery cell. The results showed that both nano-clay and PVP have significant impacts on the improvement of PVDF membranes to be used as polymer electrolyte.

  1. Study on characteristics of PVDF/nano-clay composite polymer electrolyte using PVP as pore-forming agent

    NASA Astrophysics Data System (ADS)

    Dyartanti, Endah R.; Purwanto, Agus; Widiasa, I. Nyoman; Susanto, Heru

    2016-02-01

    Polyvinylidene fluoride (PVDF) based polymer electrolytes have a high dielectric constant, which can assist in greater ionization of lithium salts. The main advantages of PVDF are its durability in long battery operation and its ability to be a good ion conductor. However, the limitation of this polymer is its crystalline molecular structure. Dispersing nano-particles in the polymer matrix may improve the characteristics of the PVDF polymer. This paper aims to investigate the impact of nano-clay addition on the characteristics of PVDF polymer to be used as a polymer electrolyte membrane. In addition, the effect of poly(vinyl pyrrolidone) (PVP) is also investigated. The membrane was prepared by phase separation method whereas the polymer electrolyte membranes was prepared by immersing into 1 M lithium hexafluorophosphate (LiPF6) in ethylene carbonate/dimethyl carbonate (EC/DMC) electrolytes for 1 h. The membranes were characterized by scanning electron microscope (SEM), porosity and electrolyte uptake and performance in battery cell. The results showed that both nano-clay and PVP have significant impacts on the improvement of PVDF membranes to be used as polymer electrolyte.

  2. Optimization of piezo-electric PVDF polymers for adaptive optics in space environments.

    SciTech Connect

    Dargaville, Tim Richard; Martin, Jeffrey W.; Clough, Roger Lee; Celina, Mathias Christopher

    2003-07-01

    Piezoelectric polymers based on PVDF are of interest for use in large aperture space-based telescopes similar to the James Web Space Telescope. Dimensional adjustments of polymer films depend on their piezoelectric properties with wireless (electron beam) shape control methods having been successfully demonstrated in the past. Such electron beam controls require a detailed understanding of the piezoelectric material responses. Similarly, space applications demand consistent, predictable, and reliable performance. While PVDF as a generic polymer type is a suitable piezoelectric material, it is also well known that fluorinated polymers are highly radiation-sensitive. Mechanical and other physical properties will suffer under various types of radiation (strong vacuum UV, {gamma}-, X-ray, e-beam, ion-beam) and atomic oxygen exposure. Likewise, extreme temperature fluctuations in space environments will result in annealing effects and cyclic stresses. While the radiative degradation chemistry of polymers is an established field there is little information available on the performance of piezoelectric features in PVDF with respect to their expected changes in these environments. Therefore, understanding such fundamental issues becomes mandatory for the design and deployment of satellite systems utilizing these materials/technology. We have investigated the degradation of PVDF and copolymers under a range of stress environments, and have studied the implications with regard to piezoelectrical properties necessary for reliable operation of thin films in space environments. Initial aging studies using {gamma}- and e-beam irradiation to explore material sensitivities for comparison with expected UV doses have shown complex material changes with lowered Curie temperatures, crystallinity, melting points and significant crosslinking, but little affect on piezoelectric d{sub 33} constants. Similar complexities of the aging processes have been observed in accelerated temperature

  3. Conductivity studies of LiCF3SO3 doped PVA: PVdF blend polymer electrolyte

    NASA Astrophysics Data System (ADS)

    Tamilselvi, P.; Hema, M.

    2014-03-01

    Different composition of lithium ion conducting PVA: PVdF: Lithium triflate (LiCF3SO3) polymer electrolytes have been prepared by solution casting technique. Dielectric and conductivity studies have been carried out for the prepared samples. The addition of salt into the polymer matrix increases the ionic conductivity of blend polymer electrolytes. The conductivity analysis reveals 80PVA: 20PVdF: 15LiCF3SO3 polymer electrolyte exhibits the maximum ionic conductivity of 2.7×10-3 S cm-1 at 303 K. The temperature dependence of ionic conductivity for all the composition of PVA: PVdF: LiCF3SO3 polymer films obey Arrhenius relation. Low activation energy has been obtained for highest conducting sample. The dielectric spectra show absolute β-relaxation peak.

  4. Molecular modeling of the piezoelectric effect in the ferroelectric polymer poly(vinylidene fluoride) (PVDF).

    PubMed

    Bystrov, Vladimir S; Paramonova, Ekaterina V; Bdikin, Igor K; Bystrova, Anna V; Pullar, Robert C; Kholkin, Andrei L

    2013-09-01

    In this work, computational molecular modeling and exploration was applied to study the nature of the negative piezoelectric effect in the ferroelectric polymer polyvinylidene fluoride (PVDF), and the results confirmed by actual nanoscale measurements. First principle calculations were employed, using various quantum-chemical methods (QM), including semi-empirical (PM3) and various density functional theory (DFT) approaches, and in addition combined with molecular mechanics (MM) methods in complex joint approaches (QM/MM). Both PVDF molecular chains and a unit cell of crystalline β-phase PVDF were modeled. This computational molecular exploration clearly shows that the nature of the so-called negative piezo-electric effect in the ferroelectric PVDF polymer has a self-consistent quantum nature, and is related to the redistribution of the electron molecular orbitals (wave functions), leading to the shifting of atomic nuclei and reorganization of all total charges to the new, energetically optimal positions, under an applied electrical field. Molecular modeling and first principles calculations show that the piezoelectric coefficient d 33 has a negative sign, and its average values lies in the range of d 33 ~ -16.6 to -19.2 pC/N (or pm/V) (for dielectric permittivity ε = 5) and in the range of d 33 ~ -33.5 to -38.5 pC/N (or pm/V) (for ε = 10), corresponding to known data, and allowing us to explain the reasons for the negative sign of the piezo-response. We found that when a field is applied perpendicular to the PVDF chain length, as polarization increases the chain also stretches, increasing its length and reducing its height. For computed value of ε ~ 5 we obtained a value of d31 ~ +15.5 pC/N with a positive sign. This computational study is corroborated by measured nanoscale data obtained by atomic force and piezo-response force microscopy (AFM/PFM). This study could be useful as a basis for further insights into other organic and molecular ferroelectrics.

  5. Parallel input parallel output high voltage bi-directional converters for driving dielectric electro active polymer actuators

    NASA Astrophysics Data System (ADS)

    Thummala, P.; Zhang, Z.; Andersen, M. A. E.; Rahimullah, S.

    2014-03-01

    Dielectric electroactive polymer (DEAP) actuators are capacitive devices which provide mechanical motions when charged electrically. The charging characteristics of a DEAP actuator depends on its size, voltage applied to its electrodes, and its operating frequency. The main idea of this paper is to design and implement driving circuits for the DEAP actuators for their use in various applications. This paper presents implementation of parallel input, parallel output, high voltage (~2.5 kV) bi-directional DC-DC converters for driving the DEAP actuators. The topology is a bidirectional flyback DC-DC converter incorporating commercially available high voltage MOSFETs (4 kV) and high voltage diodes (5 kV). Although the average current of the aforementioned devices is limited to 300 mA and 150 mA, respectively, connecting the outputs of multiple converters in parallel can provide a scalable design. This enables operating the DEAP actuators in various static and dynamic applications e.g. positioning, vibration generation or damping, and pumps. The proposed idea is experimentally verified by connecting three high voltage converters in parallel to operate a single DEAP actuator. The experimental results with both film capacitive load and the DEAP actuator are shown for a maximum charging voltage of 2 kV.

  6. Li Ion Conducting Polymer Gel Electrolytes Based on Ionic Liquid/PVDF-HFP Blends

    PubMed Central

    Ye, Hui; Huang, Jian; Xu, Jun John; Khalfan, Amish; Greenbaum, Steve G.

    2009-01-01

    Ionic liquids thermodynamically compatible with Li metal are very promising for applications to rechargeable lithium batteries. 1-methyl-3-propylpyrrolidinium bis(trifluoromethanesulfonyl)imide (P13TFSI) is screened out as a particularly promising ionic liquid in this study. Dimensionally stable, elastic, flexible, nonvolatile polymer gel electrolytes (PGEs) with high electrochemical stabilities, high ionic conductivities and other desirable properties have been synthesized by dissolving Li imide salt (LiTFSI) in P13TFSI ionic liquid and then mixing the electrolyte solution with poly(vinylidene-co-hexafluoropropylene) (PVDF-HFP) copolymer. Adding small amounts of ethylene carbonate to the polymer gel electrolytes dramatically improves the ionic conductivity, net Li ion transport concentration, and Li ion transport kinetics of these electrolytes. They are thus favorable and offer good prospects in the application to rechargeable Li batteries including open systems like Li/air batteries, as well as more “conventional” rechargeable lithium and lithium ion batteries. PMID:20354587

  7. Acrylonitrile grafted to PVDF

    SciTech Connect

    Yang, Jin; Eitouni, Hany Basam

    2015-03-31

    PVDF-g-PAN has been synthesized by grafting polyacrylonitrile onto polyvinylidene fluoride using an ATRP/AGET method. The novel polymer is ionically conducive and has much more flexibility than PVDF alone, making it especially useful either as a binder in battery cell electrodes or as a polymer electrolyte in a battery cell.

  8. Multiscale Modeling of the Electrocaloric Effect in PVDF-based Polymers

    NASA Astrophysics Data System (ADS)

    McGaughey, Alan; Yu, Ying-Ju

    We apply multi-scale modeling to explore the electrocaloric (EC) effect in PVDF-related ferroelectric polymers, which have application in active cooling of microsystems. The EC effect is the temperature rise and drop in some ferroelectric materials due to changes in the configurational entropy when an external electric field is applied and removed. The polymer is modeled as a series of bi-directional permanent dipoles and induced point dipoles distributed on its monomer sites. The flipping of these dipoles due to an applied electric field is leads to polarization changes. Flipping the dipole moment of the polymer chain requires rotation of the individual monomers, each of which has its own energy barrier. This energy pathway is predicted from atomic-level nudged elastic band method calculations for a variety of chain environments. We then use first-passage time analysis to convert each energy pathway into an average transition rate for a full polymer chain rotation. The transition rates for all chains are integrated into a kinetic Monte Carlo algorithm in which the polarization change due to the application of an electric field is determined.

  9. Figure of merit comparison of PP-based electret and PVDF-based piezoelectric polymer energy harvesters

    NASA Astrophysics Data System (ADS)

    Mrlík, M.; Leadenham, S.; AlMaadeed, M. A.; Erturk, A.

    2016-04-01

    The harvesting of mechanical strain and kinetic energy has received great attention over the past two decades in order to power wireless electronic components such as those used in passive and active monitoring applications. Piezoelectric ceramics, such as PZT (lead zirconate titanate), constitute the most commonly used electromechanical interface in vibration energy harvesters. However, there are applications in which piezoelectric ceramics cannot be used due to their low allowable curvature and brittle nature. Soft polymer PVDF (polyvinylidene fluoride) is arguably the most popular non-ceramic soft piezoelectric energy harvester material for such scenarios. Another type of polymer that has received less attention is PP (polypropylene) for electret-based energy harvesting using the thickness mode (33- mode). This work presents figure of merit comparison of PP versus PVDF for off-resonant energy harvesting in thickness mode operation, revealing substantial advantage of PP over PVDF. For thickness mode energy harvesting scenarios (e.g. dynamic compression) at reasonable ambient vibration frequencies, the figure of merit for the maximum power output is proportional to the square of the effective piezoelectric strain constant divided by the effective permittivity constant. Under optimal conditions and for the same volume, it is shown that PP can generate more than two orders of magnitude larger electrical power as compared to PVDF due to the larger effective piezoelectric strain constant and lower permittivity of the former.

  10. Flux and Passage Enhancement in Hemodialysis by Incorporating Compound Additive into PVDF Polymer Matrix

    PubMed Central

    Zhang, Qinglei; Lu, Xiaolong; Zhang, Qingzhao; Zhang, Lei; Li, Suoding; Liu, Shaobin

    2016-01-01

    In this study, Polyvinylidene fluoride (PVDF) hollow fiber hemodialysis membranes were prepared by non-solvent induced phase separation (NIPS) with compound addtive. The compound additive was made with polyvinyl pyrrolidone (PVP) and Poly ethylene glycol (PEG). The results showed that the modified PVDF membrane had better separation performance than virgin PVDF membrane. The UF flux of modified PVDF membrane can reach 684 L·h−1·m−2 and lysozyme (LZM) passage is 72.6% while virgin PVDF membrane is 313 L·h−1·m−2 and 53.2%. At the same time, the biocompatibility of PVDF membranes was also improved. Compared with commercial polysulfone hemodialysis membrane (Fresenius F60S membrane), the modified PVDF membrane had better mechanical and separation performance. The stress and tensile elongation of modified PVDF membrane was 0.94 MPa and 352% while Fresenius F60S membrane was 0.79 MPa and 59%. The LZM passage reached 72.6% while Fresenius F60S membrane was 54.4%. It was proven that the modified PVDF membrane showed better hydrophilicity, antithrombogenicity, less BSA adsorption, and lower hemolytic ratio and adhesion of platelets. Water contact angle and BSA adsorption of the modified PVDF membrane are 38° and 45 mg/m2 while Fresenius F60S membrane are 64° and 235 mg/m2. Prothrombin time (PT) and activated partial thromboplastin time (APTT) of the modified PVDF membrane are 56.5 s and 25.8 s while Fresenius F60S membrane is 35.7 s and 16.6 s. However, further biocompatibility evaluation is needed to obtain a more comprehensive conclusion. PMID:27775566

  11. Performance characteristics of guanine incorporated PVDF-HFP/PEO polymer blend electrolytes with binary iodide salts for dye-sensitized solar cells

    NASA Astrophysics Data System (ADS)

    Senthil, R. A.; Theerthagiri, J.; Madhavan, J.; Arof, A. K.

    2016-08-01

    In this work, we have investigated the influence of guanine as an organic dopant in dye-sensitized solar cell (DSSC) based on poly(vinylidinefluoride-co-hexafluoropropylene) (PVDF-HFP)/polyethylene oxide (PEO) polymer blend electrolyte along with binary iodide salts (potassium iodide (KI) and tetrabutylammonium iodide (TBAI)) and iodine (I2). The PVDF-HFP/KI + TBAI/I2, PVDF-HFP/PEO/KI + TBAI/I2 and guanine incorporated PVDF-HFP/PEO/KI + TBAI/I2 electrolytes were prepared by solution casting technique using DMF as solvent. The PVDF-HFP/KI + TBAI/I2 electrolyte showed an ionic conductivity value of 9.99 × 10-5 Scm-1, whereas, it was found to be increased to 4.53 × 10-5 Scm-1 when PEO was blended with PVDF-HFP/KI + TBAI/I2 electrolyte. However, a maximum ionic conductivity value of 3.67 × 10-4 Scm-1 was obtained for guanine incorporated PVDF-HFP/PEO/KI + TBAI/I2 blend electrolyte. The photovoltaic properties of all these polymer electrolytes in DSSCs were characterized. As a consequence, the power conversion efficiency of the guanine incorporated PVDF-HFP/PEO/KI + TBAI/I2 electrolyte based DSSC was significantly improved to 4.98% compared with PVDF-HFP/PEO/KI + TBAI/I2 electrolyte based DSSC (2.46%). These results revealed that the guanine can be an effective organic dopant to enhance the performance of DSSCs.

  12. Cellulose Electro-Active Paper: From Discovery to Technology Applications

    NASA Astrophysics Data System (ADS)

    Abas, Zafar; Kim, Heung Soo; Kim, Jaehwan; Kim, Joo-Hyung

    2014-09-01

    Cellulose electro-active paper (EAPap) is an attractive material of electro-active polymers (EAPs) family due to its smart characteristics. EAPap is thin cellulose film coated with metal electrodes on both sides. Its large displacement output, low actuation voltage and low power consumption can be used for biomimetic sensors/actuators and electromechanical system. Because cellulose EAPap is ultra-lightweight, easy to manufacture, inexpensive, biocompatible, and biodegradable, it has been employed for many applications such as bending actuator, vibration sensor, artificial muscle, flexible speaker, and can be advantageous in areas such as micro-insect robots, micro-flying objects, microelectromechanical systems, biosensors, and flexible displays.

  13. Response of Bauer piezoelectric polymer stress gauges (PVDF) (polyvinylidene fluoride) to shock loading

    SciTech Connect

    Graham, R.A.; Lee, L.M.; Bauer, F.

    1987-01-01

    Polyvinylidene fluoride (PVDF) stress gauges fabricated from high quality, biaxially stretched film, and electrically poled to high values of remanent polarization are the basis for revolutionary new gauging capabilities. In the present work, a number of PVDF films have been studied under controlled impact loading to maximum impact stresses of 35 GPa. Gauges with various degrees of polarization were studied. In the impact studies, electrical response with good fidelity was obtained to stress of 20 GPa. At 35 GPa the observed response is highly distorted. Remanent polarization is found to have a significant influence on nonlinearity and probably affects the maximum useful stress for shock gauge applications.

  14. Study of nano imprinting using soft lithography on Krafty glue & PVDF polymer thin films

    NASA Astrophysics Data System (ADS)

    Sankar, M. S. Ravi; Gangineni, Ramesh Babu

    2014-04-01

    The present work reveals soft lithography strategy based on self assembly and replica molding for carrying out micro and nanofabrication. It provides a convenient, effective and very low cost method for the formation and manufacturing of micro and nano structures. Al-layer of compact disc (sony CD-R) used as a stamp with patterned relief structures to generate patterns and structures with pattern size of 100nm height, 1.7 μm wide. In literature, PDMS (Polydimethylsiloxane) solution is widely used to get negative copy of the Al-layer. In this work, we have used inexpensive white glue (Polyvinylacetate + water), 15gm (□5) and PVDF (Polyvinylidene difluoride) spin coated films and successfully transferred the nano patterns of Al layer on to white glue and PVDF films.

  15. Study of nano imprinting using soft lithography on Krafty glue and PVDF polymer thin films

    SciTech Connect

    Sankar, M. S. Ravi Gangineni, Ramesh Babu

    2014-04-24

    The present work reveals soft lithography strategy based on self assembly and replica molding for carrying out micro and nanofabrication. It provides a convenient, effective and very low cost method for the formation and manufacturing of micro and nano structures. Al-layer of compact disc (sony CD-R) used as a stamp with patterned relief structures to generate patterns and structures with pattern size of 100nm height, 1.7 μm wide. In literature, PDMS (Polydimethylsiloxane) solution is widely used to get negative copy of the Al-layer. In this work, we have used inexpensive white glue (Polyvinylacetate + water), 15gm (□5) and PVDF (Polyvinylidene difluoride) spin coated films and successfully transferred the nano patterns of Al layer on to white glue and PVDF films.

  16. Preparation and characterization of polymer nanocomposites based on PVDF/PVC doped with graphene nanoparticles

    NASA Astrophysics Data System (ADS)

    Elashmawi, I. S.; Alatawi, Naifa S.; Elsayed, Nadia H.

    Novel nanocomposites based on PVDF/PVC blend containing graphene oxide nanoparticles (GO) were prepare using sonicator. IR analysis revealed that the addition of GO prompts a crystal transformation of α-phase of PVDF. The change of the structural before and after adding GO to PVDF/PVC were studied by X-ray diffraction. A decrease in activation energy gap from UV data was observed with increasing GO content, implying a variation of reactivity as a result of reaction extent. The variation of ε‧ with frequency is nearly the same as that of ε″ . At higher frequencies, the decrease of both ε‧ and ε″ becomes nearly constant. The dispersion at lower frequencies ε‧ of ε‧ polarization is of Maxwell-Wagner interfacial polarization but at higher frequencies, it levels off. The behavior of conductivity (σAC) tends to acquire constant values approaching it DC values. The values of σAC was increased after doped GO with exponential increase after the critical value of frequency. All nanocomposites behaved the same fashion revealing that a higher number of polarons were getting added to conducting pool in composites as graphene content was increased. Conduction mechanism appeared to be getting expedited with increasing frequency due to fact that increase in frequency enhances polaron hopping frequency.

  17. Recent Progress on Cellulose-Based Electro-Active Paper, Its Hybrid Nanocomposites and Applications

    PubMed Central

    Khan, Asif; Abas, Zafar; Kim, Heung Soo; Kim, Jaehwan

    2016-01-01

    We report on the recent progress and development of research into cellulose-based electro-active paper for bending actuators, bioelectronics devices, and electromechanical transducers. The cellulose electro-active paper is characterized in terms of its biodegradability, chirality, ample chemically modifying capacity, light weight, actuation capability, and ability to form hybrid nanocomposites. The mechanical, electrical, and chemical characterizations of the cellulose-based electro-active paper and its hybrid composites such as blends or coatings with synthetic polymers, biopolymers, carbon nanotubes, chitosan, and metal oxides, are explained. In addition, the integration of cellulose electro-active paper is highlighted to form various functional devices including but not limited to bending actuators, flexible speaker, strain sensors, energy harvesting transducers, biosensors, chemical sensors and transistors for electronic applications. The frontiers in cellulose paper devices are reviewed together with the strategies and perspectives of cellulose electro-active paper and cellulose nanocomposite research and applications. PMID:27472335

  18. Energy barriers for dipole moment flipping in PVDF-related ferroelectric polymers.

    PubMed

    Yu, Ying-Ju; McGaughey, Alan J H

    2016-01-07

    Energy barriers for flipping the transverse dipole moments in poly(vinylidene fluoride) (PVDF) and related copolymers and terpolymers are predicted using the nudged elastic band method. The dipole moments flip individually along the chain, with an order and energy barrier magnitudes (0.1-1.2 eV) that depend on the chain composition and environment. Trifluoroethylene (TrFE) and chlorofluoroethylene (CFE) monomers have larger energy barriers than VDF monomers, while a chain in an amorphous environment has a similar transition pathway as that of an isolated molecule. In a crystalline environment, TrFE and CFE monomers expand the lattice and lower the energy barriers for flipping VDF monomers. This finding is consistent with experimental observations of a large electrocaloric effect in P(VDF-TrFE-CFE) terpolymers.

  19. Energy barriers for dipole moment flipping in PVDF-related ferroelectric polymers

    NASA Astrophysics Data System (ADS)

    Yu, Ying-Ju; McGaughey, Alan J. H.

    2016-01-01

    Energy barriers for flipping the transverse dipole moments in poly(vinylidene fluoride) (PVDF) and related copolymers and terpolymers are predicted using the nudged elastic band method. The dipole moments flip individually along the chain, with an order and energy barrier magnitudes (0.1-1.2 eV) that depend on the chain composition and environment. Trifluoroethylene (TrFE) and chlorofluoroethylene (CFE) monomers have larger energy barriers than VDF monomers, while a chain in an amorphous environment has a similar transition pathway as that of an isolated molecule. In a crystalline environment, TrFE and CFE monomers expand the lattice and lower the energy barriers for flipping VDF monomers. This finding is consistent with experimental observations of a large electrocaloric effect in P(VDF-TrFE-CFE) terpolymers.

  20. The Structure Design of Piezoelectric Poly(vinylidene Fluoride) (PVDF) Polymer-Based Sensor Patch for the Respiration Monitoring under Dynamic Walking Conditions.

    PubMed

    Lei, Kin-Fong; Hsieh, Yi-Zheng; Chiu, Yi-Yuan; Wu, Min-Hsien

    2015-07-31

    This study reports a piezoelectric poly(vinylidene fluoride) (PVDF) polymer-based sensor patch for respiration detections in dynamic walking condition. The working mechanism of respiration signal generation is based on the periodical deformations on a human chest wall during the respiratory movements, which in turn mechanically stretch the piezoelectric PVDF film to generate the corresponding electrical signals. In this study, the PVDF sensing film was completely encapsulated within the sensor patch forming a mass-spring-damper mechanical system to prevent the noises generated in a dynamic condition. To verify the design of sensor patch to prevent dynamic noises, experimental investigations were carried out. Results demonstrated the respiration signals generated and the respiratory rates measured by the proposed sensor patch were in line with the same measurements based on a commercial respiratory effort transducer both in a static (e.g., sitting) or dynamic (e.g., walking) condition. As a whole, this study has developed a PVDF-based sensor patch which is capable of monitoring respirations in a dynamic walking condition with high fidelity. Other distinctive features include its small size, light weight, ease of use, low cost, and portability. All these make it a promising sensing device to monitor respirations particularly in home care units.

  1. The Structure Design of Piezoelectric Poly(vinylidene Fluoride) (PVDF) Polymer-Based Sensor Patch for the Respiration Monitoring under Dynamic Walking Conditions

    PubMed Central

    Lei, Kin-Fong; Hsieh, Yi-Zheng; Chiu, Yi-Yuan; Wu, Min-Hsien

    2015-01-01

    This study reports a piezoelectric poly(vinylidene fluoride) (PVDF) polymer-based sensor patch for respiration detections in dynamic walking condition. The working mechanism of respiration signal generation is based on the periodical deformations on a human chest wall during the respiratory movements, which in turn mechanically stretch the piezoelectric PVDF film to generate the corresponding electrical signals. In this study, the PVDF sensing film was completely encapsulated within the sensor patch forming a mass-spring-damper mechanical system to prevent the noises generated in a dynamic condition. To verify the design of sensor patch to prevent dynamic noises, experimental investigations were carried out. Results demonstrated the respiration signals generated and the respiratory rates measured by the proposed sensor patch were in line with the same measurements based on a commercial respiratory effort transducer both in a static (e.g., sitting) or dynamic (e.g., walking) condition. As a whole, this study has developed a PVDF-based sensor patch which is capable of monitoring respirations in a dynamic walking condition with high fidelity. Other distinctive features include its small size, light weight, ease of use, low cost, and portability. All these make it a promising sensing device to monitor respirations particularly in home care units. PMID:26263992

  2. Thermal, mechanical and ionic conductive behaviour of gamma-radiation induced PEO/PVDF(SIN)-LiClO 4 polymer electrolyte system

    NASA Astrophysics Data System (ADS)

    Song, Yongxian; Wu, Shuyun; Jing, Xiabing; Sun, Jiazhen; Chen, Donglin

    1997-05-01

    An effort has been made to modify the mechanical behaviour of our previously reported gel-type gamma-radiation crosslinked polyethylene oxide (PEO)-LiClO 4 polymer electrolyte. A highly polar and gamma-radiation crosslinkable crystalline polymer, polyvinylidene fluoride (PVDF), was selected to blend with PEO and then subjected to gamma-irradiation in order to make an simultaneous interpenetrating network (SIN), which was used as a polymer host to impart stiffness to the plasticized system. Experimental results have shown that the presence of PVDF in the system, through gamma-radiation induced SIN formation, could not only give a rather high mechanical modulus of 10 7 Pa at ambient temperature, but also maintain the room temperature ionic conductivity at a high level (greater than 10 -4 S/cm). DSC, DMA and conductivity measurement techniques were used to examine the effects of blending, gamma-irradiation and plasticization on the variations of glass transition and melting endotherm, on the appearance of high elastic plateau and on the temperature dependence of ionic conductivity. In addition, it was found that, in contrast with the unplasticized system, the ionic conductivity mechanism of this gel-type electrolyte seems to conform to the Arrhenius model, suggesting that, as a result of the high degree of plasticization, the polymer chains act mainly as the skeleton of the networks or polymer cages to immobilize the liquid electrolyte solution, whereas the ionic species migrate as if they were in a liquid medium.

  3. Composite polymer electrolyte based on PEO/Pvdf-HFP with MWCNT for lithium battery applications

    NASA Astrophysics Data System (ADS)

    Pradeepa, P.; Edwinraj, S.; Sowmya, G.; Kalaiselvimary, J.; Selvakumar, K.; Prabhu, M. Ramesh

    2016-05-01

    In the present study PEO and PVdF-HFP blend based composite polymer electrolytes (CPEs) has been prepared by using Multi Walled Carbon Nanotube (MWCNT), in order to examine the filler addition effect on the electrochemical properties. The complexed nanocomposite polymer electrolytes were obtained in the form of dimensionally stable and free standing films by using solution casting technique. The electrochemical properties of CPEs were measured by the AC impedance method. From the ionic conductivity results, the CPE containing MWCNT 2wt% showed the highest ionic conductivity with an excellent thermal stability at room temperature. The dielectric loss curve s for the sample 6.25wt% PEO: 18.75 wt% PVdF-HFP: 2wt% MWCNT reveal the low frequency β relaxation peak pronounced at high temperature, and it may caused by side group dipoles.

  4. 25 MHz ultrasonic transducers with lead-free piezoceramic, 1-3 PZT fiber-epoxy composite, and PVDF polymer active elements.

    PubMed

    Jadidian, Bahram; Hagh, Nader Marandian; Winder, Alan A; Safari, Ahmad

    2009-02-01

    This paper presents the fabrication and characterization of single-element ultrasonic transducers whose active elements are made of lead-free piezoceramic, 1-3 PZT/polymer composite and PVDF film. The lead free piezoelectric KNNLT- LS(K(0.44)Na(0.52)Li(0.04))(Nb(0.84)Ta(0.10)S(0.06)b)O(3) powders and ceramics were prepared under controlled humidity and oxygen flow rate during sintering. Due to its moderate longitudinal piezoelectric charge coefficient (175 pC/N) and k(t) of 0.50, the KNN-LT-LS composition may be a good candidate for high frequency transducer applications. PZT fibers with 25 microm diameter formed by the viscose suspension spinning process were incorporated into epoxy to fabricate 1-3 composites with the averaged k(t) = 0.64 and d(33) = 400 pC/N. Using KNN-LS-LT ceramic, 1-3 PZT fiber composite, and PVDF film, 3 different unfocused single element transducers with center frequencies of 25 MHz were fabricated. The acoustic characterization of the transducers demonstrated that wideband and low insertion loss could be obtained employing KNN-LS-LT ceramic. The -6 dB bandwidth and insertion loss were 70% and -21 dB, respectively. In comparison, the insertion loss of the ceramic transducer was much smaller than those made with 1-3 composite and PVDF film. This was attributed to closer electrical impedance match to 50 ohm and higher thickness coupling coefficient of the ceramic transducer.

  5. A simple but efficient strategy to enhance hydrostability of intensely fluorescent Mg-based coordination polymer (CP) via forming a composite of CP with hydrophobic PVDF.

    PubMed

    Zhai, Lu; Zhang, Wen-Wei; Zuo, Jing-Lin; Ren, Xiao-Ming

    2016-02-28

    A coordination polymer (CP) of Mg(2+) with 1,3,5-benzenetricarboxylate (BTC(3-)) was synthesized using a solvothermal method. The Mg-CP, with a formula of Mg3(BTC)(HCOO)3(DMF)3, crystallizes in the trigonal space group P3[combining macron], with cell parameters of a = b = 13.972(5) Å, c = 8.090(5) Å and V = 1367.6(11) Å(3), and shows a lamella structure built from planar rosette-type hexanuclear architectures. The Mg-CP emits intense blue fluorescence arising from π* → π transition of intra-ligand of BTC(3-) with 21.69% quantum yield, yet it exhibits poor stability to water. The composites of Mg-CP with hydrophobic polyvinylidene fluoride (PVDF) were sequentially prepared by mechanically mixed, tableted and annealed processes, which showed good compatibility between Mg-CP and PVDF, high hydrostability, and intense blue emission. This study suggests a simple but efficient method to solve the drawbacks of some functional CPs unstable to water and to promote them as practical applications in the field of functional materials.

  6. Enhanced Microwave Absorption Properties of Flexible Polymer Composite Based on Hexagonal NiCo2O4 Microplates and PVDF

    NASA Astrophysics Data System (ADS)

    Luo, Hui; Wang, Xian; Song, Kai; Yang, Jing; Gong, Rongzhou

    2016-08-01

    Hexagonal NiCo2O4 microplates were synthesized via a facile one-pot hydrothermal method and followed by a subsequent annealing process. The complex permittivity and permeability of a NiCo2O4 and polyvinylidene fluoride (PVDF) composite were investigated over 2-18 GHz. The experiment indicated that the good microwave absorption performance of NiCo2O4@PVDF depends on dielectric loss and quarter-wavelength cancellation. Our results show that the absorption frequency bandwidth of reflection loss (RL) less than -20 dB for the NiCo2O4@PVDF composite can be measured over the frequency range of 3-15.5 GHz with an absorbing thickness that varies in the range of 1.25-5 mm. Furthermore, an optimal RL of -44.8 dB was observed at 10.7 GHz with a thickness of 1.75 mm. The loss mechanism is also discussed.

  7. Coaxially electrospun PVDF-Teflon AF and Teflon AF-PVDF core-sheath nanofiber mats with superhydrophobic properties.

    PubMed

    Muthiah, Palanikkumaran; Hsu, Shu-Hau; Sigmund, Wolfgang

    2010-08-03

    This work reports the coaxial electrospinning of poly(vinylidene fluoride) (PVDF)-Teflon amorphous fluoropolymer (AF) and Teflon AF-PVDF core-sheath nanofiber mats yielding superhydrophobic properties. The coaxial electrospinning configuration allows for the electrospinning of Teflon AF, a nonelectrospinnable polymer, with the help of an electrospinnable PVDF polymer. PVDF-Teflon AF and Teflon AF-PVDF core-sheath fibers have been found to a have mean fiber diameter ranging from 400 nm to less than 100 nm. TEM micrographs exhibit a typical core-sheath fiber structure for these fibers, where the sheath fiber coats the core fiber almost thoroughly. Water contact angle measurements by sessile drop method on these core-sheath nanofiber mats exhibited superhydrophobic characteristics with contact angles close to or higher than 150 degrees. Surprisingly, PVDF-Teflon AF and Teflon AF-PVDF nanofiber mat surface properties were dominated by the fiber dimensions and less influenced by the type of sheath polymer. This suggests that highly fluorinated polymer Teflon AF does not advance the hydrophobicity beyond what surface physics and slightly fluorinated polymer PVDF can achieve. It is concluded that PVDF-Teflon AF and Teflon AF-PVDF core-sheath electrospun nanofiber mats may be used in lithium (Li)-air batteries.

  8. Experimental and numerical study of cellulose-based electro-active paper energy harvester

    NASA Astrophysics Data System (ADS)

    Abas, Zafar; Kim, Heung Soo; Zhai, Lindong; Kim, Jaehwan

    2014-04-01

    In this present study experimental and finite element analysis of cellulose based electro-active paper energy harvester is presented. Electro-active paper coated with metal electrode is a smart form of cellulose and exhibit piezoelectric effect. Specimens were prepared by depositing electrodes on both sides of the cellulose film. A 50 mm x 50 mm cellulose film coated with aluminum electrodes was bonded on 100 mm x 50 mm x 1 mm aluminum host structure. The voltage output to input acceleration frequency response across a load resistor of 1 MΩ is recorded by conventional energy harvesting experimental setup at the fundamental vibration mode of the EAPap cantilever beam. A coupled piezoelectric-circuit finite element model is developed in which load resistor is directly connected to energy scavenging device. Voltage output FRF is measured for the cases, without proof mass, and by adding a 2 grams proof mass near the tip of the cantilever. The experimental voltage FRF value is 7.6 V/g at 75.1 Hz and is improved to 13.8 V/g at 62.2 Hz when a stainless steel proof mass of 2 grams is added. The presented CPC-FEM model results agree reasonably well with the experimental results. Despite the fact that the electro-mechanical coupling coefficient of electro-active paper is lower than other available piezoelectric materials, it is biocompatible, cheap and naturally occurring polymeric material. It is also very flexible and posses similar piezoelectric characteristics such a PVDF which inspire to use EAPap in energy harvesting applications.

  9. Application of electro-active biofilms.

    PubMed

    Erable, Benjamin; Duţeanu, Narcis M; Ghangrekar, M M; Dumas, Claire; Scott, Keith

    2010-01-01

    The concept of an electro-active biofilm (EAB) has recently emerged from a few studies that discovered that certain bacteria which form biofilms on conductive materials can achieve a direct electrochemical connection with the electrode surface using it as electron exchanger, without the aid of mediators. This electro-catalytic property of biofilms has been clearly related to the presence of some specific strains that are able to exchange electrons with solid substrata (eg Geobacter sulfurreducens and Rhodoferax ferrireducens). EABs can be obtained principally from natural sites such as soils or seawater and freshwater sediments or from samples collected from a wide range of different microbially rich environments (sewage sludge, activated sludge, or industrial and domestic effluents). The capability of some microorganisms to connect their metabolisms directly in an external electrical power supply is very exciting and extensive research is in progress on exploring the possibilities of EABs applications. Indeed, the best known application is probably the microbial fuel cell technology that is capable of turning biomass into electrical energy. Nevertheless, EABs coated onto electrodes have recently become popular in other fields like bioremediation, biosynthesis processes, biosensor design, and biohydrogen production.

  10. Enhancement of β-phase in PVDF by electrospinning

    NASA Astrophysics Data System (ADS)

    Lim, Jun Young; Kim, Sehyun; Seo, Yongsok

    2015-05-01

    Poly(vinylidene fluoride) (PVDF), a polymorphic material, has useful electro active properties such as piezo-, pyro-, and ferroelectric properties. The piezoelectric crystallization polymorph is the β-phase which has an all-trans (TTTT) conformation, i.e., all of its dipoles aligned in the same direction normal to the chain axis. Elongational deformation was applied to poly(vinylidene fluoride)(PVDF) / multiwalled carbon nanotube (MWCNT) nanocomposites. Its effect on the conversion of the α-phase crystals into the β-phase crystals and on the piezoelectric propertes was investigated. Elongational deformation of PVDF molecules made it easier for the CF2 groups to arrange themselves in the same conformation by reducing the steric hindrance. However, macro-deformation was dominant in the drawn films, though the interfacial interaction between the functional groups on the MWCNTs and the CF2 dipole of PVDF chains helped the conversion of α-phase. Uniform distribution of MWCNT in the electrospun films helps efficient charge accumulation at the interface between the MWCNTs and the matrix PVDF molecules. Deploarization effect occurred in the pressed film due to the excessive charge accumulation was not observed, resulting in the high conversion of α-phase into β-phase as well as the enhancement of remanent polarization and the mechanical displacement. Added MWCNT helps the film to be extended without rupturing.

  11. Electro-active sensor, method for constructing the same; apparatus and circuitry for detection of electro-active species

    NASA Technical Reports Server (NTRS)

    Buehler, Martin (Inventor)

    2009-01-01

    An electro-active sensor includes a nonconductive platform with a first electrode set attached with a first side of a nonconductive platform. The first electrode set serves as an electrochemical cell that may be utilized to detect electro-active species in solution. A plurality of electrode sets and a variety of additional electrochemical cells and sensors may be attached with the nonconductive platform. The present invention also includes a method for constructing the aforementioned electro-active sensor. Additionally, an apparatus for detection and observation is disclosed, where the apparatus includes a sealable chamber for insertion of a portion of an electro-active sensor. The apparatus allows for monitoring and detection activities. Allowing for control of attached cells and sensors, a dual-mode circuitry is also disclosed. The dual-mode circuitry includes a switch, allowing the circuitry to be switched from a potentiostat to a galvanostat mode.

  12. Investigation of Ionic Conductivity of Nanocomposite Polymer Electrolytes Based On PVDF-HFP/PVC Blend, LiClO4 and TiO2 Nanofiller

    NASA Astrophysics Data System (ADS)

    Basri, N. H.; Mohamed, N. S.

    2010-07-01

    The effects of nanosized TiO2 on the conductivity of PVDF-HFP/PVC-LiClO4 was studied by means of impedance spectroscopy and x-ray diffraction (XRD). The addition of TiO2 nanofiller increases the crystalline phase fraction but slightly increases the conductivity of the PVDF-HFP/PVC-LiClO4 complex. The increase in conductivity is attributed to the formation of highly conducting layer at the electrolyte/filler interface. The temperature dependence of conductivity obeys the VTF type behaviour while the transference number confirms that the electrolyte containing 6 wt.% TiO2 is an ionic conductor are ionic conductors.

  13. Analysis of multilayer electro-active spherical balloons

    NASA Astrophysics Data System (ADS)

    Bortot, Eliana

    An electro-active spherical balloon is susceptible to electromechanical instability which, for certain material models, can trigger substantial size change. Hence, the electro-active balloon can conveniently be employed for application as actuator or generator. Practical applications, however, require proper electrode protection from aggressive agents and electric safety. For this purpose, the active membrane can be sandwiched between two soft protective passive layers. In this paper, the theory of nonlinear electro-elasticity for heterogeneous soft dielectrics is applied to the investigation of the electromechanical response of multilayer electro-active spherical balloons, formed either by the active membrane only (single-layer balloon) or by the coated active membrane (multilayer balloon). Numerical results showing the influence of the soft passive layers on the electromechanical response of the active membrane are presented.

  14. Enhanced performance of dye-sensitized solar cells based on organic dopant incorporated PVDF-HFP/PEO polymer blend electrolyte with g-C3N4/TiO2 photoanode

    NASA Astrophysics Data System (ADS)

    Senthil, R. A.; Theerthagiri, J.; Madhavan, J.; Murugan, K.; Arunachalam, Prabhakarn; Arof, A. K.

    2016-10-01

    This work describes the effect of 2-aminopyrimidine (2-APY) on poly(vinylidinefluoride-co-hexafluoropropylene) (PVDF-HFP)/polyethylene oxide (PEO) blend polymer electrolyte along with binary iodide salts (tetrabutylammonium iodide (TBAI) and potassium iodide (KI)) and iodine (I2) were studied for enhancing the efficiency of the dye-sensitized solar cells (DSSCs) consisting of g-C3N4/TiO2 composite as photoanode. The g-C3N4 was synthesized from low cost urea by thermal condensation method. It was used as a precursor to synthesize the various weight percentage ratios (5%, 10% and 15%) of g-C3N4/TiO2 composites by wet-impregnation method. The pure and 2-APY incorporated PVDF-HFP/PEO polymer blend electrolytes were arranged by wet chemical process (casting method) using DMF as a solvent. The synthesized g-C3N4/TiO2 composites and polymer blend electrolytes were studied and analyzed by Fourier transform infrared (FT-IR) spectroscopy, X-ray diffractometer (XRD) and scanning electron microscopy (SEM). The ionic conductivity values of the pure and 2-APY incorporated PVDF-HFP/PEO blend electrolytes were estimated to be 4.53×10-5 and 1.87×10-4 Scm-1 respectively. The UV-vis absorption spectroscopy was carried out for the pure and different wt% of g-C3N4/TiO2 composites coated FTO films after N3 dye-sensitization. The 10 wt% g-C3N4/TiO2 composite film showed a maximum absorption compared to the others. The DSSC assembled with 10 wt% g-C3N4/TiO2 as photoanode using the pure polymer blend electrolyte exhibited a power conversion efficiency (PCE) of 3.17% , which was superior than that of DSSC based pure TiO2 (2.46%). However, the PCE was increased to 4.73% for the DSSC assembled using 10 wt% g-C3N4/TiO2 as photoanode with 2-APY incorporated polymer blend electrolyte. Hence, the present study is a successful attempt to provide a new pathway to enhance the performance of DSSCs.

  15. TECHNICAL NOTE: Electrically aligned cellulose film for electro-active paper and its piezoelectricity

    NASA Astrophysics Data System (ADS)

    Yun, Sungryul; Jang, Sangdong; Yun, Gyu-Young; Kim, Jaehwan

    2009-11-01

    Electrically aligned regenerated cellulose films were fabricated and the effect of applied electric field was investigated for the piezoelectricity of electro-active paper (EAPap). The EAPap was fabricated by coating gold electrodes on both sides of regenerated cellulose film. The cellulose film was prepared by dissolving cotton pulp in LiCl/N,N-dimethylacetamide solution followed by a cellulose chain regeneration process. During the regeneration process an external electric field was applied in the direction of mechanical stretching. Alignment of cellulose fiber chains was investigated as a function of applied electric field. The material characteristics of the cellulose films were analyzed by using an x-ray diffractometer, a field emission scanning electron microscope and a high voltage electron microscope. The application of external electric fields was found to induce formation of nanofibers in the cellulose, resulting in an increase in the crystallinity index (CI) values. It was also found that samples with higher CI values showed higher in-plane piezoelectric constant, d31, values. The piezoelectricity of the current EAPap films was measured to be equivalent or better than that of ordinary PVDF films. Therefore, an external electric field applied to a cellulose film along with a mechanical stretching during the regeneration process can enhance the piezoelectricity.

  16. Synthesis of eucalyptus/tea tree oil absorbed biphasic calcium phosphate-PVDF polymer nanocomposite films: a surface active antimicrobial system for biomedical application.

    PubMed

    Bagchi, Biswajoy; Banerjee, Somtirtha; Kool, Arpan; Thakur, Pradip; Bhandary, Suman; Hoque, Nur Amin; Das, Sukhen

    2016-06-22

    A biocompatible poly(vinylidene) difluoride (PVDF) based film has been prepared by in situ precipitation of calcium phosphate precursors. Such films were surface absorbed with two essential oils namely eucalyptus and tea tree oil. Physico-chemical characterization of the composite film revealed excellent stability of the film with 10% loading of oils in the PVDF matrix. XRD, FTIR and FESEM measurements confirmed the presence of hydroxyapatite and octacalcium phosphate in the PVDF matrix which showed predominantly β phase. Strong bactericidal activity was observed with very low minimum bactericidal concentration (MBC) values on both E. coli and S. aureus. The composite films also resisted biofilm formation as observed by FESEM. The release of essential oils from the film showed an initial burst followed by a very slow release over a period of 24 hours. Antibacterial action of the film was found to be primarily due to the action of essential oils which resulted in leakage of vital fluids from the microorganisms. Both necrotic and apoptotic morphologies were observed in bacterial cells. Biocompatibility studies with the composite films showed negligible cytotoxicity to mouse mesenchymal and myoblast cells at MBC concentration.

  17. Highly durable, biomimetic electro-active paper actuator based on cellulose polypyrrole-ionic liquid (CPIL) nanocomposite.

    PubMed

    Mahadeva, Suresha K; Yun, Kiju; Kim, Jaehwan; Kim, Joo-Hyung

    2011-01-01

    Cellulose has received much attention as a emerging smart material, named as electro-active paper (EAPap), which can produce a large bending displacement with applied external electrical field. In spite of many advantages over other reported electro active polymers, there are some issues to be addressed: its actuator performance: (i) sensitive to environmental humidity, (ii) humidity dependent displacement output of the actuator and (iii) degradation of performance with time. In present paper, we have successfully developed the highly durable EAPap actuator working at ambient condition with large displacement output. To improve the performance and durability of EAPap, nanoscaled PPy layer into cellulose EAPap was formed by in-situ polymerization technique. Cellulose-PPy-IL nanocomposite based EAPap actuator showed nearly 100% improvement of the actuator performance compared that of pure cellulose based EAPap actuator systems.

  18. Silver nanowire dopant enhancing piezoelectricity of electrospun PVDF nanofiber web

    NASA Astrophysics Data System (ADS)

    Li, Baozhang; Zheng, Jianming; Xu, Chunye

    2013-08-01

    A highly sensitive flexible piezoelectric material is developed by using a composite nanofibers web of polymer and metal. The nanofibers webs are made by electrospinning a mixed solution of poly(vinylidene fluoride) (PVDF) and silver nanowires (AgNWs) in the co-solvent of dimethyl formamide and acetone. SEM images show that the obtained webs are composed of AgNWs doped PVDF fibers with diameters ranging from 200nm to 500nm. Our FTIR and XRD results indicate that doping AgNWs into PVDF fiber can enhance the contents of beta phase of the PVDF. UV-Vis spectrum shows a slightly red shift at 324 nm and 341 nm after the AgNWs doping into PVDF, proving the presence of interaction between AgNWs and the PVDF polymer chain. The piezoelectric constant d33 of the nanofibers webs tested with a homemade system, reveals a good agreement with FTIR and XRD characteristic, and the highest one is up to 29.8 pC/N for the nanofibers webs containing 1.5% AgNWs, which is close to that of poly(vinylidene fluoride-trifluoroethylene) (P(VDF-TrFE), 77/23). This study may provide a way to develop high-performance flexible sensors.

  19. PMN-PT/PVDF Nanocomposite for High Output Nanogenerator Applications

    PubMed Central

    Li, Chuan; Luo, Wenbo; Liu, Xingzhao; Xu, Dong; He, Kai

    2016-01-01

    The 0.7Pb(Mg1/3Nb2/3)O3-0.3PbTiO3(0.7PMN-0.3PT) nanorods were obtained via hydrothermal method with high yield (over 78%). Then, new piezoelectric nanocomposites based on (1−x)Pb(Mg1/3Nb2/3)O3-xPbTiO3 (PMN-PT) nanorods were fabricated by dispersing the 0.7PMN-0.3PT nanorods into piezoelectric poly(vinylidene fluoride) (PVDF) polymer. The mechanical behaviors of the nanocomposites were investigated. The voltage and current generation of PMN-PT/PVDF nanocomposites were also measured. The results showed that the tensile strength, yield strength, and Young’s modulus of nanocomposites were enhanced as compared to that of the pure PVDF. The largest Young’s modulus of 1.71 GPa was found in the samples with 20 wt % nanorod content. The maximum output voltage of 10.3 V and output current of 46 nA were obtained in the samples with 20 wt % nanorod content, which was able to provide a 13-fold larger output voltage and a 4.5-fold larger output current than that of pure PVDF piezoelectric polymer. The current density of PMN-PT/PVDF nanocomposites is 20 nA/cm2. The PMN-PT/PVDF nanocomposites exhibited great potential for flexible self-powered sensing applications. PMID:28335195

  20. Enhanced PVDF film for multi energy harvesting

    NASA Astrophysics Data System (ADS)

    Karunarathna, Ranmunige Nadeeka

    PVDF is a very important piezoelectric polymer material which has a promising range of applications in a variety of fields such as acoustic sensors and transducers, electrical switches, medical instrumentation, artificial sensitive skin in robotics, automotive detection on roads, nondestructive testing, structural health monitoring and as a biocampatible material. In this research cantilever based multi energy harvester was developed to maximize the power output of PVDF sensor. Nano mixture containing ferrofluid (FF) and ZnO nano particles were used to enhance the piezoelectric output of the sensor. The samples were tested under different energy conditions to observe the behavior of nano coated PVDF film under multi energy conditions. Composition of the ZnO and FF nano particles were changed by weight, in order to achieve the optimal composition of the nano mixture. Light energy, vibration energy, combined effect of light and vibration energy, and magnetic effect were used to explore the behavior of the sensor. The sensor with 60% ZnO and 40% FF achieved a maximum power output of 10.7 microwatts when it is under the combined effect of light and vibration energy. Which is nearly 16 times more power output than PVDF sensor. When the magnetic effect is considered the sensor with 100% FF showed the highest power output of 11.2 microwatts which is nearly 17 times more power output than pure PVDF. The effective piezoelctric volume of the sensor was 0.017 cm3. In order to explore the effect of magnetic flux, cone patterns were created on the sensor by means of a external magnetic field. Stability of the cones generated on the sensor played a major role in generated power output.

  1. A facile TiO2/PVDF composite membrane synthesis and their application in water purification

    NASA Astrophysics Data System (ADS)

    Zhang, Wei; Zhang, Yiming; Fan, Rong; Lewis, Rosmala

    2016-01-01

    In this work, we have demonstrated a facile wet chemical method to synthesise TiO2/PVDF composite membranes as alternative water purification method to traditional polymer-based membrane. For the first time, hydrothermally grown TiO2 nanofibers under alkali conditions were successfully inserted into PVDF membranes matrix. The structure, permeability and anti-fouling performance of as-prepared PVDF/TiO2 composite membranes were studied systematically. The TiO2/PVDF composite membranes prepared in this work promise great potential uses in water purification applications as microfiltration membranes due to its excellent physical/chemical resistance, anti-fouling and mechanical properties.

  2. Curved PVDF airborne transducer.

    PubMed

    Wang, H; Toda, M

    1999-01-01

    In the application of airborne ultrasonic ranging measurement, a partially cylindrical (curved) PVDF transducer can effectively couple ultrasound into the air and generate strong sound pressure. Because of its geometrical features, the ultrasound beam angles of a curved PVDF transducer can be unsymmetrical (i.e., broad horizontally and narrow vertically). This feature is desired in some applications. In this work, a curved PVDF air transducer is investigated both theoretically and experimentally. Two resonances were observed in this transducer. They are length extensional mode and flexural bending mode. Surface vibration profiles of these two modes were measured by a laser vibrometer. It was found from the experiment that the surface vibration was not uniform along the curvature direction for both vibration modes. Theoretical calculations based on a model developed in this work confirmed the experimental results. Two displacement peaks were found in the piezoelectric active direction of PVDF film for the length extensional mode; three peaks were found for the flexural bending mode. The observed peak positions were in good agreement with the calculation results. Transient surface displacement measurements revealed that vibration peaks were in phase for the length extensional mode and out of phase for the flexural bending mode. Therefore, the length extensional mode can generate a stronger ultrasound wave than the flexural bending mode. The resonance frequencies and vibration amplitudes of the two modes strongly depend on the structure parameters as well as the material properties. For the transducer design, the theoretical model developed in this work can be used to optimize the ultrasound performance.

  3. Surface energy characteristics of zeolite embedded PVDF nanofiber films with electrospinning process

    NASA Astrophysics Data System (ADS)

    Kang, Dong Hee; Kang, Hyun Wook

    2016-11-01

    Electrospinning is a nano-scale fiber production method with various polymer materials. This technique allows simple fiber diameters control by changing the physical conditions such as applied voltage and polymer solution viscosity during the fabrication process. The electrospun polymer fibers form a thin porous film with high surface area to volume ratio. Due to these unique characteristics, it is widely used for many application fields such as photocatalyst, electric sensor, and antibacterial scaffold for tissue engineering. Filtration is one of the main applications of electrospun polymer fibers for specific application of filtering out dust particles and dehumidification. Most polymers which are commonly used in electrospinning are hard to perform the filtering and dehumidification simultaneously because of their low hygroscopic property. To overcome this obstacle, the desiccant polymers are developed such as polyacrylic acid and polysulfobetaine methacrylate. However, the desiccant polymers are generally expensive and need special solvent for electrospinning. An alternating way to solve these problems is mixing desiccant material like zeolite in polymer solution during an electrospinning process. In this study, the free surface energy characteristics of electrospun polyvinylidene fluoride (PVDF) film with various zeolite concentrations are investigated to control the hygroscopic property of general polymers. Fundamental physical property of wettability with PVDF shows hydrophobicity. The electrospun PVDF film with small weight ratio with higher than 0.1% of zeolite powder shows diminished contact angles that certifying the wettability of PVDF can be controlled using desiccant material in electrospinning process. To quantify the surface energy of electrospun PVDF films, sessile water droplets are introduced on the electrospun PVDF film surface and the contact angles are measured. The contact angles of PVDF film are 140° for without zeolite and 80° for with 5

  4. Aligned PVDF-TrFE nanofibers with high-density PVDF nanofibers and PVDF core–shell structures for endovascular pressure sensing.

    PubMed

    Sharma, Tushar; Naik, Sahil; Langevine, Jewel; Gill, Brijesh; Zhang, John X J

    2015-01-01

    Nanostructures of polyvinyledenedifluoride-tetrafluoroethylene (PVDF-TrFE), a semicrystalline polymer with high piezoelectricity, results in significant enhancement of crystallinity and better device performance as sensors, actuators, and energy harvesters. Using electrospinning of PVDF to manufacture nanofibers, we demonstrate a new method to pattern high-density, highly aligned nanofibers. To further boost the charge transfer from such a bundle of nanofibers, we fabricated novel core-shell structures. Finally, we developed pressure sensors utilizing these fiber structures for endovascular applications. The sensors were tested in vitro under simulated physiological conditions. We observed significant improvements using core-shell electrospun fibers (4.5 times gain in signal intensity, 4000 μV/mmHg sensitivity) over PVDF nanofibers (280 μV/mmHg). The preliminary results showed that core-shell fiber-based devices exhibit nearly 40-fold higher sensitivity, compared to the thin-film structures demonstrated earlier.

  5. Infrared spectroscopy study of irradiated PVDF

    SciTech Connect

    Chappa, Veronica; Grosso, Mariela del; Garcia Bermudez, Gerardo; Behar, Moni

    2007-10-26

    The effects induced by 1 MeV/amu ion irradiations were compared to those induced by 4-12 MeV/amu irradiations. Structural analysis with infrared spectroscopy (FTIR) was carried out on PVDF irradiated using C and He beams with different fluences. From these spectra it was observed, as a function of fluence, an overall destruction of the polymer, amorphization of the crystalline regions and the creation of in-chain unsaturations. The track dimensions were determined using a previously developed Monte Carlo simulation code and these results were compared to a semiempirical model.

  6. Exploring Electro-active Functionality of Transparent Oxide Materials

    NASA Astrophysics Data System (ADS)

    Hosono, Hideo

    2013-09-01

    Ceramics, one of the earliest materials used by humans, have been used since the Stone Age and are also one of the core materials supporting modern society. In this article, I will review the features of transparent oxides, the main components of ceramics, and the progress of research on their electro-active functionalities from the viewpoint of material design. Specifically, the emergence of the functionality of the cement component 12CaO.7Al2O3, the application of transparent oxide semiconductors to thin-film transistors for flat panel displays, and the design of wide-gap p-type semiconductors are introduced along with the progress in their research. In addition, oxide semiconductors are comprehensively discussed on the basis of the band lineup.

  7. Hydrostatic pressure studies of polyvinylidine fluoride (PVDF) and its copolymers

    SciTech Connect

    Samara, G.A.; Bauer, F.

    1987-01-01

    The frequency, temperature and hydrostatic pressure (less than or equal to10 kbar) dependences of the dielectric properties, molecular relaxations and phase transitions in PVDF and a copolymer with a 30% trifluorethylene were investigated. For the copolymer, both the ferroelectric transition (T/sub c/) and dynamic melting (T/sub m/) temperatures exhibit large increases with pressure. PVDF itself does not exhibit a T/sub c/ below T/sub m/, but its T/sub m/ also shows a large increase with pressure. The pressure and frequency dependences suggest an explanation for why it is possible to use these polymers as piezoelectric shock wave gauges to relatively high shock pressures.

  8. High β phase content in PVDF/CoFe2O4 nanocomposites induced by DC magnetic fields

    NASA Astrophysics Data System (ADS)

    Jiang, Shenglin; Wan, Hongyan; Liu, Huan; Zeng, Yike; Liu, Jianguo; Wu, Yunyi; Zhang, Guangzu

    2016-09-01

    Flexible ferroelectrics being exploited as energy harvesting and conversion materials are highly desirable for wearable and skin-mountable electronic devices. As one of the most typical ferroelectric polymers, poly(vinylidene fluoride) (PVDF) has been widely used in modern electronic systems and devices, whose ferroelectric performance relies heavily on its β phase content. In this work, to achieve high-β-phase-content PVDF, we first introduced CoFe2O4 nanoparticles into PVDF. With the incorporation of CoFe2O4 nanoparticles used as an effective polymer nucleation agent, the percentage of the β phase in the PVDF has been significantly enhanced, e.g., 84% in the nanocomposite with 5 wt. % CoFe2O4 versus only 73% in the pure PVDF. In order to further increase the β phase content in PVDF, we subsequently proposed an easily realized strategy. By applying DC magnetic fields during the solution-casting process of the PVDF/CoFe2O4 nanocomposites, a further improved β phase content as high as 95% can be achieved. The further improvement of the β phase content is attributable to the tensile stress at the CoFe2O4/PVDF interfaces created by the coupling of magnetic field and CoFe2O4 by means of the magnetostriction effect. The high β-phase content makes the PVDF/CoFe2O4 nanocomposites a promising candidate for flexible and wearable electronic device applications.

  9. Study on the thermoelectric properties of PVDF/MWCNT and PVDF/GNP composite foam

    NASA Astrophysics Data System (ADS)

    Sun, Yu-Chen; Terakita, Daryl; Tseng, Alex C.; Naguib, Hani E.

    2015-08-01

    Thermoelectric effect is defined as the revisable translation between thermal and electrical energy. In this paper, we investigate the properties of p-type poly(vinylidene fluoride) (PVDF) based polymer composite foams that can be used in next generation energy harvesting applications. The composites were created using the continuous melt blending method. Multi-walled carbon nanotubes (MWCNTs) and graphene nano-platelets (GNPs) were used as secondary phases to strengthen the electrical conductivity of the composites. Foam structures were later generated using the super-critical carbon dioxide saturation method. We study the material properties between solid and foam samples; the results indicate a dramatic increase in overall thermoelectric properties for GNP foamed samples. We also report at least an order decrease in thermal conductivity, which is in favor of the thermoelectric effect. An unexpected drop in electrical conductivity was observed after the foaming process and can be explained by the large volumetric expansion of the foam. Finally, we report the Seebeck coefficient for both types of composite foams: 11 μV/K for 5 wt% MWCNT/PVDF foam and 58 μV/K for 15 wt% GNP/PVDF foam.

  10. Ionic liquids adsorbed cellulose electro active paper actuator

    NASA Astrophysics Data System (ADS)

    Mahadeva, Suresha K.; Nayak, Jyoti; Kim, Jaehwan

    2009-03-01

    Cellulose has been reported as a smart material that can be used as sensors and actuators. The cellulose smart material is termed as Electro-active paper (EAPap), which is made by regenerating cellulose. However, regeneration of cellulose resulted in reduced performance output of actuators at low humidity levels. To solve this drawback, EAPap bending actuators were made by activating wet cellulose films in three different room temperature ionic liquids BMIPF6, BMICL and BMIBF4. Results showed that the actuator performance was dependent on the type of anions in the ionic liquids and it was in the order of BF4 > Cl > PF6Â. BMIBF4 activated actuator showed the maximum displacement of 3.8 mm with low electrical power consumption at relatively low humidity level. Also, it found that, although size of PF6 anion is larger than BF4 anion it showed the low displacement output due to poor adsorption as indicated the FTIR analysis.

  11. Micro transfer printing on cellulose electro-active paper

    NASA Astrophysics Data System (ADS)

    Kim, Jaehwan; Bae, Seung-Hun; Lim, Hyun-Gyu

    2006-06-01

    A micro-patterning technique regarded as micro transfer printing is studied for gold electrode patterning on cellulose electro-active paper (EAPap), aiming at biodegradable and flexible MEMS fabrication. EAPap is known as a smart material due to the interesting actuation phenomenon of cellulose paper. Accordingly, EAPap can be used for sensor and actuator devices. Since EAPap is made with cellulose, a biodegradable and flexible MEMS device can be made with this material. However, since cellulose-based EAPap is hydrophilic and flexible, conventional lithography and etching techniques cannot be used for micro-patterning. This paper reports a new micro-patterning technique using the micro transfer printing (MTP) method on flexible EAPap material. The MTP technique consists of a master fabrication, a polydimethylsiloxane (PDMS) stamp construction, and a micro pattern transfer. Details of the technique and key issues are addressed. To demonstrate the feasibility of the MTP technique, a gold electrode pattern for a surface acoustic wave (SAW) MEMS device and a gold micro-strip pattern for a microwave dipole rectenna are made on cellulose paper substrates.

  12. An ionic electro-active actuator made with graphene film electrode, chitosan and ionic liquid

    NASA Astrophysics Data System (ADS)

    He, Qingsong; Yu, Min; Yang, Xu; Kim, Kwang Jin; Dai, Zhendong

    2015-06-01

    A newly developed ionic electro-active actuator composed of an ionic electrolyte layer sandwiched between two graphene film layers was investigated. Scanning electronic microscopy observation and x-ray diffraction analysis showed that the graphene sheets in the film stacked in a nearly face-to-face fashion but did not restack back to graphite, and the resulting graphene film with low sheet resistance (10 Ω sq-1) adheres well to the electrolyte membrane. Contact angle measurement showed the surface energy (37.98 mJ m-2) of the ionic electrolyte polymer is 2.67 times higher than that (14.2 mJ m-2) of the Nafion membrane, contributing to the good adhesion between the graphene film electrode and the electrolyte membrane. An electric double-layer is formed at the interface between the graphene film electrode and the ionic electrolyte membrane under the input potential, resulting in a higher capacitance of 27.6 mF cm-2. We report that this ionic actuator exhibits adequate bending strain, ranging from 0.032 to 0.1% (305 to 945 μm) as functions of voltage.

  13. Electrical Properties of PVDF Based Nanocomposites

    NASA Astrophysics Data System (ADS)

    Contreras, Jerry; Foltz, Heinrich D.; Duan, Yuping; Hhuq, Hasina F.; Tidrow, Steven C.; Chipara, Mircea

    2015-03-01

    Nanocomposites based on polyvinylidene fluoride (PVDF) have been obtained by melt mixing, loading the polymeric matrix with various weight fraction (between 0 % to 40 %) of different fillers (multiwalled carbon nanotubes, carbon nanofibers, and barium titanate). Pellets of nanocomposites have been obtained by hot pressing at about 175 oC. Copper contacts have been deposited on the as obtained pellets and the electrical features have been measured by using the two point technique. PVDF is a semicrystalline ferroelectric and piezoelectric polymer with a glass transition temperature of -35 oC and a melting temperature of about 175 oC. Electrical measurements have been performed in a wide range of frequencies starting from dc to ac (up to about 250 MHz). The dependence of the resistivity and dielectric constant on frequency and temperature (between -50 oC to 150 oC) was investigated in detail. Supplementary DSC, WAXS, and Raman data provided detailed information regarding the effect of fillers on phase transitions (glass, crystallization, and melting) and crystalline composition/structure of these nanocomposites.

  14. Development of a high sensitive MEMS hydrophone using PVDF

    NASA Astrophysics Data System (ADS)

    Varadan, Vijay K.; Zhu, Bei; K. A, Jose

    2002-05-01

    The design and experimental evaluation of a PVDF-based MEMS hydrophone is presented in this paper. The basic structure of the hydrophone was fabricated on a silicon wafer using standard NMOS process technology. A MOSFET with extended gate electrode was designed as the interface circuit to the sensing material, which is a piezoelectric polymer, polyvinylidene difluoride (PVDF). Acoustic impedance possessed by this piezoelectric material provides a reasonable match to water, which makes it very attractive for underwater applications. The electrical signal generated by the PVDF film was directly coupled to the gate of the MOSFET. To minimize the parasitic capacitance underneath the PVDF film and hence improve the device sensitivity, a thick photoresist was first employed as the dielectric layer under the extended gate electrode. For underwater operation, a waterproof Rho-C rubber encapsulated the hydrophone. A silicon nitride layer passivated the active device, which is a good barrier material to most mobile ions and solvents. The device after passivation also shows a lower noise level. The theoretical model developed to predict the sensitivity of the hydrophone shows a reasonable agreement between the theory and the experiment.

  15. Preparation of hydrophobic PVDF hollow fiber membranes for desalination through membrane distillation.

    PubMed

    Hou, Deyin; Wang, Jun; Qu, Dan; Luan, Zhaokun; Zhao, Changwei; Ren, Xiaojing

    2009-01-01

    Fabrication of polyvinylidene fluoride (PVDF) hydrophobic asymmetric hollow fiber membranes was studied by introducing inorganic salt LiCl and water soluble polymer polyethylene glycol (PEG) 1500, using N,N-dimethylacetamide (DMAc) as solvent and tap water as the coagulation medium. The membranes properties also were tested and characterized. It is found that the non-solvent additive can increase membranes porosity, ether LiCl or PEG 1500. Because of the addition of PEG 1500, the PVDF membranes obtained a rough topography on the membrane surface and the contact angle of the PVDF membranes increased to 113.50 degrees compared to 89.82 degrees of the PVDF membranes spun without an additive. During direct contact membrane distillation (DCMD) of 0.6 M sodium chloride solution, the PVDF membranes spun with PEG 1500 as a non-solvent additive achieved higher water permeation flux compared to the membranes spun from PVDF/DMAc and PVDF/DMAC/LiCl dopes, but the latter two membranes exhibited higher salt rejection rate.

  16. Nanomanufacturing and analysis of novel continuous ferroelectric PVDF and P(VDF-TrFE) nanofibers

    NASA Astrophysics Data System (ADS)

    Ren, Xi

    Poly(vinylidene fluoride) (PVDF) and PVDF copolymers are well known for their ferroelectric and piezoelectric properties. Currently, they are mainly used in applications in the form of films. Thin PVDF films have been shown to possess unique ferroelectric properties in the nanoscale range. However, their two-dimensional nature limits their applicability in active engineering materials and structures. One-dimensional PVDF nanofibers can be expected to combine ferroelectric behavior with enhanced mechanical properties and ultrahigh flexibility providing critical advantages for applications. In this work, novel continuous PVDF nanofibers were nanomanufactured and systematically studied for the first time. Nanofibers from PVDF and P(VDF-TrFE) copolymer with several molecular weights and co-polymer compositions were manufactured by electrospinning. The method consists of spinning polymer solutions in high electric fields. Effects of process parameters on nanofiber diameters and morphology were studied. Resulting nanofibers were characterized by FE-SEM, TEM, XRD, FTIR, DSC and TGA. Effects of annealing on copolymer nanofibers were analyzed. Nanofiber-reinforced composites were manufactured and their polarization behavior studied using a specially designed experimental device. A number of pioneering observations and discoveries were made as a result of this analysis. For example, analysis of crystalline structure of PVDF nanofibers showed that the initial a phase of the PVDF raw material was converted to beta phase during electrospinning. This result is very encouraging as the beta phase is primarily responsible for the piezo- and ferroelectric behavior of PVDF polymers. It was also shown for the first time that nanofabricated P(VDF-TrFE) nanofibers exhibited distinct Curie points and different structures than their raw materials. Annealing was shown to be an effective way to modify properties of P(VDF-TrFE) co-polymer nanofibers. Overall, the results demonstrated for the

  17. Fabrication of protein-resistant blend based on PVDF-HFP and amphiphilic brush copolymer made from PMMA and PEGMA

    NASA Astrophysics Data System (ADS)

    Hwangbo, Kyung-Hee; Kim, Yu-Jeong; Cho, Kuk Young

    2012-12-01

    Polymeric blends provide a facile route to obtaining materials with various synergistic properties arising from the individual components. Poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP), a hydrophobic polymer, is finding new applications in polymer electrolytes, membranes, and heat-resistant structural materials owing to its high thermal stability, mechanical strength, and weatherability. In this report, blends of PVDF-HFP and polymer brush were prepared with enhanced water uptake and protein resistance, which are important requirements for membranes used in food and biological applications. Polymer brush is composed of poly(methyl methacrylate) main chains, which are miscible with PVDF-HFP, and hydrophilic poly(ethylene glycol) (PEG) brush chains. Incorporation of PEG chains through the polymer brush structure not only enhanced water uptake and protein adsorption resistance but also produced a well-distributed morphology of the blending components through the matrix as evidenced by observation of the morphology after selective extraction of polymer brush from the matrix.

  18. Structural phase study in un-patterned and patterned PVDF semi-crystalline films

    SciTech Connect

    Pramod, K. Gangineni, Ramesh Babu

    2014-04-24

    This work explores the structural phase studies of organic polymer- polyvinylidene fluoride (PVDF) thin films in semi-crystallized phase and nano-patterned PVDF thin films. The nanopatterns are transferred with the CD layer as a master using soft lithography technique. The semi-crystalline PVDF films were prepared by a still and hot (SH) method, using a homemade spin coater that has the proficiency of substrate heating by a halogen lamp. Using this set up, smooth PVDF thin films in semi-crystalline α-phase were prepared using 2-Butanone as solvent. XRD, AFM and confocal Raman microscope have been utilized to study the structural phase, crystallinity and quality of the films.

  19. Proton exchange membranes based on PVDF/SEBS blends

    NASA Astrophysics Data System (ADS)

    Mokrini, A.; Huneault, M. A.

    Proton-conductive polymer membranes are used as an electrolyte in the so-called proton exchange membrane fuel cells. Current commercially available membranes are perfluorosulfonic acid polymers, a class of high-cost ionomers. This paper examines the potential of polymer blends, namely those of styrene-(ethylene-butylene)-styrene block copolymer (SEBS) and polyvinylidene fluoride (PVDF), in the proton exchange membrane application. SEBS/PVDF blends were prepared by twin-screw extrusion and the membranes were formed by calendering. SEBS is a phase-segregated material where the polystyrene blocks can be selectively functionalized offering high ionic conductivity, while PVDF insures good dimensional stability and chemical resistance to the films. Proton conductivity of the films was obtained by solid-state grafting of sulfonic acid moieties. The obtained membranes were characterized in terms of conductivity, ionic exchange capacity and water uptake. In addition, the membranes were characterized in terms of morphology, microstructure and thermo-mechanical properties to establish the blends morphology-property relationships. Modification of interfacial properties between SEBS and PVDF was found to be a key to optimize the blends performance. Addition of a methyl methacrylate-butyl acrylate-methyl methacrylate block copolymer (MMA-BA-MMA) was found to compatibilize the blend by reducing the segregation scale and improving the blend homogeneity. Mechanical resistance of the membranes was also improved through the addition of this compatibilizer. As little as 2 wt.% compatibilizer was sufficient for complete interfacial coverage and lead to improved mechanical properties. Compatibilized blend membranes also showed higher conductivities, 1.9 × 10 -2 to 5.5 × 10 -3 S cm -1, and improved water management.

  20. Evaluation of reduced graphene oxide/ZnO effect on properties of PVDF nanocomposite films

    NASA Astrophysics Data System (ADS)

    Jaleh, B.; Jabbari, A.

    2014-11-01

    In this work, we report the preparation and characterization of PVDF/reduced graphene oxide (RGO)-ZnO nanocomposite films via synthesis of reduced graphene oxide-ZnO nanocomposite by solution casting method. Different weight ratios of RGO-ZnO nanocomposites were produced and compounded with PVDF by solution mixing. The compounding was followed by solution casting and drying to form nanocomposite films. Fourier transform infrared (FTIR) spectroscopy and X-ray diffraction techniques (XRD), revealed an obvious α to β-phase transformation compared to pure PVDF which a maximum content of 83% for β-phase was calculated by using FTIR techniques. The morphology of the nanocomposites was investigated using scanning electron microscope (SEM). SEM micrographs showed a decrease in size of spherulitic crystal structure of PVDF/RGO-ZnO nanocomposites compared with pure PVDF which has an obvious relation with β-phase enhancement. The thermal behaviors of PVDF/RGO-ZnO nanocomposite films have been investigated by employing thermogravimetric analysis (TGA). Since the interface between PVDF and the nanoparticles has an important role in the nucleation of the polymer phase, thermogravimetric analysis was used in order to identify and quantify the interface region and to correlate it with the β-phase content. It is found that an intimate relation exists between the size of the interface region and the piezoelectric β-phase formation that depends on the RGO-ZnO content. The interface value and the β-phase content increase with increasing RGO-ZnO. The PVDF nanocomposites showed higher thermal stability than the pure polymer.

  1. Nanocomposites for Improved Physical Durability of Porous PVDF Membranes

    PubMed Central

    Lai, Chi Yan; Groth, Andrew; Gray, Stephen; Duke, Mikel

    2014-01-01

    Current commercial polymer membranes have shown high performance and durability in water treatment, converting poor quality waters to higher quality suitable for drinking, agriculture and recycling. However, to extend the treatment into more challenging water sources containing abrasive particles, micro and ultrafiltration membranes with enhanced physical durability are highly desirable. This review summarises the current limits of the existing polymeric membranes to treat harsh water sources, followed by the development of nanocomposite poly(vinylidene fluoride) (PVDF) membranes for improved physical durability. Various types of nanofillers including nanoparticles, carbon nanotubes (CNT) and nanoclays were evaluated for their effect on flux, fouling resistance, mechanical strength and abrasion resistance on PVDF membranes. The mechanisms of abrasive wear and how the more durable materials provide resistance was also explored. PMID:24957121

  2. Nanocomposites for Improved Physical Durability of Porous PVDF Membranes.

    PubMed

    Lai, Chi Yan; Groth, Andrew; Gray, Stephen; Duke, Mikel

    2014-02-24

    Current commercial polymer membranes have shown high performance and durability in water treatment, converting poor quality waters to higher quality suitable for drinking, agriculture and recycling. However, to extend the treatment into more challenging water sources containing abrasive particles, micro and ultrafiltration membranes with enhanced physical durability are highly desirable. This review summarises the current limits of the existing polymeric membranes to treat harsh water sources, followed by the development of nanocomposite poly(vinylidene fluoride) (PVDF) membranes for improved physical durability. Various types of nanofillers including nanoparticles, carbon nanotubes (CNT) and nanoclays were evaluated for their effect on flux, fouling resistance, mechanical strength and abrasion resistance on PVDF membranes. The mechanisms of abrasive wear and how the more durable materials provide resistance was also explored.

  3. Ionic Liquids in Electro-active Devices (ILED)

    DTIC Science & Technology

    2013-12-12

    controlled-morphology aligned carbon nanotube /Nafion nanocomposite electrodes, Advanced Functional Materials, (07 2010): . doi: J. Li, K...polymer actuators based on ultra-high volume fraction vertically aligned carbon nanotube /Nafion nanocomposites, (10 2009) S. Liu, W. Liu, Y. Liu, J. Lin...Long, T. E., The preparation of cation-functionalized multi-wall carbon nanotube /sulfonated polyurethane composites. Carbon 2013, (54), 133-142

  4. Carbon nanotube network evolution during deformation of PVDF-MWNT nanocomposites

    NASA Astrophysics Data System (ADS)

    Rizvi, Reza; Naguib, Hani E.

    2013-04-01

    The emergence of novel electronic systems and their requirements have necessitated the evolution of new material classes. The traditional electronic semiconductors and components are shifting from silicon based substrates to polymers and other organic compounds. Sensor components are no exceptions, where compliant polymeric materials offer the possibility of flexible electronics. This paper examines the fabrication and characterization of piezoresistive nanocomposites for pressure sensing applications. The matrix material employed was Polyvinylidene Fluoride (PVDF). The PVDF phase was reinforced with conductive particles, in order to form a conductive filler network throughout the nanocomposite. Multiwall carbon nanotubes (MWNT) were selected as conductive particles to form the networks. The composites were prepared by melt mixing the PVDF and conductive particles in compositions ranging from 0.25 to 10 wt% conductive particle in PVDF. The dielectric permittivity and electrical conductivity of the composites was characterized and the electrical percolation behavior of PVDF nanocomposites fitted to the statistical percolation model. Scanning electron was employed to understand the morphology of the filler networks in the PVDF nanocomposites. Quasi-static piezoresistance of the nanocomposites was characterized using a custom-built force-resistance measurement setup under compressive loading conditions.

  5. Preparation and Characterization of Hydrophilically Modified PVDF Membranes by a Novel Nonsolvent Thermally Induced Phase Separation Method.

    PubMed

    Hu, Ningen; Xiao, Tonghu; Cai, Xinhai; Ding, Lining; Fu, Yuhua; Yang, Xing

    2016-11-18

    In this study, a nonsolvent thermally-induced phase separation (NTIPS) method was first proposed to fabricate hydrophilically-modified poly(vinylidene fluoride) (PVDF) membranes to overcome the drawbacks of conventional thermally-induced phase separation (TIPS) and nonsolvent-induced phase separation (NIPS) methods. Hydrophilically-modified PVDF membranes were successfully prepared by blending in hydrophilic polymer polyvinyl alcohol (PVA) at 140 °C. A series of PVDF/PVA blend membranes was prepared at different total polymer concentrations and blend ratios. The morphological analysis via SEM indicated that the formation mechanism of these hydrophilically-modified membranes was a combined NIPS and TIPS process. As the total polymer concentration increased, the tensile strength of the membranes increased; meanwhile, the membrane pore size, porosity and water flux decreased. With the PVDF/PVA blend ratio increased from 10:0 to 8:2, the membrane pore size and water flux increased. The dynamic water contact angle of these membranes showed that the hydrophilic properties of PVDF/PVA blend membranes were prominently improved. The higher hydrophilicity of the membranes resulted in reduced membrane resistance and, hence, higher permeability. The total resistance Rt of the modified PVDF membranes decreased significantly as the hydrophilicity increased. The irreversible fouling related to pore blocking and adsorption fouling onto the membrane surface was minimal, indicating good antifouling properties.

  6. Preparation and Characterization of Hydrophilically Modified PVDF Membranes by a Novel Nonsolvent Thermally Induced Phase Separation Method

    PubMed Central

    Hu, Ningen; Xiao, Tonghu; Cai, Xinhai; Ding, Lining; Fu, Yuhua; Yang, Xing

    2016-01-01

    In this study, a nonsolvent thermally-induced phase separation (NTIPS) method was first proposed to fabricate hydrophilically-modified poly(vinylidene fluoride) (PVDF) membranes to overcome the drawbacks of conventional thermally-induced phase separation (TIPS) and nonsolvent-induced phase separation (NIPS) methods. Hydrophilically-modified PVDF membranes were successfully prepared by blending in hydrophilic polymer polyvinyl alcohol (PVA) at 140 °C. A series of PVDF/PVA blend membranes was prepared at different total polymer concentrations and blend ratios. The morphological analysis via SEM indicated that the formation mechanism of these hydrophilically-modified membranes was a combined NIPS and TIPS process. As the total polymer concentration increased, the tensile strength of the membranes increased; meanwhile, the membrane pore size, porosity and water flux decreased. With the PVDF/PVA blend ratio increased from 10:0 to 8:2, the membrane pore size and water flux increased. The dynamic water contact angle of these membranes showed that the hydrophilic properties of PVDF/PVA blend membranes were prominently improved. The higher hydrophilicity of the membranes resulted in reduced membrane resistance and, hence, higher permeability. The total resistance Rt of the modified PVDF membranes decreased significantly as the hydrophilicity increased. The irreversible fouling related to pore blocking and adsorption fouling onto the membrane surface was minimal, indicating good antifouling properties. PMID:27869711

  7. Chitin nanowhisker (ChNW)-functionalized electrospun PVDF membrane for enhanced removal of Indigo carmine.

    PubMed

    Gopi, Sreerag; Balakrishnan, Preetha; Pius, Anitha; Thomas, Sabu

    2017-06-01

    In this study, an active functional adsorbent membrane developed by combining both hydrophilic bio polymer filler such as chitin nanowhiskers (ChNW) which contains two functional groups and a hydrophobic polymer matrix such as polyvinylidene fluoride (PVDF) using electrospinning technique. Here ChNW were successfully extracted by excluding proteins and mineral and well characterized using FTIR, XRD, SEM and TEM. The optimized combination of PVDF/ChNW (15%:1%) membrane was fabricated and well characterized using SEM, water contact angle and FTIR spectroscopy. There was a remarkable difference in contact angle observed for PVDF/ChNW (22.72°) compared to neat PVDF (93.1°) membrane. Ultimately the membrane used for indigo carmine (IC) adsorption and an enhanced removal efficiency (88.9%) and adsorption capacity (72.6mgg(-1)) were observed compared to neat PVDF. In the future, the overall idea can make leads to various applications such as proteins, virus and hormones adsorption from the contaminated sources.

  8. Attenuating microwave radiation by absorption through controlled nanoparticle localization in PC/PVDF blends.

    PubMed

    Biswas, Sourav; Kar, Goutam Prasanna; Bose, Suryasarathi

    2015-11-07

    Nanoscale ordering in a polymer blend structure is indispensable to obtain materials with tailored properties. It was established here that controlling the arrangement of nanoparticles, with different characteristics, in co-continuous PC/PVDF (polycarbonate/poly(vinylidene fluoride)) blends can result in outstanding microwave absorption (ca. 90%). An excellent reflection loss (RL) of ca. -71 dB was obtained for a model blend structure wherein the conducting (multiwall carbon nanotubes, MWNTs) and the magnetic inclusions (Fe3O4) are localized in PVDF and the dielectric inclusion (barium titanate, BT) is in PC. The MWNTs were modified using polyaniline, which facilitates better charge transport in the blends. Furthermore, by introducing surface active groups on BT nanoparticles and changing the macroscopic processing conditions, the localization of BT nanoparticles can be tailored, otherwise BT nanoparticles would localize in the preferred phase (PVDF). In this study, we have shown that by ordered arrangement of nanoparticles, the incoming EM radiation can be attenuated. For instance, when PANI-MWNTs were localized in PVDF, the shielding was mainly through reflection. Now by localizing the conducting inclusion and the magnetic lossy materials in PVDF and the dielectric materials in PC, an outstanding shielding effectiveness of ca. -37 dB was achieved where shielding was mainly through absorption (ca. 90%). Thus, this study clearly demonstrates that lightweight microwave absorbers can be designed using polymer blends as a tool.

  9. Resistance switching in polyvinylidene fluoride (PVDF) thin films

    SciTech Connect

    Pramod, K.; Sahu, Binaya Kumar; Gangineni, R. B.

    2015-06-24

    Polyvinylidene fluoride (PDVF), one of the best electrically active polymer material & an interesting candidate to address the electrical control of its functional properties like ferroelectricity, piezoelectricity, pyroelectricity etc. In the current work, with the help of spin coater and DC magnetron sputtering techniques, semi-crystallized PVDF thin films prominent in alpha phase is prepared in capacitor like structure and their electrical characterization is emphasized. In current-voltage (I-V) and resistance-voltage (R-V) measurements, clear nonlinearity and resistance switching has been observed for films prepared using 7 wt% 2-butanone and 7 wt% Dimethyl Sulfoxide (DMSO) solvents.

  10. PVDFSTRESS: A PC-based computer program to reduce Bauer PVDF stress-rate gauge data

    SciTech Connect

    Wackerbarth, D E; Anderson, M U; Graham, R A

    1992-02-01

    A computer program has been developed to reduce and analyze data from a standardized piezoelectric polymer (PVDF) shock-wave stress rate gauge. The program is menu driven with versatile graphic capabilities, input/output file options, hard copy options, and unique data processing capabilities. This program was designed to analyze digital current-mode'' data recorded from a Bauer PVDF stress-rate gauge and reduce it to a stress-versus-time record. The program was also designed to combine two simulanteously recorded data channels.

  11. Pure β-phase formation in polyvinylidene fluoride (PVDF)-carbon nanotube composites

    NASA Astrophysics Data System (ADS)

    Kabir, Ekramul; Khatun, M.; Nasrin, L.; Raihan, Mustafa J.; Rahman, M.

    2017-04-01

    Polyvinylidene fluoride (PVDF) and its copolymers with a particular semi-crystalline conformation (β) have evolved as lead (Pb)-free alternatives to electroactive perovskite piezo-, pyro-, and ferroelectric materials. In particular, semi-crystalline ferroelectric polymers are suitable for a large variety of flexible devices and have attracted tremendous research interest. Realizing the application potential of this polar form, there have been numerous attempts to enhance and stabilize this β crystalline phase. A completely pure (100%) β crystalline phase has been achieved in a nanocomposite of PVDF with carbon nanotubes (CNTs) with proper functionalization. With an emphasis on pure ferroelectric β-phase formation and related issues, this paper presents a timely review of the literature on recent sequential development and understanding of PVDF-CNT composites.

  12. Poly(vinylimidazole) radiografted PVDF nanospheres as alternative binder for high temperature PEMFC electrodes

    NASA Astrophysics Data System (ADS)

    Galbiati, Samuele; Coulon, Pierre-Eugène; Rizza, Giancarlo; Clochard, Marie-Claude; Castellino, Micaela; Sangermano, Marco; Nayoze, Christine; Morin, Arnaud

    2015-11-01

    Within the framework of high-temperature polymer fuel cells doped with phosphoric acid, we investigate the replacement of the conventional binder in the catalyst layers by functionalized solid PVDF nanospheres. Aim of this study is to develop and test an innovative binder which might create enhanced electrode porosity and acid distribution. Aqueous suspensions of PVDF nanospheres (d ∼ 200 nm) are obtained by radical emulsion polymerization and are functionalized by Vinyl-Imidazole (VI) groups via in situ γ-radiation. As a consequence the nanospheres can interact with H3PO4 to obtain proton conductivity. Catalyst inks are prepared mixing the nanospheres with commercial Pt/C electrocatalyst powder, solvents and phosphoric acid. Prototype electrodes are deposited by spraying and preliminary fuel cell tests are carried out at 160 °C under dry H2/air. Electrodes with grafted PVDF nanospheres as solid binder are demonstrated and its understanding is in progress. Further improvements are outlined.

  13. Molecular dynamics simulations and morphology analysis of TEM imaged PVDF nanofibers

    NASA Astrophysics Data System (ADS)

    Miao, Jiayuan; Reneker, Darrell; Tsige, Mesfin; Taylor, Philip

    With the goal of elucidating the structure of polyvinylidene fluoride (PVDF) nanofibers, all-atom molecular dynamics simulations were performed, and the results compared with structures observed in high resolution transmission electron microscopy (TEM) at the molecular level. Simulation shows that the stability of the β-phase component in a PVDF nanofiber is influenced by its thickness and processing history. When exposed to irradiation, as in a TEM observation, the structure is then further modified by the effects of chain scission. The transformation from the β phase into a paraelectric phase can explain the spindle formation and serpentine motion of molecular segments observed by Zhong et al. (Polymer, 54, 2013, 3745-3756) in irradiated PVDF nanofibers. From a comparison between simulated and experimental TEM images it was possible to identify numerous features that are useful in unveiling the inherent structure of PVDF nanofibers. The experimental TEM images appear to match well with those predicted by a model based on α-phase PVDF, while also being consistent with an alternative model (Nanoscale 2015, DOI: 10.1039/c5nr01619c). Work supported by the Petroleum Research Fund of the ACS.

  14. Graphene Oxide Quantum Dots Covalently Functionalized PVDF Membrane with Significantly-Enhanced Bactericidal and Antibiofouling Performances

    PubMed Central

    Zeng, Zhiping; Yu, Dingshan; He, Ziming; Liu, Jing; Xiao, Fang-Xing; Zhang, Yan; Wang, Rong; Bhattacharyya, Dibakar; Tan, Timothy Thatt Yang

    2016-01-01

    Covalent bonding of graphene oxide quantum dots (GOQDs) onto amino modified polyvinylidene fluoride (PVDF) membrane has generated a new type of nano-carbon functionalized membrane with significantly enhanced antibacterial and antibiofouling properties. A continuous filtration test using E. coli containing feedwater shows that the relative flux drop over GOQDs modified PVDF is 23%, which is significantly lower than those over pristine PVDF (86%) and GO-sheet modified PVDF (62%) after 10 h of filtration. The presence of GOQD coating layer effectively inactivates E. coli and S. aureus cells, and prevents the biofilm formation on the membrane surface, producing excellent antimicrobial activity and potentially antibiofouling capability, more superior than those of previously reported two-dimensional GO sheets and one-dimensional CNTs modified membranes. The distinctive antimicrobial and antibiofouling performances could be attributed to the unique structure and uniform dispersion of GOQDs, enabling the exposure of a larger fraction of active edges and facilitating the formation of oxidation stress. Furthermore, GOQDs modified membrane possesses satisfying long-term stability and durability due to the strong covalent interaction between PVDF and GOQDs. This study opens up a new synthetic avenue in the fabrication of efficient surface-functionalized polymer membranes for potential waste water treatment and biomolecules separation. PMID:26832603

  15. Graphene Oxide Quantum Dots Covalently Functionalized PVDF Membrane with Significantly-Enhanced Bactericidal and Antibiofouling Performances

    NASA Astrophysics Data System (ADS)

    Zeng, Zhiping; Yu, Dingshan; He, Ziming; Liu, Jing; Xiao, Fang-Xing; Zhang, Yan; Wang, Rong; Bhattacharyya, Dibakar; Tan, Timothy Thatt Yang

    2016-02-01

    Covalent bonding of graphene oxide quantum dots (GOQDs) onto amino modified polyvinylidene fluoride (PVDF) membrane has generated a new type of nano-carbon functionalized membrane with significantly enhanced antibacterial and antibiofouling properties. A continuous filtration test using E. coli containing feedwater shows that the relative flux drop over GOQDs modified PVDF is 23%, which is significantly lower than those over pristine PVDF (86%) and GO-sheet modified PVDF (62%) after 10 h of filtration. The presence of GOQD coating layer effectively inactivates E. coli and S. aureus cells, and prevents the biofilm formation on the membrane surface, producing excellent antimicrobial activity and potentially antibiofouling capability, more superior than those of previously reported two-dimensional GO sheets and one-dimensional CNTs modified membranes. The distinctive antimicrobial and antibiofouling performances could be attributed to the unique structure and uniform dispersion of GOQDs, enabling the exposure of a larger fraction of active edges and facilitating the formation of oxidation stress. Furthermore, GOQDs modified membrane possesses satisfying long-term stability and durability due to the strong covalent interaction between PVDF and GOQDs. This study opens up a new synthetic avenue in the fabrication of efficient surface-functionalized polymer membranes for potential waste water treatment and biomolecules separation.

  16. Graphene Oxide Quantum Dots Covalently Functionalized PVDF Membrane with Significantly-Enhanced Bactericidal and Antibiofouling Performances.

    PubMed

    Zeng, Zhiping; Yu, Dingshan; He, Ziming; Liu, Jing; Xiao, Fang-Xing; Zhang, Yan; Wang, Rong; Bhattacharyya, Dibakar; Tan, Timothy Thatt Yang

    2016-02-02

    Covalent bonding of graphene oxide quantum dots (GOQDs) onto amino modified polyvinylidene fluoride (PVDF) membrane has generated a new type of nano-carbon functionalized membrane with significantly enhanced antibacterial and antibiofouling properties. A continuous filtration test using E. coli containing feedwater shows that the relative flux drop over GOQDs modified PVDF is 23%, which is significantly lower than those over pristine PVDF (86%) and GO-sheet modified PVDF (62%) after 10 h of filtration. The presence of GOQD coating layer effectively inactivates E. coli and S. aureus cells, and prevents the biofilm formation on the membrane surface, producing excellent antimicrobial activity and potentially antibiofouling capability, more superior than those of previously reported two-dimensional GO sheets and one-dimensional CNTs modified membranes. The distinctive antimicrobial and antibiofouling performances could be attributed to the unique structure and uniform dispersion of GOQDs, enabling the exposure of a larger fraction of active edges and facilitating the formation of oxidation stress. Furthermore, GOQDs modified membrane possesses satisfying long-term stability and durability due to the strong covalent interaction between PVDF and GOQDs. This study opens up a new synthetic avenue in the fabrication of efficient surface-functionalized polymer membranes for potential waste water treatment and biomolecules separation.

  17. Synergistic effect of self-assembled carboxylic acid-functionalized carbon nanotubes and carbon fiber for improved electro-activated polymeric shape-memory nanocomposite

    NASA Astrophysics Data System (ADS)

    Lu, Haibao; Min Huang, Wei

    2013-06-01

    The present work studies the synergistic effect of self-assembled carboxylic acid-functionalized carbon nanotube (CNT) and carbon fiber on the electrical property and electro-activated recovery behavior of shape memory polymer (SMP) nanocomposites. The combination of CNT and carbon fiber results in improved electrical conductivity in the SMP nanocomposites. Carboxylic acid-functionalized CNTs are grafted onto the carbon fibers and then self-assembled by deposition to significantly enhance the reliability of the bonding between carbon fiber and SMP via van der Waals and covalent crosslink. Furthermore, the self-assembled carboxylic acid-functionalized CNTs and carbon fibers enable the SMP nanocomposites for Joule heating triggered shape recovery.

  18. Numerical Simulation of Output Response of PVDF Sensor Attached on a Cantilever Beam Subjected to Impact Loading.

    PubMed

    Dung, Cao Vu; Sasaki, Eiichi

    2016-04-27

    Polyvinylidene Flouride (PVDF) is a film-type polymer that has been used as sensors and actuators in various applications due to its mechanical toughness, flexibility, and low density. A PVDF sensor typically covers an area of the host structure over which mechanical stress/strain is averaged and converted to electrical energy. This study investigates the fundamental "stress-averaging" mechanism for dynamic strain sensing in the in-plane mode. A numerical simulation was conducted to simulate the "stress-averaging" mechanism of a PVDF sensor attached on a cantilever beam subjected to an impact loading, taking into account the contribution of piezoelectricity, the cantilever beam's modal properties, and electronic signal conditioning. Impact tests and FEM analysis were also carried out to verify the numerical simulation results. The results of impact tests indicate the excellent capability of the attached PVDF sensor in capturing the fundamental natural frequencies of the cantilever beam. There is a good agreement between the PVDF sensor's output voltage predicted by the numerical simulation and that obtained in the impact tests. Parametric studies were conducted to investigate the effects of sensor size and sensor position and it is shown that a larger sensor tends to generate higher output voltage than a smaller one at the same location. However, the effect of sensor location seems to be more significant for larger sensors due to the cancelling problem. Overall, PVDF sensors exhibit excellent sensing capability for in-plane dynamic strain induced by impact loading.

  19. Numerical Simulation of Output Response of PVDF Sensor Attached on a Cantilever Beam Subjected to Impact Loading

    PubMed Central

    Dung, Cao Vu; Sasaki, Eiichi

    2016-01-01

    Polyvinylidene Flouride (PVDF) is a film-type polymer that has been used as sensors and actuators in various applications due to its mechanical toughness, flexibility, and low density. A PVDF sensor typically covers an area of the host structure over which mechanical stress/strain is averaged and converted to electrical energy. This study investigates the fundamental “stress-averaging” mechanism for dynamic strain sensing in the in-plane mode. A numerical simulation was conducted to simulate the “stress-averaging” mechanism of a PVDF sensor attached on a cantilever beam subjected to an impact loading, taking into account the contribution of piezoelectricity, the cantilever beam’s modal properties, and electronic signal conditioning. Impact tests and FEM analysis were also carried out to verify the numerical simulation results. The results of impact tests indicate the excellent capability of the attached PVDF sensor in capturing the fundamental natural frequencies of the cantilever beam. There is a good agreement between the PVDF sensor’s output voltage predicted by the numerical simulation and that obtained in the impact tests. Parametric studies were conducted to investigate the effects of sensor size and sensor position and it is shown that a larger sensor tends to generate higher output voltage than a smaller one at the same location. However, the effect of sensor location seems to be more significant for larger sensors due to the cancelling problem. Overall, PVDF sensors exhibit excellent sensing capability for in-plane dynamic strain induced by impact loading. PMID:27128919

  20. Design and development of PVDF-based MEMS hydrophone and accelerometer

    NASA Astrophysics Data System (ADS)

    Zhu, Bei

    It is always desirable to fabricate low-cost, highly sensitive and miniaturized sensors for various applications. In this thesis, the design and processing of PVDF-based MEMS hydrophones and accelerometers have been investigated. The basic structure of the hydrophone was fabricated on a silicon wafer using standard NMOS process technology. A MOSFET with extended gate electrode was designed as the interface circuit to a sensing material, which is a piezoelectric polymer, polyvinylidene difluoride (PVDF). Acoustic impedance possessed by this piezoelectric material provides a reasonable match to that of water, which makes it very attractive for underwater applications. The electrical signal generated by the PVDF film was directly coupled to the gate of the MOSFET. In order to minimize the parasitic capacitance underneath the PVDF film and hence improve the device sensitivity, a thick photoresist, SU-8, was first employed as the dielectric layer under the extended gate electrode. For underwater operation, the hydrophone was encapsulated by a waterproof Rho-C rubber. However, it was found that the rubber induced the degradation of the MOSFET. To improve the reliability of the hydrophone, the active device was passivated by a silicon nitride layer, which is a good barrier material to most mobile ions and solvents. The device after passivation also shows a lower noise level. A theoretical model was developed to predict the sensitivity of the hydrophone. A reasonable agreement between the theoretical and experimental results was obtained. MEMS accelerometers based on the PVDF-MOSFET structure by attaching a seismic mass on top of the PVDF film were also fabricated. The accelerometer was calibrated using a comparison method and an average sensitivity of 0.28 mV/g was achieved. A dynamic model of the accelerometer was derived and the calculated results are in good agreement with the measured results.

  1. Ultrasonic material characterization using large-aperture PVDF receivers.

    PubMed

    Adamowski, J C; Buiochi, F; Higuti, R T

    2010-02-01

    This work describes the use of a large-aperture PVDF receiver in the measurement of liquid density and composite material elastic constants. The density measurement of several liquids is obtained with accuracy of 0.2% using a conventional NDE emitter transducer and a 70-mm-diameter, 52-microm P(VDF-TrFE) membrane with gold electrodes. The determination of the elastic constants is based on the phase velocity measurement. Diffraction can lead to errors around 1% in velocity measurement when using alternatively the conventional pair of ultrasonic transducers (1-MHz frequency and 19-mm-diameter) operating in through-transmission mode, separated by a distance of 100 mm. This effect is negligible when using a pair of 10-MHz, 19-mm-diameter transducers. Nevertheless, the dispersion at 10 MHz can result in errors of about 0.5%, when measuring the velocity in composite materials. The use of an 80-mm diameter, 52-microm-thick PVDF membrane receiver practically eliminates the diffraction effects in phase velocity measurement. The elastic constants of a carbon fiber reinforced polymer were determined and compared with the values obtained by a tensile test.

  2. Monitoring of composite structures using a network of integrated PVDF film transducers

    NASA Astrophysics Data System (ADS)

    Guzmán, Enrique; Cugnoni, Joël; Gmür, Thomas

    2015-05-01

    Aiming to reduce costs, polyvinylidene difluoride (PVDF) film patches are an emerging alternative to more classic piezoelectric technologies, like ceramic patches, as transducers to measure local deformation in many structural applications. This choice is supported by advantages such as the low weight and mechanical flexibility of PVDF, making this polymer suitable for embedding inside full scale polymer based composite structures. Piezoelectric transducer patches can be used as actuators to dynamically excite full-scale composite structures, and as sensors to measure the strain. The main objective of this paper is to verify that the PVDF transducers can provide exploitable signals in the context of structural health monitoring. In order to do so, two aspects of the design of transducer network are investigated: the optimization of the sensor network, for which the effective independence method is proposed, and the use of operational modal analysis (OMA), since it is a simple method to extract the natural frequencies of a structure from a time series. The results of the analysis are compared to a reference set issued from experimental modal analysis (EMA), a simple, well-known, classic method, which is carried out using accelerometers and an impact hammer. By statistical means, it is shown that there is no significant difference between the two methods, and an optimized PVDF transducer network combined with OMA can perform the dynamic analysis of a structure as well as a classic EMA setup would do. This leads the way to the use of low-cost PVDF embedded transducer networks for robust composite material characterization.

  3. Palpation sensor using two PVDF films

    NASA Astrophysics Data System (ADS)

    Okuyama, Takeshi; Sone, Mikiko; Tanahashi, Yoshikatsu; Tanaka, Mami

    2010-01-01

    In this work, a prototype polyvinylidene fluoride (PVDF) palpation sensor has been developed. The sensor aims to measure stiffness, which is one of the information of biomedical tissue by palpation. The sensor is composed of two PVDF films, a silicone cylindrical column, and an aluminum cylinder. And the classification of hardness is concerned with the ratio of these PVDF outputs. In this paper, the output behavior of the palpation sensor was evaluated in detail by the experimental and numerical approach, and the suitable design to diagnose by the stiffness of tissue was investigated. Using the finite element analysis, the sensor output behavior was predicted. It is confirmed that the analysis is available for investigation of the dimension and the limitation of the sensor against the measuring object.

  4. Palpation sensor using two PVDF films

    NASA Astrophysics Data System (ADS)

    Okuyama, Takeshi; Sone, Mikiko; Tanahashi, Yoshikatsu; Tanaka, Mami

    2009-12-01

    In this work, a prototype polyvinylidene fluoride (PVDF) palpation sensor has been developed. The sensor aims to measure stiffness, which is one of the information of biomedical tissue by palpation. The sensor is composed of two PVDF films, a silicone cylindrical column, and an aluminum cylinder. And the classification of hardness is concerned with the ratio of these PVDF outputs. In this paper, the output behavior of the palpation sensor was evaluated in detail by the experimental and numerical approach, and the suitable design to diagnose by the stiffness of tissue was investigated. Using the finite element analysis, the sensor output behavior was predicted. It is confirmed that the analysis is available for investigation of the dimension and the limitation of the sensor against the measuring object.

  5. Energy harvesting from pavements via PVDF: hybrid piezo-pyroelectric effects

    NASA Astrophysics Data System (ADS)

    Tao, Junliang; Hu, Jie; Wu, Guangxi

    2016-04-01

    In the U.S., there are over 4 million miles (6 million km) of roadways and more than 250 million registered vehicles. The energy lost in the pavement system due to traffic-induced vibration and deformation is enormous. If effectively harvested, such energy can serve as an alternative sustainable energy source that can be easily integrated to the transportation system. The potential of PVDF, which is a piezoelectric polymer material, is investigated as a potential energy harvester integrated in pavement systems. The uniqueness of this study lies in that the electrical response of PVDF under coupled mechanical and thermal stimulations are studied. It is well known that most piezoelectric materials are also pyroelectric materials, which convert temperature change into electricity. However, the potential of PVDF as a hybrid piezo-pyroelectric energy harvester has been seldom studied. Through series of well controlled experiments, it is found that there exists interesting coupling phenomenon between piezoelectric and pyroelectric effects of PVDF: the voltage generated by simultaneous mechanical and thermal stimulations is the sum of voltages generated by separate stimulations. In addition, an estimation of power generation through piezoelectric and pyroelectric effect is conducted. Finally, the overall effects of temperature on hybrid piezo-pyroelectric energy harvesting are discussed.

  6. Superhydrophobic PVDF and PVDF-HFP nanofibrous mats with antibacterial and anti-biofouling properties

    NASA Astrophysics Data System (ADS)

    Spasova, M.; Manolova, N.; Markova, N.; Rashkov, I.

    2016-02-01

    Superhydrophobic nanofibrous materials of poly(vinylidene fluoride) (PVDF) and poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) were prepared by one-pot electrospinning technique. The mats were decorated with ZnO nanoparticles with silanized surface and a model drug - 5-chloro-8-hydroxyquinolinol (5Cl8HQ). The obtained hybrid nanofibrous materials were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), contact angle measurements, mechanical and microbiological tests. The results showed that the incorporation of ZnO nanoparticles into PVDF and PVDF-HFP nanofibers increased the hydrophobicity (contact angle 152°), improved the thermal stability and imparted to the nanofibrous materials anti-adhesive and antimicrobial properties. The mats containing the model drug possessed antibacterial activity against Escherichia coli and Staphylococcus aureus. The results suggested that the obtained hybrid mats could find potential biomedical applications requiring antibacterial and anti-biofouling properties.

  7. Optimized permeation and antifouling of PVDF hybrid ultrafiltration membranes: synergistic effect of dispersion and migration for fluorinated graphene oxide

    NASA Astrophysics Data System (ADS)

    Li, Mingming; Shi, Jie; Chen, Cheng; Li, Nan; Xu, Zhiwei; Li, Jing; Lv, Hanming; Qian, Xiaoming; Jiao, Xiaoning

    2017-03-01

    Nanoparticles may have suffered from low modification efficiency in hybrid membranes due to embedding and aggregating in polymer matrix. In order to analyze the modification mechanisms of nanoparticle migration and dispersion on the properties of hybrid membranes, we designed different F/ O ratios ( R F/ O ) of fluorinated graphene oxide (FGO, diameter = 1.5 17.5 μm) by carbon tetrafluoride (CF4) plasma treatment GO for 3, 5, 10, 15, and 20 min and successfully prepared novel PVDF hybrid membranes containing FGO via the phase inversion method. After a prolonged plasma treatment, the R F/ O of FGO was enhanced sharply, indicating an increasing compatibility of FGO with the matrix, especially FGO-20 (GO treated for 20 min). FGO contents in the top layer, sublayer, and the whole of membranes were probed by X-ray photoelectron spectroscopy, energy-dispersive spectrometer, and indirect computation, respectively. In the top layer of membranes, FGO contents declined from 13.14 wt% (PVDF/GO) to 4.00 wt% (PVDF/FGO-10) and 1.96 wt% (PVDF/FGO-20) due to the reduced migration ability of FGO. It is worth mentioning that PVDF/FGO-10 membranes exhibited an excellent water flux and flux recovery rate (up to 406.90 L m-2 h-1 and 88.9%), which were improved by 67.3% and 14.6% and 52.5% and 24.0% compared with those of PVDF/GO and PVDF/FGO-20 membranes, respectively, although the dispersion and migration ability of FGO-10 was maintained at a moderate level. It indicated that the migration and dispersion of FGO in membranes could result in dynamic equilibrium, which played a key role in making the best use of nanomaterials to optimize membrane performance.

  8. Effect of polyelectrolyte nanocoating on the performance and durability of cellulose electro-active paper actuator.

    PubMed

    Mahadeva, Suresha K; Kim, Jaehwan

    2009-10-01

    The effect of Polyelectrolyte nanocoating on a cellulose electro-active paper (EAPap) was investigated to improve the actuator performance and durability of EAPap actuators. Nanocoatings of Poly(styrenesulfonate) (PSS) and poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT-PSS) were carried out by immersing cationized cellulose films in to aqueous solutions of PSS and PEDOT:PSS. 2,3-epoxypropyltrimethylammonium chloride was used as cationic reactant. UV-visible spectroscopy and X-ray photoelectron spectroscopy (XPS) analysis showed the successful build up of PSS and PEDOT:PSS nanolayers over the cationized cellulose films. Results revealed that, nanocoating not only improved the durability of the actuators but it also greatly reduced (90%) the energy consumption of the actuators. Preparation, characterization and performance test of the actuators are explained.

  9. Possibility of cellulose-based electro-active paper energy scavenging transducer.

    PubMed

    Abas, Zafar; Kim, Heung Soo; Zhai, Lindong; Kim, Jaehwan; Kim, Joo Hyung

    2014-10-01

    In this paper, a cellulose-based Electro-Active Paper (EAPap) energy scavenging transducer is presented. Cellulose is proven as a smart material, and exhibits piezoelectric effect. Specimens were prepared by coating gold electrodes on both sides of cellulose film. The fabricated specimens were tested by a base excited aluminum cantilever beam at resonant frequency. Different tests were performed with single and multiple parallel connected electrodes coated on the cellulose film. A maximum of 131 mV output voltage was measured, when three electrodes were connected in parallel. It was observed that voltage output increases significantly with the area of electrodes. From these results, it can be concluded that the piezoelectricity of cellulose-based EAPap can be used in energy transduction application.

  10. Haptic device development based on electro static force of cellulose electro active paper

    NASA Astrophysics Data System (ADS)

    Yun, Gyu-young; Kim, Sang-Youn; Jang, Sang-Dong; Kim, Dong-Gu; Kim, Jaehwan

    2011-04-01

    Haptic is one of well-considered device which is suitable for demanding virtual reality applications such as medical equipment, mobile devices, the online marketing and so on. Nowadays, many of concepts for haptic devices have been suggested to meet the demand of industries. Cellulose has received much attention as an emerging smart material, named as electro-active paper (EAPap). The EAPap is attractive for mobile haptic devices due to its unique characteristics in terms of low actuation power, suitability for thin devices and transparency. In this paper, we suggest a new concept of haptic actuator with the use of cellulose EAPap. Its performance is evaluated depending on various actuation conditions. As a result, cellulose electrostatic force actuator shows a large output displacement and fast response, which is suitable for mobile haptic devices.

  11. Enhanced dielectric performance of BaTiO3/PVDF composites prepared by modified process for energy storage applications.

    PubMed

    Niu, Yujuan; Yu, Ke; Bai, Yuanyuan; Wang, Hong

    2015-01-01

    Ceramic-polymer composites have attracted extensive attention in electrical applications due to their high permittivity and low loss. In this work, we report the studies on the preparation and properties of barium titanate (BT)/ poly(vinylidenefluoride) (PVDF) composite thin films. The composite film was prepared by a modified process rather than the conventional method. The modified process adopted ballmilling technique instead of the stirring method to disperse BT nanoparticles into PVDF solution. Scanning electron microscopy images of the obtained composites show that the BT nanoparticles are incorporated into the PVDF network and are well dispersed in the matrix. When the BT volume fraction is 30%, the permittivity and breakdown strength of the composites reach their optimal values and the energy density reaches maximum value (5.3 J/cm3), an increase of 80% compared with that of the composites prepared using the stirring method. Another modification is the use of acetone and butanone mixed solution instead of N,N-dimethylformamide to dissolve the PVDF, which is beneficial to form pure α-PVDF composite films on the polyethylene terephthalate substrate by tape casting. The composites prepared by the modified process, with high permittivity and significantly enhanced breakdown strength, are useful candidates for energy storage applications.

  12. Effects of magnetic field treatment on dielectric properties of CCTO@Ni/PVDF composite with low concentration of ceramic fillers

    SciTech Connect

    Chi, Q. G. E-mail: empty-cy@l63.com; Gao, L.; Wang, X.; Chen, Y. E-mail: empty-cy@l63.com; Dong, J. F.; Cui, Y.; Lei, Q. Q.

    2015-11-15

    Using melt mixing, we produced a ceramic/polymer composite with a matrix of polyvinylidene fluoride (PVDF) and a filler of 5 vol.% Ni-deposited CaCu{sub 3}Ti{sub 4}O{sub 12} core-shell ceramic particles (CCTO@Ni), and studied its prominent dielectric characteristics for the first. Its phase composition and morphology were analyzed by X-ray diffraction and scanning electron microscopy, respectively. After treating the composite films with various durations of a magnetic field treatment, we compared their dielectric properties. We found that the CCTO@Ni ceramic had a typical urchin-like core-shell structure, and that different durations of the magnetic field treatment produced different distributions of ceramic particles in the PVDF matrix. The dielectric permittivity of the untreated CCTO@Ni/PVDF composite was 20% higher than that of neat PVDF, and it had a low loss tangent. However, only the composite treated for 30 min in the magnetic field had an ultra-high dielectric permittivity of 1.41 × 10{sup 4} at 10 Hz, three orders of magnitude higher than the untreated composite, which declined dramatically with increasing frequency, accompanied by an insulating-conducting phase transition and an increase in loss tangent. Our results demonstrate that changes in the dielectric properties of PVDF composites with magnetic field treatment are closely related to the percolation effect and interfacial polarization.

  13. PVDF:TiO2 Composite Thin Films for Capacitive Energy Storage

    NASA Astrophysics Data System (ADS)

    Ewen, Crystal; Dillingham, Randy; Stufflebeam, Terry; Brickley, Eric

    2014-03-01

    Thin films composed of the polymer polyvinylidene fluoride (PVDF) and the ceramic nanoparticle titanium dioxide (TiO2) are fabricated via thermal vapor deposition. This combination is ideal since it is light weight and improves the energy density. The elemental composition of the films are determined with energy dispersive x-ray spectroscopy using a scanning electron microscope. Elemental mapping of the films shows that the polymer and nanoparticles are homogeneously distributed. The ideal initial concentrations of PVDF and TiO2 were determined to be 83 % and 17 % respectively. The final films yield a Ti weight percent of 20. Parallel plate capacitors were fabricated by combining thermal vapor deposition and sputter coating. For the electrodes the parallel plates are gold-palladium (AuPd) with PVDF:TiO2 as the dielectric. The AuPd electrodes were deposited via sputter coating. Each electrode was sputtered for 100s, which yields a thickness of 33nm. Current research is working to improve the amount of Ti deposited by varying the temperature and deposition time, obtain more accurate thickness measurements, and improve on its electrical properties.

  14. Electro-activation of sweet defatted whey: Impact on the induced Maillard reaction products and bioactive peptides.

    PubMed

    Kareb, Ourdia; Gomaa, Ahmed; Champagne, Claude P; Jean, Julie; Aïder, Mohammed

    2017-04-15

    Electro-activation was used to add value to sweet defatted whey. This study aimed to investigate and to characterize the bioactive compounds formed under different electro-activation conditions by molecular and proteomic approaches. The effects of electric current intensity (400, 500 or 600mA) and whey concentration (7, 14 or 21% (w/v)) as a function of the electro-activation time (0, 15, 30 or 45min) were evaluated. The targeted dependent variables were the formation of Maillard reaction products (MRPs), protein hydrolysates and glycated compounds. It was shown that the MRPs derived from electro-activated whey at a concentration of 14% had the highest potential of biological activity. SDS-PAGE analyses indicated the formation of hydrolysates and glycated compounds with different molecular weight distributions. FTIR indicated the predominance of intermediate MRPs, such as the Schiff base compounds. LC-MS/MS and proteomics analysis showed the production of multi-functional bioactive peptides due to the hydrolysis of whey proteins.

  15. Orientation of PVDF α and γ crystals in nanolayered films.

    PubMed

    Jurczuk, Kinga; Galeski, Andrzej; Mackey, Matthew; Hiltner, Anne; Baer, Eric

    Wide-angle X-ray scattering in conjunction with pole figure technique was used to study the texture of poly(vinylidene fluoride) (PVDF) α and γ phase crystals in nanolayered polysulfone/poly(vinylidene fluoride) films (PSF/PVDF) produced by layer-multiplying coextrusion. In all as-extruded PSF/PVDF films, the PVDF nanolayers crystallized into the α phase crystals. A large fraction of those crystals was oriented with macromolecular chains perpendicular to the PSF/PVDF interface as evidenced from the (021) pole figures. Further refinement of the texture occurs during isothermal recrystallization at 170 °C in conjunction with transformation of α to γ crystals. The γ crystals orientation was probed with the (004) pole figures showing the c-axis of PVDF γ crystals perpendicular to the PSF/PVDF interface. The thinner the PVDF layers the stronger the orientation of γ crystals. It was proven that the X-ray reflections from the (021) planes of α crystals and from the (004) planes of γ crystals are not overlapped with other reflections and can be effectively used for the texture determination of PVDF nanolayers in multilayered PSF/PVDF films.

  16. Highly Sensitive Flexible Human Motion Sensor Based on ZnSnO3/PVDF Composite

    NASA Astrophysics Data System (ADS)

    Yang, Young Jin; Aziz, Shahid; Mehdi, Syed Murtuza; Sajid, Memoon; Jagadeesan, Srikanth; Choi, Kyung Hyun

    2017-02-01

    A highly sensitive body motion sensor has been fabricated based on a composite active layer of zinc stannate (ZnSnO3) nano-cubes and poly(vinylidene fluoride) (PVDF) polymer. The thin film-based active layer was deposited on polyethylene terephthalate flexible substrate through D-bar coating technique. Electrical and morphological characterizations of the films and sensors were carried out to discover the physical characteristics and the output response of the devices. The synergistic effect between piezoelectric ZnSnO3 nanocubes and β phase PVDF provides the composite with a desirable electrical conductivity, remarkable bend sensitivity, and excellent stability, ideal for the fabrication of a motion sensor. The recorded resistance of the sensor towards the bending angles of -150° to 0° to 150° changed from 20 MΩ to 55 MΩ to 100 MΩ, respectively, showing the composite to be a very good candidate for motion sensing applications.

  17. Superhydrophobicity and regeneration of PVDF/SiO2 composite films

    NASA Astrophysics Data System (ADS)

    Liu, Tao; Li, Xianfeng; Wang, Daohui; Huang, Qinglin; Liu, Zhen; Li, Nana; Xiao, Changfa

    2017-02-01

    Superhydrophobicity of polymers is easily destroyed by careless touching due to the softness of microstructures. In this study, based on a well-constructed polyvinylidene fluoride (PVDF) surface, a novel superhydrophobic PVDF/SiO2 composite film was fabricated by adding hydrophobic SiO2 nanoparticle and solvent into a coagulation bath. The water contact angle of the composite film reached 162.3° and the sliding angle was as low as 1.5°. More importantly, the composite film could be regenerated only through immersing the composite film in the designed regeneration agent. The composition of the designed regeneration agent ensured that SiO2 nanoparticles were firmly adhered on the film surface even under the ultrasonic cleaning. Hence, the superhydrophobicity and self-cleaing property could be regenerated and maintained effectively, and moreover, these propeties could resist a proper pressure. In addition, after many rubbing-regenerating cycles, the regeneration method was still valid.

  18. Ferroelectric all-polymer hollow Bragg fibers for terahertz guidance

    NASA Astrophysics Data System (ADS)

    Skorobogatiy, Maksim; Dupuis, Alexandre

    2007-03-01

    Design of hollow all-polymer Bragg fibers using periodic multilayers of ferroelectric polyvinylidene fluoride (PVDF) polymer and a low loss polycarbonate (PC) polymer is demonstrated. Efficient band gap guiding is predicted near the transverse optical frequency of a PVDF material in the terahertz regime. Optimal reflector designs are investigated in the whole terahertz region. Depending on frequency, the lowest loss hollow Bragg fiber can be one of the following: a photonic crystal fiber guiding in the band gap regime, a metamaterial fiber with a subwavelength reflector period, a single PC, or a PVDF tube.

  19. Energy Harvesting Using PVDF Piezoelectric Nanofabric

    NASA Astrophysics Data System (ADS)

    Shafii, Chakameh Shafii

    Energy harvesting using piezoelectric nanomaterial provides an opportunity for advancement towards self-powered electronics. The fabrication complexities and limited power output of these nano/micro generators have hindered these advancements thus far. This thesis presents a fabrication technique with electrospinning using a grounded cylinder as the collector. This method addresses the difficulties with the production and scalability of the nanogenerators. The non-aligned nanofibers are woven into a textile form onto the cylindrical drum that can be easily removed. The electrical poling and mechanical stretching induced by the electric field and the drum rotation increase the concentration of the piezoelectric beta phase in the PVDF nanofabric. The nanofabric is placed between two layers of polyethylene terephthalate (PET) that have interdigitated electrodes painted on them with silver paint. Applying continuous load onto the flexible PVDF nanofabric at 35Hz produces a peak voltage of 320 mV and maximum power of 2200 pW/(cm2) .

  20. Research on polyvinylidene fluoride (PVDF) hollow-fiber hemodialyzer.

    PubMed

    Zhang, Qinglei; Lu, Xiaolong; Zhao, Lihua; Liu, Juanjuan; Wu, Chunfeng

    2016-06-01

    In this study, polyvinylidene fluoride (PVDF) hollow-fiber hemodialysis membranes were prepared by non-solvent-induced phase separation. The PVDF hollow-fiber hemodialyzers were prepared by centrifugal casting. The results showed that the PVDF membrane had better mechanical and separation properties when the membrane wall thickness was 40 μm and the N,N-dimethylacetamide in the core was 70 Vol%. Compared with commercial polysulfone hemodialysis membrane (Fresenius F60S membrane), the PVDF membrane had better mechanical property and ultrafiltration (UF) flux of pure water. The PVDF dialyzer's removal efficiency for middle molecules was proven to be much higher than that of the F60S dialyzer. The UF coefficient of a high-flux PVDF dialyzer is 62.6 ml/h/mm Hg, whereas F60S is 42.5 ml/h/mm Hg, which can promote clearance for middle molecules.

  1. Application of PVDF composite for lithium-ion battery separator

    NASA Astrophysics Data System (ADS)

    Sabrina, Q.; Majid, N.; Prihandoko, B.

    2016-11-01

    In this study a composite observed in PVDF composite as lithium ion battery separator. Observation of performance cell battery with cyclic voltametry and charge discharge capacity. Surface morphology PVDF separator and commercial separator observed with Scanning electron microscopy (SEM). Cyclic Voltamerty test (CV) and Charge Discharge (CD) showed a capacity value on the coin cell. Coin cell is composed of material LiFePO4 cathode, anode material of lithium metal and varies as graphite, liquid electrolyte varied use LiBOB and LiPF6. While the PVDF as compared to the commercial separator. Coin cell commercial separator has a better high capacity value when compared with Coin cell with the PVDF separator. Life cycle coin cell with the commercial separator material is still longer than coin cell separator with PVDF Copolymer. Development of PVDF as separator remains to be done in order to improve the performance of the battery exceeds the usage of commercial material.

  2. Dynamic Characterization of Thin Deformable PVDF Mirror

    DTIC Science & Technology

    2005-03-01

    86 A.6 ‘Real Time’ Data Collection with the MATLAB Computer . . . . . . . 87 Appendix B. MATLAB Code ...20.827 m=5 8.7716 12.339 15.700 18.98 22.218 The deformation patterns given in Figure 17 are generated with a Matlab R© code (see Appen- dix B.6...the actuation direction which was assumed in the development of the thin membrane theory . However, actuation with the PVDF patches causes the patch to

  3. Influence of organic additive to PVDF-HFP mixed iodide electrolytes on the photovoltaic performance of dye-sensitized solar cells

    NASA Astrophysics Data System (ADS)

    Senthil, R. A.; Theerthagiri, J.; Madhavan, J.; Ganesan, S.; Arof, A. K.

    2017-02-01

    The influence of 5-amino-1,3,4-thiadiazole-2-thiol (ATDT) on the ionic conductivity of poly(vinylidinefluoride-co-hexafluoropropylene) (PVDF-HFP) polymer electrolytes with mixed iodide salts (potassium iodide (KI) and tetrabutylammonium iodide (TBAI)) and iodine (I2) were studied for dye-sensitized solar cells (DSSCs). The pure and different weight percentage (wt%) ratios (2%, 3%, 4%, 5% and 6%) of ATDT modified PVDF-HFP/KI+TBAI/I2 electrolyte films were prepared by solution casting technique using DMF as a solvent. The polymer electrolyte films were characterized by Fourier transform infrared (FT-IR) spectroscopy, X-ray diffractometer (XRD), electrochemical impedance spectroscopy and scanning electron microscopy (SEM). The pure PVDF-HFP/TBAI+KI/I2 electrolyte exhibited the ionic conductivity value of 9.99×10-6 S cm-1 at room temperature, which was found to be improved to a maximum value of 2.82×10-4 S cm-1 at 4 wt% of ATDT modified polymer electrolyte. The photovoltaic characterization studies showed higher power conversion efficiency of 4.64% for DSSC assembled with the optimized wt% of ATDT modified polymer electrolyte than the pure PVDF-HFP/KI+TBAI/I2 electrolyte (1.88%) at an illumination intensity of 60 mW/cm2. Hence, the studies concluded that the ATDT modified polymer electrolyte can be a suitable material for DSSC applications.

  4. Characterization, performance and optimization of PVDF as a piezoelectric film for advanced space mirror concepts.

    SciTech Connect

    Jones, Gary D.; Assink, Roger Alan; Dargaville, Tim Richard; Chaplya, Pavel Mikhail; Clough, Roger Lee; Elliott, Julie M.; Martin, Jeffrey W.; Mowery, Daniel Michael; Celina, Mathew Christopher

    2005-11-01

    Piezoelectric polymers based on polyvinylidene fluoride (PVDF) are of interest for large aperture space-based telescopes as adaptive or smart materials. Dimensional adjustments of adaptive polymer films depend on controlled charge deposition. Predicting their long-term performance requires a detailed understanding of the piezoelectric material features, expected to suffer due to space environmental degradation. Hence, the degradation and performance of PVDF and its copolymers under various stress environments expected in low Earth orbit has been reviewed and investigated. Various experiments were conducted to expose these polymers to elevated temperature, vacuum UV, {gamma}-radiation and atomic oxygen. The resulting degradative processes were evaluated. The overall materials performance is governed by a combination of chemical and physical degradation processes. Molecular changes are primarily induced via radiative damage, and physical damage from temperature and atomic oxygen exposure is evident as depoling, loss of orientation and surface erosion. The effects of combined vacuum UV radiation and atomic oxygen resulted in expected surface erosion and pitting rates that determine the lifetime of thin films. Interestingly, the piezo responsiveness in the underlying bulk material remained largely unchanged. This study has delivered a comprehensive framework for material properties and degradation sensitivities with variations in individual polymer performances clearly apparent. The results provide guidance for material selection, qualification, optimization strategies, feedback for manufacturing and processing, or alternative materials. Further material qualification should be conducted via experiments under actual space conditions.

  5. Electro-active device using radial electric field piezo-diaphragm for sonic applications

    NASA Technical Reports Server (NTRS)

    Bryant, Robert G. (Inventor); Fox, Robert L. (Inventor)

    2005-01-01

    An electro-active transducer for sonic applications includes a ferroelectric material sandwiched by first and second electrode patterns to form a piezo-diaphragm coupled to a mounting frame. When the device is used as a sonic actuator, the first and second electrode patterns are configured to introduce an electric field into the ferroelectric material when voltage is applied to the electrode patterns. When the device is used as a sonic sensor, the first and second electrode patterns are configured to introduce an electric field into the ferroelectric material when the ferroelectric material experiences deflection in a direction substantially perpendicular thereto. In each case, the electrode patterns are designed to cause the electric field to: i) originate at a region of the ferroelectric material between the first and second electrode patterns, and ii) extend radially outward from the region of the ferroelectric material (at which the electric field originates) and substantially parallel to the plane of the ferroelectric material. The mounting frame perimetrically surrounds the peizo-diaphragm and enables attachment of the piezo-diaphragm to a housing.

  6. Magnetic and electric field alignments of cellulose chains for electro-active paper actuator

    NASA Astrophysics Data System (ADS)

    Yun, Sungryul; Chen, Yi; Lee, Sang Woo; Kim, Jaehwan; Kim, Heung Soo

    2008-03-01

    To improve the piezoelectricity of cellulose electro-active paper (EAPap), electrical field and magnetic field alignments were investigated. EAPap is made with cellulose by dissolving cotton pulp and regenerating cellulose with aligned cellulose fibers. EAPap made with cellulose has piezoelectric property due to its structural crystallinity. Noncentro-symmetric crystal structure of EAPap, which is mostly cellulose II, can exhibit piezoelectricity. However, EAPap has ordered crystal parts as well as disordered parts of cellulose. Thus, well alignment of cellulose chains in EAPap is important to improve its piezoelectricity. In this paper, uniaxial alignments of cellulose chains were investigated by applying electric field and magnetic field. As exposing different fields to EAPap samples, the changed characteristics were analyzed by X-Ray diffractometer (XRD) and Scanning electron microscopy (SEM). Finally, the piezoelectricity of EAPap samples was evaluated by comparing their piezoelectric charge constant [d 31]. As increasing applied electric field up to 40V/mm, d 31 value was gradually improved due to increased cellulose crystallinity as well as alignment of cellulose chains. Also the alignment of cellulose chains was improved with increasing the exposing time to magnetic field (5.3T) and well alignment was achieved by exposing EAPap sample on the magnetic field for 180min.

  7. The preparation, characterization and actuation behavior of polyaniline and cellulose blended electro-active paper

    NASA Astrophysics Data System (ADS)

    John, Amalraj; Mahadeva, Suresha K.; Kim, Jaehwan

    2010-04-01

    This paper reports polyaniline and cellulose blended electro-active paper (EAPap) that can produce large bending displacement at ambient humidity conditions with long lifetime durability. A novel solution processable polyaniline-p-toluene sulfonate (PANI-PTSA) salt was prepared by an inverted emulsion polymerization technique using benzoyl peroxide and p-toluene sulfonic acid. Cellulose solution prepared by dissolving cotton with lithium chloride/N, N-dimethylacetamide was mixed with the PANI emaraldine salt solution and a cellulose-PANI blended film was obtained. The obtained cellulose-PANI film was characterized by ultraviolet-visible (UV-visible), x-ray diffraction, scanning electron microscopy and tensile test methods. A cellulose-PANI EAPap actuator was made by depositing very thin gold electrodes on both sides of the cellulose-PANI film. When the actuator performance of the cellulose-PANI EAPap was evaluated in terms of bending displacement with respect to the actuation frequencies, voltages and relative humidity levels, a large bending displacement was shown at ambient humidity conditions with long lifetime durability.

  8. Preparation of hydrophilic PVDF/PPTA blend membranes by in situ polycondensation and its application in the treatment of landfill leachate

    NASA Astrophysics Data System (ADS)

    Li, Hongbin; Shi, Wenying; Zhang, Yufeng; Zhou, Rong; Zhang, Haixia

    2015-08-01

    High modulus poly(p-phenylene terephtalamide) (PPTA) reinforced composites are of great scientific interests. But the thermodynamic difference makes the polymer pairs incompatible and endows the composites with inferior physical-chemical properties. In this study, hydrophilic poly(vinylidene fluoride) (PVDF)/poly(p-phenylene terephtalamide) (PPTA) blend membrane with improved hydrophilicity and mechanical strength was prepared through in situ polycondensation of p-phenylene diamine (PPD) and terephthaloyl chloride (TPC) in PVDF solution and subsequent immersion precipitation phase inversion process. The effects of PPTA concentration in polymer dopes on membrane formation process, structure, morphology and performance were systematically investigated. The results showed that thermodynamically, PPTA acted as a demixing enhancer which accelerated the phase inversion process. Dynamically, liquid-liquid phase separation was still in control of membrane formation process especially in the later period, whereas the addition of PPTA mainly promoted the early emergence of the liquid-liquid demixing. The surface hydrophilicity, ant-fouling properties and mechanical strength were significantly improved when PPTA content was 17 wt%. When PPTA content increased to 26 wt%, membrane bursting pressure increased to nearly 0.6 MPa which was 1.5 times higher than that of PVDF membrane. The resultant PVDF/PPTA blend membrane exhibited an improved antifouling property than that of PVDF membrane when applied in the MBR in the treatment of landfill leachate and also showed a relatively high removal rate of chemical oxygen demand (COD) and chrom.

  9. Composites PVDF-TrFE/BT used as bioactive membranes for enhancing bone regeneration

    NASA Astrophysics Data System (ADS)

    Gimenes, Rossano; Zaghete, Maria A.; Bertolini, Marcio; Varela, Jose A.; Coelho, Luciane O.; Silva, Nelson F., Jr.

    2004-07-01

    In this paper a piezoelectric composite membranes were developed for charge generator to promoter bone regeneration on defects sites. Is known that the osteogenesis process is induced by interactions between biological mechanisms and electrical phenomena. The membranes were prepared by mixing Barium Titanate (BT) powders and PVDF-TrFE (PVDF:TrFE = 60:40 mol%) on dimethylformamide medium. This precursor solution was dried and crystallized at 100oC for 12 hours. Composites membranes were obtained by following methods: solvent casting (SC), spincoating (SP), solvent extraction by water addition (WS) and hot pressing (HP). The microstructural analysis performed by SEM showed connectivity type 3-0 and 3-1 with high homogeneity for samples of ceramic volume fraction major than 0.50. Powder agglomerates within the polymer matrix was evidenced were observed for composites with the BT volume fraction major than 40%. The composite of ceramic fraction of 0.55 presented the best values of remanent polarization (~33mC/cm2), but the flexibility of these composites with the larger ceramic fraction was significantly affected. For in vivo evaluation PVDF-TrFE/BT 90/10 membranes with 3cm larger were longitudinally implanted under tibiae of male rabbit. After 21 days the animals were sacrificed. By histological analyses were observed neo formed bone with a high mitotic activity. In the interface bone-membrane was evidenced a pronounced callus formation. These results encourage further applications of these membranes in bone-repair process.

  10. Preparation of Polyvinylidene Fluoride (PVDF) Hollow Fiber Hemodialysis Membranes.

    PubMed

    Zhang, Qinglei; Lu, Xiaolong; Zhao, Lihua

    2014-02-27

    In this study, the polyvinylidene fluoride (PVDF) hollow fiber hemodialysis membranes were prepared by non-solvent induced phase separation (NIPS). The influences of PVDF membrane thickness and polyethylene glycol (PEG) content on membrane morphologies, pore size, mechanical and permeable performance were investigated. It was found that membrane thickness and PEG content affected both the structure and performance of hollow fiber membranes. The tensile strength and rejection of bovine serum albumin (BSA) increased with increasing membrane thickness, while the Ultrafiltration flux (UF) flux of pure water was the opposite. The tensile strength, porosity and rejection of BSA increased with increasing PEG content within a certain range. Compared with commercial F60S membrane, the PVDF hollow fiber membrane showed higher mechanical and permeable performance. It was proven that PVDF material had better hydrophilicity and lower BSA adsorption, which was more suitable for hemodialysis. All the results indicate that PVDF hollow fiber membrane is promising as a hemodialysis membrane.

  11. Giant Electric-Field-Induced Strain in PVDF-Based Battery Separator Membranes Probed by Electrochemical Strain Microscopy.

    PubMed

    Romanyuk, Konstantin; Costa, Carlos M; Luchkin, Sergey Yu; Kholkin, Andrei L; Lanceros-Méndez, Senentxu

    2016-05-31

    Efficiency of lithium-ion batteries largely relies on the performance of battery separator membrane as it controls the mobility and concentration of Li-ions between the anode and cathode electrodes. Recent advances in electrochemical strain microscopy (ESM) prompted the study of Li diffusion and transport at the nanoscale via electromechanical strain developed under an application of inhomogeneous electric field applied via the sharp ESM tip. In this work, we observed unexpectedly high electromechanical strain developed in polymer membranes based on porous poly(vinylidene fluoride) (PVDF) and poly(vinylidene fluoride-co-chlorotrifluoroethylene) (PVDF-CTFE) and, using it, could study a dynamics of electroosmotic flow of electrolyte inside the pores. We show that, independently of the separator membrane, electric field-induced deformation observed by ESM on wetted membrane surfaces can reach up to 10 nm under a moderate bias of 1 V (i.e., more than an order of magnitude higher than that in best piezoceramics). Such a high strain is explained by the electroosmotic flow in a porous media composed of PVDF. It is shown that the strain-based ESM method can be used to extract valuable information such as average pore size, porosity, elasticity of membrane in electrolyte solvent, and membrane-electrolyte affinity expressed in terms of zeta potential. Besides, such systems can, in principle, serve as actuators even in the absence of apparent piezoelectricity in amorphous PVDF.

  12. Reciprocated suppression of polymer crystallization toward improved solid polymer electrolytes: Higher ion conductivity and tunable mechanical properties

    SciTech Connect

    Bi, Sheng; Sun, Che-Nan; Zawodzinski, Thomas A.; Ren, Fei; Keum, Jong Kahk; Ahn, Suk-Kyun; Li, Dawen; Chen, Jihua

    2015-08-06

    Solid polymer electrolytes based on lithium bis(trifluoromethanesulfonyl) imide and polymer matrix were extensively studied in the past due to their excellent potential in a broad range of energy related applications. Poly(vinylidene fluoride) (PVDF) and polyethylene oxide (PEO) are among the most examined polymer candidates as solid polymer electrolyte matrix. In this paper, we study the effect of reciprocated suppression of polymer crystallization in PVDF/PEO binary matrix on ion transport and mechanical properties of the resultant solid polymer electrolytes. With electron and X-ray diffractions as well as energy filtered transmission electron microscopy, we identify and examine the appropriate blending composition that is responsible for the diminishment of both PVDF and PEO crystallites. Laslty, a three-fold conductivity enhancement is achieved along with a highly tunable elastic modulus ranging from 20 to 200 MPa, which is expected to contribute toward future designs of solid polymer electrolytes with high room-temperature ion conductivities and mechanical flexibility.

  13. Polymers.

    ERIC Educational Resources Information Center

    Tucker, David C.

    1986-01-01

    Presents an open-ended experiment which has students exploring polymer chemistry and reverse osmosis. This activity involves construction of a polymer membrane, use of it in a simple osmosis experiment, and application of its principles in solving a science-technology-society problem. (ML)

  14. Spectroscopic Investigations on PVDF-MWCNTs Nanocomposites

    NASA Astrophysics Data System (ADS)

    Guerrero, Oscar; Ramirez, Samantha; Jones, Robert; Yust, Brian; Hinthorne, James; Chipara, Mircea

    Nanocomposites have been obtained by dispersing Multi Walled Carbon Nanotubes (MWCNTs) within polyvinylidene fluoride. Various samples loaded by 0 to 20 % wt. MWCNTs have been obtained by melt mixing using a Haake RheoMixer, with two counter rotating screws. The effect of the nanofiller concentration on the glass, melting, and crystallization temperatures, as determined from Differential Scanning Calorimetry measurements, is reported. Small shifts towards higher temperatures as the loading with MWCNTs was increased have been noticed. A detailed analysis on the effect of MWCNTs on the degree of crystallinity of PVDF is reported. Raman data obtained by using a Renishaw InVia spectrometer have been used to estimate the stress transfer. Additional information was obtained by FTIR and Wide Angle X-Ray Scattering. The nature of the crystalline phases was determined for each sample. Thermogravimetric data showed a small increase of the thermal stability of the polymeric matrix upon the loading with MWCNTs.

  15. Superhydrophilic In-Situ-Cross-Linked Zwitterionic Polyelectrolyte/PVDF-Blend Membrane for Highly Efficient Oil/Water Emulsion Separation.

    PubMed

    Zhu, Yuzhang; Xie, Wei; Zhang, Feng; Xing, Tieling; Jin, Jian

    2017-03-22

    Because of weak hydrophilicity, membranes always experience fouling problems during separations. This phenomenon seriously impedes the development of membrane technologies for practical industrial-oil wastewater treatment. In this work, we successfully fabricated a superhydrophilic zwitterionic poly(vinylidene fluoride) (PVDF) membrane using a two-part process with an in situ cross-linking reaction during nonsolvent-induced phase separation and a subsequent sulfonation reaction. To prepare this zwitterionic PVDF membrane, a copolymer poly(dimethylaminoethyl methacrylate-co-2-hydroxyethyl methacrylate) (PDH) was synthesized as a zwitterionic polymer precursor and used as an additive in membrane preparation. This zwitterionic additive is well-immobilized in the membrane using in situ cross-linking to ensure the long-term stability of the membrane, and subsequent sulfonation transforms the precursor to a zwitterionic polymer to produce a superhydrophilic membrane. This superhydrophilic zwitterionic PVDF membrane exhibits high water permeation flux and good antifouling properties for separating oil-in-water emulsions with high separation efficiency.

  16. Electrospinning of PVDF nanofibrous membranes with controllable crystalline phases

    NASA Astrophysics Data System (ADS)

    Lei, Tingping; Zhu, Ping; Cai, Xiaomei; Yang, Le; Yang, Fan

    2015-07-01

    Effectively controlling crystalline phases of electrospun polyvinylidene fluoride (PVDF) nanofibers is crucial to produce membranes with special properties for specific applications. Here, the heating treatment during or after electrospinning has been investigated to determine an effective way to control crystalline phase of PVDF nanofibers. By simultaneously controlling the collector temperature and the flow rate during the fiber deposition, a comparatively lower temperature (≤70 °C) is required for obtaining α-, β-, or γ-phase-dominant nanofibrous membranes, whereas a much higher temperature (≥150 °C) is necessary for post-heating of already-deposited fibers. On the other hand, through finely tuning the heating during or after electrospinning, crosslinked nanofibrous membranes can be also obtained, which undoubtedly enhance mechanical performance of the membranes. Therefore, it is hopeful to fabricate high-performance electrospun PVDF nanofibrous membranes with synchronous control of crystalline phases and morphologies, which will further broaden the applications of PVDF materials.

  17. A flexible piezoelectric force sensor based on PVDF fabrics

    NASA Astrophysics Data System (ADS)

    Wang, Y. R.; Zheng, J. M.; Ren, G. Y.; Zhang, P. H.; Xu, C.

    2011-04-01

    Polyvinylidene fluoride (PVDF) film has been widely investigated as a sensor and transducer material due to its high piezo-, pyro- and ferroelectric properties. To activate these properties, PVDF films require a mechanical treatment, stretching or poling. In this paper, we report on a force sensor based on PVDF fabrics with excellent flexibility and breathability, to be used as a specific human-related sensor. PVDF nanofibrous fabrics were prepared by using an electrospinning unit and characterized by means of scanning electron microscopy (SEM), FTIR spectroscopy and x-ray diffraction. Preliminary force sensors have been fabricated and demonstrated excellent sensitivity and response to external mechanical forces. This implies that promising applications can be made for sensing garment pressure, blood pressure, heartbeat rate, respiration rate and accidental impact on the human body.

  18. X-Ray Diffraction Studies of the Structure of Ordered Polymers and Related Electro-Active Materials

    DTIC Science & Technology

    1990-12-31

    Crystalline Order in Polybenzobisoxazole and Polybenzobisthiazole Fibers ," A.V. Fratini, P.G. Lenhert, T.J. Resch and W.W. Adams, Proceedings of Materials...phenylenebenzobisoxazole) (PBO) fibers have been determined byfiber diffraction techniques (see Reprint 4 for details). D-spacings wereobtained from...refinement procedure.A packing model has been proposed for each fiber in which two independentmolecular chains are displaced longitudinally by

  19. Influence Of Zwitterions on Properties and Morphology of Ionomers: Implications for Electro-Active Applications

    DTIC Science & Technology

    2010-08-01

    acrylate and n-butyl acrylate ( nBA ) based sulfobetaine-containing polymers.13,14 They demonstrated that the incorporation of zwitterionic functionalities...propanesulfonate (SBMA). Through copolymerizing the two charge-containing monomers with nBA , a series of zwitterionomers and their corresponding...graciously provided by Raschig GmbH. n-Butyl acrylate ( nBA ), dimethyl sulfoxide (DMSO, 99.9+%) and hydroquinone (99%) were purchased from Alfa Aesar. 2

  20. Influence of electro-activated solutions of weak organic acid salts on microbial quality and overall appearance of blueberries during storage.

    PubMed

    Liato, Viacheslav; Hammami, Riadh; Aïder, Mohammed

    2017-06-01

    The aim of this work was to study the potential of diluted electro-activated solutions of weak organic acid salts (potassium acetate, potassium citrate and calcium lactate) to extend the shelf life of blueberries during post-harvest storage. The sanitizing capacity of these solutions was studied against pathogenic bacteria Listeria monocytogenes and E. coli O157:H7 as well as phytopathogenic fungi A. alternata, F. oxysporum and B. cinerea. The results showed that a 5-min treatment of inoculated blueberries with electro-activated solutions resulted in a 4 log CFU/g reduction in Listeria monocytogenes for all solutions. For E. coli O157:H7, the electro-activated potassium acetate and potassium citrate solutions achieved a decrease of 3.5 log CFU/g after 5 min of berry washing. The most important fungus reduction was found when blueberries were washed with an electro-activated solution of potassium acetate and a NaOCl solution. After 5 min of blueberry washing with an electro-activated potassium acetate solution, a very high reduction effect was observed for A. alternata, F. oxysporum and B. cinerea, which showed survival levels of only 2.2 ± 0.16, 0.34 ± 0.15 and 0.21 ± 0.16 log CFU/g, respectively. Regarding the effect of the washing on the organoleptic quality of blueberries, the obtained results showed no negative effect on the product color or textural profile. Finally, this work suggests that washing with electro-activated solutions of weak organic acid salts can be used to enhance the shelf-life of blueberries during post-harvest storage.

  1. Electro-Active Transducer Using Radial Electric Field To Produce/Motion Sense Out-Of-Plane Transducer

    NASA Technical Reports Server (NTRS)

    Bryant, Robert G. (Inventor); Fox, Robert L. (Inventor)

    2006-01-01

    An electro-active transducer includes a ferroelectric material sandwiched by first and second electrode patterns. When the device is used as an actuator, the first and second electrode patterns are configured to introduce an electric field into the ferroelectric material when voltage is applied to the electrode patterns. When the device is used as a sensor. the first and second electrode patterns are configured to introduce an electric field into the ferroelectric material when the ferroelectric material experiences deflection in a direction substantially perpendicular thereto. In each case, the electrode patterns are designed to cause the electric field to: i) originate at a region of the ferroelectric material between the first and second electrode patterns. and ii) extend radially outward from the region of the ferroelectric material (at which the electric field originates) and substantially parallel to the ferroelectric material s plane.

  2. Studies of redox reactions in electro-active proteins using optical impedance spectroscopy at single-mode waveguides

    NASA Astrophysics Data System (ADS)

    Han, Xue; Mendes, Sergio B.

    2013-09-01

    An electro-active platform based on a single-mode integrated optical waveguide over-coated with a 13-nm indium tin oxide film was developed for highly sensitive investigations on the kinetics of redox reactions from a sub-monolayer of cytochrome-c proteins. Optical impedance spectra (with and without cytochrome-c proteins present in the spectroelectrochemical flow-cell) were measured with the single-mode integrated optical waveguide for a 10-mV ac electric potential modulation. Significant changes in the ac component of the optical baseline response were observed, and a new analysis was developed to factor out the working electrode effects and deliver accurate results for the Faradaic process. Faradaic current density and active surface coverage were reconstructed at several modulation frequencies. As small as 7x10-14 mole/cm2 of cytochrome-c proteins were detected under such electric potential modulation leading to a faradaic current of about 200 nA/cm2. Such level of faradaic current is extremely difficult to be isolated by other electrochemical techniques (e.g. electrical impedance measurements) due to the strong background created by an always present electric double layer. We were able to achieve those detection limits because the optical signal is immune to those events and can be tuned solely to the Faradaic process. This highly sensitive and accurate strategy of spectro-electrochemistry is proved powerful for measurements of extreme small amount of electro-active proteins and has the potential to be used in many other important electrochemical processes.

  3. Fabrication and evaluation of thin layer PVDF composites using MWCNT reinforcement: Mechanical, electrical and enhanced electromagnetic interference shielding properties

    NASA Astrophysics Data System (ADS)

    Bhaskara Rao, B. V.; Kale, Nikita; Kothavale, B. S.; Kale, S. N.

    2016-06-01

    Radar X-band electromagnetic interference shielding (EMS) is one of the prime requirements for any air vehicle coating; with limitations on the balance between strength and thickness of the EMS material. Nanocomposite of multiwalled-carbon-nanotubes (MWCNT) has been homogeneously integrated (0 - 9 wt%) with polymer, poly (vinylidene fluoride, PVDF) to yield 300 micron film. The PVDF + 9 wt% MWCNT sample of density 1.41 g/cm3 show specific shielding effectiveness (SSE) of 17.7 dB/(g/cm3) (99.6% EMS), with maintained hardness and improved conductivity. With multilayer stacking (900 microns) of these films of density 1.37 g/cm3, the sample showed increase in SSE to 23.3 dB/(g/cm3) (99.93% EMS). Uniform dispersion of MWCNTs in the PVDF matrix gives rise to increased conductivity in the sample beyond 5 wt% MWCNT reinforcement. The results are correlated to the hardness, reflection loss, absorption loss, percolation threshold, permittivity and the conductivity data. An extremely thin film with maximum EMS property is hence proposed.

  4. Development of Bench and Full-Scale Temperature and pH Responsive Functionalized PVDF Membranes with Tunable Properties.

    PubMed

    Xiao, Li; Isner, Austin; Waldrop, Krysta; Saad, Anthony; Takigawa, Doreen; Bhattacharyya, Dibakar

    2014-05-01

    Temperature and pH responsive polymers (poly(N-isopropylacrylamide) (PNIPAAm), and polyacrylic acid, PAA) were synthesized in one common macrofiltration PVDF membrane platform by pore-filling method. The microstructure and morphology of the PNIPAAm-PVDF, and PNIPAAm-FPAA-PVDF membranes were studied by attenuated total reflectance Fourier transform infrared (ATR-FTIR), thermogravimetric analysis (TGA), scanning electron microscopy (SEM) and atomic force microscopy (AFM). The membrane pore size was controlled by the swelling and shrinking of the PNIPAAm at the temperature around lower critical solution temperature (LCST). The composite membrane demonstrated a rapid and reversible swelling and deswelling change within a small temperature range. The controllable flux makes it possible to utilize this temperature responsive membrane as a valve to regulate filtration properties by temperature change. Dextran solution (Mw=2,000,000g/mol, 26 nm diameter) was used to evaluate the separation performance of the temperature responsive membranes. The ranges of dextran rejection are from 4% to 95% depending on the temperature, monomer amount and pressure. The full-scale membrane was also developed to confirm the feasibility of our bench-scale experimental results. The full-scale membrane also exhibited both temperature and pH responsivity. This system was also used for controlled nanoparticles synthesis and for dechlorination reaction.

  5. Characteristics of PVDF Membranes Irradiated by Electron Beam.

    PubMed

    Jaleh, Babak; Gavary, Negin; Fakhri, Parisa; Muensit, Nakatan; Taheri, Soheil Mohammad

    2015-01-05

    Polyvinylidene fluoride (PVDF) membranes were exposed vertically to a high energy electron beam (EB) in air, at room temperature. The chemical changes were examined by Fourier Transform Infrared Spectroscopy (FTIR). The surface morphologies were studied by Scanning Electron Microscopy (SEM) and showed some changes in the pore size. Thermogravimetric (TGA) analysis represented an increase in the thermal stability of PVDF due to irradiation. Electron paramagnetic resonance (EPR) showed the presence of free radicals in the irradiated PVDF. The effect of EB irradiation on the electrical properties of the membranes was analyzed in order to determine the dielectric constant, and an increase in the dielectric constant was found on increasing the dose. The surface hydrophilicity of the modified membrane was characterized by water contact angle measurement. The contact angle decreased compared to the original angle, indicating an improvement of surface hydrophilicity. Filtration results also showed that the pure water flux (PWF) of the modified membrane was lower than that of the unirradiated membrane.

  6. Robot gripper control system using PVDF piezoelectric sensors.

    PubMed

    Barsky, M F; Lindner, D K; Claus, R O

    1989-01-01

    A novel robot gripper control system is presented that uses PVDF (polyvinylidene fluoride) piezoelectric sensors to damp exerted force actively. By monitoring the current developed by the PVDF sensor, an output proportional to the rate of change of the force exerted by the gripper is obtained. The signals from the PVDF sensor and strain-gauge force sensor are arranged in a proportional and derivative control system for the control of force. The control system was tested on an instrumented Rhino XR-1 manipulator hand. The capabilities of the control system are analyzed and are verified experimentally. The results for this particular gripper indicate that the additional sensory feedback can decrease the force step response rise time by 88% while maintaining a monotonic zero-overshoot response. The inclusion of the rate feedback increases the damping ratio of the dominant poles while maintaining the step response rise time.

  7. Development of an endoscopic tactile sensor using PVDF films

    NASA Astrophysics Data System (ADS)

    Okuyama, Takeshi; Sone, Mikiko; Tanahashi, Yoshikatsu; Chonan, Seiji; Tanaka, Mami

    2007-12-01

    In this work, a prototype Polyvinylidene Fluoride (PVDF) tactile sensor for endoscopic application has been developed. The sensor aims to measure hardness, which is one of the information of tactile perceptions, of biomedical tissue. This sensor is composed of two PVDF films, a silicone cylindrical column, and an aluminum cylinder. And the classification of hardness is concerned with the ratio of these PVDF outputs. In this paper, two sensors are fabricated using two silicone cylindrical columns with different Young's modulus. The performance evaluation of each sensor is conducted using 6 silicone rubbers as measuring object. The experimental results correspond with the simplified theoretical analysis and the proposed sensor can distinguish a difference of elastic property.

  8. A comprehensive overview on electro-active biofilms, role of exo-electrogens and their microbial niches in microbial fuel cells (MFCs).

    PubMed

    Saratale, Ganesh Dattatraya; Saratale, Rijuta Ganesh; Shahid, Muhammad Kashif; Zhen, Guangyin; Kumar, Gopalakrishnan; Shin, Han-Seung; Choi, Young-Gyun; Kim, Sang-Hyoun

    2017-07-01

    Microbial fuel cells (MFCs) are biocatalyzed systems which can drive electrical energy by directly converting chemical energy using microbial biocatalyst and are considered as one of the important propitious technologies for sustainable energy production. Much research on MFCs experiments is under way with great potential to become an alternative to produce clean energy from renewable waste. MFCs have been one of the most promising technologies for generating clean energy industry in the future. This article summarizes the important findings in electro-active biofilm formation and the role of exo-electrogens in electron transfer in MFCs. This study provides and brings special attention on the effects of various operating and biological parameters on the biofilm formation in MFCs. In addition, it also highlights the significance of different molecular techniques used in the microbial community analysis of electro-active biofilm. It reviews the challenges as well as the emerging opportunities required to develop MFCs at commercial level, electro-active biofilms and to understand potential application of microbiological niches are also depicted. Thus, this review is believed to widen the efforts towards the development of electro-active biofilm and will provide the research directions to overcome energy and environmental challenges.

  9. Cratering studies in Polyvinylidene Fluoride (PVDF) thin films

    NASA Astrophysics Data System (ADS)

    Shu, Anthony; Bugiel, Sebastian; Grün, Eberhard; Hillier, Jon; Horányi, Mihály; Munsat, Tobin; Srama, Ralf

    2013-12-01

    Thin, permanently polarized Polyvinylidene Fluoride (PVDF) films have been used as dust detectors on a number of missions including the Dust Counter and Mass Analyzer (DUCMA) instrument on Vega 1 and 2 to comet 1P/Halley, the High Rate Detector (HRD) on the Cassini Mission to Saturn, the Student Dust Counter (SDC) on New Horizons to Pluto, the Dust Flux Monitor Instrument (DFMI) on the Stardust mission to comet 81P/Wild 2, the Space Dust (SPADUS) instrument on the Earth orbiting Advanced Research and Global Observation Satellite (ARGOS) and the Cosmic Dust Experiment (CDE) on the Aeronomy of Ice in the Mesosphere (AIM) mission in orbit around the Earth. Due to their low power requirements and light weight, large surface area detectors can be built for observing low dust fluxes. The operation principle behind metal-coated PVDF detectors is that a micrometeorite impact removes a portion of the metal surface layer, exposing the permanently polarized PVDF dielectric underneath. This changes the local electric potential near the crater, and the surface charge of the metal layer, which can be recorded as a transient current. The dimensions of the crater determine the strength of the potential change and thus the signal generated by the PVDF. Currently used scaling laws relating impactor parameters to crater geometry, which are used to predict PVDF response, are suspected to have systematic errors. Work is being undertaken to develop a new crater diameter scaling law using iron particles in PVDF. Cratered samples are analyzed using a 3D reconstruction technique using stereo image pairs taken in a Scanning Electron Microscope (SEM) and cross sections taken in a Focused Ion Beam (FIB). We report on the details of the reconstruction techniques and the initial findings of the crater parameter scaling law study.

  10. Quantitative PVP mapping in PVDF hollow fiber membranes by using Raman spectroscopy coupled with spectral chemiometrics analysis

    NASA Astrophysics Data System (ADS)

    Dufour, E.; Gassara, S.; Petit, E.; Pochat-Bohatier, C.; Deratani, A.

    2015-07-01

    Fabrication of fouling resistant UF membranes requires the use of hydrophilic polymer additives that must be trapped in the polymer matrix during the phase separation processing. The knowledge of the polymeric additive distribution across the whole thickness should help to the design of more efficient membranes. This paper aims at developing a new methodology based on Raman microscopy spectroscopy owing to its high spatial resolution. A UF hollow fiber made from a blend of PVDF as polymer matrix and PVP as additive was chosen as a model membrane for this study. The PVP concentration profile along the cross-section radial axis was determined by using two ways of spectrum treatment including the analytical method by the peak intensity ratio calculation and a multivariate analysis with a partial least-squares regression model. The feasibility of the two approaches was discussed.

  11. Study of the Melting Latent Heat of Semicrystalline PVDF applied to High Gamma Dose Dosimetry

    SciTech Connect

    Batista, Adriana S.M.; Gual, Maritza R.; Faria, Luiz O.; Lima, Claubia P.B.

    2015-07-01

    Poly(vinylidene fluoride) homopolymers [PVDF] homopolymers were irradiated with gamma doses ranging from 0.5 to 2.75 MGy. Differential scanning calorimetry (DSC) and FTIR spectrometry were used in order to study the effects of gamma radiation in the amorphous and crystalline polymer structures. The FTIR data revealed absorption bands at 1730 and 1853 cm{sup -1} which were attributed to the stretch of C=O bonds, at 1715 and 1754 cm{sup -1} which were attributed to the C=C stretching and at 3518, 3585 and 3673 cm{sup -1} which were associated with NH stretch of NH{sub 2} and OH. The melting latent heat (LM) measured by DSC was used to construct an unambiguous relationship with the delivered dose. Regression analyses revealed that the best mathematical function that fits the experimental calibration curve is a 4-degree polynomial function, with an adjusted Rsquare of 0.99817. (authors)

  12. Polarization-electric field hysteresis of ferroelectric PVDF films: comparison of different measurement regimes.

    PubMed

    Wegener, Michael

    2008-10-01

    Polarization-electric field hysteresis is an important property of ferroelectric materials. Different experimental procedures and measurement regimes are demonstrated and frequently used in order to determine this hysteresis behavior. For the characterization of the poling behavior of ferroelectric polymers it is common to analyze the poling current and separate current contributions, which are based on charging the sample capacitance as well as on conductivity. Experimentally this can be realized with two different measurement regimes, either poling of the sample with bipolar cycles or with a sequence of bipolar and unipolar cycles of the applied electric field. Here, we demonstrate the comparison of both measurement routines by performing poling experiments on the same ferroelectric PVDF sample.

  13. Multifunctional Nanofibers Comprised of Conducting and Ferroelectric Polymer Composites

    DTIC Science & Technology

    2015-08-04

    Structure characterization and stress shearing effects on the organic ferroelectric polymer P(VDF-TrFE)” (2012) 3) F. Wong, D. Colon, G. Perez, M...Bonilla and L.G. Rosa, “Band bending on polymer blens of the organic semiconducting polymer P3HT and the organic ferroelectric” (2012). 4) A. Rosado...Fabrication of the Ferroelectric Polymer PVDF Thin Films by AFM Rosette Gonzalez.  Stress Shearing Effects on the Polarization of the Organic

  14. Self-assembled structures of 1,3:2,4-di(3,4-dimethylbenzylidene) sorbitol in hydrophobic polymer matrices prepared using different heat treatments

    NASA Astrophysics Data System (ADS)

    Lai, Wei-Chi; Tseng, Shen-Jhen; Huang, Po-Hsun

    2015-11-01

    We report a method for tuning the nanoarchitectures of 1,3:2,4-di(3,4-dimethylbenzylidene) sorbitol (DMDBS) with poly(vinylidene fluoride) (PVDF) polymer matrices. Hydrophobic PVDF facilitated the formation of nanofibrils during heating. The self-assembly behaviors of DMDBS were further tuned by altering the different heat treatments. When the samples were prepared with a rapid heating rate (shorter annealing time), smaller amounts of melted PVDF were excluded due to the shorter time for aggregation of DMDBS, leading to larger complex structures of DMDBS and PVDF. Therefore, longer and thicker nanofibrils (around 100 nm) were observed using scanning electron microscopy. As the samples were prepared with a slow heating rate (longer annealing time), DMDBS had more time to aggregate, and therefore, larger amounts of melted PVDF were excluded. Smaller complex structures of DMDBS and PVDF caused the formation of shorter and thinner nanofibrils (around 40 nm). In addition, small-angle X-ray scattering results indicated that the longer and thicker nanofibrils were mostly excluded outside the PVDF crystalline bundles after cooling because they were too large to be easily incorporated between the PVDF crystalline lamellae. However, a large portion of the smaller and thinner nanofibrils was trapped between the crystalline lamellae after cooling due to their smaller sizes. As expected, the PVDF spherulitic morphologies were affected, but the PVDF crystalline microstructures were not significantly altered by the addition of DMDBS, as shown by the results from polarized optical microscopy and Fourier transform infrared spectroscopy.

  15. Performance of electric double layer capacitors with polymer gel electrolytes

    SciTech Connect

    Ishikawa, Masashi; Kishino, Takahiro; Katada, Naoji; Morita, Masayuki

    2000-07-01

    Polymer gel electrolytes consisting of poly(vinylidene fluoride) (PVdF), tetraethylammonium tetrafluoroborate (TEABF{sub 4}), and propylene carbonate (PC) as a plasticizer have been investigated for electric double layer capacitors. The PVdF gel electrolytes showed high ionic conductivity (ca. 6 mS/cm at 298 K). To assemble model capacitors with the PVdF gel electrolytes and activated carbon fiber cloth electrodes, a pair of the fixed electrodes was soaked in a precursor solution containing PC, PVdF, and TEABF{sub 4}, followed by evaporation of the PC solvent in a vacuum oven. The resulting gel electrolytes were in good contact with the electrodes. The model capacitors with the PVdF gel electrolytes showed a large value of capacitance and high coulombic efficiency in operation voltage ranges of 1--2 and 1--3 V. It is worth noting that the capacitors with the PVdF electrolytes showed long voltage retention in a self-discharge test. These good characteristics of the gel capacitors were comparable to those of typical double layer capacitors with a liquid organic electrolyte containing PC and TEABF{sub 4}; rather, the voltage retentivity of the PVdF gel capacitors was much superior to that of the capacitors with the organic electrolyte.

  16. Structural changes in PVDF fibers due to electrospinning and its effect on biological function.

    PubMed

    Damaraju, Sita M; Wu, Siliang; Jaffe, Michael; Arinzeh, Treena Livingston

    2013-08-01

    Polyvinylidine fluoride (PVDF) is being investigated as a potential scaffold for bone tissue engineering because of its proven biocompatibility and piezoelectric property, wherein it can generate electrical activity when mechanically deformed. In this study, PVDF scaffolds were prepared by electrospinning using different voltages (12-30 kV), evaluated for the presence of the piezoelectric β-crystal phase and its effect on biological function. Electrospun PVDF was compared with unprocessed/raw PVDF, films and melt-spun fibers for the presence of the piezoelectric β-phase using differential scanning calorimetry, Fourier transform infrared spectroscopy and x-ray diffraction. The osteogenic differentiation of human mesenchymal stem cells (MSCs) was evaluated on scaffolds electrospun at 12 and 25 kV (PVDF-12 kV and PVDF-25 kV, respectively) and compared to tissue culture polystyrene (TCP). Electrospinning PVDF resulted in the formation of the piezoelectric β-phase with the highest β-phase fraction of 72% for electrospun PVDF at 25 kV. MSCs cultured on both the scaffolds were well attached as indicated by a spread morphology. Cells on PVDF-25 kV scaffolds had the greatest alkaline phosphatase activity and early mineralization by day 10 as compared to TCP and PVDF-12 kV. The results demonstrate the potential for the use of PVDF scaffolds for bone tissue engineering applications.

  17. High Dielectric and Mechanical Properties Achieved in Cross-Linked PVDF/α-SiC Nanocomposites with Elevated Compatibility and Induced Polarization at the Interface.

    PubMed

    Feng, Yefeng; Miao, Bei; Gong, Honghong; Xie, Yunchuan; Wei, Xiaoyong; Zhang, Zhicheng

    2016-07-27

    Remarkably improved dielectric properties including high-k, low loss, and high breakdown strength combined with promising mechanical performance such as high flexibility, good heat, and chemical resistivity are hard to be achieved in high-k dielectric composites based on the current composite fabrication strategy. In this work, a family of high-k polymer nanocomposites has been fabricated from a facile suspension cast process followed by chemical cross-linking at elevated temperature. Internal double bonds bearing poly(vinylidene fluoride-chlorotrifluoroethylene) (P(VDF-CTFE-DB)) in total amorphous phase are employed as cross-linkable polymer matrix. α-SiC particles with a diameter of 500 nm are surface modified with 3-aminpropyltriethoxysilane (KH-550) as fillers for their comparable dielectric performance with PVDF polymer matrix, low conductivity, and high breakdown strength. The interface between SiC particles and PVDF matrix has been finely tailored, which leads to the significantly elevated dielectric constant from 10 to over 120 in SiC particles due to the strong induced polarization. As a result, a remarkably improved dielectric constant (ca. 70) has been observed in c-PVDF/m-SiC composites bearing 36 vol % SiC, which could be perfectly predicted by the effective medium approximation (EMA) model. The optimized interface and enhanced compatibility between two components are also responsible for the depressed conductivity and dielectric loss in the resultant composites. Chemical cross-linking constructed in the composites results in promising mechanical flexibility, good heat and chemical stability, and elevated tensile performance of the composites. Therefore, excellent dielectric and mechanical properties are finely balanced in the PVDF/α-SiC composites. This work might provide a facile and effective strategy to fabricate high-k dielectric composites with promising comprehensive performance.

  18. Poling of PVDF matrix composites for integrated structural load sensing

    NASA Astrophysics Data System (ADS)

    Haghiashtiani, Ghazaleh; Greminger, Michael A.; Zhao, Ping

    2014-03-01

    The purpose of this study is to create and evaluate a smart composite structure that can be used for integrated load sensing and structural health monitoring. In this structure, PVDF films are used as the matrix material instead of epoxy resin or other thermoplastics. The reinforcements are two layers of carbon fiber with one layer of Kevlar separating them. Due to the electrical conductivity properties of carbon fiber and the dielectric effect of Kevlar, the structure acts as a capacitor. Furthermore, the piezoelectric properties of the PVDF matrix can be used to monitor the response of the structure under applied loads. In order to exploit the piezoelectric properties of PVDF, the PVDF material must be polarized to align the dipole moments of its crystalline structure. The optimal condition for poling the structure was found by performing a 23 factorial design of experiment (DoE). The factors that were studied in DoE were temperature, voltage, and duration of poling. Finally, the response of the poled structure was monitored by exposing the samples to an applied load.

  19. Improving Dielectric Properties of PVDF Composites by Employing Surface Modified Strong Polarized BaTiO₃ Particles Derived by Molten Salt Method.

    PubMed

    Fu, Jing; Hou, Yudong; Zheng, Mupeng; Wei, Qiaoyi; Zhu, Mankang; Yan, Hui

    2015-11-11

    BaTiO3/polyvinylidene fluoride (BT/PVDF) is the extensive reported composite material for application in modern electric devices. However, there still exists some obstacles prohibiting the further improvement of dielectric performance, such as poor interfacial compatibility and low dielectric constant. Therefore, in depth study of the size dependent polarization and surface modification of BT particle is of technological importance in developing high performance BT/PVDF composites. Here, a facile molten-salt synthetic method has been applied to prepare different grain sized BT particles through tailoring the calcination temperature. The size dependent spontaneous polarizationof BT particle was thoroughly investigated by theoretical calculation based on powder X-ray diffraction Rietveld refinement data. The results revealed that 600 nm sized BT particles possess the strong polarization, ascribing to the ferroelectric size effect. Furthermore, the surface of optimal BT particles has been modified by water-soluble polyvinylprrolidone (PVP) agent, and the coated particles exhibited fine core-shell structure and homogeneous dispersion in the PVDF matrix. The dielectric constant of the resulted composites increased significantly, especially, the prepared composite with 40 vol % BT loading exhibited the largest dielectric constant (65, 25 °C, 1 kHz) compared with the literature values of BT/PVDF at the same concentration of filler. Moreover, the energy storage density of the composites with tailored structure was largely enhanced at the low electric field, showing promising application as dielectric material in energy storage device. Our work suggested that introduction of strong polarized ferroelectric particles with optimal size and construction of core-shell structured coated fillers by PVP in the PVDF matrix are efficacious in improving dielectric performance of composites. The demonstrated approach can also be applied to the design and preparation of other polymers

  20. Surface self-assembled PEGylation of fluoro-based PVDF membranes via hydrophobic-driven copolymer anchoring for ultra-stable biofouling resistance.

    PubMed

    Lin, Nien-Jung; Yang, Hui-Shan; Chang, Yung; Tung, Kuo-Lun; Chen, Wei-Hao; Cheng, Hui-Wen; Hsiao, Sheng-Wen; Aimar, Pierre; Yamamoto, Kazuo; Lai, Juin-Yih

    2013-08-13

    Stable biofouling resistance is significant for general filtration requirements, especially for the improvement of membrane lifetime. A systematic group of hyper-brush PEGylated diblock copolymers containing poly(ethylene glycol) methacrylate (PEGMA) and polystyrene (PS) was synthesized using an atom transfer radical polymerization (ATRP) method and varying PEGMA lengths. This study demonstrates the antibiofouling membrane surfaces by self-assembled anchoring PEGylated diblock copolymers of PS-b-PEGMA on the microporous poly(vinylidene fluoride) (PVDF) membrane. Two types of copolymers are used to modify the PVDF surface, one with different PS/PEGMA molar ratios in a range from 0.3 to 2.7 but the same PS molecular weights (MWs, ∼5.7 kDa), the other with different copolymer MWs (∼11.4, 19.9, and 34.1 kDa) but the similar PS/PEGMA ratio (∼1.7 ± 0.2). It was found that the adsorption capacities of diblock copolymers on PVDF membranes decreased as molar mass ratios of PS/PEGMA ratio reduced or molecular weights of PS-b-PEGMA increased because of steric hindrance. The increase in styrene content in copolymer enhanced the stability of polymer anchoring on the membrane, and the increase in PEGMA content enhanced the protein resistance of membranes. The optimum PS/PEGMA ratio was found to be in the range between 1.5 and 2.0 with copolymer MWs above 20.0 kDa for the ultrastable resistance of protein adsorption on the PEGylated PVDF membranes. The PVDF membrane coated with such a diblock copolymer owned excellent biofouling resistance to proteins of BSA and lysozyme as well as bacterium of Escherichia coli and Staphylococcus epidermidis and high stable microfiltration operated with domestic wastewater solution in a membrane bioreactor.

  1. The double effects of silver nanoparticles on the PVDF membrane: Surface hydrophilicity and antifouling performance

    NASA Astrophysics Data System (ADS)

    Li, Jian-Hua; Shao, Xi-Sheng; Zhou, Qing; Li, Mi-Zi; Zhang, Qi-Qing

    2013-01-01

    In this study, silver nanoparticles were used to endow poly(vinylidene fluoride) (PVDF) membrane with excellent surface hydrophilicity and outstanding antifouling performance. Silver nanoparticles were successfully immobilized onto PVDF membrane surface under the presence of poly(acrylic acid) (PAA). The double effects of silver nanoparticles on PVDF membrane, i.e., surface hydrophilicity and anti-fouling performance, were systematically investigated. Judging from result of water static contact measurement, silver nanoparticles had provided a significant improvement in PVDF membrane surface hydrophilicity. And the possible explanation on the improvement of PVDF membrane surface hydrophilicity with silver nanoparticles was firstly proposed in this study. Membrane permeation and anti-bacterial tests were carried out to characterize the antifouling performance of PVDF membrane. Flux recovery ratio (FRR) increased about 40% after the presence of silver nanoparticles on the PVDF membrane surface, elucidating the anti-organic fouling performance of PVDF membrane was elevated by silver nanoparticles. Simultaneously, anti-bacterial test confirmed that PVDF membrane showed superior anti-biofouling activity because of silver nanoparticles. The above-mentioned results clarified that silver nanoparticles can endow PVDF membrane with both excellent surface hydrophilicity and outstanding antifouling performance in this study.

  2. PVDF-based copolymers, terpolymers and their multi-component material systems for capacitor applications

    NASA Astrophysics Data System (ADS)

    Chu, Baojin

    Miniature of power electronics, scaling-down of microelectronics and other electrical and electronic systems, and development of many technologies (such as hybrid vehicles or implantable heart defibrillators) require capacitors with high energy density to improve the weight and volume efficiency of the whole system. Various capacitor technologies are investigated to meet the requirements of developing future technologies. Among these technologies, polymer film capacitor technology is one of the most promising. Besides high energy density, polymer-based capacitors possess the merits of high power density, low loss, high reliability (self-healing), easy processing, and feasibility (in size, shape and energy level). Due to the ferroelectricity of polyvinylidene fluoride (PVDF)-based polymers, they exhibit much higher polarization response under an electric field, in comparison with other linear dielectric polymers for capacitor applications. The maximum polarization level of PVDF-based polymers can be as high as 0.1 C/m2 and the breakdown field can be higher than 600 MV/m. An estimated energy density of around 30 J/cm3 can be expected in this class of materials. However, this value is much higher than the energy density that can be achieved in the PVDF homopolymer and the poly(vinylidene fluoride-trifluoroethylene) (P(VDF-TrFE)) copolymers due to the polarization hysteresis in these polymers. Therefore, in this thesis, PVDF-based polymer materials were investigated and developed to approach this expected energy density by various strategies. An energy density of higher than 24 J/cm 3, which is close to the predicted value, was found in PVDF-based copolymers. Recently, the poly(vinylidene fluoride-trifluoroethylene-chlorofluoroethylene) (P(VDF-TrFE-CFE)) terpolymer was developed in Prof. Qiming Zhang's group. Previous works have shown that incorporation of CTE into P(VDF-TrFE) copolymers, in which bulky CFE acts as a defect, could convert the copolymer into relaxor

  3. Local probing of magnetoelectric properties of PVDF/Fe3O4 electrospun nanofibers by piezoresponse force microscopy.

    PubMed

    Zheng, Tian; Yue, Zhilian; Wallace, Gordon G; Du, Yi; Martins, Pedro; Lanceros-Mendez, Senentxu; Higgins, Michael J

    2017-02-10

    The coupling of magnetic and electric properties in polymer-based magnetoelectric composites offers new opportunities to develop contactless electrodes, effectively without electrical connections, for less-invasive integration into devices such as energy harvesters, sensors, wearable and implantable electrodes. Understanding the macroscale-to-nanoscale conversion of the properties is important, as nanostructured and nanoscale magnetoelectric structures are increasingly fabricated. However, whilst the magnetoelectric effect at the macroscale is well established both theoretically and experimentally, it remains unclear how this effect translates to the nanoscale, or vice versa. Here, PVDF/Fe3O4 polymer-based composite nanofibers are fabricated using electrospinning to investigate their piezoelectric and magnetoelectric properties at the single nanofiber level.

  4. Local probing of magnetoelectric properties of PVDF/Fe3O4 electrospun nanofibers by piezoresponse force microscopy

    NASA Astrophysics Data System (ADS)

    Zheng, Tian; Yue, Zhilian; Wallace, Gordon G.; Du, Yi; Martins, Pedro; Lanceros-Mendez, Senentxu; Higgins, Michael J.

    2017-02-01

    The coupling of magnetic and electric properties in polymer-based magnetoelectric composites offers new opportunities to develop contactless electrodes, effectively without electrical connections, for less-invasive integration into devices such as energy harvesters, sensors, wearable and implantable electrodes. Understanding the macroscale-to-nanoscale conversion of the properties is important, as nanostructured and nanoscale magnetoelectric structures are increasingly fabricated. However, whilst the magnetoelectric effect at the macroscale is well established both theoretically and experimentally, it remains unclear how this effect translates to the nanoscale, or vice versa. Here, PVDF/Fe3O4 polymer-based composite nanofibers are fabricated using electrospinning to investigate their piezoelectric and magnetoelectric properties at the single nanofiber level.

  5. Effect of non-solvent additives on the morphology, pore structure, and direct contact membrane distillation performance of PVDF-CTFE hydrophobic membranes.

    PubMed

    Zheng, Libing; Wu, Zhenjun; Zhang, Yong; Wei, Yuansong; Wang, Jun

    2016-07-01

    Four common types of additives for polymer membrane preparation including organic macromolecule and micromolecule additives, inorganic salts and acids, and the strong non-solvent H2O were used to prepare poly (vinylidene fluoride-co-chlorotrifluoroethylene) (PVDF-CTFE) hydrophobic flat-sheet membranes. Membrane properties including morphology, porosity, hydrophobicity, pore size and pore distribution were investigated, and the permeability was evaluated via direct contact membrane distillation (DCMD) of 3.5g/L NaCl solution in a DCMD configuration. Both inorganic and organic micromolecule additives were found to slightly influence membrane hydrophobicity. Polyethylene glycol (PEG), organic acids, LiCl, MgCl2, and LiCl/H2O mixtures were proved to be effective additives to PVDF-CTFE membranes due to their pore-controlling effects and the capacity to improve the properties and performance of the resultant membranes. The occurrence of a pre-gelation process showed that when organic and inorganic micromolecules were added to PVDF-CTFE solution, the resultant membranes presented a high interconnectivity structure. The membrane prepared with dibutyl phthalate (DBP) showed a nonporous surface and symmetrical cross-section. When H2O and LiCl/H2O mixtures were also used as additives, they were beneficial for solid-liquid demixing, especially when LiCl/H2O mixed additives were used. The membrane prepared with 5% LiCl+2% H2O achieved a flux of 24.53kg/(m(2)·hr) with 99.98% salt rejection. This study is expected to offer a reference not only for PVDF-CTFE membrane preparation but also for other polymer membranes.

  6. Investigating the effect of electro-active ion concentration on spectral induced polarization signatures arising from biomineralization pathways

    NASA Astrophysics Data System (ADS)

    Ntarlagiannis, D.; Slater, L. D.; Williams, K. H.; Hubbard, S. S.; Wu, Y.

    2010-12-01

    Spectral induced polarization (SIP) is a proven geophysical method for detecting biomineral formation with promising applications for monitoring biogeochemical products during microbial induced sequestration of heavy metals and radionuclides in soils. SIP has been used to monitor the evolution of bioremediation-induced end-products at the uranium-contaminated U.S. Department of Energy Rifle Integrated Field Research Challenge site in Colorado. Although a significant SIP response was detected, the quantitative interpretation is non-trivial as the polarization of metallic minerals depends both on the mineral surface properties and the electrolyte chemistry. In previous experiments SIP mechanisms were studied under complex environments and individual source mechanisms could not be evaluated. Here we examine the role of electrolyte chemistry by comparing the effect of redox active / inactive ions on metallic polarization. In these abiotic experiments magnetite was used as a proxy biomineral and dispersed within columns packed with sand. Parallel columns were saturated with solutions of different concentrations of active (Fe2+) and inactive (Ca2+) ions (0.01mM-10mM) and SIP measurements made (0.1-1000 Hz). Experimental results show small, but detectable, differences in the effect of active ion and inactive ion concentration on the SIP response. To better characterize the effect of electro-active ions on metallic minerals we used a Cole - Cole type relaxation model, to describe the SIP responses. In order to better resolve the relaxation model parameters, we followed a two-step approach whereby we started with a Bayesian based inversion to resolve for the initial parameter estimates, and subsequently used these estimates as a starting model for a deterministic solution. Our results suggest that changes in the active ion concentration, in the presence of magnetite, alone are unlikely to fully explain recent SIP monitoring data from the Rifle site.

  7. Response of the polymers KEL-F, polysulfone, high density polyethylene and polymethylmethacrylate to shock loading and release from 0. 3 to 2. 4 GPa

    SciTech Connect

    Anderson, M.U.

    1991-01-01

    The Bauer PVDF stress-rate gauge has been used to study the response of the cited polymers from measurements at the impact surface and in-situ'' at sample thicknesses of 1.5 and 3 mm. The PVDF stress- rate dependent piezoelectric output combined with appropriate signal recording techniques allow accurate recording over the broad range of stress rates encountered during shock compression of polymers. Strong viscous response effects are observed. The release velocity is found to increase strongly with pressure, and the release-rate history is recorded with PVDF as a continuous function of pressure. 12 refs., 4 figs., 1 tab.

  8. Models for 31-Mode PVDF Energy Harvester for Wearable Applications

    PubMed Central

    Zhao, Jingjing; You, Zheng

    2014-01-01

    Currently, wearable electronics are increasingly widely used, leading to an increasing need of portable power supply. As a clean and renewable power source, piezoelectric energy harvester can transfer mechanical energy into electric energy directly, and the energy harvester based on polyvinylidene difluoride (PVDF) operating in 31-mode is appropriate to harvest energy from human motion. This paper established a series of theoretical models to predict the performance of 31-mode PVDF energy harvester. Among them, the energy storage one can predict the collected energy accurately during the operation of the harvester. Based on theoretical study and experiments investigation, two approaches to improve the energy harvesting performance have been found. Furthermore, experiment results demonstrate the high accuracies of the models, which are better than 95%. PMID:25114981

  9. Piezoelectric and dielectric properties of nanoporous polyvinylidence fluoride (PVDF) films

    NASA Astrophysics Data System (ADS)

    Zhao, Ping; Wang, Shifa; Kadlec, Alec

    2016-04-01

    A nanoporous polyvinylidene Fluoride (PVDF) thin film was developed for applications in energy harvesting, medical surgeries, and industrial robotics. This sponge-like nanoporous PVDF structure dramatically enhanced the piezoelectric effect because it yielded considerably large deformation under a small force. A casting-etching method was adopted to make films, which is effective to control the porosity, flexibility, and thickness of the film. The films with various Zinc Oxide (ZnO) mass fractions ranging from 10 to 50% were fabricated to investigate the porosity effect. The piezoelectric coefficient d33 as well as dielectric constant and loss of the films were characterized. The results were analyzed and the optimal design of the film with the right amount of ZnO nanoparticles was determined.

  10. The immobilization of lipase on PVDF-co-HFP membrane

    NASA Astrophysics Data System (ADS)

    Kayhan, Naciye; Eyüpoǧlu, Volkan; Adem, Şevki

    2016-04-01

    Lipase is an enzyme having a lot of different industrial applications such as biodiesel production, biopolymer synthesis, enantiopure pharmaceutical productions, agrochemicals, etc. Its immobilized form on different substances is more conventional and useful than its free form. Supporting material was prepared using PVDF-co-HFP in laboratory conditions and attached 1,4-diaminobutane (DA) and epichlorohydrin (EPI) ligands to the membrane to immobilize lipase enzyme. The immobilization conditions such as enzyme amount, pH, the concentration of salt, thermal stability and activity were stabilized for our experimental setup. Then, biochemical characterizations were performed on immobilized lipase PVDF-co-HFP regarding optimal pH activity, temperature and thermal stability. Also, the desorption ratios of immobilized enzyme in two different pathway were investigated to confirm immobilization stability for 24 hours.

  11. Impedance characteristics of nanoparticle-LiCoO{sub 2}+PVDF

    SciTech Connect

    Panjaitan, Elman Kartini, Evvy Honggowiranto, Wagiyo

    2016-02-08

    The impendance of np-LiCoO{sub 2}+xPVDF, as a cathode material candidate for lithium-ion battery (LIB), has been characterized using impedance spectroscopy for x = 0, 5, 10, 15 and 20 volume percentage (%v/v) and for frequencies in the 42 Hz to 5 MHz range. Both real and imaginary components of the impedance were found to be frequency dependent, and both tend to increase for increasing PVDF (polyvinyilidene fluoride) concentration, except that for 10% PVDF both real and imaginary components of impedance are smaller than for 5%. The mechanism for relaxation time for each addition of PVDF was analyzed using Cole-Cole plots. The analysis showed that the relaxation times of the nanostructured LiCoO{sub 2} with PVDF additive is relatively constant. Further, PVDF addition increases the bulk resistance and decreases the bulk capacitance of the nanostructured LiCoO{sub 2}.

  12. Elastic properties of poly(vinyldene fluoride) (PVDF) crystals: A density functional theory study

    NASA Astrophysics Data System (ADS)

    Pei, Yong; Zeng, Xiao Cheng

    2011-05-01

    We computed structural and elastic properties of totally nine phases of poly(vinyldene fluoride) (PVDF) crystals using the density-functional theory (DFT) method with and without inclusion of the dispersion corrections. In addition to the four known crystalline forms, mechanic properties of five theoretically predicted crystalline forms of PVDF are also investigated. The all-trans form Ip exhibits the largest cohesive energy, bulk, and Young's modulus among the nine crystalline forms. The DFT calculations suggest that the δ crystalline forms (IIIau, IIIpu, IIIpd, and IIIad) possess poor chain rigidity among the nine PVDF crystalline forms. In contrast, a change of relative orientation of PVDF chains does not lead to significant change in cohesive energy and mechanic properties. A comparison of the cohesive energies of nine crystalline forms of PVDF suggests that the theoretically proposed crystalline forms of PVDF are quite stable.

  13. Laparoscopic Repair of Morgagni Hernia Using Polyvinylidene Fluoride (PVDF) Mesh.

    PubMed

    Godazandeh, Gholamali; Mortazian, Meysam

    2012-10-01

    We report the cases of two patients diagnosed with Morgagni hernia who presented with nonspecific abdominal symptoms. Both underwent laparoscopic surgery that used a dual-sided mesh, polyvinylidene fluoride (PVDF; Dynamesh IPOM®). The procedures were successful and both patients were discharged with no complications. There was no recurrence in 18 months of follow up.Herein is the report of these cases and a literature review.

  14. Laparoscopic Repair of Morgagni Hernia Using Polyvinylidene Fluoride (PVDF) Mesh

    PubMed Central

    Godazandeh, Gholamali; Mortazian, Meysam

    2012-01-01

    We report the cases of two patients diagnosed with Morgagni hernia who presented with nonspecific abdominal symptoms. Both underwent laparoscopic surgery that used a dual-sided mesh, polyvinylidene fluoride (PVDF; Dynamesh IPOM®). The procedures were successful and both patients were discharged with no complications. There was no recurrence in 18 months of follow up.Herein is the report of these cases and a literature review. PMID:24829663

  15. A PVDF transducer for low-frequency acceleration measurements.

    PubMed

    Daku, Brian L F; Mohamed, Enas M A; Prugger, Arnfinn F

    2004-07-01

    A unique acceleration transducer, using piezoelectric PVDF, has been developed for low-frequency vibration monitoring. The paper develops the theoretical model for this low-cost, robust sensor. The theoretical model is validated using experimental results from laboratory tests. The sensor was also installed in an underground potash mine alongside a commercial geophone for a three-month in-mine test producing results that show a close correspondence between the two transducers.

  16. Piezoelectric PU/PVDF electrospun scaffolds for wound healing applications.

    PubMed

    Guo, Hong-Feng; Li, Zhen-Sheng; Dong, Shi-Wu; Chen, Wei-Jun; Deng, Ling; Wang, Yu-Fei; Ying, Da-Jun

    2012-08-01

    Previous studies have shown that piezoelectric materials may be used to prepare bioactive electrically charged surfaces. In the current study, polyurethane/polyvinylidene fluoride (PU/PVDF) scaffolds were prepared by electrospinning. The mechanical property and piezoelectric property of the scaffolds were evaluated. The crystalline phase of PVDF in the scaffolds was characterised by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and differential scanning calorimetry (DSC). In vitro cell culture was performed to investigate cytocompatibility of the scaffolds. Wound-healing assay, cell-adhesion assay, quantitative RT-PCR and Western blot analyses were performed to investigate piezoelectric effect of the scaffolds on fibroblast activities. Further, the scaffolds were subcutaneously implanted in Sprague-Dawley (SD) rats to investigate their biocompatibility and the piezoelectric effect on fibrosis in vivo. The results indicated that the electrospinning process had changed PVDF crystalline phase from the nonpiezoelectric α phase to the piezoelectric β phase. The fibroblasts cultured on the scaffolds showed normal morphology and proliferation. The fibroblasts cultured on the piezoelectric-excited scaffolds showed enhanced migration, adhesion and secretion. The scaffolds that were subcutaneously implanted in SD rats showed higher fibrosis level due to the piezoelectrical stimulation, which was caused by random animal movements followed by mechanical deformation of the scaffolds. The scaffolds are potential candidates for wound healing applications.

  17. Feasibility of a PVDF Receiver for Monitoring of Transcranial Therapy

    NASA Astrophysics Data System (ADS)

    O'Reilly, Meaghan A.; Hynynen, Kullervo

    2010-03-01

    An MRI compatible PVDF receiver was designed and manufactured for integration into a transcranial therapy array. 4.8 mm diameter, 110 μm thick PVDF film was air-backed by clamping it across brass tubing. A preamplifier was enclosed within the tubing to improve SNR and drive the long coaxial cables required to reach outside the MRI. The receiver was mounted inside a ring element from an existing array. The receiver performance was compared with a commercial needle hydrophone and tested for MRI compatibility. The PVDF receiver displayed a higher sensitivity than the needle hydrophone and a better capability to reject electrical coupling with the transmit element. MRI image artifacts created by the device were small, and diagnostic ultrasound was possible with the device while simultaneously obtaining an MRI image. Microbubble contrast agent was sonicated both directly, and through a fragment of human skull. The transmit/receive pair was successful in sonicating the microbubbles transcranially and detecting the returning microbubble emissions. A second generation receiver with a diameter of 2.4 mm was manufactured, without sacrificing sensitivity, to increase the field of view of the device. Future work will focus on developing a multi-element receiver array and its testing for brain treatment monitoring.

  18. The preparation of γ-crystalline non-electrically poled photoluminescant ZnO-PVDF nanocomposite film for wearable nanogenerators

    NASA Astrophysics Data System (ADS)

    Jana, Santanu; Garain, Samiran; Ghosh, Sujoy Kumar; Sen, Shrabanee; Mandal, Dipankar

    2016-11-01

    Polyvinylidene fluoride (PVDF) films are filled with various mass fractions (wt%) of zinc oxide nanoparticles (ZnO-NPs) to fabricate the high performance of a wearable polymer composite nanogenerator (PCNG). The ZnO-NPs can induced a fully γ-crystalline phase in PVDF, where traditional electrical poling is not necessary for the generation of piezoelectric properties. The PCNG delivers up to 28 V of open circuit voltage and 450 nA of short circuit current by simple repeated human finger imparting (under a pressure amplitude of 8.43 kPa) that generates sufficient power to turn on at least 48 commercial blue light emitting diodes (LEDs) instantly. Furthermore, it also successfully charged the capacitors, signifying practical applicability as a piezoelectric based nanogenerator for self-powering devices. The applicability of PCNG by wearable means is clarified when it gives rise to a sensible response, say up to 400 mV of output voltage synchronized with the PCNG embedded human finger in a bending and releasing gesture. UV-visible absorption spectral analysis revealed the possibility of estimating a change in the optical band gap value (E g), refractive index (n) and optical activation energy (E a) in different concentrations of ZnO-NP incorporated PVDF nanocomposite films, and it possesses a useful methodology where ZnO-NPs can be used as an optical probe. Near blue light emission is observed from photoluminescence spectra, which are clearly shown from a Commission Internationale de L’Eclairage (CIE) diagram. The piezoelectric charge coefficient of the nanocomposite film is estimated to be -6.4 pC/N, where even electrical poling treatment is not employed. In addition, dielectric properties have been studied to understand the role of molecular kinetic and interfacial polarization occurring in nanocomposite films at different applied frequencies.

  19. Aniosotropically organized LDH on PVDF: a geometrically templated electrospun substrate for advanced anion conducting membranes.

    PubMed

    Sailaja, G S; Zhang, Peilin; Anilkumar, Gopinathan M; Yamaguchi, Takeo

    2015-04-01

    A bioinspired geometric templating of an electrospun PVDF substrate with hexagonal platelets of Mg-Al layered double hydroxide (LDH), an intrinsic anion conductor, is presented. The distinctive morphology restructures the internal pore geometry and modulates the dynamic wetting profile of PVDF, transforming it into a highly functional substrate for SAFC anion conducting membranes. The membrane fabricated with PVDF-LDH substrate exhibited exceptionally high durability (>140 °C), high anionic conductivity, ion exchange capacity (IEC), restricted swelling, and improved tensile strength, overcoming critical challenges associated with PVDF electrospun substrates and validating its immense potential as a high-temperature-stable and durable substrate for advanced fuel cell membrane applications.

  20. Improved drug delivery properties of PVDF membranes functionalized with beta-cyclodextrin--application to guided tissue regeneration in periodontology.

    PubMed

    Boschin, F; Blanchemain, N; Bria, M; Delcourt-Debruyne, E; Morcellet, M; Hildebrand, H F; Martel, B

    2006-10-01

    The purpose of this study was to develop a membrane for guided tissue regeneration applicable in periodontology that could release antimicrobial agent during the healing period. Our strategy consisted to graft beta-cyclodextrin (beta-CD), a molecule that is known to form inclusion complexes with a large variety of drugs, onto PVDF membranes. Grafting occurred by using citric acid that provoked a crosslinking reaction of beta-CD, and the resulting polymer was imprisoned into the porous structure of the PVDF membrane. The reaction produced a weight increase of the membrane, the range of which depended on the temperature and on the time of curing applied in the process. The biological behavior of the membranes evaluated by proliferation and vitality tests showed good proliferation and improved activity of L132 epithelial cells on the raw and on the grafted membranes. Doxycyclin (DOX) and chlorhexidine (CHX) were used as antimicrobial agents. Their inclusion into the beta-CD cavity in aqueous solutions was confirmed by NMR spectroscopy. After the impregnation of the membranes with DOX and CHX, their release was studied in vitro in batch type experiments and measured by UV spectrophotometry. Low amounts of DOX and CHX were delivered from the raw membranes within the first few hours of tests. Grafted membranes, however, delivered DOX and CHX in larger quantities within 24 h and 10 days respectively.

  1. Temperature dependent structural, elastic, and polar properties of ferroelectric polyvinylidene fluoride (PVDF) and trifluoroethylene (TrFE) copolymers

    NASA Astrophysics Data System (ADS)

    Sun, Fu-Chang; Dongare, Avinash; Asandei, Alexandru; Alpay, Pamir; Nakhmanson, Serge; University of Connecticut Team

    We use molecular dynamics to calculate the structural, elastic, and polar properties of crystalline ferroelectric β-poly(vinylidene fluoride), PVDF (-CH2-CF2-)n with randomized trifluoroethylene TrFE (-CHF-CF2-)n as a function of TrFE content (0-50%) in the temperature range of 0-400 K. There is a very good agreement between the experimentally obtained and the computed values of the lattice parameters, thermal expansion coefficients, elastic constants, polarization, and pyroelectric coefficients. A continuous decrease in Young's modulus with increasing TrFE content was observed and attributed to the increased intramolecular and intermolecular repulsive interactions between fluorine atoms. The computed polarization displayed a similar trend, with the room temperature spontaneous polarization decreasing by 44% from 13.8 μC/cm2 (pure PVDF) to 7.7 μC/cm2 [50/50 poly(VDF-co-TrFE)]. Our results show that molecular dynamics can be used as a practical tool to predict the mechanical and polarization-related behavior of ferroelectric poly(VDF-co-TrFE). Such an atomistic model can thus serve as a guide for practical applications of this important multifunctional polymer.

  2. Poly(4-vinyl pyridine) radiografted PVDF track etched membranes as sensors for monitoring trace mercury in water

    NASA Astrophysics Data System (ADS)

    Bessbousse, H.; Zran, N.; Fauléau, J.; Godin, B.; Lemée, V.; Wade, T.; Clochard, M.-C.

    2016-01-01

    By a radiation-induced grafting technique, we have functionalized track-etched nanoporous polymer membranes with mercury sensitive poly-4-vinyl pyridine (P4VP). Coating of these membranes with a very thin layer of gold results in an electrochemical sensor that is very selective and highly sensitive for mercury LOD 5 ng/L - well below the norms for water (0.015 μg/L potable water and 0.5 μg/L residual waters-French water norms of 27 October 2011). E-beam irradiation permitted optimization of the radiografting synthesis on PVDF thin films prior to ion-track grafting. Synthesis and characterization by EPR, FESEM and FTIR are described in detail. A comparison between FTIR in ATR and transmission modes enabled us to localize the grafting on the surface of the e-beam irradiated PVDF films allowing us to extrapolate what happens on the etched tracks. Using Square Wave Anodic Stripping Voltammetry (SW-ASV), mercury concentrations of 1 μg/L are detected in 2 h and low ng/L concentrations are detected after 24 h of adsorption. The adsorption is passive so sensors do not require instrumentation and the analysis takes only 3-4 min. Also, the P4VP functionalized sensor appears insensitive to pH variations (pHs 3-9), high salt concentrations (up to 1 g/L) and the presence of other heavy metals in the same solution.

  3. Electrospun and functionalized PVDF/PAN nanocatalyst-loaded composite for dechlorination and photodegradation of pesticides in contaminated water.

    PubMed

    Nthumbi, Richard M; Ngila, Jane C

    2016-10-01

    A novel approach for the electrospinning and functionalization of nanocatalyst-loaded polyvinylidene fluoride/polyacrylonitrile (PVDF/PAN) composite grafted with acrylic acid (AA; which form polyacrylic acid (PAA) brush) and decorated with silver (Ag/PAN/PVDF-g-PAA-TiO2/Fe-Pd) designed for the dechlorination and photodegradation of pesticides was carried out. PAN was used both as a nitrogen dopant as well as a co-polymer. Smooth nanofibers were obtained by electrospinning a solution of 12:2 wt.% PVDF/PAN blend using dimethylformamide (DMF) as solvent. The nanofibers were grafted with AA by free-radical polymerization using 2,2'azobis(2-methylpropionitrile) (AIBN) as initiator. Both bimetallic iron-palladium (Fe-Pd) and titania (TiO2) nanoparticles (NP) were anchored on the grafted nanofibers via the carboxylate groups by in situ and ex situ synthesis. The Fe-Pd and nitrogen-doped TiO2 nanoparticles were subsequently used for dechlorination and oxidation of target pollutants (dieldrin, chlorpyrifos, diuron, and fipronil) to benign products. Structural and chemical characterizations of the composites were done using various techniques. These include surface area and porosity analyzer (ASAP) using the technique by Brunner Emmett Teller (BET), Fourier transform infrared (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscope (TEM) analyses were done. After dechlorination, the transformation products (TPs) for dieldrin, chlorpyrifos, diuron, and fipronil were obtained and identified using two-dimensional gas chromatography (time-of-flight) with a mass spectrometer detector (GCxGC-TOFMS). Analysis of total organic carbon (TOC) was carried out and used to extrapolate percentage mineralization. Experimental results showed that dechlorination efficiencies of 96, 93, 96, and 90 % for 1, 2, 2, and 3 h treatment period were respectively achieved for 5 ppm solutions of dieldrin, chlorpyrifos, diuron, and fipronil. The

  4. Improved surface property of PVDF membrane with amphiphilic zwitterionic copolymer as membrane additive

    NASA Astrophysics Data System (ADS)

    Li, Jian-Hua; Li, Mi-Zi; Miao, Jing; Wang, Jia-Bin; Shao, Xi-Sheng; Zhang, Qi-Qing

    2012-06-01

    An attempt to improve hydrophilicity and anti-fouling properties of PVDF membranes, a novel amphiphilic zwitterionic copolymer poly(vinylidene fluoride)-graft-poly(sulfobetaine methacrylate) (PVDF-g-PSBMA) was firstly synthesized by atom transfer radical polymerization (ATRP) and used as amphiphilic copolymer additive in the preparation of PVDF membranes. The PVDF-g-PSBMA/PVDF blend membranes were prepared by immersion precipitation process. Fourier transform infrared attenuated reflection spectroscopy (FTIR-ATR) and X-ray photoelectronic spectroscopy (XPS) measurements confirmed that PSBMA brushes from amphiphilic additives were preferentially segregated to membrane-coagulant interface during membrane formation. The morphology of membranes was characterized by scanning electron microscopy (SEM). Water contact angle measurements showed that the surface hydrophilicity of PVDF membranes was improved significantly with the increasing of amphiphilic copolymer PVDF-g-PSBMA in cast solution. Protein static adsorption experiment and dynamic fouling resistance experiment revealed that the surface enrichment of PSBMA brush endowed PVDF blend membrane great improvement of surface anti-fouling ability.

  5. Structure and properties of PVDF membrane with PES-C addition via thermally induced phase separation process

    NASA Astrophysics Data System (ADS)

    Wu, Lishun; Sun, Junfen

    2014-12-01

    Polyvinylidene fluoride (PVDF) membrane and PVDF membrane with phenolphthalein polyethersulfone (PES-C) addition were prepared via thermally induced phase separation (TIPS) method by using diphenyl carbonate (DPC) and dimethyl acetamide (DMAc) as mixed diluents. The effects of coagulation temperature and pre-evaporation time on structure and properties of membranes were studied. The changes of sewage flux in MBR and the attenuation coefficient of sewage flux were investigated. The resistance distributions of PVDF and PVDF/PES-C membranes were compared by resistance analysis. Membrane composition and structure were characterized by ATR-FTIR, TGA, SEM and AFM. The foulant on membranes was analyzed by FTIR. The contact angle of PVDF/PES-C membrane was lower than that of PVDF membrane. A thinner skin layer and a porous cellular support layer formed in PVDF/PES-C membrane and resulted in a higher porosity and pure water flux. The pure water flux and porosity of PVDF/PES-C membrane increased with rising coagulation temperature and decreased with extending pre-evaporation time. The flux attenuation coefficient, the cake layer resistance and internal fouling resistance of PVDF/PES-C membrane in MBR were smaller than those of PVDF membrane in MBR. The FTIR spectrum of foulant on membrane indicated that the foulant on PVDF/PES-C membrane was mostly composed of protein and polysaccharide, while the foulant on pure PVDF membrane included biopolymer clusters besides protein and polysaccharide.

  6. Enhanced piezoresponse of electrospun PVDF mats with a touch of nickel chloride hexahydrate salt.

    PubMed

    Dhakras, Dipti; Borkar, Vivek; Ogale, Satishchandra; Jog, Jyoti

    2012-02-07

    PVDF nanofibers are prepared using electrospinning. The effect of addition of a hydrated salt, nickel chloride hexahydrate (NiCl(2)·6H(2)O), on the phase formation is examined. Addition of the hydrated salt (NC) is found to enhance the polar β phase by about 30%. The peak to peak piezo-voltage generated for PVDF NC is almost 0.762 V, a factor of 3 higher than that for PVDF. The fiber mats exhibit a significantly enhanced dynamic strain sensor response. The voltage generated per unit micro-strain developed during the free vibration test for PVDF was 0.119 mV whereas it was 0.548 mV for PVDF NC, exhibiting a non-linearly enhanced performance vis a vis the increase in the β phase component.

  7. Low percolation threshold of graphene/polymer composites prepared by solvothermal reduction of graphene oxide in the polymer solution

    PubMed Central

    2013-01-01

    Graphene/polyvinylidene fluoride (PVDF) composites were prepared using in-situ solvothermal reduction of graphene oxide in the PVDF solution. The electrical conductivity of the composites was greatly improved by doping with graphene sheets. The percolation threshold of such composite was determined to be 0.31 vol.%, being much smaller than that of the composites prepared via blending reduced graphene sheets with polymer matrix. This is attributed to the large aspect ratio of the SRG sheets and their uniform dispersion in the polymer matrix. The dielectric constant of PVDF showed a marked increase from 7 to about 105 with only 0.5 vol.% loading of SRG content. Like the other conductor-insulator systems, the AC conductivity of the system also obeyed the universal dynamic response. In addition, the SRG/PVDF composite shows a much stronger nonlinear conduction behavior than carbon nanotube/nanofiber based polymer composite, owing to intense Zener tunneling between the SRG sheets. The strong electrical nonlinearity provides further support for a homogeneous dispersion of SRG sheets in the polymer matrix. PMID:23522102

  8. Low percolation threshold of graphene/polymer composites prepared by solvothermal reduction of graphene oxide in the polymer solution.

    PubMed

    He, Linxiang; Tjong, Sie Chin

    2013-03-22

    Graphene/polyvinylidene fluoride (PVDF) composites were prepared using in-situ solvothermal reduction of graphene oxide in the PVDF solution. The electrical conductivity of the composites was greatly improved by doping with graphene sheets. The percolation threshold of such composite was determined to be 0.31 vol.%, being much smaller than that of the composites prepared via blending reduced graphene sheets with polymer matrix. This is attributed to the large aspect ratio of the SRG sheets and their uniform dispersion in the polymer matrix. The dielectric constant of PVDF showed a marked increase from 7 to about 105 with only 0.5 vol.% loading of SRG content. Like the other conductor-insulator systems, the AC conductivity of the system also obeyed the universal dynamic response. In addition, the SRG/PVDF composite shows a much stronger nonlinear conduction behavior than carbon nanotube/nanofiber based polymer composite, owing to intense Zener tunneling between the SRG sheets. The strong electrical nonlinearity provides further support for a homogeneous dispersion of SRG sheets in the polymer matrix.

  9. Enhanced piezoresponse of electrospun PVDF mats with a touch of nickel chloride hexahydrate salt

    NASA Astrophysics Data System (ADS)

    Dhakras, Dipti; Borkar, Vivek; Ogale, Satishchandra; Jog, Jyoti

    2012-01-01

    PVDF nanofibers are prepared using electrospinning. The effect of addition of a hydrated salt, nickel chloride hexahydrate (NiCl2.6H2O), on the phase formation is examined. Addition of the hydrated salt (NC) is found to enhance the polar β phase by about 30%. The peak to peak piezo-voltage generated for PVDF NC is almost 0.762 V, a factor of 3 higher than that for PVDF. The fiber mats exhibit a significantly enhanced dynamic strain sensor response. The voltage generated per unit micro-strain developed during the free vibration test for PVDF was 0.119 mV whereas it was 0.548 mV for PVDF NC, exhibiting a non-linearly enhanced performance vis a vis the increase in the β phase component.PVDF nanofibers are prepared using electrospinning. The effect of addition of a hydrated salt, nickel chloride hexahydrate (NiCl2.6H2O), on the phase formation is examined. Addition of the hydrated salt (NC) is found to enhance the polar β phase by about 30%. The peak to peak piezo-voltage generated for PVDF NC is almost 0.762 V, a factor of 3 higher than that for PVDF. The fiber mats exhibit a significantly enhanced dynamic strain sensor response. The voltage generated per unit micro-strain developed during the free vibration test for PVDF was 0.119 mV whereas it was 0.548 mV for PVDF NC, exhibiting a non-linearly enhanced performance vis a vis the increase in the β phase component. Electronic supplementary information (ESI) available. See DOI: 10.1039/c2nr11841f

  10. Polyethylene-supported polyvinylidene fluoride-cellulose acetate butyrate blended polymer electrolyte for lithium ion battery

    NASA Astrophysics Data System (ADS)

    Liu, Jiansheng; Li, Weishan; Zuo, Xiaoxi; Liu, Shengqi; Li, Zhao

    2013-03-01

    The polyethylene (PE)-supported polymer membranes based on the blended polyvinylidene fluoride (PVDF) and cellulose acetate butyrate (CAB) are prepared for gel polymer electrolyte (GPE) of lithium ion battery. The performances of the prepared membranes and the resulting GPEs are investigated by scanning electron microscopy, electrochemical impedance spectroscopy, linear potential sweep, and charge-discharge test. The effect of the ratio of PVDF to CAB on the performance of the prepared membranes is considered. It is found that the GPE based on the blended polymer with PVDF:CAB = 2:1 (in weight) has the largest ionic conductivity (2.48 × 10-3 S cm-1) and shows good compatibility with anode and cathode of lithium ion battery. The LiCoO2/graphite battery using this GPE exhibits superior cyclic stability at room temperature, storage performance at elevated temperature, and rate performance.

  11. Low Crossover Polymer Electrolyte Membranes for Direct Methanol Fuel Cells

    NASA Technical Reports Server (NTRS)

    Prakash, G. K. Surya; Smart, Marshall; Atti, Anthony R.; Olah, George A.; Narayanan, S. R.; Valdez, T.; Surampudi, S.

    1996-01-01

    Direct Methanol Fuel Cells (DMFC's) using polymer electrolyte membranes are promising power sources for portable and vehicular applications. State of the art technology using Nafion(R) 117 membranes (Dupont) are limited by high methanol permeability and cost, resulting in reduced fuel cell efficiencies and impractical commercialization. Therefore, much research in the fuel cell field is focused on the preparation and testing of low crossover and cost efficient polymer electrolyte membranes. The University of Southern California in cooperation with the Jet Propulsion Laboratory is focused on development of such materials. Interpenetrating polymer networks are an effective method used to blend polymer systems without forming chemical links. They provide the ability to modify physical and chemical properties of polymers by optimizing blend compositions. We have developed a novel interpenetrating polymer network based on poly (vinyl - difluoride)/cross-linked polystyrenesulfonic acid polymer composites (PVDF PSSA). Sulfonation of polystyrene accounts for protonic conductivity while the non-polar, PVDF backbone provides structural integrity in addition to methanol rejection. Precursor materials were prepared and analyzed to characterize membrane crystallinity, stability and degree of interpenetration. USC JPL PVDF-PSSA membranes were also characterized to determine methanol permeability, protonic conductivity and sulfur distribution. Membranes were fabricated into membrane electrode assemblies (MEA) and tested for single cell performance. Tests include cell performance over a wide range of temperatures (20 C - 90 C) and cathode conditions (ambient Air/O2). Methanol crossover values are measured in situ using an in-line CO2 analyzer.

  12. Uniaxially-aligned PVDF nanofibers as a sensor and transmitter for biotelemetry.

    PubMed

    Edmondson, Dennis; Jana, Soumen; Wood, David; Fang, Chen; Zhang, Miqin

    2013-12-07

    Biotelemetry has become an important part of medical research for patient care by remotely monitoring continuing biological processes and physiological functions. However, current biotelemetry systems are complex requiring multiple electronic components to function: a battery, a sensor, and a transmitter, and a receiver. Another paramount concern of biotelemetry is the coupling of its in vivo portion to external supporting equipment. Here we report a novel biotelemetry device made primarily of a coiled bundle of uniaxially-aligned biocompatible polyvinylidene fluoride (PVDF) nanofibers of ∼200 nm in diameter and with piezoelectric properties that can serve concurrently as a power source, sensor, and transmitter. We tested this device on a cantilever beam that was periodically deflected at its free end. Without a power supply the coil of a nanofiber bundle is shown to generate and transmit an electrical signal wirelessly in response to the beam deflection which was received by an external receiver. The coil of a nanofiber bundle was encapsulated in a thin biocompatible polymer shell for device integrity and moisture isolation. Our results suggest that the device can potentially serve as a mechanical sensor and biotelemeter for various in vitro and in vivo biomedical applications.

  13. A comparative approach to predicting effective dielectric, piezoelectric and elastic properties of PZT/PVDF composites

    NASA Astrophysics Data System (ADS)

    Ahmad, Zeeshan; Prasad, Ashutosh; Prasad, K.

    2009-11-01

    The present study addresses the problem of quantitative prediction of effective relative permittivity, dielectric loss factor, piezoelectric charge coefficient, and Young's modulus of PZT/PVDF diphasic ceramic-polymer composite as a function of volume fraction of PZT in the different compositions. Theoretical results for effective relative permittivity derived from several dielectric mixture equations like those of Knott, Rother-Lichtenecker, Bruggeman, Maxwell-Wagner-Webmann-Skipetrov or Dias-Dasgupta, Furukawa, Lewin, Wiener, Jayasundere-Smith, Modified Cule-Torquato, Taylor, Poon-Shin and Rao et al. were fitted to the experimental data taken from previous works of Yamada et al. Similarly, the results for effective piezoelectric coefficient and Young's modulus, derived from different appropriate equations were fitted to the corresponding experimental data taken from the literature. The study revealed that only a few equations like modified Rother-Lichtenecker equation, Dias-Dasgupta equation and Rao equation for dielectric and piezoelectric properties while the four new equations developed in the present study of elastic property (Young's modulus) well fitted the corresponding experimental results. Further, the acceptable data put to various regression analyses showed that in most of the cases the third order polynomial regression analysis provided more acceptable fits.

  14. Reciprocated suppression of polymer crystallization toward improved solid polymer electrolytes: Higher ion conductivity and tunable mechanical properties

    DOE PAGES

    Bi, Sheng; Sun, Che-Nan; Zawodzinski, Thomas A.; ...

    2015-08-06

    Solid polymer electrolytes based on lithium bis(trifluoromethanesulfonyl) imide and polymer matrix were extensively studied in the past due to their excellent potential in a broad range of energy related applications. Poly(vinylidene fluoride) (PVDF) and polyethylene oxide (PEO) are among the most examined polymer candidates as solid polymer electrolyte matrix. In this paper, we study the effect of reciprocated suppression of polymer crystallization in PVDF/PEO binary matrix on ion transport and mechanical properties of the resultant solid polymer electrolytes. With electron and X-ray diffractions as well as energy filtered transmission electron microscopy, we identify and examine the appropriate blending composition thatmore » is responsible for the diminishment of both PVDF and PEO crystallites. Laslty, a three-fold conductivity enhancement is achieved along with a highly tunable elastic modulus ranging from 20 to 200 MPa, which is expected to contribute toward future designs of solid polymer electrolytes with high room-temperature ion conductivities and mechanical flexibility.« less

  15. Ag induced electromagnetic interference shielding of Ag-graphite/PVDF flexible nanocomposites thinfilms

    SciTech Connect

    Kumaran, R.; Alagar, M.; Dinesh Kumar, S.; Subramanian, V.; Dinakaran, K.

    2015-09-14

    We report Ag nanoparticle induced Electromagnetic Interference (EMI) shielding in a flexible composite films of Ag nanoparticles incorporated graphite/poly-vinylidene difluoride (PVDF). PVDF nanocomposite thin-films were synthesized by intercalating Ag in Graphite (GIC) followed by dispersing GIC in PVDF. The X-ray diffraction analysis and the high-resolution transmission electron microscope clearly dictate the microstructure of silver nanoparticles in graphite intercalated composite of PVDF matrix. The conductivity values of nanocomposites are increased upto 2.5 times when compared to neat PVDF having a value of 2.70 S/cm at 1 MHz. The presence of Ag broadly enhanced the dielectric constant and lowers the dielectric loss of PVDF matrix proportional to Ag content. The EMI shielding effectiveness of the composites is 29.1 dB at 12.4 GHz for the sample having 5 wt. % Ag and 10 wt. % graphite in PVDF.

  16. Raman spectral analysis of high efficiency PVDF: nanocomposite films doped with MWCNT

    NASA Astrophysics Data System (ADS)

    Guggilla, Padmaja; Kassu, Aschalew; Powell, Rachel

    2016-09-01

    Nanocomposite films are of great interest in the development of infrared detectors and other technology. Polyvinylidenefluoride (PVDF) with excellent pyroelectric and piezoelectric properties such as fast, dynamic response has great potential for use in touch/tactile sensors, infrared detectors and thermal vidicon/imaging devices. PVDF:LiNbO3, PVDF:LiTaO3, and PVDF:BaTiO3 nanocomposites are fabricated with optimal characteristics using the solution casting technique. All these nanocomposite films are doped with multi-walled carbon nanotubes (MWCNT) with various weight percentages. The objective of this research was to characterize the low-frequency dielectric constant, dielectric loss and the pyroelectric properties of these composite films and thus the materials figures of merit for their use in space applications. Nanocomposites are also characterized using Raman Spectroscopy to get the finger print of these materials and their existence in the composite film. Dielectric constant and dielectric loss results are presented as a function of temperature and frequency, and pyroelectric coefficient as a function of temperature. Raman Spectrum of the nanocomposite materials is presented using 785nm laser. Obtained Raman spectrum matches with the literature available. Authors also observed that both microscopic structure and environmental conditions contributed to observed properties. Dielectric loss resulted from electromagnetic energy loss as manifested through phase differences between low-frequency input signal to the films and time varying polarization. In addition, both the dielectric constant and dielectric loss were observed to be highest for MWCNT doped nanocomposite materials compared to pure PVDF and pure PVDF:LiNbO3, PVDF:LiTaO3, and PVDF:BaTiO3. Among all the MWCNT doped nanocomposite materials PVDF:LiTaO3 showed the highest Pyroelectric coefficient which would make the best material to be used in space applications compared to the other materials at test.

  17. Significant enhancement in energy density of polymer composites induced by dopamine-modified Ba0.6Sr0.4TiO3 nanofibers

    NASA Astrophysics Data System (ADS)

    Song, Yu; Shen, Yang; Hu, Penghao; Lin, Yuanhua; Li, Ming; Nan, C. W.

    2012-10-01

    Ba0.6Sr0.4TiO3 (BST) nanofibers prepared via electrospinning and modified by dopamine are used as dielectric fillers in polyvinylidene fluoride (PVDF)-based composites. With 4.4 vol. % of BST nanofibers, the extractable energy density of the BST/PVDF composites is more than doubled as compared with pure PVDF matrix. Such significant enhancement is attributed to the combined effect of both surface modification by dopamine and large aspect ratio of the BST nanofibers. Paraelectric or anti-ferroelectric fillers of large aspect ratio may serve as a general strategy for enhanced electric energy density in polymer composites.

  18. Preparation and characterization of PVDF-glass fiber composite membrane reinforced by interfacial UV-grafting copolymerization.

    PubMed

    Luo, Nan; Xu, Rongle; Yang, Min; Yuan, Xing; Zhong, Hui; Fan, Yaobo

    2015-12-01

    A novel inorganic-organic composite membrane, namely poly(vinylidene fluoride) PVDF-glass fiber (PGF) composite membrane, was prepared and reinforced by interfacial ultraviolet (UV)-grafting copolymerization to improve the interfacial bonding strength between the membrane layer and the glass fiber. The interfacial polymerization between inorganic-organic interfaces is a chemical cross-linking reaction that depends on the functionalized glass fiber with silane coupling (KH570) as the initiator and the polymer solution with acrylamide monomer (AM) as the grafting block. The Fourier transform infrared spectrometer-attenuated total reflectance (FTIR-ATR) spectra and the energy dispersive X-ray (EDX) pictures of the interface between the glass fiber and polymer matrix confirmed that the AM was grafted to the surface of the glass fiber fabric and that the grafting polymer was successfully embedded in the membrane matrix. The formation mechanisms, permeation, and anti-fouling performance of the PGF composite membrane were measured with different amounts of AM in the doping solutions. The results showed that the grafting composite membrane improved the interfacial bonding strength and permeability, and the peeling strength was improved by 32.6% for PGF composite membranes with an AM concentration at 2wt.%.

  19. Optimization Of PVDF-TrFE Processing Conditions For The Fabrication Of Organic MEMS Resonators

    PubMed Central

    Ducrot, Pierre-Henri; Dufour, Isabelle; Ayela, Cédric

    2016-01-01

    This paper reports a systematic optimization of processing conditions of PVDF-TrFE piezoelectric thin films, used as integrated transducers in organic MEMS resonators. Indeed, despite data on electromechanical properties of PVDF found in the literature, optimized processing conditions that lead to these properties remain only partially described. In this work, a rigorous optimization of parameters enabling state-of-the-art piezoelectric properties of PVDF-TrFE thin films has been performed via the evaluation of the actuation performance of MEMS resonators. Conditions such as annealing duration, poling field and poling duration have been optimized and repeatability of the process has been demonstrated. PMID:26792224

  20. Interaction of 1-butyl-1-methylpyrrolidinium bis(trifluoromethanesulfonyl)imide with an electrospun PVdF membrane: Temperature dependence of the concentration of the anion conformers.

    PubMed

    Vitucci, F M; Palumbo, O; Trequattrini, F; Brubach, J-B; Roy, P; Meschini, I; Croce, F; Paolone, A

    2015-09-07

    We measured the temperature dependence of the infrared absorption spectrum of 1-butyl-1-methylpyrrolidinium bis(trifluoromethanesulfonyl)imide (PY R14-TFSI) between 160 and 330 K, through all the phase transitions presented by this compound. The comparison of the experimental spectra with the calculated vibration modes of different conformers of the ions composing the ionic liquid allowed to detect the presence of both conformers of TFSI in the liquid, supercooled, and glass phases, while only the trans-conformer is retained in both solid phases. When the ionic liquid swells a polyvinylidenefluoride (PVdF) electrospun membrane, the cis-rotamer is detected in all phases, since the interaction between the polymer and the ionic liquid inhibits the complete transformation of TFSI into the trans-conformer in the solid phases. Computational results confirm that in the presence of a PVdF chain, cis-TFSI becomes the lowest energy conformer. Therefore, the interaction with the polymer alters the physical properties of the ionic liquid.

  1. Interaction of 1-butyl-1-methylpyrrolidinium bis(trifluoromethanesulfonyl)imide with an electrospun PVdF membrane: Temperature dependence of the concentration of the anion conformers

    NASA Astrophysics Data System (ADS)

    Vitucci, F. M.; Palumbo, O.; Trequattrini, F.; Brubach, J.-B.; Roy, P.; Meschini, I.; Croce, F.; Paolone, A.

    2015-09-01

    We measured the temperature dependence of the infrared absorption spectrum of 1-butyl-1-methylpyrrolidinium bis(trifluoromethanesulfonyl)imide (PY R14-TFSI) between 160 and 330 K, through all the phase transitions presented by this compound. The comparison of the experimental spectra with the calculated vibration modes of different conformers of the ions composing the ionic liquid allowed to detect the presence of both conformers of TFSI in the liquid, supercooled, and glass phases, while only the trans-conformer is retained in both solid phases. When the ionic liquid swells a polyvinylidenefluoride (PVdF) electrospun membrane, the cis-rotamer is detected in all phases, since the interaction between the polymer and the ionic liquid inhibits the complete transformation of TFSI into the trans-conformer in the solid phases. Computational results confirm that in the presence of a PVdF chain, cis-TFSI becomes the lowest energy conformer. Therefore, the interaction with the polymer alters the physical properties of the ionic liquid.

  2. PVDF gauge characterization of hypervelocity-impact-generated debris clouds

    SciTech Connect

    Boslough, M.B.; Chhabildas, L.C.; Reinhart, W.D.; Hall, C.A.; Miller, J.M.; Hickman, R.; Mullin, S.A.; Littlefield, D.L.

    1993-08-01

    We have used PVDF gauges to determine time-resolved stresses resulting from interaction between hypervelocity-impact-generated debris clouds and various target gauge blocks. Debris clouds were generated from three different impact configurations: (1) steel spheres impacting steel bumper sheets at 4.5 to 6.0 km/s, (2) aluminum inhibited shaped-charge jets impacting aluminum bumper sheets at 11.4 km/s, and (3) titanium disks impacting titanium bumper sheets at 7.6 to 10.1 km/s. Additional data were collected from the various experiments using flash X-ray radiography, pulsed laser photography, impact flash measurements, time-resolved strain gauge measurements, and velocity interferometry (VISAR). Data from these various techniques are in general agreement with one another and with hydrocode predictions, and provide a quantitative and comprehensive picture of impact-generated debris clouds.

  3. The Effect of Nano-Morphology Modification Using an Amphiphilic Polymer on the Proton Conductivity of Composite Membrane for a Polymer Membrane-Based Fuel Cell.

    PubMed

    Roh, Sung-Hee; Rho, Seon-Gyun; Kim, Sang-Chai; Kim, Ju-Young; Jung, Ho-Young

    2016-02-01

    The effect of morphology modification using an amphiphilic polymer on the proton conductivity of composite membrane for a polymer membrane-based fuel cell was investigated. The proton conductivity of each composite membrane was analyzed by the electrochemical impedance spectroscopy (EIS). The morphological change was confirmed by scanning electron microscope (SEM). In the composite membrane, the proton conductive component was sulfonated poly(ether ether ketone) (sPEEK), while the nonconductive component was poly(vinylidenedifluoride) and the amphiphilic polymer as a compatibilizer was urethane acrylate non-ionomer (UAN). UAN as a compatibilizer improved the interfacial stability between sPEEK and PVdF polymers, even though two polymers were apparently immiscible. The homogeneous distribution of sPEEK and PVdF domains in the composite membrane was obtained with the introduction of UAN due to the amphiphilicity. Therefore, it was found that the proton conductivity of the composite membrane increased with the incorporation of UAN as a compatibilizer.

  4. A super hydrophilic modification of poly(vinylidene fluoride) (PVDF) nanofibers: By in situ hydrothermal approach

    NASA Astrophysics Data System (ADS)

    Sheikh, Faheem A.; Zargar, Mohammad Afzal; Tamboli, Ashif H.; Kim, Hern

    2016-11-01

    Nanofibers fabricated from Poly(vinylidene fluoride) (PVDF) possesses potential applications in the field of filtrations, because of their excellent resistance towards harsh chemicals. However, the hydrophobicity restricts its further application. In this work, we focus on optimal parameters for post-electrospun tethering of Poly(vinyl alcohol) (PVA) as superhydrophilic domain onto each individual PVDF nanofibers by exploiting the in situ hydrothermal approach. The results indicated an increase in nanofiber diameters due to coating of PVA and improved surface wettability of PVDF nanofibers. The tensile tests of nanofibers indicated that mechanical properties of PVDF nanofibers could be sharply tuned from rigid to ductile. Furthermore, the studies strongly suggest that in situ hydrothermal treatment of post-electrospun nanofibers can improve the water contact angle and these nanofibers can be used in varied applications (e.g., in water purification systems).

  5. Enhanced power output of an electrospun PVDF/MWCNTs-based nanogenerator by tuning its conductivity.

    PubMed

    Yu, Hao; Huang, Tao; Lu, Mingxia; Mao, Mengye; Zhang, Qinghong; Wang, Hongzhi

    2013-10-11

    PVDF nanofibre-based piezoelectric nanogenerators are directly prepared via electrospinning without any post-poling treatment. The effect of the addition of multi-walled carbon nanotubes (MWCNTs) on the fibre diameter, mechanical properties, β-phase composition, surface and volume conductivities, output voltage and output power are investigated. Increased surface conductivity of the poly-vinylidene fluoride (PVDF) nanofibre mats, which plays an important role in the enhancement of output power, is first found by the addition of an appropriate amount of MWCNTs. The maximum generated piezo-voltage exhibited by PVDF nanofibre mats in the presence of 5 wt% MWCNTs is as high as 6 V, while the average capacitor charging power is 81.8 nW, increases of 200% and 44.8%, respectively, compared with bare PVDF nanofibre mats.

  6. Enhanced power output of an electrospun PVDF/MWCNTs-based nanogenerator by tuning its conductivity

    NASA Astrophysics Data System (ADS)

    Yu, Hao; Huang, Tao; Lu, Mingxia; Mao, Mengye; Zhang, Qinghong; Wang, Hongzhi

    2013-10-01

    PVDF nanofibre-based piezoelectric nanogenerators are directly prepared via electrospinning without any post-poling treatment. The effect of the addition of multi-walled carbon nanotubes (MWCNTs) on the fibre diameter, mechanical properties, β-phase composition, surface and volume conductivities, output voltage and output power are investigated. Increased surface conductivity of the poly-vinylidene fluoride (PVDF) nanofibre mats, which plays an important role in the enhancement of output power, is first found by the addition of an appropriate amount of MWCNTs. The maximum generated piezo-voltage exhibited by PVDF nanofibre mats in the presence of 5 wt% MWCNTs is as high as 6 V, while the average capacitor charging power is 81.8 nW, increases of 200% and 44.8%, respectively, compared with bare PVDF nanofibre mats.

  7. PVDF based ion exchange membrane prepared by radiation grafting of ethyl styrenesulfonate and sequent hydrolysis

    NASA Astrophysics Data System (ADS)

    Wang, Yicheng; Peng, Jing; Li, Jiuqiang; Zhai, Maolin

    2017-01-01

    A new synthesis route for poly(vinylidene fluoride)-g-polystyrene sulfonic acid ion exchange membrane (PVDF-g-PSSA IEM) has been developed via preradiation-induced grafting of ethyl styrenesulfonate and sequent hydrolysis. A high grafting yield (GY) 120% for PETSS grafted onto PVDF could be obtained at a reaction time of 3 h and dose of 50 kGy. The structure of PVDF-g-PSSA IEM was testified by FTIR, XPS, TGA and SEM analysis. At the GY above 80%, the ion exchange capacity, water uptake and proton conductivity of the resultant PVDF-g-PSSA IEM exceeds Nafion 117 membrane. This work provides an environmental method for the preparation of the IEM used in fuel cell or water treatment.

  8. Design and fabrication of a metal core PVDF fiber for an air flow sensor

    NASA Astrophysics Data System (ADS)

    Bian, Yixiang; Liu, Rongrong; Huang, Xiaomei; Hong, Jin; Huang, Huiyu; Hui, Shen

    2015-10-01

    To track prey or avoid predators, many arthropods can detect variations in airflow and pressure gradients using an array of very thin and sensitive filiform hairs. In this study, metal core piezoelectric poly(vinylidene fluoride) (PVDF) fibers were prepared to mimic such hair sensors. The flexibility of the fibers was very good, which was helpful for overcoming the typical brittleness of piezoelectric ceramic fibers. At the same time, the diameter of the fibers was very small (down to 50 μm in diameter). In order to mimic the insects’ hairs to the maximum extent, which was expected to greatly improve the sensitivity of such PVDF fiber-based sensors, a feasible process to prepare and extract electrodes on the surface of the fibers had to be developed. Compared with stainless steel filament-core fibers, the molybdenum filament-core PVDF fibers were easy to stretch. The molybdenum filament was then covered by a cylindrical PVDF layer with a diameter of 400 μm. One half of the longitudinal surface of the fibers was spray-coated with a conductive silver adhesive. The metal core was then used as one electrode, and the conductive silver adhesive was used as the other electrode. After polarization, a single metal-core PVDF fiber could be used as an airflow sensor. The surface structure and the sections of the PVDF fiber were analyzed by scanning electron microscopy. The results of the mechanical stretching tests showed that the metal core greatly enhanced the mechanical properties of the PVDF fibers. X-ray diffraction revealed that the greater the stretching ratio, the higher the α-to-β-phase conversion rate during the preparation of the PVDF fibers. A single metal-core PVDF fiber was used as a bionic airflow sensor, and a mechanical model of this sensor was derived. The airflow sensing capability of the PVDF fiber was experimentally confirmed in a miniature wind tunnel. The results showed that a cantilevered metal-core PVDF fiber is capable of detecting the range

  9. First principles-based multiscale modeling of ferroelectric polymers

    SciTech Connect

    Strachan, A. H.; Su, Haibin; Goddard, W. A. , III

    2004-01-01

    We use Density Functional Theory [within the generalized gradient approximation (DFT-GGA)] and molecular dynamics (MD) to characterize electromechanical properties of PVDF and its random copolymer with TrFE. Our simulations predict that large electrostrictive strains ({approx}5%) at extremely high frequencies (up to 10{sup 9} Hz) can be obtained in a poly(vinylidene fluoride) (PVDF) nano-actuator if the inter-chain packing density is appropriately chosen. We control the packing density by assembling the polymer chains on a Si <111> surface with 1/2 coverage. Under these conditions the equilibrium conformation of the polymer contains a combination of Gauche and Trans bonds which can be easily transformed to an all-Trans conformation by applying an electric field. Such molecular transformation is accompanied by a large deformation along the polymer chain direction.

  10. Fabrication and characterization of PbO2 electrode modified with polyvinylidene fluoride (PVDF)

    NASA Astrophysics Data System (ADS)

    Li, Xiaoliang; Xu, Hao; Yan, Wei

    2016-12-01

    A novel PbO2 electrode with a high oxygen evolution potential (OEP) and long service life was successfully fabricated by doping polyvinyl fluoride (PVDF) (marked as PbO2-PVDF) through co-deposition method. The morphology (SEM), elemental analysis (EDX), hydrophobic property (contact angle), crystalline structure (XRD), chemical state (XPS), electrochemical performances (Lsv and EIS) and stability (accelerated life test) were characterized. The results showed that PVDF doping could improve the film morphology, increase oxygen evolution potential (OEP) and reduce the electrode film impedance. In addition, the proportion of adsorbed hydroxyl oxygen (Oad) on the electrode also increased. During the electrochemical oxidation process, the PbO2-PVDF(2.0) electrode showed the best performance on degradation of phenol due to the highest removal rate, lowest energy consumption and minimum Pb dissolution, which could be attributed to its hydrophobic surface, high oxygen evolution potential (OEP) and strong capability of HOrad generation. Furthermore, the stability of the electrodes were greatly improved after PVDF modification. PbO2-PVDF(1.0) electrode showed the longest service life (501 h), which was more than 4 times longer than PbO2 electrode (118.5 h).

  11. Synthesis of PVDF ultrafiltration membranes supported on polyester fabrics for separation of organic matter from water

    NASA Astrophysics Data System (ADS)

    Mhlanga, Sabelo D.; Tshabalala, Tumelo G.; Nxumalo, Edward N.; Mamba, Bhekie B.

    2014-08-01

    Polyvinylidene flouride (PVDF) membranes supported on non-woven fabrics (NWF) of polyester are reported. The PVDF membranes were fabricated using the phase inversion method followed by modification of the active top layer of the PVDF thin film by adding polyvinylpyrolidone (PVP) into the cast solution. A PVDF resin was used with N- methyl-2-pyrrolidone (NMP) as a solvent. Sessile drop contact angle measurements and scanning electron microscopy (SEM) were used to study the physical properties of the membranes. Membrane rejection of humic acid was studied using a cross-flow membrane testing unit. The contact angle results revealed that the hydrophilicity of PVDF membranes increased as the PVP concentration was increased from 3 to 10 wt%. SEM analysis of the membranes revealed that the membrane pore sizes increased when PVP was added. AFM analysis also showed that membrane roughness changed when PVP was added. Total organic carbon (TOC) analysis of water samples spiked with humic acid was performed to test the rejection capacity of the membranes. Rejections of up to 97% were achieved for PVDF membranes supported on polyester NWF1, which had smaller thickness and higher permeability compared to polyester NWF2. The NWFs provided the high strength required for the membranes despite the modifications done on the PDVF surface and microstructure.

  12. Preparation Method of Crack-free PVDF Microfiltration Membrane with Enhanced Antifouling Characteristics.

    PubMed

    Woo, Sahng Hyuck; Lee, Ju Sung; Lee, Hyun Ho; Park, Jinwon; Min, Byoung Ryul

    2015-08-05

    This study proposes a method to prepare a crack-free poly(vinylidene fluoride) (PVDF) microfiltration (MF) membrane with enhanced antifouling property. In the study, blending 4% poly(vinylidene fluoride)-graft-poly(sulfopropyl methacrylate) (PVDF-g-PSPMA) and 1.5% potassium perchlorate (KClO4) led to crack prevention during membrane preparation via nonsolvent induced phase separation (NIPS) when compared with blending with 4% PVDF-g-PSPMA only (without KClO4). The resulting crack-free membrane (A3) had both smooth surface structure and hydrophilicity in comparison with pristine PVDF membrane (A1). In addition, blending with PVDF-g-PSPMA and KClO4 also allowed the A3 membrane to exhibit uniform pore size distribution (PSD) and smooth surface structure, compared with PVDF membrane commercially available from company "M" in Germany. The aforementioned properties led to antifouling characteristics in the crack-free membrane (A3). According to flux performances, flux recovery and cumulative permeate volume (between 120 and 240 min) of crack-free membrane (A3) were 11.41 and 17.41% superior to those of commercial membrane, respectively.

  13. First-principles investigation of high energy density in PVDF copolymers

    NASA Astrophysics Data System (ADS)

    Ranjan, V.; Lu, Liping; Buongiorno Nardelli, M.; Bernholc, J.

    2008-03-01

    PVDF and its copolymers exhibit excellent electromechanical properties and in the case of PVDF-CTFE also a very high energy density [1]. We have investigated the phase diagram of these systems and can quantitatively explain the observed energy density of PVDF-CTFE as due to a para to ferroelectric phase transition in a disordered, multidomain structure [2]. Our results show that pure PVDF prefers the α phase at zero field. Electric field lowers the free energy of the β phase, resulting in a structural phase transition at a sufficiently high field. Copolymer admixture lowers the critical field and eventually leads to an energetic preference for the β phase even at zero field. For PVDF-CTFE with CTFE content below 17 %, the α phase is still preferred and the field-induced phase transformation reversibly stores large amounts of energy. For PVDF-TeFE, the total energy difference between the two phases is much smaller, resulting in substantially smaller energy density. [1] B. Chu et al., Science 313, 334 (2006). [2] V. Ranjan et al., PRL 99, 047801 (2007).

  14. [Surface modification of polyvinylidene fluoride (PVDF) membrane by using the zwitterionic substance].

    PubMed

    Zhou, Gui-Hu; Xiao, Feng; Xiao, Ping; Wang, Dong-Sheng; Duan, Jin-Ming'; Shi, Jian; Zang, Li

    2013-10-01

    In order to enhance the hydrophilicity of the membrane and improve the antifouling properties, poly (2-hydroxyethyl methacry-late) (poly(HEMA)) was grafted to the surface of the poly(vinylidene fluoride) (PVDF) membrane by using the atom transfer radical polymerization (ATRP) method. After that, ceric ammonium nitrate (CAN) as the initiator, N, N'-methylene bisacrylamide as a cross-linking agent, a zwitterionic polymer, poly (3-( methacryloylamino) propyl-dimethyl-(3-sulfopropyl) ammonium hydroxide) (poly(MPDSAH)) were successfully grafted onto the membrane surface by radical polymerization reaction. Attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS), scanning electron microscope (SEM) and contact angle measuring were employed to analyze the property and the morphology of structures before and after the membrane surface-modification. The grafting density (GD) gradually increased, with the grafting time increasing, the pore size of the membrane became smaller, and the porosity decreased, but the surface hydrophilicity of membrane was significantly enhanced at the same time. The adsorption of bovine serum albumin (BSA) tests and filtration experiments were carried out to investigate anti-fouling performances of membrane before and after modification. With the GD increasing, the amount of adsorption on the film surface significantly reduced in the high-concentration BSA solution. The water contact angle (CA) decreased most, from 77. 2 degrees to 41.7 degrees within 5 s to 0, and a flux recovery ratio up to 94. 961% , when the GD reached 288. 340 microg.cm-2. Therefore, the optimal grafting time was 2 h, with the grafting density of 288. 340 microg.cm-2.

  15. Enhanced pervaporation performance of multi-layer PDMS/PVDF composite membrane for ethanol recovery from aqueous solution.

    PubMed

    Zhan, Xia; Li, Jiding; Huang, Junqi; Chen, Cuixian

    2010-01-01

    Multi-layer PDMS/PVDF composite membrane with an alternative PDMS/PVDF/non-woven-fiber/PVDF/PDMS configuration was prepared in this paper. The porous PVDF substrate was obtained by casting PVDF solution on both sides of non-woven fiber with immersion precipitation phase inversion method. Polydimethylsiloxane (PDMS) was then cured by phenyltrimethoxylsilane (PTMOS) and coated onto the surface of porous PVDF substrate one layer by the other to obtain multi-layer PDMS/PVDF composite membrane. The multi-layer composite membrane was used for ethanol recovery from aqueous solution by pervaporation, and exhibited enhanced separation performance compared with one side PDMS/PVDF composite membranes, especially in the low ethanol concentration range. The maximum separation factor of multi-layer PDMS/PVDF composite membrane was obtained at 60 degrees C, and the total flux increased exponentially along with the increase of temperature. The composite membrane gave the best pervaporation performance with a separation factor of 15, permeation rate of 450 g/m(2)h with a 5 wt.% ethanol concentration at 60 degrees C.

  16. Preparation and pre-characterization of epoxidized natural rubber (ENR) / poly(vinylidene fluoride) (PVDF) (ENR/PVDF) thin film composite membrane

    NASA Astrophysics Data System (ADS)

    Mod, Norliyana; Othaman, Rizafizah

    2015-09-01

    Epoxidised Natural Rubber (ENR) / Poly (Vinylidene Fluoride) (PVDF) (ENR/PVDF) (60:40 wt%) thin film composite membrane was prepared by using solution casting technique. The focuses of this paper are to prepare ENR/PVDF membrane with ratio of ENR to PVDF 60:40 wt%, and to study the effectiveness of treating Palm Oil Mill Effluent (POME) using the membrane. The prepared membrane was analyzed using optical microscope and the treatment of POME was investigated using dead-end stirred cell. Treated and untreated POME was analyzed to test the percentage of biochemical oxygen demand (BOD) and chemical oxygen demand (COD) removal. Optical microscope micrographs showed that the surface of the membrane was slightly uneven. The rate of flux which passed through the membrane was 0.60 L/hm2. Both BOD and COD decreased by 23.6 % and 49.32 % respectively, after single treatment. This showed that the membrane can be used for POME treatment. The value of BOD and COD removal can be increased by recycling the treated POME for more than two cycles, which will be further studied by authors.

  17. Interfacial polymerization on hydrophobic PVDF UF membranes surface: Membrane wetting through pressurization

    NASA Astrophysics Data System (ADS)

    Lee, Ju Sung; Lee, Hyun Ho; Seo, Jin Ah; Park, Hyun Sic; Park, Jinwon; Min, Byoung Ryul

    2015-11-01

    PVDF is widely used in water treatment membranes because of it high chemical resistance and thermal stability levels, and desirable mechanical properties. On the other hand, it is seldom used as support membrane for RO membranes, as it is difficult to undertake interfacial polymerization by traditional methods due to characteristic of hydrophobic surface. However, if the MPD solution is applied at pressures which exceed the pressure at which the PVDF membrane pushes water away, then it can be wetted within the membrane and PA/PVDF composite membrane can be prepared through the reaction of the wetted MPD and TMC. The theoretical penetration pressure needed to wet MPD solution in PVDF with pore size of 10 nm, calculated using Jurin's Law, is 8.8 bar. In this study, PVDF membrane was immersed in MPD solution for 4 h at pressures higher than theoretical penetration pressure using N2 gas at 25 °C. Interfacial polymerization with TMC was undertaken with surface of the PVDF membrane wetted in MPD solution in this manner to form a thin but consistent PA layer, which was verified through FT-IR and SEM. Salt rejection and permeation flux measurements for NaCl 5000 ppm was conducted for the PA/PVDF membranes prepared in this manner at 25 °C, 30 bar using cross-flow water permeation system. PA/PVDF composite membrane wetted with MPD solution and interfacial polymerization undertaken at 10, 16 and 20 bar with N2 gas displayed salt rejection ratio of 37.94, 41.79 and 51.03%, and permeation flux of 7.38, 5.26 and 7.94LMH, respectively. The salt rejection ratio for membrane wetted with MPD at 16 bar with CO2 gas displayed salt rejection ratio of 78.26% and permeation flux of 4.91LMH. The results confirmed the possibility of using PVDF UF membrane of superior properties as support membrane for NF and RO.

  18. A robust superhydrophobic PVDF composite coating with wear/corrosion-resistance properties

    NASA Astrophysics Data System (ADS)

    Wang, Huaiyuan; Liu, Zhanjian; Wang, Enqun; Yuan, Ruixia; Gao, Dong; Zhang, Xiguang; Zhu, Yanji

    2015-03-01

    A robust wear/corrosion-resistant superhydrophobic polyvinylidene fluoride (PVDF)/fluorinated ethylene propylene (FEP)/carbon nanofibers (CNFs) composite coating with a water contact angle (WCA) of 164 ± 1.5° and a slide angle of 5 ± 0.2° has been fabricated through the combination of chemical etching and spraying technique. The WCA of the coating still maintains 141 ± 1.2° after 10,000 times rubbing due to the designed internal nano/micro-structure and the slide angle increases from 5 ± 0.2° to 20 ± 0.5°. The prepared coating also demonstrates excellent corrosion-resistance property under strongly acidic or alkaline conditions for 15 days. The wear-resistance of the superhydrophobic coating is approximately 5 times higher than the pure PVDF coating and commercial fluorocarbon coating. These excellent mechanical properties are attributed to the new groups of Cdbnd C and Csbnd C by dehydrofluorination of PVDF and the new β-phase of PVDF by recrystallization of the α-phase. Furthermore, the enhanced adhesive ability of the coating corresponds with Grade 1 according to GB/T9286, mainly because that the interaction force among PVDF macromolecules can be intensified by chemical cross-linking and the hydroxyl groups formed on the surface of the aluminum plate by etching. It is believed that this robust multifunctional superhydrophobic coating may have the potential values in large-scale application.

  19. Piezoelectric electrospun nanocomposite comprising Au NPs/PVDF for nerve tissue engineering.

    PubMed

    Motamedi, Asma Sadat; Mirzadeh, Hamid; Hajiesmaeilbaigi, Fereshteh; Bagheri Khoulenjani, Shadab; Shokrgozar, Mohammad Ali

    2017-03-03

    In this study, gold nanoparticles/Polyvinylidenefluoride composite electrospun mat with enhanced piezoelectricity were fabricated and characterized. Gold colloidal nanoparticles (Au NPs) were prepared via laser ablation of metallic targets in liquid media. The active Q-switched Nd:YAG laser was used as an irradiation source. Then, PVDF (Polyvinylidenefluoride) was dissolved in Au NPs colloidal solution at 30% wt for the synthesis of Au NPs/PVDF composite nanofibers by electrospinning. The optical absorbance spectra of Au NPS and the polymeric solutions were obtained by the UV-Visible spectroscopy. Moreover, the morphology of Au NPS, nanostructures of fibers and diameter size distribution of nanofibers were analyzed by Scanning Electron Microscopy (SEM), Field Emission Scanning Electron Microscopy (FESEM) and Transmitted Electron Microscopy (TEM) methods. The crystallinity and piezoelectricity of PVDF and Au NPs/PVDF composite nanofibers mats were measured by X-Ray Diffraction (XRD) and Fourier Transform Infrared (FTIR) methods. Subsequently, in vitro cytocompatibility was evaluated by MTT assay and the attachment and morphology of PC-12 cells cultured on scaffolds were studied. It was found that laser ablated Au NPs can be used in electrospun nanofibers of PVDF with adequate structural properties and increase piezoelectricity of nanofibers which might be suitable for applying as nerve tissue engineering scaffolds. This article is protected by copyright. All rights reserved.

  20. SPEEK/PVDF/PES Composite as Alternative Proton Exchange Membrane for Vanadium Redox Flow Batteries

    NASA Astrophysics Data System (ADS)

    Fu, Zhimin; Liu, Jinying; Liu, Qifeng

    2016-01-01

    A membrane consisting of a blend of sulfonated poly(ether ether ketone) (SPEEK), poly(vinylidene fluoride) (PVDF), and poly(ether sulfone) (PES) has been fabricated and used as an ion exchange membrane for application in vanadium redox flow batteries (VRBs). The vanadium ion permeability of the SPEEK/PVDF/PES membrane was one order of magnitude lower than that of Nafion 117 membrane. The low-cost composite membrane exhibited better performance than Nafion 117 membrane at the same operating condition. A VRB single cell with SPEEK/PVDF/PES membrane showed significantly lower capacity loss, higher coulombic efficiency (>95%), and higher energy efficiency (>82%) compared with Nafion 117 membrane. In the self-discharge test, the duration of the cell with the SPEEK/PVDF/PES membrane was nearly two times longer than that with Nafion 117 membrane. Considering these good properties and its low cost, SPEEK/PVDF/PES membrane is expected to have excellent commercial prospects as an ion exchange membrane for VRB systems.

  1. Enhancement of polar crystalline phase formation in transparent PVDF-CaF2 composite films

    NASA Astrophysics Data System (ADS)

    Lee, Sang Goo; Ha, Jong-Wook; Sohn, Eun-Ho; Park, In Jun; Lee, Soo-Bok

    2016-12-01

    We consider the influence of calcium fluoride (CaF2) nanoparticles on the crystalline phase formation of poly(vinylidene fluoride) (PVDF) for the first time. The transparent PVDF-CaF2 composite films were prepared by casting on PET substrates using N,N-dimethylacetamide (DMAc) as a solvent. It was found that CaF2 promoted the formation of polar crystalline phase of PVDF in composites, whereas nonpolar α-phase was dominant in the neat PVDF film prepared at the same condition. The portion of polar crystalline phase increased in proportional to the weight fraction of CaF2 in the composite films up to 10 wt%. Further addition of CaF2 suppressed completely the α-phase formation. Polar crystalline phase observed in as-cast composite films was a mixture of β- and γ-polymorph structures. It was also shown that much ordered γ-phase could be obtained through thermal treatment of as-cast PVDF-CaF2 composite film at the temperatures above the melting temperature of the composite films, but below that of γ-phase.

  2. Fabrication, polarization, and characterization of PVDF matrix composites for integrated structural load sensing

    NASA Astrophysics Data System (ADS)

    Haghiashtiani, Ghazaleh; Greminger, Michael A.

    2015-04-01

    The focus of this work is to evaluate a new carbon fiber reinforced composite structure with integrated sensing capabilities. In this composite structure, the typical matrix material used for carbon fiber reinforced composites is replaced with the thermoplastic polyvinylidene difluoride (PVDF). Since PVDF has piezoelectric properties, it enables the structure to be used for integrated load sensing. In addition, the electrical conductivity property of the carbon fabric is harnessed to form the electrodes of the integrated sensor. In order to prevent the carbon fiber electrodes from shorting to each other, a thin Kevlar fabric layer is placed between the two carbon fiber electrode layers as a dielectric. The optimal polarization parameters were determined using a design of experiments approach. Once polarized, the samples were then used in compression and tensile tests to determine the effective d33 and d31 piezoelectric coefficients. The degree of polarization of the PVDF material was determined by relating the effective d33 coefficient of the composite to the achieved d33 of the PVDF component of the composite using a closed form expression. Using this approach, it was shown that optimal polarization of the composite material results in a PVDF component d33 of 3.2 pC N-1. Moreover, the Young’s modulus of the composite structure has been characterized.

  3. Microsequence analysis of electroblotted proteins. II. Comparison of sequence performance on different types of PVDF membranes.

    PubMed

    Reim, D F; Speicher, D W

    1992-11-15

    The influence of different types of polyvinylidene difluoride (PVDF) membranes on gas phase sequence performance has been evaluated. These PVDF membranes have been classified as either high retention (Trans-Blot and ProBlott) or low retention membranes (Immobilon-P) based on their ability to bind proteins during electroblotting from gels. Initial yields, repetitive yields, and extraction efficiency of the anilinothiazolinone amino acid derivatives have been compared for several standard proteins that have been either electroblotted or loaded onto PVDF membranes by direct adsorption. These results show that the major differences in initial sequence yields between membranes arise from differences in the amount of protein actually transferred to the membrane rather than sequencer-related factors. In contrast to several previous observations from other laboratories, more tightly bound proteins do not sequence with lower initial yields and initial yields are not affected by the ratio of surface area to protein. The stronger binding on high retention PVDF membranes does not adversely affect recoveries of difficult to extract, or very hydrophobic, amino acid derivatives. Several amino acids, especially tryptophan, are actually recovered in dramatically higher yield on high retention membranes compared with either Immobilon or glass filters. At the same time, the protein and peptide binding properties of high retention membranes will frequently improve the repetitive yield by minimizing sample extraction during the sequencer cycle. Stronger protein binding together with improved electroblotting yields offer substantially improved sequence performance when high retention PVDF membranes are used.

  4. Improved antifouling properties of PVDF membranes modified with oppositely charged copolymer.

    PubMed

    Shen, Xiang; Zhao, Yiping; Feng, Xia; Bi, Sixin; Ding, Wenbin; Chen, Li

    2013-01-01

    Biofouling resulting from the attachment of microorganisms communities to the membrane surface is the major obstacle for the widespread application of membrane technology. This work develops a feasible approach to prepare an anti-biofouling poly(vinylidene fluoride) (PVDF) membrane. A copolymer that possessed oppositely charged groups was first synthesized via radical copolymerization with methyl methacrylate, 2-methacryloxy ethyltrimethyl ammonium chloride and 2-acrylamide-2-methyl propane sulphonic acid as monomers. The copolymer was blended with the PVDF powder to prepare the antifouling membrane via the immersed phase inversion method. The antifouling properties of the modified PVDF membrane were studied by X-ray photoelectron spectroscopy, field emission scanning electron microscopy, water contact angle measurement, zeta-potential measurement, protein adsorption, microbial adhesion and filtration experiments. The modified PVDF membrane showed limited adsorption and adhesion of protein bovine serum albumin and microbes (Escherichia coli and Saccharomyces cerevisiae) with increasing copolymer concentration in the casting solution. The modified PVDF membrane exhibited excellent antibiofouling properties.

  5. Dispersion strategies and role of interfacial phenomena in dielectric polymer nanocomposites

    NASA Astrophysics Data System (ADS)

    Khodaparast, Payam

    Owing to unique characteristics of nanoparticles such as high surface to volume ratio, it is postulated that nanoparticle-modified polymers exhibit properties beyond those predicted by effective media theories. In the case of dielectric nanoparticles in a polymer, it is expected that dielectric properties of the nanocomposite are dominated by the expansive interface rather than anticipated by the inherent properties of individual components. An in-depth review of dielectric polymer nanocomposites shows conflicting trends where addition of nano-sized particles resulted in increase or decrease in dielectric properties. This contradictory behavior could mainly stem from 1- the state of dispersion of nanoparticles and 2-The unique nature of interface based on the particle-polymer system. The hypothesis of the proposed research is that the role of the interfacial region is not only influenced by its expansive nature but is also governed by their interaction at nanoscale regime. In order to achieve a high internal surface area, the first important challenge to address is controlling the state of dispersion and disaggregation of nanoparticles. Therefore the first goal of this research is studying the effectiveness of different processing methods in achieving uniform nanoscale dispersion in dielectric polymer nanocomposites. Silane functionalization of titania nanoparticles is investigated as one possible solution of better dispersion of titania in PVDF polymer where two coupling agents namely, aminopropyltriethoxy silane called as APS, and Nonafluorohexyltriethoxysilane called as FHES, are studied. FHES is shown to be more effective in reducing the average aggregate size of titania nanoparticles in PVDF matrix to below 100nm, whereas the average aggregate size in untreated and APS-functionalized TiO2/PVDF nanocomposite was approximately one to two orders of magnitude higher than that. Dielectric permittivity of FHES-functionalized TiO2/PVDF nanocomposite, showed

  6. Effect of electro-activated brine solution on the migration of metallic ions from the cans to the product in sterilized canned sweet corn.

    PubMed

    Liato, Viacheslav; Labrie, Steve; Benali, Marzouk; Aider, Mohammed

    2016-11-01

    Tinplate cans were used to study if electro-activated brine solution (EAS) is more corrosive than conventional one by ICP analysis. The results showed different effects of EAS on cans, alone or filled with product. Acidic EAS (pH 2-3) and Redox +900 to +1200 mV highly reacted with the cans. The concentrations of Zn, Fe, and Cu in the solution were 0.028, 28.81, and 0.022 ppm, respectively. No Sn migration was observed in this case. When neutral or acidic chlorine-free EAS was used, no significant difference was observed in comparison with the corrosivity of standard NaCl brine. Alkaline EAS with pH>10 and negative E (≤-966 mV) did not affect Zn, Fe, and Cu migration. However, it affected tin migration. Nevertheless, it is important to mention that even if some corrosion was observed, it was in the limit of the permitted level of concentration when the cans were filled with a product.

  7. Clarification of Orange Press Liquors by PVDF Hollow Fiber Membranes

    PubMed Central

    Simone, Silvia; Conidi, Carmela; Ursino, Claudia; Cassano, Alfredo; Figoli, Alberto

    2016-01-01

    Press liquors are typical by-products of the citrus juice processing characterized by a high content of organic compounds and associated problems of environmental impact, which imply high treatment costs. However, these wastes contain a great number of health promoting substances, including fibers, carotenoids and phenolic compounds (mainly flavonoids), whose recovery against waste-destruction technologies is very attractive for new business opportunities. In this work, the clarification of orange press liquor by using microfiltration (MF) membranes is studied as a preliminary step to obtain a permeate stream enriched in antioxidant compounds which can be further processed to produce extracts of nutraceutical and/or pharmaceutical interest. MF poly(vinylidene fluoride) (PVDF) hollow fibers were prepared by the dry/wet spinning technique. A series of fibers was produced from the same polymeric dope, in order to investigate the effect of selected spinning parameters, i.e., bore fluid composition and flowrate, on their properties. The morphology of the produced fibers was analyzed by Scanning Electron Microscopy (SEM). Fibers were further characterized for their mechanical properties, porosity, bubble point, pore size distribution and pure water permeability (PWP). Some of the produced fibers exhibited high permeability (pure water permeability ~530 L/m2·h·bar), coupled to good mechanical resistance and pore size in the range of MF membranes. These fibers were selected and used for the clarification of press liquor from orange peel processing. In optimized operating conditions, the selected fibers produced steady-state fluxes of about 41 L/m2·h with rejections towards polyphenols and total antioxidant activity of 4.1% and 1.4%, respectively. PMID:26805899

  8. Clarification of Orange Press Liquors by PVDF Hollow Fiber Membranes.

    PubMed

    Simone, Silvia; Conidi, Carmela; Ursino, Claudia; Cassano, Alfredo; Figoli, Alberto

    2016-01-20

    Press liquors are typical by-products of the citrus juice processing characterized by a high content of organic compounds and associated problems of environmental impact, which imply high treatment costs. However, these wastes contain a great number of health promoting substances, including fibers, carotenoids and phenolic compounds (mainly flavonoids), whose recovery against waste-destruction technologies is very attractive for new business opportunities. In this work, the clarification of orange press liquor by using microfiltration (MF) membranes is studied as a preliminary step to obtain a permeate stream enriched in antioxidant compounds which can be further processed to produce extracts of nutraceutical and/or pharmaceutical interest. MF poly(vinylidene fluoride) (PVDF) hollow fibers were prepared by the dry/wet spinning technique. A series of fibers was produced from the same polymeric dope, in order to investigate the effect of selected spinning parameters, i.e., bore fluid composition and flowrate, on their properties. The morphology of the produced fibers was analyzed by Scanning Electron Microscopy (SEM). Fibers were further characterized for their mechanical properties, porosity, bubble point, pore size distribution and pure water permeability (PWP). Some of the produced fibers exhibited high permeability (pure water permeability ~530 L/m²·h·bar), coupled to good mechanical resistance and pore size in the range of MF membranes. These fibers were selected and used for the clarification of press liquor from orange peel processing. In optimized operating conditions, the selected fibers produced steady-state fluxes of about 41 L/m²·h with rejections towards polyphenols and total antioxidant activity of 4.1% and 1.4%, respectively.

  9. Fabrication of Poly(vinylidene fluoride) (PVDF) Nanofibers Containing Nickel Nanoparticles as Future Energy Server Materials.

    PubMed

    Sheikh, Faheem A; Cantu, Travis; Macossay, Javier; Kim, Hern

    2011-04-01

    In the present study, we introduce Poly(vinylidene fluoride) (PVDF) nanofibers containing nickel (Ni) nanoparticles (NPs) as a result of an electrospinning. Typically, a colloidal solution consisting of PVDF/Ni NPs was prepared to produce nanofibers embedded with solid NPs by electrospinning process. The resultant nanostructures were studied by SEM analyses, which confirmed well oriented nanofibers and good dispersion of Ni NPs over them. The XRD results demonstrated well crystalline feature of PVDF and Ni in the obtained nanostructures. Physiochemical aspects of prepared nano-structures were characterized for TEM which confirmed nanofibers were well-oriented and had good dispersion of Ni NPs. Furthermore, the prepared nano-structures were studied for hydrogen production applications. Due to high surface to volume ratio of nanofibers form than the thin film ones, there was tremendous increase in the rate of hydrogen production. Overall, results satisfactorily confirmed the use of these materials in hydrogen production.

  10. Evolution of polyvinylidene fluoride (PVDF) hierarchical morphology during slow gelation process and its superhydrophobicity.

    PubMed

    Li, Xianfeng; Zhou, Chong; Du, Runhong; Li, Nana; Han, Xutong; Zhang, Yufeng; An, Shulin; Xiao, Changfa

    2013-06-26

    In the paper, we proposed an evolution process of polyvinylidene fluoride (PVDF) macromolecular aggregation in a mixed solvent through the simple and slow gelation process at room temperature. The mixed solvent is prepared with a room-temperature solvent and a high-temperature solvent. The evolution process can be terminated by quenching and exchanging with nonsolvent in a nonsolvent coagulation bath properly, and then the vivid petal-like nanostructure and microspherulite is formed simultaneously. This hierarchical morphology endows PVDF with superhydrophobic and self-cleaning properties, which is useful to PVDF coating and membrane materials. The evolution processes are investigated through the measurements of differential scanning calorimetry (DSC), X-ray diffraction (XRD). In addition, the rheological properties of solution, dry gel and wet gel, are explored.

  11. Hybrid energy harvester based on nanopillar solar cells and PVDF nanogenerator.

    PubMed

    Lee, Dae-Yeong; Kim, Hyunjin; Li, Hua-Min; Jang, A-Rang; Lim, Yeong-Dae; Cha, Seung Nam; Park, Young Jun; Kang, Dae Joon; Yoo, Won Jong

    2013-05-03

    A tandem device which integrates a PVDF nanogenerator and silicon (Si) nanopillar solar cell is fabricated. The Si nanopillar solar cell was fabricated using a mask-free plasma etching technique and annealing process. The PVDF nanogenerator was stacked on top of the Si nanopillar solar cell using a spinning method. The optical properties and the device performance of nanowire solar cells have been characterized, and the dependence of device performance versus annealing time or method has been investigated. Furthermore, the PVDF nanogenerator was operated with a 100 dB sound wave and a 0.8 V peak to peak output voltage was generated. This tandem device can successfully harvest energy from both sound vibration and solar light, demonstrating its strong potential as a future ubiquitous energy harvester.

  12. Effects of CNT inclusions on structure and dielectric properties of PVDF/CNT nanocomposites

    NASA Astrophysics Data System (ADS)

    Kripotou, Sotiria; Sovatzoglou, Spyridon; Pandis, Christos; Kuliček, Jaroslav; Mičušík, Matej; Omastova, Maria; Kyritsis, Apostolos; Konsta, Amalia; Pissis, Polycarpos

    2016-08-01

    The effects of multiwall carbon nanotube (CNT) inclusions on the crystalline structure of poly(vinylidene fluoride) (PVDF), and on the dielectric properties of PVDF/CNT nanocomposites (NCs), prepared by melt mixing, were investigated by employing X-ray diffraction, differential scanning calorimetry, and dielectric spectroscopy techniques. Our results imply that, in the NCs, the formation of β-phase crystals depends on specific compression treatment in the melt and fast cooling. Dielectric measurements on NCs, with CNT concentrations below the electrical percolation threshold, reveal that the dielectric strength of the two relaxation processes in the amorphous phase and dielectric permittivity, ɛ‧, measured within the broad temperature range from -150 °C to 60 °C, increase strongly with increasing CNT concentration. This enhancement of amorphous PVDF polarizability has been attributed to the increase of the local electric field, due to local polarization generated at the surface of conductive inclusions/CNT clusters.

  13. Hydrophobic asymmetric ultrafiltration PVDF membranes: an alternative separator for VFB with excellent stability.

    PubMed

    Wei, Wenping; Zhang, Huamin; Li, Xianfeng; Zhang, Hongzhang; Li, Yun; Vankelecom, Ivo

    2013-02-14

    Polyvinylidene fluoride (PVDF) ultrafiltration membranes were investigated for the first time in vanadium redox flow battery (VFB) applications. Surprisingly, PVDF ultrafiltration membranes with hydrophobic pore walls and relatively large pore sizes of several tens of nanometers proved able to separate vanadium ions and protons efficiently, thus being suitable as a VFB separator. The ion selectivity of this new type of VFB membrane could be tuned readily by controlling the membrane morphology via changes in the composition of the membrane casting solution, and the casting thickness. The results showed that the PVDF membranes offered good performances and excellent stability in VFB applications, where it could, performance-wise, truly substitute Nafion in VFB applications, but at a much lower cost.

  14. Alternating magnetic field heat behaviors of PVDF fibrous mats filled with iron oxide nanoparticles

    NASA Astrophysics Data System (ADS)

    Kim, Jinu; Choi, Jung-Su; Yang, Heejae; Ko, Frank K.; Kim, Ki Hyeon

    2016-05-01

    To study the magnetic heat behaviors, iron oxide nanoparticles (IONPs) and the polyvinylidene fluoride (PVDF) fibrous mats filled with IONPs were prepared by using coprecipitaion method and the electrospinning technique. The synthesized IONPs exhibited a magnetization of about 72 emu/g with average diameter of about 10 nm. The magnetizations of PVDF fibrous mats filled with IONPs showed 2.6 emu/g, 5.5 emu/g and 9.9 emu/g for 5 wt.%, 10 wt.% and 20 wt.% IONPs concentration, respectively. The heat of the magnetic fibrous mats were measured under various alternating magnetic fields (90, 128, and 167 Oe), frequencies (190, 250 and 355 kHz). The maximum saturated temperature showed up to 62 °C for 20 wt.% IONPs filled in PVDF fibrous mat under 167 Oe and 355 kHz.

  15. The effect of PVDF-TrFE scaffolds on stem cell derived cardiovascular cells.

    PubMed

    Hitscherich, Pamela; Wu, Siliang; Gordan, Richard; Xie, Lai-Hua; Arinzeh, Treena; Lee, Eun Jung

    2016-07-01

    Recently, electrospun polyvinylidene fluoride (PVDF) and polyvinylidene fluoride-trifluoroethylene (PVDF-TrFE) scaffolds have been developed for tissue engineering applications. These materials have piezoelectric activity, wherein they can generate electric charge with minute mechanical deformations. Since the myocardium is an electroactive tissue, the unique feature of a piezoelectric scaffold is attractive for cardiovascular tissue engineering applications. In this study, we examined the cytocompatibility and function of pluripotent stem cell derived cardiovascular cells including mouse embryonic stem cell-derived cardiomyocytes (mES-CM) and endothelial cells (mES-EC) on PVDF-TrFE scaffolds. MES-CM and mES-EC adhered well to PVDF-TrFE and became highly aligned along the fibers. When cultured on scaffolds, mES-CM spontaneously contracted, exhibited well-registered sarcomeres and expressed classic cardiac specific markers such as myosin heavy chain, cardiac troponin T, and connexin43. Moreover, mES-CM cultured on PVDF-TrFE scaffolds responded to exogenous electrical pacing and exhibited intracellular calcium handling behavior similar to that of mES-CM cultured in 2D. Similar to cardiomyocytes, mES-EC also demonstrated high viability and maintained a mature phenotype through uptake of low-density lipoprotein and expression of classic endothelial cell markers including platelet endothelial cell adhesion molecule, endothelial nitric oxide synthase, and the arterial specific marker, Notch-1. This study demonstrates the feasibility of PVDF-TrFE scaffold as a candidate material for developing engineered cardiovascular tissues utilizing stem cell-derived cells. Biotechnol. Bioeng. 2016;113: 1577-1585. © 2015 Wiley Periodicals, Inc.

  16. Microsequence analysis of electroblotted proteins. I. Comparison of electroblotting recoveries using different types of PVDF membranes.

    PubMed

    Mozdzanowski, J; Speicher, D W

    1992-11-15

    The most effective protein purification method of low picomole amounts for sequence analysis involves polyacrylamide gel electrophoresis followed by electroblotting to polyvinylidene difluoride (PVDF) membranes. Since a critical factor in this procedure is the protein recovery at the blotting step, different types of PVDF membranes were systematically evaluated for their ability to bind proteins during electrotransfer. Differences in electroblotting recoveries occurred between types of PVDF membranes for some proteins. Some variability persisted even when optimized electroblotting procedures were used which reduce the sodium dodecyl sulfate (SDS) concentration in the gel and improve protein-PVDF binding. The membranes which were evaluated could be grouped as either "high retention" membranes (ProBlott, Trans-Blot, and Immobilon-PSQ) or "low retention" membranes (Immobilon-P and Westran). The high retention membranes showed higher protein recoveries under most conditions tested, especially for small proteins or peptides. These high retention membranes were also less sensitive to the exact electroblotting conditions, especially those factors which affect the amount of SDS present during either electrotransfer or direct adsorption from protein solutions. High retention PVDF membranes are therefore preferred in most cases for optimal protein or peptide recovery prior to direct sequence analysis. In contrast, low retention membranes are preferred for procedures where subsequent extraction of the proteins from the membranes is required. Even under identical conditions, substantial protein-to-protein variation for both adsorption and subsequent extraction is routinely observed for both groups of membranes, indicating that the nature of protein-PVDF interactions is more complex than simple hydrophobic interactions.

  17. Preparation of Sulfobetaine-Grafted PVDF Hollow Fiber Membranes with a Stably Anti-Protein-Fouling Performance

    PubMed Central

    Li, Qian; Lin, Han-Han; Wang, Xiao-Lin

    2014-01-01

    Based on a two-step polymerization method, two sulfobetaine-based zwitterionic monomers, including 3-(methacryloylamino) propyl-dimethyl-(3-sulfopropyl) ammonium hydroxide (MPDSAH) and 2-(methacryloyloxyethyl) ethyl-dimethyl-(3-sulfopropyl) ammonium (MEDSA), were successfully grafted from poly(vinylidene fluoride) (PVDF) hollow fiber membrane surfaces in the presence of N,N′-methylene bisacrylamide (MBAA) as a cross-linking agent. The mechanical properties of the PVDF membrane were improved by the zwitterionic surface layers. The surface hydrophilicity of PVDF membranes was significantly enhanced and the polyMPDSAH-g-PVDF membrane showed a higher hydrophilicity due to the higher grafting amount. Compared to the polyMEDSA-g-PVDF membrane, the polyMPDSAH-g-PVDF membrane showed excellent significantly better anti-protein-fouling performance with a flux recovery ratio (RFR) higher than 90% during the cyclic filtration of a bovine serum albumin (BSA) solution. The polyMPDSAH-g-PVDF membrane showed an obvious electrolyte-responsive behavior and its protein-fouling-resistance performance was improved further during the filtration of the protein solution with 100 mmol/L of NaCl. After cleaned with a membrane cleaning solution for 16 days, the grafted MPDSAH layer on the PVDF membrane could be maintain without any chang; however, the polyMEDSA-g-PVDF membrane lost the grafted MEDSA layer after this treatment. Therefore, the amide group of sulfobetaine, which contributed significantly to the higher hydrophilicity and stability, was shown to be imperative in modifying the PVDF membrane for a stable anti-protein-fouling performance via the two-step polymerization method. PMID:24957171

  18. Preparation of Sulfobetaine-Grafted PVDF Hollow Fiber Membranes with a Stably Anti-Protein-Fouling Performance.

    PubMed

    Li, Qian; Lin, Han-Han; Wang, Xiao-Lin

    2014-04-08

    Based on a two-step polymerization method, two sulfobetaine-based zwitterionic monomers, including 3-(methacryloylamino) propyl-dimethyl-(3-sulfopropyl) ammonium hydroxide (MPDSAH) and 2-(methacryloyloxyethyl) ethyl-dimethyl-(3-sulfopropyl) ammonium (MEDSA), were successfully grafted from poly(vinylidene fluoride) (PVDF) hollow fiber membrane surfaces in the presence of N,N'-methylene bisacrylamide (MBAA) as a cross-linking agent. The mechanical properties of the PVDF membrane were improved by the zwitterionic surface layers. The surface hydrophilicity of PVDF membranes was significantly enhanced and the polyMPDSAH-g-PVDF membrane showed a higher hydrophilicity due to the higher grafting amount. Compared to the polyMEDSA-g-PVDF membrane, the polyMPDSAH-g-PVDF membrane showed excellent significantly better anti-protein-fouling performance with a flux recovery ratio (RFR) higher than 90% during the cyclic filtration of a bovine serum albumin (BSA) solution. The polyMPDSAH-g-PVDF membrane showed an obvious electrolyte-responsive behavior and its protein-fouling-resistance performance was improved further during the filtration of the protein solution with 100 mmol/L of NaCl. After cleaned with a membrane cleaning solution for 16 days, the grafted MPDSAH layer on the PVDF membrane could be maintain without any chang; however, the polyMEDSA-g-PVDF membrane lost the grafted MEDSA layer after this treatment. Therefore, the amide group of sulfobetaine, which contributed significantly to the higher hydrophilicity and stability, was shown to be imperative in modifying the PVDF membrane for a stable anti-protein-fouling performance via the two-step polymerization method.

  19. Crystallization and mechanical behavior of the ferroelectric polymer nonwoven fiber fabrics for highly durable wearable sensor applications

    NASA Astrophysics Data System (ADS)

    Liu, Z. H.; Pan, C. T.; Yen, C. K.; Lin, L. W.; Huang, J. C.; Ke, C. A.

    2015-08-01

    The mechanical characterization of the electrospinning polyvinylidene fluoride (PVDF) nonwoven fiber fabrics (NFFs) doped with multi-walled carbon nanotubes (MWCNTs) was investigated. Piezoelectric composite nanofibers of the PVDF/MWCNTs were directly electrospun by the hollow cylindrical near-field electrospinning (HCNFES) without any post-poling treatment. We have made the HCNFES NFFs consisted of high-orderly arranged nanofiber assemblies for further characterizing the effect of MWCNTs filling PVDF nanofibers. An in situ electrical poling and high uniaxial stretching imparted on the polymer jet during the HCNFES process, which naturally align the dipoles in the PVDF crystals and promote the formation of the polar β-crystalline phase within the fibers. Moreover, the reinforcement of the HCNFES PVDF nanofibers indicated the improvement in mechanical properties and the degree of high oriented extended-chain crystallites through adding adequate contents of MWCNTs. In the case of alignment of the all-trans polymer chains in the vicinity of MWCNTs along the fiber axis, X-ray diffraction (XRD) patterns showed the strongest diffraction peak of the β-crystalline phase. In the comparison of the near-field electrospinning (NFES), the HCNFES nanofibers with smooth surface and smaller diameter can easily form high density structural NFFs. After nano-indentation and tensile strength measurements, the results indicated that the mechanical properties of the HCNFES NFFs are better than the NFES ones. When 16 wt% PVDF solution doped with 0.03 wt% MWCNTs, the results reveal that Young's modulus, hardness, yield stress, yield strain, ultimate tensile strength, and strain at break of the HCNFES composite NFFs are obviously enhanced to 1.39 GPa, 39.6 MPa, 28 MPa, 48.17 MPa, 3.3%, and 32.5%, respectively. Finally, a flexible wearable sensor made of three-dimensional piezoelectric NFFs was actually experimented. Outstanding mechanical properties with highly deformable of PVDF

  20. Polymer-Enriched 3D Graphene Foams for Biomedical Applications.

    PubMed

    Wang, Jun Kit; Xiong, Gordon Minru; Zhu, Minmin; Özyilmaz, Barbaros; Castro Neto, Antonio Helio; Tan, Nguan Soon; Choong, Cleo

    2015-04-22

    Graphene foams (GFs) are versatile nanoplatforms for biomedical applications because of their excellent physical, chemical, and mechanical properties. However, the brittleness and inflexibility of pristine GF (pGF) are some of the important factors restricting their widespread application. Here, a chemical-vapor-deposition-assisted method was used to synthesize 3D GFs, which were subsequently spin-coated with polymer to produce polymer-enriched 3D GFs with high conductivity and flexibility. Compared to pGF, both poly(vinylidene fluoride)-enriched GF (PVDF/GF) and polycaprolactone-enriched GF (PCL/GF) scaffolds showed improved flexibility and handleability. Despite the presence of the polymers, the polymer-enriched 3D GF scaffolds retained high levels of electrical conductivity because of the presence of microcracks that allowed for the flow of electrons through the material. In addition, polymer enrichment of GF led to an enhancement in the formation of calcium phosphate (Ca-P) compounds when the scaffolds were exposed to simulated body fluid. Between the two polymers tested, PCL enrichment of GF resulted in a higher in vitro mineralization nucleation rate because the oxygen-containing functional group of PCL had a higher affinity for Ca-P deposition and formation compared to the polar carbon-fluorine (C-F) bond in PVDF. Taken together, our current findings are a stepping stone toward future applications of polymer-enriched 3D GFs in the treatment of bone defects as well as other biomedical applications.

  1. Polymer-ZnO nanocomposites foils and thin films for UV protection

    SciTech Connect

    Shanshool, Haider Mohammed; Yahaya, Muhammad; Abdullah, Ibtisam Yahya; Yunus, Wan Mahmood Mat

    2014-09-03

    The damage of UV radiation on human eye and skin is extensively studied. In the present work, the nanocomposites foils and thin films have been prepared by using casting method and spin coating, respectively. Nanocomposites were prepared by mixing ZnO nanoparticles with Polymethyl methacrylate (PMMA) and Polyvinylidene fluoride (PVDF) as polymer matrix. Different contents of ZnO nanoparticles were used as filler in the nanocomposites. UV-Vis spectra showed very low transmittance in UV region that decreases with increase content of ZnO. PVDF/ZnO samples showed the lowest transmittance. The rough surface of PVDF was observed from SEM image. While a homogeneous dispersion of ZnO nanoparticles in PMMA were indicated by FESEM images.

  2. Dye-sensitized solar cells using polymer electrolytes based on poly(vinylidene fluoride-hexafluoro propylene) nanofibers by electrospinning method.

    PubMed

    Park, Sung-Hae; Kim, Ji-Un; Lee, Seong-Yeop; Lee, Won-Ki; Lee, Jin-Kook; Kim, Mi-Ra

    2008-09-01

    The dye-sensitized solar cell (DSSC) devices using polymer electrolytes based on electrospun poly(vinylidene fluoride-hexafluoro propylene) (PVDF-HFP) nanofibers were fabricated and investigated the photovoltaic performances. The electrospun PVDF-HFP nanofibers were prepared by various parameters such as; polymer concentrations, applied voltages, and tip to collector distances (TCD) by the electrospinning method. The open circuit voltage (V(OC)), short circuit current (J(SC)), fill factor (FF), and overall power conversion efficiency (eta) of DSSC devices using electro-spun PVDF-HFP nanofibers were 0.7180-0.7420 V, 9.7200-10.8837 mA/cm2, 0.5610-0.6250, and 4.1700-5.0186%, respectively. When 15 wt% of polymer concentration, 14 kV of applied voltage, and 14 cm of TCD is applied to fabricate the PVDF-HFP nanofiber, the electrospun PVDF-HFP nanofiber should be the regular diameter of a nanofiber, the power conversion efficiency of the DSSC device reached 5.0186% as the best result.

  3. Multiscale Simulations of Energy Storage in Polymers

    NASA Astrophysics Data System (ADS)

    Ranjan, V.; van Duin, A.; Buongiorno Nardelli, M.; Bernholc, J.

    2012-02-01

    Polypropelene is the most used capacitor dielectric for high energy density storage. However, exotic materials such as copolymerized PVDF and, more recently, polythiourea, could potentially lead to an order of magnitude increase in the stored energy density [1,2]. In our previous investigations we demonstrated that PVDF-CTFE possesses non-linear dielectric properties under applied electric field. These are characterized by transitions from non-polar to polar phases that lead enhanced energy density. Recent experiments [3] have also suggested that polythiourea may be another potential system with high energy-density storage and low loss. However, the characteristics of this emerging material are not yet understood and even its preferred crystalline phases are not known. We have developed a multiscale approach to predicting polymer self-organization using the REAX force field and molecular dynamics simulations. We find that polythiourea chains tend to coalesce in nanoribbon-type structures and prefer an anti-polar interchain ordering similar to PVDF. These results suggest a possible role of topological phase transitions in shaping energy storage in this system.[4pt] [1] B. Chu et al, Science 313, 334 (2006).[0pt] [2] V. Ranjan et al., PRL 99, 047801 (2007).[0pt] [3] Q. Zhang, private communication

  4. Ferroelectric polymer-ceramic composite thick films for energy storage applications

    SciTech Connect

    Singh, Paritosh; Borkar, Hitesh; Singh, B. P.; Singh, V. N.; Kumar, Ashok

    2014-08-15

    We have successfully fabricated large area free standing polyvinylidene fluoride -Pb(Zr{sub 0.52}Ti{sub 0.48})O{sub 3} (PVDF-PZT) ferroelectric polymer-ceramic composite (wt% 80–20, respectively) thick films with an average diameter (d) ∼0.1 meter and thickness (t) ∼50 μm. Inclusion of PZT in PVDF matrix significantly enhanced dielectric constant (from 10 to 25 at 5 kHz) and energy storage capacity (from 11 to 14 J/cm{sup 3}, using polarization loops), respectively, and almost similar leakage current and mechanical strength. Microstructural analysis revealed the presence of α and β crystalline phases and homogeneous distribution of PZT crystals in PVDF matrix. It was also found that apart from the microcrystals, well defined naturally developed PZT nanocrystals were embedded in PVDF matrix. The observed energy density indicates immense potential in PVDF-PZT composites for possible applications as green energy and power density electronic elements.

  5. Performance of Stainless Steel Mesh Cathode and PVDF-graphite Cathode in Microbial Fuel Cells

    NASA Astrophysics Data System (ADS)

    Huang, Liping; Tian, Ying; Li, Mingliang; He, Gaohong; Li, Zhikao

    2010-11-01

    Inexpensive and conductive materials termed as stainless steel mesh and polyvinylidene fluoride (PVDF)-graphite were currently used as the air cathode electrodes in MFCs for the investigation of power production. By loading PTFE (poly(tetrafluoroethylene)) on the surface of stainless steel mesh, electricity production reached 3 times as high as that of the naked stainless steel. A much high catalytic activity for oxygen reduction was exhibited by Pt based and PTFE loading stainless steel mesh cathode, with an electricity generation of 1144±44 mW/m2 (31±1 W/m3) and a Coulombic efficiency (CE) of 77±2%. When Pt was replaced by an inexpensive transition metal based catalyst (cobalt tetramethylphenylporphyrin, CoTMPP), power production and CE were 845±21 mW/m2 (23±1 W/m3) and 68±1%, respectively. Accordingly, power production from PVDF-graphite (hydrophobic) MFC and PVDF-graphite (hydrophile) MFC were 286±20 mW/m2(8±1 W/m3) and 158±13 mW/m2(4±0.4 W/m3), respectively using CoTMPP as catalyst. These results give us new insight into materials like stainless steel mesh and PVDF-graphite as low cost cathode for reducing the costs of MFCs for wastewater treatment applications.

  6. Structural and friction characteristics of g-C3N4/PVDF composites

    NASA Astrophysics Data System (ADS)

    Zhu, Lin; Wang, Ya; Hu, Fang; Song, Haojie

    2015-08-01

    This paper introduced the preparation, structural, and friction characteristics of graphite-like carbon nitride (g-C3N4)/poly(vinylidene difluoride) (PVDF) composites. The g-C3N4/PVDF composites with different g-C3N4 contents were prepared via wet mixing and hot press molding technique. The structure, morphology, thermal properties, and friction characteristics were studied by X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy, scanning electron microscopy (SEM), thermo-gravimetric analysis (TGA), and universal micro-tribotester under dry sliding conditions. The XRD and FT-IR studies confirmed the incorporation of g-C3N4 into the PVDF matrix. The SEM results showed good dispersion of g-C3N4 in PVDF matrix. The "onset" temperature To of the composites increased with increasing the content of g-C3N4 filler, which confirmed the enhancement of thermal stability of the composites. The friction characteristics results indicated that small amount of g-C3N4 filler was not beneficial to reduce friction coefficient of the composite while large amount of filler had little effect on it. In addition, the g-C3N4 filler was beneficial to reduce wear loss of the composite, and the wear loss decreased with increasing the content of g-C3N4 filler.

  7. Process induced electroactive β-polymorph in PVDF: effect on dielectric and ferroelectric properties.

    PubMed

    Sharma, Maya; Madras, Giridhar; Bose, Suryasarathi

    2014-07-28

    The effects of various processing conditions, like annealing, poling, mechanical rolling and their combinations, on the dielectric and ferroelectric properties of PVDF [poly(vinylidene fluoride)] were systematically studied in this work. Further, the effect of processing sequence on the structure and properties was investigated. While all the processing conditions adopted here resulted in phase transformation of the α- to electroactive β-polymorph in PVDF, the fraction of β-phase developed was observed to be strongly contingent on the adopted process. The transformation of α to electroactive β-polymorph was determined by X-ray diffraction and FTIR. The neat PVDF showed only α-phase, whereas mechanically rolled samples exhibited the highest ca. 85% β-phase in PVDF. Both the permittivity and the loss tangent decreased in the samples which had undergone different processing conditions. The polarization-electric field (P-E) loops for all the samples were evaluated. Interestingly, the energy density, estimated from the electrical displacement-electric field (D-E) loops, was observed to be highest for the poled samples which were initially rolled. The results indicate that various processing conditions can influence the dielectric and the ferroelectric properties differently.

  8. A Basic Experimental Study for Imaging by Monopolar Pulse Radiated from Concave Polyvinylidene Fluoride (PVDF) Transducer

    NASA Astrophysics Data System (ADS)

    Ooyashiki, Atsuko; Yoshida, Yasuo; Inoue, Hiroshi; Murata, Kenji

    2004-05-01

    Monopolar C-mode imaging using a concaved polyvinylidene fluoride (PVDF) transducer was developed. The basic characteristics of the spreading of the ultrasound field are measured and discussed with respect to the imaging, along with the spatial resolution, and the C-mode image of a printed circuit board (PCB) surface.

  9. Quantitative electrochemical and electrochromic behavior of terthiophene and carbazole containing conjugated polymer network film precursors: EC-QCM and EC-SPR.

    PubMed

    Taranekar, Prasad; Fulghum, Timothy; Baba, Akira; Patton, Derek; Advincula, Rigoberto

    2007-01-16

    A comparative analysis of the copolymerization behavior between an electro-active terthiophene and a carbazole moiety of a conjugated polymer precursor was investigated using electrochemical and hyphenated electrochemical methods. Five different precursor polymers were first synthesized and characterized using NMR, IR, and GPC. The polymers include homopolymers of individual electro-active groups (P3T, P-CBZ) and different compositions of 25, 50, and 75% (P3TC-25, P3TC50, and P3TC-75) with respect to the two electro-active groups. Since the oxidation potentials of terthiophene and carbazole lie very close to each other, highly cross-linked copolymer films of varying extent were produced depending on the composition. The copolymerization extent was found to be dependent primarily on the amount of the terthiophene, which in this case provided for a more efficient carbazole polymerization and copolymerization than with just carbazole alone (homopolymer). The extent of copolymerization, electrochromic properties, and viscoelastic changes was quantitatively investigated using a number of hyphenated electrochemistry techniques: spectro-electrochemistry, electrochemical quartz crystal microbalance studies (EC-QCM), and electrochemical surface plasmon resonance spectroscopy (EC-SPR). Each technique revealed a unique aspect of the electrocopolymerization behavior that was used to define structure-property relationships and the deposition/copolymerization mechanism.

  10. Drawing of the hollow all-polymer Bragg fibers

    NASA Astrophysics Data System (ADS)

    Pone, Elio; Dubois, Charles; Gu, Ning; Gao, Yan; Dupuis, Alexandre; Boismenu, Francis; Lacroix, Suzanne; Skorobogatiy, Maksim

    2006-06-01

    Drawing of the hollow all-polymer Bragg fibers based on PMMA/PS and PVDF/PC materials combinations are demonstrated. Hole collapse during drawing effects the uniformity of a photonic crystal reflector in the resultant fiber. We first investigate how the core collapse effects fiber transmission properties. We then present modelling of fluid dynamics of hollow multilayer polymer fiber drawing. Particularly, hole collapse during drawing and layer thickness non-uniformity are investigated as a function of draw temperature, draw ratio, feeding speed, core pressurization and mismatch of material properties in a multilayer. Both the newtonian and non-newtonian cases are considered assuming slender geometries.

  11. Characterization of dielectric electroactive polymer transducers

    NASA Astrophysics Data System (ADS)

    Nielsen, Dennis; Møller, Martin B.; Sarban, Rahimullah; Lassen, Benny; Knott, Arnold; Andersen, Michael A. E.

    2014-03-01

    Throughout this paper, a small-signal model of the Dielectric Electro Active Polymer (DEAP) transducer is analyzed. The DEAP transducer have been proposed as an alternative to the electrodynamic transducer in sound reproduction systems. In order to understand how the DEAP transducer works, and provide guidelines for design optimization, accurate characterization of the transducer must be established. A small signal model of the DEAP transducer is derived and its validity is investigated using impedance measurements. Impedance measurements are shown for a push-pull DEAP based loudspeaker, and the dependency of the biasing voltage is explained. A measuring setup is proposed, which allows the impedance to be measured, while the DEAP transducer is connected to its biasing source.

  12. Haptic interfaces using dielectric electroactive polymers

    NASA Astrophysics Data System (ADS)

    Ozsecen, Muzaffer Y.; Sivak, Mark; Mavroidis, Constantinos

    2010-04-01

    Quality, amplitude and frequency of the interaction forces between a human and an actuator are essential traits for haptic applications. A variety of Electro-Active Polymer (EAP) based actuators can provide these characteristics simultaneously with quiet operation, low weight, high power density and fast response. This paper demonstrates a rolled Dielectric Elastomer Actuator (DEA) being used as a telepresence device in a heart beat measurement application. In the this testing, heart signals were acquired from a remote location using a wireless heart rate sensor, sent through a network and DEA was used to haptically reproduce the heart beats at the medical expert's location. A series of preliminary human subject tests were conducted that demonstrated that a) DE based haptic feeling can be used in heart beat measurement tests and b) through subjective testing the stiffness and actuator properties of the EAP can be tuned for a variety of applications.

  13. Application of a PVDF-based stress gauge in determining dynamic stress-strain curves of concrete under impact testing

    NASA Astrophysics Data System (ADS)

    Meng, Yi; Yi, Weijian

    2011-06-01

    Polyvinylidene fluoride (PVDF) piezoelectric material has been successfully applied in many engineering fields and scientific research. However, it has rarely been used for direct measurement of concrete stresses under impact loading. In this paper, a new PVDF-based stress gauge was developed to measure concrete stresses under impact loading. Calibrated on a split Hopkinson pressure bar (SHPB) with a simple measurement circuit of resistance strain gauges, the PVDF gauge was then used to establish dynamic stress-strain curves of concrete cylinders from a series of axial impact testing on a drop-hammer test facility. Test results show that the stress curves measured by the PVDF-based stress gauges are more stable and cleaner than that of the stress curves calculated with the impact force measured from a load cell.

  14. Preparation and characterization of a novel PVDF ultrafiltration membrane by blending with TiO2-HNTs nanocomposites

    NASA Astrophysics Data System (ADS)

    Zeng, Guangyong; He, Yi; Yu, Zongxue; Zhan, Yingqing; Ma, Lan; Zhang, Lei

    2016-05-01

    Novel polyvinylidene fluoride (PVDF) ultrafiltration membranes were prepared by blending with different contents of titanium dioxide-halloysite nanotubes (TiO2-HNTs) composites into the PVDF matrix. The effects of TiO2-HNTs content on the membrane performances, such as hydrophilicity, rejection ratio and antifouling properties were investigated in detail. X-ray diffraction (XRD), thermo-gravimetric analyzer (TGA) and scanning electron microscope (SEM) analyses showed that TiO2 was loaded on the surface of HNTs successfully and homogeneously by sol-gel method. The morphologies and microstructure of the membranes were characterized by SEM and atomic force microscopy (AFM). The contact angle (CA) tests indicated that the hydrophilicity of membranes was significantly increased with the addition of TiO2-HNTs. The pure water flux of 3%TiO2-HNTs/PVDF was increased by 264.8% and 35.6%, respectively, compared with pure PVDF membrane and 3%TiO2/PVDF membrane, although the rejection of bovine serum albumin (BSA) was slightly decreased. More importantly, TiO2-HNTs/PVDF membrane exhibited an excellent anti-fouling performance, which was attributed to the hydrophobic contaminants being resisted by hydrophilic nanoparticles. It can be expected that this work may provide some references to solve the dispersion of nanoparticle in the membrane and improve the anti-fouling performance of membrane in the field of wastewater treatment.

  15. Design and analysis of MEMS based PVDF ultrasonic transducers for vascular imaging.

    PubMed

    Chandrana, Chaitanya; Talman, James; Pan, Tao; Roy, Shuvo; Fleischman, Aaron

    2010-01-01

    Polyvinilidene fluoride (PVDF) single-element transducers for high-frequency (>30 MHz) ultrasound imaging applications have been developed using MEMS (Micro-electro-Mechanical Systems) compatible techniques. Performance of these transducers has been investigated by analyzing the sources and effects of on-chip parasitic capacitances on the insertion-loss of the transducers. Modeling and experimental studies showed that on-chip parasitic capacitances degraded the performance of the transducers and an improved method of fabrication was suggested and new devices were built. New devices developed with minimal parasitic effects were shown to improve the performance significantly. A 1-mm aperture PVDF device developed with minimal parasitic effects has resulted in a reduction of insertion loss of 21 dB compared with devices fabricated using a previous method.

  16. Wideband spherically focused PVDF acoustic sources for calibration of ultrasound hydrophone probes.

    PubMed

    Selfridge, A; Lewin, P A

    2000-01-01

    Several broadband sources have been developed for the purpose of calibrating hydrophones. The specific configuration described is intended for the calibration of hydrophones In a frequency range of 1 to 40 MHz. All devices used 25 /spl mu/m film of PVDF bonded to a matched backing. Two had radii of curvatures (ROC) of 25.4 and 127 mm with f numbers of 3.8 and 19, respectively. Their active element diameter was 0.28 in (6.60 mm). The active diameter of the third source used was 25 mm, and it had an ROC of 254 mm and an f number of 10. The use of a focused element minimized frequency-dependent diffraction effects, resulting in a smooth variation of acoustic pressure at the focus from 1 to 40 MHz. Also, using a focused PVDF source permitted calibrations above 20 MHz without resorting to harmonic generation via nonlinear propagation.

  17. A method to modify PVDF microfiltration membrane via ATRP with low-temperature plasma pretreatment

    NASA Astrophysics Data System (ADS)

    Han, Yu; Song, Shuijun; Lu, Yin; Zhu, Dongfa

    2016-08-01

    The hydrophilic modification of a polyvinylidene fluoride (PVDF) microfiltration membrane via pretreatment with argon plasma and direct surface-initiated atom transfer radical polymerization (ATRP) was studied. Both modified and unmodified PVDF membranes were characterized by Fourier transform infrared spectroscopy (FTIR), water contact angle, scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and pore size distribution measurements. FTIR and XPS spectra confirmed that sulfobetaine methacrylate (SBMA) had been grafted onto the membrane surface. The initial contact angle decreased from 87.0° to 29.8° and a water drop penetrated into the modified membrane completely in 8 s. The pore size distribution of the modified membrane exhibited a smaller mean value than that of the original membrane. The antifouling properties of the modified PVDF membrane were evaluated by a filtration test using bovine serum albumin (BSA) solution. The results showed that the initial flux of the modified membrane increased from 2140.1 L/m2 h to 2812.7 L/m2 h and the equilibrium flux of BSA solution increased from 31 L/m2 h to 53 L/m2 h.

  18. Positive temperature coefficient of magnetic anisotropy in polyvinylidene fluoride (PVDF)-based magnetic composites

    PubMed Central

    Liu, Yiwei; Wang, Baomin; Zhan, Qingfeng; Tang, Zhenhua; Yang, Huali; Liu, Gang; Zuo, Zhenghu; Zhang, Xiaoshan; Xie, Yali; Zhu, Xiaojian; Chen, Bin; Wang, Junling; Li, Run-Wei

    2014-01-01

    The magnetic anisotropy is decreased with increasing temperature in normal magnetic materials, which is harmful to the thermal stability of magnetic devices. Here, we report the realization of positive temperature coefficient of magnetic anisotropy in a novel composite combining β-phase polyvinylidene fluoride (PVDF) with magnetostrictive materials (magnetostrictive film/PVDF bilayer structure). We ascribe the enhanced magnetic anisotropy of the magnetic film at elevated temperature to the strain-induced anisotropy resulting from the anisotropic thermal expansion of the β-phase PVDF. The simulation based on modified Stoner-Wohlfarth model and the ferromagnetic resonance measurements confirms our results. The positive temperature coefficient of magnetic anisotropy is estimated to be 1.1 × 102 J m−3 K−1. Preparing the composite at low temperature can enlarge the temperature range where it shows the positive temperature coefficient of magnetic anisotropy. The present results may help to design magnetic devices with improved thermal stability and enhanced performance. PMID:25311047

  19. Hydrophilic modification of PVDF microfiltration membranes by adsorption of facial amphiphile cholic acid.

    PubMed

    Hu, Meng-Xin; Li, Ji-Nian; Zhang, Shi-Lin; Li, Liang; Xu, Zhi-Kang

    2014-11-01

    Amphiphilic molecules have been widely used in surface modification of polymeric materials. Bile acids are natural biological compounds and possess special facial amphiphilic structure with a unusual distribution of hydrophobic and hydrophilic regions. Based on the facial amphiphilicity, cholic acid (CA), one of the bile acids, was utilized for the hydrophilic modification of poly(vinylidene fluoride) (PVDF) microfiltration membranes via the hydrophobic interactions between the hydrophobic face of CA and the membrane surfaces. Ethanol, methanol, and water were respectively used as solvent during CA adsorption procedure. Their polarity affects the CA adsorption amount, as similar to CA concentration and adsorption time. There are no changes on the membrane surface morphology after CA adsorption. The hydrophilicity of PVDF membranes is greatly enhanced and the water drops permeates into the CA modified membranes quickly after modification. All these factors benefit to the permeation flux of membrane for water. When CA concentration is higher than 0.088 M, the water permeation flux is doubled as compared with the nascent PVDF membrane and shows a good stability during filtration procedure. These results reveal the promising potential of facial amphiphilic bile acids for the surface modification of polymeric materials.

  20. Effect of roll hot press temperature on crystallite size of PVDF film

    SciTech Connect

    Hartono, Ambran Sanjaya, Edi; Djamal, Mitra; Satira, Suparno; Bahar, Herman; Ramli

    2014-03-24

    Fabrication PVDF films have been made using Hot Roll Press. Preparation of samples carried out for nine different temperatures. This condition is carried out to see the effect of Roll Hot Press temperature on the size of the crystallite of PVDF films. To obtain the diffraction pattern of sample characterization is performed using X-Ray Diffraction. Furthermore, from the diffraction pattern is obtained, the calculation to determine the crystallite size of the sample by using the Scherrer equation. From the experimental results and the calculation of crystallite sizes obtained for the samples with temperature 130 °C up to 170 °C respectively increased from 7.2 nm up to 20.54 nm. These results show that increasing temperatures will also increase the size of the crystallite of the sample. This happens because with the increasing temperature causes the higher the degree of crystallization of PVDF film sample is formed, so that the crystallite size also increases. This condition indicates that the specific volume or size of the crystals depends on the magnitude of the temperature as it has been studied by Nakagawa.

  1. Tailor-made asymmetric PVDF hollow fibers for soluble gas removal

    SciTech Connect

    Li, K.; Kong, J.F.; Wang, D.; Teo, W.K.

    1999-06-01

    Tailor-made polyvinylidene fluoride (PVDF) asymmetric hollow-fiber membranes and their membrane modules were employed for soluble gas removal, such as H{sub 2}S from waste gas streams. This study focused on the techniques of fabricating and characterizing the PVDF asymmetric hollow-fiber membranes and their membrane modules for removal of H{sub 2}S using an aqueous solution containing 10% NaOH. A laminar parabolic velocity profile was used to characterize the flow of the H{sub 2}S gas mixture in the hollow-fiber lumen. Effects of operating conditions and the morphological structures of the membranes on the membrane`s coefficient, k{sub AM}, were examined both theoretically and experimentally. The capabilities of the hollow-fiber membranes developed for removal of H{sub 2}S from waste gas streams were evaluated and compared with conventional symmetric hydrophobic hollow-fiber membranes, such as polypropylene. An analysis of H{sub 2}S transfer across the more developed PVDF membranes reveals that the membrane`s coefficient, k{sub AM}, evaluated from its structure parameters, such as the effective surface porosity and mean radius, agreed well with the experimental data obtained from absorption experiments.

  2. Improved PVDF membrane performance by doping extracellular polymeric substances of activated sludge.

    PubMed

    Guan, Yan-Fang; Huang, Bao-Cheng; Qian, Chen; Wang, Long-Fei; Yu, Han-Qing

    2017-04-15

    Polyvinylidene fluoride (PVDF) membrane has been widely applied in water and wastewater treatment because of its high mechanical strength, thermal stability and chemical resistance. However, the hydrophobic nature of PVDF membrane makes it readily fouled, substantially reducing water flux and overall membrane rejection ability. In this work, an in-situ blending modifier, i.e., extracellular polymeric substances (EPS) from activated sludge, was used to enhance the anti-fouling ability of PVDF membrane. Results indicate that the pure water flux of the membrane and its anti-fouling performance were substantially improved by blending 8% EPS into the membrane. By introducing EPS, the membrane hydrophilicity was increased and the cross section morphology was changed when it interacted with polyvinl pyrrolidone, resulting in the formation of large cavities below the finger-like pores. In addition, the fraction of pores with a size of 100-500 nm increased, which was also beneficial to improving membrane performance. Surface thermodynamic calculations indicate the EPS-functionalized membrane had a higher cohesion free energy, implying its good pollutant rejection and anti-fouling ability. This work provides a simple, efficient and cost-effective method to improve membrane performance and also extends the applications of EPS.

  3. Polymer films

    DOEpatents

    Granick, Steve; Sukhishvili, Svetlana A.

    2004-05-25

    A film contains a first polymer having a plurality of hydrogen bond donating moieties, and a second polymer having a plurality of hydrogen bond accepting moieties. The second polymer is hydrogen bonded to the first polymer.

  4. Polymer films

    DOEpatents

    Granick, Steve; Sukhishvili, Svetlana A.

    2008-12-30

    A film contains a first polymer having a plurality of hydrogen bond donating moieties, and a second polymer having a plurality of hydrogen bond accepting moieties. The second polymer is hydrogen bonded to the first polymer.

  5. Strain properties analysis and wireless collection system of PVDF for structural local health monitoring of civil engineering structures

    NASA Astrophysics Data System (ADS)

    Yu, Yan; Wang, Yang; Dong, Weijie; Jin, Yajing; Ou, Jinping

    2009-07-01

    For large civil engineering structures and base establishments, for example, bridges, super-high buildings, long-span space structures, offshore platforms and pipe systems of water & gas supply, their lives are up to a few decades or centuries. Damaged by environmental loads, fatigue effects, corrosion effects and material aging, these structures experience inevitably such side effects as damage accumulation, resistance reduction and even accidents. The traditional civil structure is a kind of passive one, whose performance and status are unpredictable to a great extent, but the informatics' introduction breaks a new path to obtain the status of the structure, thus it is an important research direction to evaluate and improve reliability of civil structures by the use of monitoring and health diagnosis technique, and this also assures the security of service for civil engineering structures. Smart material structure, originated from the aerospace sector, has been a research hotspot in civil engineering, medicine, shipping, and so on. For structural health monitoring of civil engineering, the research about high-performance sensing unit of smart material structure is very important, and this will possibly push further the development and application of monitoring and health diagnosis techniques. At present, piezoelectric materials are one of the most widely used sensing materials among the research of smart material structures. As one of the piezoelectric materials, PVDF(Polyvinylidene Fluoride)film is widely considered for the advantages of low cost, good mechanical ability, high sensibility, the ability of being easily placed and resistance of corrosion. However, only a few studies exit about building a mature monitoring system using PVDF. In this paper, for the sake of using PVDF for sensing unit for structural local monitoring of civil engineering, the strain sensing properties of PVDF are studied in detail. Firstly, the operating mechanism of PVDF is analyzed

  6. Polymer electrolytes for a rechargeable li-Ion battery

    SciTech Connect

    Argade, S.D.; Saraswat, A.K.; Rao, B.M.L.; Lee, H.S.; Xiang, C.L.; McBreen, J.

    1996-10-01

    Lithium-ion polymer electrolyte battery technology is attractive for many consumer and military applications. A Li{sub x}C/Li{sub y}Mn{sub 2}O{sub 4} battery system incorporating a polymer electrolyte separator base on novel Li-imide salts is being developed under sponsorship of US Army Research Laboratory (Fort Monmouth NJ). This paper reports on work currently in progress on synthesis of Li-imide salts, polymer electrolyte films incorporating these salts, and development of electrodes and cells. A number of Li salts have been synthesized and characterized. These salts appear to have good voltaic stability. PVDF polymer gel electrolytes based on these salts have exhibited conductivities in the range 10{sup -4} to 10{sub -3} S/cm.

  7. Molecular modeling of the piezoelectric properties of ferroelectric composites containing polyvinylidene fluoride (PVDF) and either graphene or graphene oxide.

    PubMed

    Bystrov, Vladimir S; Bdikin, Igor K; Silibin, Maksim; Karpinsky, Dmitry; Kopyl, Svitlana; Paramonova, Ekaterina V; Goncalves, Gil

    2017-04-01

    Molecular modeling of ferroelectric composites containing polyvinylidene fluoride (PVDF) and either graphene (G) or graphene oxide (GO) were performed using the semi-empirical quantum approximation PM3 in HyperChem. The piezo properties of the composites were analyzed and compared with experimental data obtained for P(VDF-TrFE)-GO films. Qualitative agreement was obtained between the results of the modeling and the experimental results in terms of the properties of the measured effective piezoelectric coefficient d 33eff and its decrease in the presence of G/GO in comparison with the average computed piezoelectric coefficient . When models incorporating one or several G layers with 54 carbon atoms were investigated, the average piezoelectric coefficient was found to decrease to -9.8 pm/V for the one-sided model PVDF/G and to -18.98 pm/V for the sandwich model G/PVDF/G as compared with the calculated piezoelectric coefficient for pure PVDF ( = -42.2 pm/V computed in present work, and = -38.5 pm/V, obtained from J Mol Model 35 (2013) 19:3591-3602). When models incorporating one or several GO layers with 98 carbon atoms were considered, the piezoelectric coefficient was found to decrease to -14.6 pm/V for the one-sided PVDF/GO model and to -29.8 pm/V for the sandwich GO/PVDF/GO model as compared with the same calculated piezoelectric coefficient for pure PVDF.

  8. Honeycomb-like porous gel polymer electrolyte membrane for lithium ion batteries with enhanced safety

    NASA Astrophysics Data System (ADS)

    Zhang, Jinqiang; Sun, Bing; Huang, Xiaodan; Chen, Shuangqiang; Wang, Guoxiu

    2014-08-01

    Lithium ion batteries have shown great potential in applications as power sources for electric vehicles and large-scale energy storage. However, the direct uses of flammable organic liquid electrolyte with commercial separator induce serious safety problems including the risk of fire and explosion. Herein, we report the development of poly(vinylidene difluoride-co-hexafluoropropylene) polymer membranes with multi-sized honeycomb-like porous architectures. The as-prepared polymer electrolyte membranes contain porosity as high as 78%, which leads to the high electrolyte uptake of 86.2 wt%. The PVDF-HFP gel polymer electrolyte membranes exhibited a high ionic conductivity of 1.03 mS cm-1 at room temperature, which is much higher than that of commercial polymer membranes. Moreover, the as-obtained gel polymer membranes are also thermally stable up to 350°C and non-combustible in fire (fire-proof). When applied in lithium ion batteries with LiFePO4 as cathode materials, the gel polymer electrolyte demonstrated excellent electrochemical performances. This investigation indicates that PVDF-HFP gel polymer membranes could be potentially applicable for high power lithium ion batteries with the features of high safety, low cost and good performance.

  9. Preparation and characterization of modified nano-porous PVDF membrane with high antifouling property using UV photo-grafting

    NASA Astrophysics Data System (ADS)

    Rahimpour, A.; Madaeni, S. S.; Zereshki, S.; Mansourpanah, Y.

    2009-05-01

    In this study, the poly(vinylidene fluoride) (PVDF) membrane was prepared via immersion precipitation technique and modified by UV photo-grafting of hydrophilic monomers on the top membrane surface. Acrylic acid (AA) and 2-hydroxyethylmethacrylate (HEMA) as acrylic monomers and 2,4-phenylenediamine (PDA) and ethylene diamine (EDA) as amino monomers were used at different concentrations to modify the membrane and improve the hydrophilicity with less fouling tendency. Moreover the presence of benzophenon as photo-initiator for grafting the hydrophilic monomers onto PVDF membrane surface was elucidated. The virgin and modified PVDF membranes were characterized by contact angle, ATR-FTIR, SEM and cross-flow filtration. The contact angle measurements demonstrated that the hydrophilicities of the membranes were significantly enhanced by UV photo-grafting of hydrophilic monomers onto the membrane surface. The ATR-FTIR confirmed the occurrence of modification on PVDF membrane by UV photo-grafting. The pure water flux of membranes was declined by UV photo-grafting but the milk water permeation and protein rejection were slightly improved. Moreover the antifouling properties and flux recovery of PVDF membrane were improved by UV photo-grafting of hydrophilic monomers.

  10. Polymer-Ceramic Composite Materials for Pyroelectric Infrared Detectors: An Overview

    NASA Technical Reports Server (NTRS)

    Aggarwal, M. D; Currie, J. R.; Penn, B. G.; Batra, A. K.; Lal, R. B.

    2007-01-01

    Ferroelectrics:Polymer composites can be considered an established substitute for conventional electroceramics and ferroelectric polymers. The composites have a unique blend of polymeric properties such as mechanical flexibility, high strength, formability, and low cost, with the high electro-active properties of ceramic materials. They have attracted considerable interest because of their potential use in pyroelectric infrared detecting devices and piezoelectric transducers. These flexible sensors and transducers may eventually be useful for their health monitoring applications for NASA crew launch vehicles and crew exploration vehicles being developed. In the light of many technologically important applications in this field, it is worthwhile to present an overview of the pyroelectric infrared detector theory, models to predict dielectric behavior and pyroelectric coefficient, and the concept of connectivity and fabrication techniques of biphasic composites. An elaborate review of Pyroelectric-Polymer composite materials investigated to date for their potential use in pyroelectric infrared detectors is presented.

  11. Facile synthesis of nano cauliflower and nano broccoli like hierarchical superhydrophobic composite coating using PVDF/carbon soot particles via gelation technique.

    PubMed

    Sahoo, Bichitra Nanda; Balasubramanian, Kandasubramanian

    2014-12-15

    We have elucidated a cost effective fabrication technique to produce superhydrophobic polyvinylidene fluoride (PVDF/DMF/candle soot particle and PVDF/DMF/camphor soot particle composite) porous materials. The water repellent dry composite was formed by the interaction of non-solvent (methanol) into PVDF/carbon soot particles suspension in N,N-dimethylformamide (DMF). It is seen that longer quenching time effectively changes the surface morphology of dry composites. The nano broccoli like hierarchical microstructure with micro or nano scaled roughen surface was obtained for PVDF/DMF/camphor soot particle, which reveals water contact angle of 172° with roll off angle of 2°. However, composite coating of PVDF/DMF/candle soot particle shows nano cauliflower like hierarchical, which illustrates water contact angle of 169° with roll off angle of 3°. To elucidate the enhancement of water repellent property of PVDF composites, we further divulge the evolution mechanism of nano cauliflower and nano broccoli structure. In order to evaluate the water contact angle of PVDF composites, surface diffusion of water inside the pores is investigated. Furthermore, the addition of small amount of carbon soot particles in composite not only provides the crystallization of PVDF, but also leads to dramatical amendment of surface morphology which increases the surface texture and roughness for superhydrophobicity.

  12. Assessing the effects of sodium hypochlorite exposure on the characteristics of PVDF based membranes.

    PubMed

    Abdullah, Syed Z; Bérubé, Pierre R

    2013-09-15

    Sodium hypochlorite is commonly used as a cleaning agent to remove adsorbed foulants from PVDF based micro/ultra filtration membranes in water and wastewater treatment applications. Although effective for fouling control, extended sodium hypochlorite exposure can affect the physical/chemical characteristics and hinder the treatment performance of these membranes. To assess these effects, PVDF based membranes were exposed to sodium hypochlorite at different concentrations for varying periods of time, and the physical/chemical characteristics of the virgin and sodium hypochlorite exposed membranes were compared. The membranes were characterized based on chemical composition (FTIR and NMR), mechanical strength (yield strength), surface hydrophilicity (contact angle), pore size and porosity (scanning electron microscopy and challenge test), and membrane resistance (clean water permeation test). The results indicated that exposure dose and concentration of the sodium hypochlorite used have significant influence on the membrane characteristics. The impact of sodium hypochlorite exposure on the parameters investigated could be most accurately and consistently correlated to an exposure dose relationship of the form C(n)t (where, C = concentration and t = exposure time) rather than the Ct relationship commonly used to define the extent of exposure to cleaning agents. For all the parameters investigated, the power coefficient n was less than 1 indicating that time had a greater impact on the changes than did the concentration of the sodium hypochlorite. The results suggest that the use of sodium hypochlorite for chemical cleaning, at concentrations that are higher than those typically used for chemical cleaning would have less of an effect on the characteristics of the membrane materials. Changes in the characteristics were attributed to the oxidation of the hydrophilic additives (HA) present in blended PVDF membranes.

  13. Self-powered flexible Fe-doped RGO/PVDF nanocomposite: an excellent material for a piezoelectric energy harvester

    NASA Astrophysics Data System (ADS)

    Karan, Sumanta Kumar; Mandal, Dipankar; Khatua, Bhanu Bhusan

    2015-06-01

    In this work, we report the superior piezoelectric energy harvester ability of a non-electrically poled Fe-doped reduced graphene oxide (Fe-RGO)/poly(vinylidene fluoride) (PVDF) nanocomposite film prepared through a simple solution casting technique that favors the nucleation and stabilization of ~99% relative proportion of polar γ-phase. The piezoelectric energy harvester was made with non-electrically poled Fe-RGO/PVDF nanocomposite film that gives an open circuit output voltage and short circuit current up to 5.1 V and 0.254 μA by repetitive human finger imparting. The improvement of the output performance is influenced by the generation of the electroactive polar γ-phase in the PVDF, due to the electrostatic interactions among the -CH2-/-CF2- dipoles of PVDF and the delocalized π-electrons and remaining oxygen functionalities of Fe-doped RGO via ion-dipole and/or hydrogen bonding interactions. Fourier transform infrared spectroscopy (FT-IR) confirmed the nucleation of the polar γ-phase of PVDF by electrostatic interactions and Raman spectroscopy also supported the molecular interactions between the dipoles of PVDF and the Fe-doped RGO nanosheets. In addition, the nanocomposite shows a higher electrical energy density of ~0.84 J cm-3 at an electric field of 537 kV cm-1, which indicates that it is appropriate for energy storage capabilities. Moreover, the surface of the prepared nanocomposite film is electrically conducting and shows an electrical conductivity of ~3.30 × 10-3 S cm-1 at 2 wt% loading of Fe-RGO.In this work, we report the superior piezoelectric energy harvester ability of a non-electrically poled Fe-doped reduced graphene oxide (Fe-RGO)/poly(vinylidene fluoride) (PVDF) nanocomposite film prepared through a simple solution casting technique that favors the nucleation and stabilization of ~99% relative proportion of polar γ-phase. The piezoelectric energy harvester was made with non-electrically poled Fe-RGO/PVDF nanocomposite film that gives

  14. Patterned, highly stretchable and conductive nanofibrous PANI/PVDF strain sensors based on electrospinning and in situ polymerization

    NASA Astrophysics Data System (ADS)

    Yu, Gui-Feng; Yan, Xu; Yu, Miao; Jia, Meng-Yang; Pan, Wei; He, Xiao-Xiao; Han, Wen-Peng; Zhang, Zhi-Ming; Yu, Liang-Min; Long, Yun-Ze

    2016-01-01

    A facile fabrication strategy via electrospinning and followed by in situ polymerization to fabricate a patterned, highly stretchable, and conductive polyaniline/poly(vinylidene fluoride) (PANI/PVDF) nanofibrous membrane is reported. Owing to the patterned structure, the nanofibrous PANI/PVDF strain sensor can detect a strain up to 110%, for comparison, which is 2.6 times higher than the common nonwoven PANI/PVDF mat and much larger than the previously reported values (usually less than 15%). Meanwhile, the conductivity of the patterned strain sensor shows a linear response to the applied strain in a wide range from 0% to about 85%. Additionally, the patterned PANI/PVDF strain sensor can completely recover to its original electrical and mechanical values within a strain range of more than 22%, and exhibits good durability over 10 000 folding-unfolding tests. Furthermore, the strain sensor also can be used to detect finger motion. The results demonstrate promising application of the patterned nanofibrous membrane in flexible electronic fields.A facile fabrication strategy via electrospinning and followed by in situ polymerization to fabricate a patterned, highly stretchable, and conductive polyaniline/poly(vinylidene fluoride) (PANI/PVDF) nanofibrous membrane is reported. Owing to the patterned structure, the nanofibrous PANI/PVDF strain sensor can detect a strain up to 110%, for comparison, which is 2.6 times higher than the common nonwoven PANI/PVDF mat and much larger than the previously reported values (usually less than 15%). Meanwhile, the conductivity of the patterned strain sensor shows a linear response to the applied strain in a wide range from 0% to about 85%. Additionally, the patterned PANI/PVDF strain sensor can completely recover to its original electrical and mechanical values within a strain range of more than 22%, and exhibits good durability over 10 000 folding-unfolding tests. Furthermore, the strain sensor also can be used to detect finger

  15. PVDF-Nafion nanomembranes coated microneedles for in vivo transcutaneous implantable glucose sensing.

    PubMed

    Chen, Dajing; Wang, Cang; Chen, Wei; Chen, Yuquan; Zhang, John X J

    2015-12-15

    We demonstrate that microporous PVDF membranes sandwiched between multiple layers of nanomaterials can be used for continuous monitoring of glucose level in vivo. This is achieved by coating needle electrodes with Polyaniline nanofiber, Platinum nanoparticles, glucose oxidase enzyme and porous layers, successfully fabricated with layer-by-layer deposition. Nanoparticles incorporated into conductive Polyaniline nanofibers resulted in high surface to volume ratio and electrocatalytic activity for glucose enzyme. A composite coating membrane of porous PVDF and nano-sphere Nafion limited the glucose transportation and increased the lifetime of in vivo measurements. The glucose biosensor exhibited a sub-microamperometric output current, fast response time of less than 30s and a sensitivity of 0.23 μA/mM. The linear sensing range in terms of glucose concentration was from 0 to 20mM. Implantable experiments using mice models showed excellent response to the variation of blood glucose concentration while maintaining biocompatibility with the surrounding tissues. The sensitivity was shown to remain within 10% close to initial sensitivity within the 7 days of continuous monitoring, and maintain at 70% of the initial sensitivity within 21 days.

  16. PVDF array sensor for Lamb wave reception: Aircraft structural health monitoring

    NASA Astrophysics Data System (ADS)

    Ren, Baiyang; Lissenden, Cliff J.

    2016-02-01

    Fracture critical structures need structural health monitoring (SHM) to improve safety and reliability as well as reduce downtime and maintenance costs. Lamb waves provide promising techniques for on-line SHM systems because of their large volumetric coverage and good sensitivity to defects. Extensive research has focused on using features derived from time signals obtained at sparse locations distributed across the structure. Commonly used features are wave amplitude, energy, and time of arrival. However, the modal content of received Lamb waves contains valuable information about the existence and characteristics of defects, but cannot be determined from these signal features. Wave scattering at a defect often results in mode conversions in both transmitted and reflected waves. Features like change in time of arrival or amplitude reduction can be interpreted as being a result of mode conversion. This work is focused on the design of a 1D array sensor such that received wave signals at equally spaced locations are available for modal analysis in the wavenumber-frequency domain. PVDF (polyvinylidene fluoride) is selected as the active material of the sensor because of its low interference with wave fields in structures. The PVDF array sensor is fabricated to have 16 independent channels and its capability to detect and characterize different types of defects is demonstrated experimentally.

  17. Shock initiation studies of low density HMX using electromagnetic particle velocity and PVDF stress gauges

    SciTech Connect

    Sheffield, S.A.; Gustavsen, R.L.; Alcon, R.R.; Graham, R.A.; Anderson, M.U.

    1993-09-01

    Magnetic particle velocity and PVDF stress rate gauges have been used to measure the shock response of low density octotetramethylene tetranitramine (HMX) (1.24 &/cm{sup 3}). In experiments done at LANL, magnetic particle velocity gauges were located on both sides of the explosive. In nearly identical experiments done at SNL, PVDF stress rate gauges were located at the same positions so both particle velocity and stress histories were obtained for a particular experimental condition. Unreacted Hugoniot data were obtained and an EOS was developed by combining methods used by Hayes, Sheffield and Mitchell (for describing the Hugoniot of HNS at various densities) with Hermann`s P-{alpha} model. Using this technique, it is only necessary to know some thermodynamic constants or the Hugoniot of the initially solid material and the porous material sound speed to obtain accurate unreacted Hugoniots for the porous explosive. Loading and reaction paths were established in the stress-particle velocity plane for some experimental conditions. This information was used to determine a global reaction rate of {approx} 0.13 {mu}s{sup {minus}1} for porous HMX shocked to 0.8 GPa. At low input stresses the transmitted wave profiles had long rise times (up to 1 {mu}s) due to the compaction processes.

  18. Development of Cellulose/PVDF-HFP Composite Membranes for Advanced Battery Separators

    NASA Astrophysics Data System (ADS)

    Castillo, Alejandro; Agubra, Victor; Alcoutlabi, Mataz; Mao, Yuanbing

    Improvements in battery technology are necessary as Li-ion batteries transition from consumer electronic to vehicular and industrial uses. An important bottle-neck in battery efficiency and safety is the quality of the separators, which prevent electric short-circuits between cathode and anode, while allowing an easy flow of ions between them. In this study, cellulose acetate was dissolved in a mixed solvent with poly(vinylpyrrolidone) (PVP), and the mixture was forcespun in a peudo paper making process to yield nanofibrillated nonwoven mats. The mats were soaked in NaOH/Ethanol to strip PVP and regenerate cellulose from its acetate precursor. The cellulose mats were then dipped in poly(vinylidenefluoride-co-hexafluoropropylene) (PVDF-HFP) to yield the cellulose/PVDF-HFP composte membranes. These membranes were characterized chemically through FTIR spectroscopy and solvent-stability tests, thermally through DSC, physically by stress/strain measurements along with weight-based electrolyte uptake, and electrically by AC-impedance spectroscopy combined with capacitative cycling.

  19. Molecular Dynamics Simulations of Spinodal-Assisted Polymer Crystallization

    SciTech Connect

    Gee, R H; Lacevic, N M; Fried, L

    2005-07-08

    Large scale molecular dynamics simulations of bulk melts of polar (poly(vinylidene fluoride) (pVDF)) polymers are utilized to study chain conformation and ordering prior to crystallization under cooling. While the late stages of polymer crystallization have been studied in great detail, recent theoretical and experimental evidence indicates that there are important phenomena occurring in the early stages of polymer crystallization that are not understood to the same degree. When the polymer melt is quenched from a temperature above the melting temperature to the crystallization temperature, crystallization does not occur instantaneously. This initial interval without crystalline order is characterized as an induction period. It has been thought of as a nucleation period in the classical theories of polymer crystallization, but recent experiments, computer simulations, and theoretical work suggest that the initial period in polymer crystallization is assisted by a spinodal decomposition type mechanism. In this study we have achieved physically realistic length scales to study early stages of polymer ordering, and show that spinodal-assisted ordering prior to crystallization is operative in polar polymers suggesting general applicability of this process.

  20. A composite membrane based on a biocompatible cellulose as a host of gel polymer electrolyte for lithium ion batteries

    NASA Astrophysics Data System (ADS)

    Xiao, S. Y.; Yang, Y. Q.; Li, M. X.; Wang, F. X.; Chang, Z.; Wu, Y. P.; Liu, X.

    2014-12-01

    A composite polymer membrane is prepared by coating poly(vinylidene fluoride) (PVDF) on the surface of a membrane based on methyl cellulose (MC) which is environmentally friendly and cheap. Its characteristics are investigated by scanning electron microscopy, FT-IR, thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The outer PVDF layers are porous which results in high electrolyte uptake and the lithium ion transference number is much larger than that of the pure MC. Moreover, the cell based on Li//LiFePO4 delivers high discharge capacity and good rate behavior in the range of 4.2-2.5 V when the composite membrane is used as the separator and the host of a gel polymer electrolyte, lithium as the counter and reference electrode, and LiFePO4 as cathode. The obtained results suggest that this unique composite membrane shows great attraction in the lithium ion batteries with high safety and low cost.

  1. Study of transport through an electro responsive polymer membrane

    NASA Astrophysics Data System (ADS)

    Das, D.; Datta, A.; Contractor, A. Q.

    2015-02-01

    Conducting polymers have been used widely for development of several electronic, sensing devices because of its electro active nature. In the present work porous polycarbonate (PC) support was coated with a thin gold layer. An electrochemically synthesized polyaniline (PANI) film was deposited on gold coated PC and characterisation was done by field emission gun scanning electron microscopy (FEG-SEM), transmission electron microscopy (TEM) and atomic force microscopy (AFM). For measuring the concentration of potassium ion (K+) inductively coupled plasma atomic emission spectrometry (ICP-AES) was used. Potassium ion transport across PANI membrane at various potential showed the gradual opening of the coiled PANI. In this work an effort has been given to picture the situation in the membrane electrolyte junction on application of potential.

  2. Microgravity Polymers

    NASA Technical Reports Server (NTRS)

    1986-01-01

    A one-day, interactive workshop considering the effects of gravity on polymer materials science was held in Cleveland, Ohio, on May 9, 1985. Selected programmatic and technical issues were reviewed to introduce the field to workshop participants. Parallel discussions were conducted in three disciplinary working groups: polymer chemistry, polymer physics, and polymer engineering. This proceedings presents summaries of the workshop discussions and conclusions.

  3. Contribution to the production of lactulose-rich whey by in situ electro-isomerization of lactose and effect on whey proteins after electro-activation as confirmed by matrix-assisted laser desorption/ionization time-of-flight-mass spectrometry and sodium dodecyl sulfate-polyacrylamide gel electrophoresis.

    PubMed

    Kareb, Ourdia; Champagne, Claude P; Aïder, Mohammed

    2016-04-01

    Cheese-whey, a major co-product of the dairy industry, has recently been the subject of many technological applications. We studied the bioconversion of whey into valuable bio-products such as a potential lactulose prebiotic and compounds with antioxidant properties. This paper examines efficiency, safety, and economics of electro-activation as an eco-friendly technology for a maximum valorization of whey. Thus, a bottom-up approach was therefore addressed. The effect of 4 experimental parameters--low working temperatures (0, 10, and 25 °C), current intensities (400, 600, and 800 mA), volume conditions (100, 200, and 300 mL), and feed concentrations [7, 14, and 28% (wt/vol)]--on lactose-whey isomerization to lactulose under electro-activation process were studied. Structural characteristics of whey proteins and antioxidant functionality were also investigated. The results showed a compromise to be reached between both parameters. Therefore, the maximum yield of 35% of lactulose was achieved after 40 min of reaction at the working temperature of 10 °C under 400 mA electric current field and 100-mL volume conditions with using feed solution at 7% (wt/vol). The isomerization of lactose to lactulose is accomplished by subsequent degradation to galactose, but only at a very small amount. Additionally, whey electro-activation showed significantly elevated antioxidant capacity compared with the untreated samples. The enhancement of antioxidant functionality of whey electro-activation resulted from the synergistic effect of its partial hydrolysis and the formation of antioxidant components that were able to scavenge free radicals. In conclusion, the findings of this study reveal that the whey treated by the safety electro-activation technology has both lactulose-prebiotic and antioxidant properties and could have a substantial application in the manufacture of pharmaceutical and functional foods.

  4. Direct-write PVDF nonwoven fiber fabric energy harvesters via the hollow cylindrical near-field electrospinning process

    NASA Astrophysics Data System (ADS)

    Liu, Z. H.; Pan, C. T.; Lin, L. W.; Huang, J. C.; Ou, Z. Y.

    2014-02-01

    One-dimensional piezoelectric nanomaterials have attracted great attention in recent years for their possible applications in mechanical energy scavenging devices. However, it is difficult to control the structural diameter, length, and density of these fibers fabricated by micro/nano-technologies. This work presents a hollow cylindrical near-field electrospinning (HCNFES) process to address production and performance issues encountered previously in either far-field electrospinning (FFES) or near-field electrospinning (NFES) processes. Oriented polyvinylidene fluoride (PVDF) fibers in the form of nonwoven fabric have been directly written on a glass tube for aligned piezoelectricity. Under a high in situ electrical poling field and strong mechanical stretching (the tangential speed on the glass tube collector is about 1989.3 mm s-1), the HCNFES process is able to uniformly deposit large arrays of PVDF fibers with good concentrations of piezoelectric β-phase. The nonwoven fiber fabric (NFF) is transferred onto a polyethylene terephthalate (PET) substrate and fixed at both ends using copper foil electrodes as a flexible textile-fiber-based PVDF energy harvester. Repeated stretching and releasing of PVDF NFF with a strain of 0.05% at 7 Hz produces a maximum peak voltage and current at 76 mV and 39 nA, respectively.

  5. Patterned, highly stretchable and conductive nanofibrous PANI/PVDF strain sensors based on electrospinning and in situ polymerization.

    PubMed

    Yu, Gui-Feng; Yan, Xu; Yu, Miao; Jia, Meng-Yang; Pan, Wei; He, Xiao-Xiao; Han, Wen-Peng; Zhang, Zhi-Ming; Yu, Liang-Min; Long, Yun-Ze

    2016-02-07

    A facile fabrication strategy via electrospinning and followed by in situ polymerization to fabricate a patterned, highly stretchable, and conductive polyaniline/poly(vinylidene fluoride) (PANI/PVDF) nanofibrous membrane is reported. Owing to the patterned structure, the nanofibrous PANI/PVDF strain sensor can detect a strain up to 110%, for comparison, which is 2.6 times higher than the common nonwoven PANI/PVDF mat and much larger than the previously reported values (usually less than 15%). Meanwhile, the conductivity of the patterned strain sensor shows a linear response to the applied strain in a wide range from 0% to about 85%. Additionally, the patterned PANI/PVDF strain sensor can completely recover to its original electrical and mechanical values within a strain range of more than 22%, and exhibits good durability over 10,000 folding-unfolding tests. Furthermore, the strain sensor also can be used to detect finger motion. The results demonstrate promising application of the patterned nanofibrous membrane in flexible electronic fields.

  6. Acoustic and optoelectronic nature and interfacial durability of modified CNT and GnP-PVDF composites with nanostructural control

    NASA Astrophysics Data System (ADS)

    Park, Joung-Man; Kwon, Dong-Jun; Wang, Zuo-Jia; DeVries, Lawrence

    2014-03-01

    Nano- and hetero-structures of modified carbon nanotube (CNT) and Graphene nano Platelet (GnP) can control significantly piezoresistive and optoelectronic properties in Microelectromechanical Systems (MEMS) as acoustic actuators. Interfacial durability and electrical properties of modified CNT and GnP embedded in poly (vinylidene fluoride) (PVDF) nanocomposites were investigated for use in acoustic actuator applications. Modified GnP coated PVDF nanocomposite exhibited better electrical conductivity than neat and modified CNT due to the unique electrical nature of GnP. Modified GnP coating also exhibited good acoustical properties. Contact angle, surface energy, work of adhesion, and spreading coefficient measurements were contributed to explore the interfacial adhesion durability between neat CNT or plasma treated CNT and plasma treated PVDF. Acoustic actuation performance of modified GnP coated PVDF nanocomposites were investigated for different radii of curvature and different coating conditions, using a sound level meter. Modified GnP can be a more appropriate acoustic actuator than CNT cases because of improved electrical properties. Optimum radius of curvature and coating thickness was also obtained for the most appropriate sound pressure level (SPL) performance. This study can provide manufacturing parameters of transparent sound actuators with good quality practically.

  7. Quantitative verification of thin-film polyvinylidene fluoride (PVDF) transducer array performance up to 60 °C

    NASA Astrophysics Data System (ADS)

    Hakoda, Christopher; Ren, Baiyang; Lissenden, Cliff J.; Rose, Joseph L.

    2017-02-01

    Thin-film PVDF (polyvinylidene fluoride) transducers are appealing as low cost, light weight, durable, and flexible sensors for structural health monitoring applications in aircraft structures. However, due to the relatively low Curie temperature of PVDF, there is a concern that it's performance will drop below acceptable levels during elevated-temperature operating conditions. To verify acceptable performance in these environmental operating conditions, temperature history data were collected between 23-60 °C. The effect of temperature on the thin-film PVDF was investigated and a temperature-independent damage feature was assessed. The temperature dependence of the signal's peak amplitude was investigated in both the time domain and the spectral domain to get two damage features. It was found that the measurement of the incident guided wave by the thin-film PVDF transducer had a temperature dependence that varied with frequency. A third damage feature, the mode ratio, was also calculated in the spectral domain with the goal of defining a damage feature that is temperature independent. A comparison of how well these damage features performed when used to identify a notch in an aluminum plate was made using receiver operating characteristic curves and their respective area under the curve values. This result demonstrated that a temperature-independent damage feature can be calculated, to some degree, by using a mode ratio between two modes of similar temperature dependence.

  8. Effect of Acid-Base Property of Inorganic Nanoparticles on Antifouling Performance of PVDF Composite Ultrafiltration Membranes

    NASA Astrophysics Data System (ADS)

    He, Mingjia; Shi, Baoli

    Pure poly(vinylidene fluoride) (PVDF) membrane and PVDF composite membranes modified by three kinds of inorganic nanoparticles (SiO2, Al2O3, and TiO2) were made using a phase inversion method and characterized by pure water flux, retention efficiency of Bovine serum albumin (BSA), flux reduction coefficient, and scanning electron microscope (SEM). The results of flux reduction coefficient illustrated that PVDF membrane modified by nanoparticles had better antifouling property in the order of TiO2, Al2O3, SiO2. The Lewis acid-base properties of the nanoparticle materials were measured by inverse gas chromatography (IGC). The Lewis acid number, Ka, and Lewis base number, Kb, had the following order Ka TiO2 < Ka Al2O3 < Ka SiO2, and Kb TiO2 > Kb Al2O3 > Kb SiO2. The experimental results indicated that PVDF membrane modified by nanoparticles with relatively strong base exhibited excellent antifouling performance.

  9. Effects of configurational changes on molecular dynamics in polyvinylidene fluoride and poly(vinylidene fluoride-trifluoroethylene) ferroelectric polymers

    SciTech Connect

    Jalarvo, N. E-mail: abhijit.pramanick@gmail.com; Pramanick, A. E-mail: abhijit.pramanick@gmail.com; Do, C.; Diallo, S. O. E-mail: abhijit.pramanick@gmail.com

    2015-08-24

    We present a comparative study of proton dynamics in unpoled non-ferroelectric polymer polyvinylidene fluoride (PVDF) and in its trifluoroethylene containing ferroelectric copolymer (with 70/30 molar proportion), using quasi-elastic neutron scattering. The neutron data reveal the existence of two distinct types of molecular motions in the temperature range investigated. The slower motion, which is characterized in details here, is ascribed to protons jump diffusion along the polymeric carbon chains, while the faster motion could be attributed to localized rotational motion of methylene groups. At temperatures below the Curie point (T{sub c} ∼ 385 K) of the composite polymer, the slower diffusive mode experiences longer relaxation times in the ferroelectric blend than in the bare PVDF, although the net corresponding diffusion coefficient remains comparatively the same in both polymers with characteristic activation energy of E{sub A} ≈ 27–33 kJ/mol. This arises because of a temperature dependent jump length r{sub 0}, which we observe to be effectively longer in the copolymer, possibly due to the formation of ordered ferroelectric domains below T{sub c}. Above T{sub c}, there is no appreciable difference in r{sub 0} between the two systems. This observation directly relates the known dependence of T{sub c} on molar ratio to changes in r{sub 0}, providing fundamental insight into the ferroelectric properties of PVDF-based copolymers.

  10. Effects of configurational changes on molecular dynamics in polyvinylidene fluoride and poly(vinylidene fluoride-trifluoroethylene) ferroelectric polymers

    SciTech Connect

    Jalarvo, N.; Pramanick, A.; Do, C.; Diallo, S. O.

    2015-08-28

    Here, we present a comparative study of proton dynamics in unpoled non-ferroelectric polymer polyvinylidene fluoride (PVDF) and in its trifluoroethylene containing ferroelectric copolymer (with 70/30 molar proportion), using quasi-elastic neutron scattering. The neutron data reveal the existence of two distinct types of molecular motions in the temperature range investigated. Moreover, the slower motion, which is characterized in details here, is ascribed to protons jump diffusion along the polymeric carbon chains, while the faster motion could be attributed to localized rotational motion of methylene groups. At temperatures below the Curie point (T-c similar to 385 K) of the composite polymer, the slower diffusive mode experiences longer relaxation times in the ferroelectric blend than in the bare PVDF, although the net corresponding diffusion coefficient remains comparatively the same in both polymers with characteristic activation energy of E-A approximate to 27-33 kJ/mol. This arises because of a temperature dependent jump length r(0), which we observe to be effectively longer in the copolymer, possibly due to the formation of ordered ferroelectric domains below Tc. Above Tc, there is no appreciable difference in r(0) between the two systems. Our observation directly relates the known dependence of Tc on molar ratio to changes in r(0), providing fundamental insight into the ferroelectric properties of PVDF-based copolymers.

  11. Effects of configurational changes on molecular dynamics in polyvinylidene fluoride and poly(vinylidene fluoride-trifluoroethylene) ferroelectric polymers

    DOE PAGES

    Jalarvo, N.; Pramanick, A.; Do, C.; ...

    2015-08-28

    Here, we present a comparative study of proton dynamics in unpoled non-ferroelectric polymer polyvinylidene fluoride (PVDF) and in its trifluoroethylene containing ferroelectric copolymer (with 70/30 molar proportion), using quasi-elastic neutron scattering. The neutron data reveal the existence of two distinct types of molecular motions in the temperature range investigated. Moreover, the slower motion, which is characterized in details here, is ascribed to protons jump diffusion along the polymeric carbon chains, while the faster motion could be attributed to localized rotational motion of methylene groups. At temperatures below the Curie point (T-c similar to 385 K) of the composite polymer, themore » slower diffusive mode experiences longer relaxation times in the ferroelectric blend than in the bare PVDF, although the net corresponding diffusion coefficient remains comparatively the same in both polymers with characteristic activation energy of E-A approximate to 27-33 kJ/mol. This arises because of a temperature dependent jump length r(0), which we observe to be effectively longer in the copolymer, possibly due to the formation of ordered ferroelectric domains below Tc. Above Tc, there is no appreciable difference in r(0) between the two systems. Our observation directly relates the known dependence of Tc on molar ratio to changes in r(0), providing fundamental insight into the ferroelectric properties of PVDF-based copolymers.« less

  12. Enhanced noradrenergic axon regeneration into schwann cell-filled PVDF-TrFE conduits after complete spinal cord transection.

    PubMed

    Lee, Yee-Shuan; Wu, Siliang; Arinzeh, Treena Livingston; Bunge, Mary Bartlett

    2017-02-01

    Schwann cell (SC) transplantation has been utilized for spinal cord repair and demonstrated to be a promising therapeutic strategy. In this study, we investigated the feasibility of combining SC transplantation with novel conduits to bridge the completely transected adult rat spinal cord. This is the first and initial study to evaluate the potential of using a fibrous piezoelectric polyvinylidene fluoride trifluoroethylene (PVDF-TrFE) conduit with SCs for spinal cord repair. PVDF-TrFE has been shown to enhance neurite growth in vitro and peripheral nerve repair in vivo. In this study, SCs adhered and proliferated when seeded onto PVDF-TrFE scaffolds in vitro. SCs and PVDF-TrFE conduits, consisting of random or aligned fibrous inner walls, were transplanted into transected rat spinal cords for 3 weeks to examine early repair. Glial fibrillary acidic protein (GFAP)(+) astrocyte processes and GFP (green fluorescent protein)-SCs were interdigitated at both rostral and caudal spinal cord/SC transplant interfaces in both types of conduits, indicative of permissivity to axon growth. More noradrenergic/DβH(+) (dopamine-beta-hydroxylase) brainstem axons regenerated across the transplant when greater numbers of GFAP(+) astrocyte processes were present. Aligned conduits promoted extension of DβH(+) axons and GFAP(+) processes farther into the transplant than random conduits. Sensory CGRP(+) (calcitonin gene-related peptide) axons were present at the caudal interface. Blood vessels formed throughout the transplant in both conduits. This study demonstrates that PVDF-TrFE conduits harboring SCs are promising for spinal cord repair and deserve further investigation. Biotechnol. Bioeng. 2017;114: 444-456. © 2016 Wiley Periodicals, Inc.

  13. Thermal Vapor Deposition and Characterization of Polymer-Ceramic Nanoparticle Thin Films and Capacitors

    NASA Astrophysics Data System (ADS)

    Iwagoshi, Joel A.

    Research on alternative energies has become an area of increased interest due to economic and environmental concerns. Green energy sources, such as ocean, wind, and solar power, are subject to predictable and unpredictable generation intermittencies which cause instability in the electrical grid. This problem could be solved through the use of short term energy storage devices. Capacitors made from composite polymer:nanoparticle thin films have been shown to be an economically viable option. Through thermal vapor deposition, we fabricated dielectric thin films composed of the polymer polyvinylidine fluoride (PVDF) and the ceramic nanoparticle titanium dioxide (TiO2). Fully understanding the deposition process required an investigation of electrode and dielectric film deposition. Film composition can be controlled by the mass ratio of PVDF:TiO2 prior to deposition. An analysis of the relationship between the ratio of PVDF:TiO2 before and after deposition will improve our understanding of this novel deposition method. X-ray photoelectron spectroscopy and energy dispersive x-ray spectroscopy were used to analyze film atomic concentrations. The results indicate a broad distribution of deposited TiO2 concentrations with the highest deposited amount at an initial mass concentration of 17% TiO2. The nanoparticle dispersion throughout the film is analyzed through atomic force microscopy and energy dispersive x-ray spectroscopy. Images from these two techniques confirm uniform TiO2 dispersion with cluster size less than 300 nm. These results, combined with spectroscopic analysis, verify control over the deposition process. Capacitors were fabricated using gold parallel plates with PVDF:TiO 2 dielectrics. These capacitors were analyzed using the atomic force microscope and a capacohmeter. Atomic force microscope images confirm that our gold films are acceptably smooth. Preliminary capacohmeter measurements indicate capacitance values of 6 nF and break down voltages of 2.4 V

  14. Nanoscale Structural Engineering of Ferroelectric Polymers. Final Report for July 2001-June 2005

    SciTech Connect

    Adenwalla, S.

    2005-12-01

    This final report describes the interaction between multilavered films of polymer ferroelectrics, in our case the copolymers of PVDF formed with TrFE. Langmuir Blodgett deposition of these films allows the deposition of thin, uniform, highly crystalline films. Two type of multilayer stacks are made and characterized. The first consists of multilayer stacks of the copolymer films with 2 different TrFE contents-50% and 20%. By varying the period of the multilayer stacks we see evidence of interaction at short length scales, evidenced in the thermodynamic transition temperatures of the multilayer films. The second set consists of a P(VDF - TrFE) film sandwiched between two Cobalt electrodes. In these we see evidence of a large magnetoelectric coupling.

  15. Sub percolation threshold carbon nanotube based polyvinylidene fluoride polymer-polymer composites

    NASA Astrophysics Data System (ADS)

    Jacob, Cedric Antony

    The study of piezoelectric materials has traditionally focused largely on homogeneous crystalline or semi-crystalline materials. This research focuses on the concept of piezoelectric composites using selective microstructural reinforcement in the piezoelectric material to improve the piezoelectric properties. This is done using a polyvinylidene fluoride (PVDF) and carbon nanotube composite as the model system. A multi-tiered engineering approach is taken to understand the material (experimental and computational analyses) and design a composite system which provides an effective platform for future research in piezoelectric improvement. A finite element analysis is used to evaluate the ability of carbon nanotubes to generate a heterogeneous electric field where local improvements in electric field produce an increase in the effective piezoelectric strength. The study finds that weight percent and aspect ratio of the carbon nanotubes are of key importance while formations of percolating networks are detrimental to performance. This motivates investigation into electrospinning into a method of producing sub percolation threshold composites with large carbon nanotube content. However, the electrospun fabrics have too low of a dielectric strength to sustain high strength electric fields. This is studied within the context of high voltage physics and a solution inspired by traditional composites manufacturing is proposed wherein the electrospun fiber mat is used as the fiber reinforcing component of a polymer-polymer composite. This composite is thoroughly analyzed to show that it allows for a high dielectric strength combined with high carbon nanotube content. It is also shown that the PVDF contains the proper crystal structure to allow for piezoelectric properties. Furthermore, the addition of carbon nanotubes greatly improves the strength and stiffness of the composite, as well as affecting the internal electric field response to an applied voltage. These qualities

  16. Measurement of cylindrical Rayleigh surface waves using line-focused PVDF transducers and defocusing measurement method.

    PubMed

    Lin, Chun-I; Lee, Yung-Chun

    2014-08-01

    Line-focused PVDF transducers and defocusing measurement method are applied in this work to determine the dispersion curve of the Rayleigh-like surface waves propagating along the circumferential direction of a solid cylinder. Conventional waveform processing method has been modified to cope with the non-linear relationship between phase angle of wave interference and defocusing distance induced by a cylindrically curved surface. A cross correlation method is proposed to accurately extract the cylindrical Rayleigh wave velocity from measured data. Experiments have been carried out on one stainless steel and one glass cylinders. The experimentally obtained dispersion curves are in very good agreement with their theoretical counterparts. Variation of cylindrical Rayleigh wave velocity due to the cylindrical curvature is quantitatively verified using this new method. Other potential applications of this measurement method for cylindrical samples will be addressed.

  17. Mechanical and electrical properties of electrospun PVDF/MWCNT ultrafine fibers using rotating collector

    PubMed Central

    2014-01-01

    Poly(vinylidene fluoride) (PVDF) ultrafine fibers with different proportions of multi-walled carbon nanotube (MWCNT) embedded have been fabricated using a modified electrospinning device with a rotating collector. With the increasing of MWCNT content, the β phase was noticeable enhanced, and the fibers became more elastic, which was manifested by Young's modulus decreased drastically. Furthermore, with adding the amounts of MWCNTs, the density of carbon nanotube (CNT)-CNT junctions among the fibers increased accordingly. When the MWCNT content was of 1.2 wt.%, a stable three-dimensional conducting network was formed. After this percolation threshold, the density of CNT-CNT junctions among the fibers tended to be a constant quantity, leading to a stabilized conductivity consequently. It is hoped that our results can be helpful for the fabrication of flexible devices, piezoelectric devices, force transducer, and so on. PACS 81.05.Qk; 81.16.-c PMID:25288915

  18. Enhanced performance of PVDF nanocomposite membrane by nanofiber coating: A membrane for sustainable desalination through MD.

    PubMed

    Efome, Johnson E; Rana, Dipak; Matsuura, Takeshi; Lan, Christopher Q

    2016-02-01

    Membrane distillation (MD) is a promising separation technique capable of being used in the desalination of marine and brackish water. Poly(vinylidene fluoride) (PVDF) flat sheet nano-composite membranes were surface modified by coating with electro-spun PVDF nano-fibres to increase the surface hydrophobicity. For this purpose, the nano-composite membrane containing 7 wt.% superhydrophobic SiO2 nano-particles, which showed the highest flux in our previous work, was first subjected to pore size augmentation by increasing the concentration of the pore forming agent (Di-ionized water). Then, the prepared flat sheet membranes were subjected to nanofibres coating by electro-spinning. The uncoated and coated composite fabricated membranes were characterized using contact angle, liquid entry pressure of water, and scanning electron microscopy. The membranes were further tested for 6 h desalination by direct contact membrane distillation (DCMD) and vacuum membrane distillation (VMD), with a 3.5 wt.% synthetic NaClaq as the feed. In DCMD the feed liquid and permeate side temperature were maintained at 27.5 °C and 15 °C, respectively. For VMD, the feed liquid temperature was 27 °C and a vacuum of 94.8 kPa was applied on the permeate side. The maximum permeate flux achieved was 3.2 kg/m(2).h for VMD and 6.5 kg/m(2).h for DCMD. The salt rejection obtained was higher than 99.98%. The coated membranes showed a more stable flux than the uncoated membranes indicating that the double layered membranes have great potential in solving the pore wetting problem in MD.

  19. Strain-dependent characterization of electrode and polymer network of electrically activated polymer actuators

    NASA Astrophysics Data System (ADS)

    Töpper, Tino; Osmani, Bekim; Weiss, Florian M.; Winterhalter, Carla; Wohlfender, Fabian; Leung, Vanessa; Müller, Bert

    2015-04-01

    Fecal incontinence describes the involuntary loss of bowel content and affects about 45 % of retirement home residents and overall more than 12 % of the adult population. Artificial sphincter implants for treating incontinence are currently based on mechanical systems with failure rates resulting in revision after three to five years. To overcome this drawback, artificial muscle sphincters based on bio-mimetic electro-active polymer (EAP) actuators are under development. Such implants require polymer films that are nanometer-thin, allowing actuation below 24 V, and electrodes that are stretchable, remaining conductive at strains of about 10 %. Strain-dependent resistivity measurements reveal an enhanced conductivity of 10 nm compared to 30 nm sputtered Au on silicone for strains higher than 5 %. Thus, strain-dependent morphology characterization with optical microscopy and atomic force microscopy could demonstrate these phenomena. Cantilever bending measurements are utilized to determine elastic/viscoelastic properties of the EAP films as well as their long-term actuation behavior. Controlling these properties enables the adjustment of growth parameters of nanometer-thin EAP actuators.

  20. Recent Progress on Ferroelectric Polymer-Based Nanocomposites for High Energy Density Capacitors: Synthesis, Dielectric Properties, and Future Aspects.

    PubMed

    Prateek; Thakur, Vijay Kumar; Gupta, Raju Kumar

    2016-04-13

    Dielectric polymer nanocomposites are rapidly emerging as novel materials for a number of advanced engineering applications. In this Review, we present a comprehensive review of the use of ferroelectric polymers, especially PVDF and PVDF-based copolymers/blends as potential components in dielectric nanocomposite materials for high energy density capacitor applications. Various parameters like dielectric constant, dielectric loss, breakdown strength, energy density, and flexibility of the polymer nanocomposites have been thoroughly investigated. Fillers with different shapes have been found to cause significant variation in the physical and electrical properties. Generally, one-dimensional and two-dimensional nanofillers with large aspect ratios provide enhanced flexibility versus zero-dimensional fillers. Surface modification of nanomaterials as well as polymers adds flavor to the dielectric properties of the resulting nanocomposites. Nowadays, three-phase nanocomposites with either combination of fillers or polymer matrix help in further improving the dielectric properties as compared to two-phase nanocomposites. Recent research has been focused on altering the dielectric properties of different materials while also maintaining their superior flexibility. Flexible polymer nanocomposites are the best candidates for application in various fields. However, certain challenges still present, which can be solved only by extensive research in this field.

  1. Piezoelectric Polymers

    NASA Technical Reports Server (NTRS)

    Harrison, J. S.; Ounaies, Z.; Bushnell, Dennis M. (Technical Monitor)

    2001-01-01

    The purpose of this review is to detail the current theoretical understanding of the origin of piezoelectric and ferroelectric phenomena in polymers; to present the state-of-the-art in piezoelectric polymers and emerging material systems that exhibit promising properties; and to discuss key characterization methods, fundamental modeling approaches, and applications of piezoelectric polymers. Piezoelectric polymers have been known to exist for more than forty years, but in recent years they have gained notoriety as a valuable class of smart materials.

  2. Comparison of the solubility of PVF and PVDF in supercritical CH{sub 2}F{sub 2} and CO{sub 2} and in CO{sub 2} with acetone, dimethyl ether, and ethanol

    SciTech Connect

    Lora, M.; Lim, J.S.; McHugh, M.A.

    1999-04-08

    Cloud-point data are reported at temperatures to 245 C and pressures to 2700 bar for poly(vinyl fluoride) (PVF) and poly(vinylidene fluoride) (PVDF) in CO{sub 2}, CH{sub 2}F{sub 2}, dimethyl ether (DME), acetone, and ethanol and in mixtures of CO{sub 2} with acetone, DME, and ethanol. PVF does not dissolve in CO{sub 2} even at 245 C and 2700 bar, but, PVF does dissolve in CH{sub 2}F{sub 2} at 180 C and pressures in excess of 1500 bar. To dissolve PVF in DME, pressures in excess of 550 bar and temperatures in excess of 130 C are needed although it only takes {approximately}100 bar to maintain a single phase to temperatures of {approximately}220 C with ethanol and acetone. Compared to the conditions needed to dissolve PVF, it takes hundreds of bar less pressure to dissolve PVDF in CO{sub 2}, CH{sub 2}F{sub 2}, and DME and {approximately}60 bar less pressure to dissolve it in acetone, but it does take {approximately}60 bar more pressure to dissolve it in ethanol. With CO{sub 2}, ethanol is a better cosolvent than acetone for both fluoropolymers at high temperatures and at low ethanol concentrations. However, when the temperature is decreased or the ethanol concentration is increased, it acts as an antisolvent probably due to ethanol self-association. Compared to ethanol and acetone, DME is not as good a cosolvent more than likely as a result of its lower density and smaller dipole moment. For all three cosolvents, their impact on the reduction of the cloud-point pressure diminishes with increasing cosolvent concentration. It is also evident that CO{sub 2} is an effective antisolvent since small amounts of it added to the polymer-cosolvent mixtures greatly increase the pressures needed to obtain a single phase.

  3. Synthesis and Properties of Polymer Nanocomposites with Tunable Electromagnetic Response

    NASA Astrophysics Data System (ADS)

    Stojak, Kristen L.

    Multifunctional polymer nanocomposites (PNCs) are attractive for the design of tunable RF and microwave components such as flexible electronics, attenuators, and antennas due to cost-effectiveness and durability of polymeric matrices. In this work, three separate PNCs were synthesized. Magnetite (Fe 3O4) and cobalt ferrite (CFO) nanoparticles, synthesized by thermal decomposition, were used as PNC fillers. Polymers used in this work were a commercial polymer provided by the Rogers Corporation (RP) and polyvinylidene fluoride (PVDF). PNCs in this thesis consist of Fe3O 4 in RP, CFO in RP, and Fe3O4 in PVDF. Characterization techniques for determining morphology of the nanoparticles, and their resulting PNCs, include x-ray diffraction, transmission electron microscopy and magnetometry. All magnetometry measurements were taken using a Quantum Design Physical Property Measurement System with a superconducting magnet. Temperature and external magnetic field magnetization measurements revealed that all samples exhibit superparamagnetic behavior at room temperature. Blocking temperature, coercivity and reduced remnant magnetization do not vary with concentration. Tunable saturation magnetization, based on nanoparticle loading, was observed across all PNCs, regardless of polymer or nanoparticle choice, indicating that this is an inherent property in all similar PNC materials. Tunability studies of the magneto-dielectric PNCs were carried out by adding the PNC to cavity and microstrip linear resonator devices, and passing frequencies of 1-6 GHz through them in the presence of transverse external magnetic fields of up to 4.5 kOe, provided by an electromagnet. Microwave characteristics were extracted from scattering parameters of the PNCs. In all cases, losses were reduced, quality factor was increased, and tunability of the resonance frequency was demonstrated. Strong magnetic field dependence was observed across all samples measured in this study.

  4. Enhanced bacterial affinity of PVDF membrane: its application as improved sea water sampling tool for environmental monitoring.

    PubMed

    Kumar, Sweta Binod; Sharnagat, Preeti; Manna, Paramita; Bhattacharya, Amit; Haldar, Soumya

    2017-02-01

    Isolation of diversified bacteria from seawater is a major challenge in the field of environmental microbiology. In the present study, an attempt has been made to select specific membrane with improved property of attaching diversified bacteria. Initially, different concentrations (15, 18, and 20% W/W) of polysulfone (PSF) were used to check their affinity for the attachment of selected gram-positive (Bacillus subtilis) and gram-negative (Escherichia coli) bacteria. Among these, 20% W/W PSF showed maximum attachment. Therefore, membrane prepared with other materials such as polyvinylidene fluoride (PVDF) and polyether sulfone (PES) were used with the same concentration (20% W/W) to check their improved bacterial attachment property. Comparative study of bacterial attachment on three different membranes revealed that PVDF possessed the highest affinity towards both the groups of bacteria. This property was confirmed by different analytical methods viz. contact angle, atomic force microscopy, zeta potential, and flux study and further validated with seawater samples collected from seven sites of western coast and Lakshadweep island of India, using Biolog EcoPlate™. All the samples showed that bacterial richness and diversity was high in PVDF membrane in comparison to surrounding seawater samples. Interestingly, affinity for more diversified bacteria was reported to be higher in water sample with less turbidity and low bacteria load. This finding can facilitate the development of PVDF (20% W/W) membrane as a simple, cheap, and less labor intensive environmental sampling tool for the isolation of diversified bacteria from seawater sample wih different physiochemical properties. Graphical abstract ᅟ.

  5. Fabrication of Stretchable Nanocomposites with High Energy Density and Low Loss from Cross-Linked PVDF Filled with Poly(dopamine) Encapsulated BaTiO3.

    PubMed

    Xie, Yunchuan; Yu, Yangyang; Feng, Yefeng; Jiang, Wanrong; Zhang, Zhicheng

    2017-01-25

    In this report, a simple solution-cast method was employed to prepare poly(dopamine) (PDA) encapsulated BaTiO3 (BT) nanoparticle (PDA@BT) filled composites using PVDF matrix cross-linked by the free radical initiator. The effects of both the particle encapsulation and matrix cross-linking on the mechanical and dielectric properties of the composites were carefully investigated. The results suggested that the introduction of BT particles improved permittivity of the composites to ∼30 at 100 Hz when particle contents of only 7 wt % were utilized. This was attributed to the enhanced polarization, which was induced by high permittivity ceramic particles. Compared to bare BT, PDA@BT particles could be dispersed more homogeneously in the matrix, and the catechol groups of PDA layer might form chelation with free ions present in the matrix. The latter might depress the ion conduction loss in the composites. Other results revealed that the formation of hydrogen-bonding between the PDA layer and the polymer, especially the chemical cross-linking across the matrix, resulted in increased Young' modulus by ∼25%, improved breakdown strength by ∼40%, and declined conductivity by nearly 1 order of magnitude when compared to BT filled composites. The composite films filled with PDA@BTs indicated greater energy storage capacities by nearly 190% when compared to the pristine matrix. More importantly, the excellent mechanical performance allowed the composite films to adopt uni- or biaxially stretching, a crucial feature required for the realization of high breakdown strength. This work provided a facile strategy for fabrication of flexible and stretchable dielectric composites with depressed dielectric loss and enhanced energy storage capacity at low filler loadings (<10 wt %).

  6. Construction of a Fish-like Robot Based on High Performance Graphene/PVDF Bimorph Actuation Materials.

    PubMed

    Xiao, Peishuang; Yi, Ningbo; Zhang, Tengfei; Huang, Yi; Chang, Huicong; Yang, Yang; Zhou, Ying; Chen, Yongsheng

    2016-06-01

    Smart actuators have many potential applications in various areas, so the development of novel actuation materials, with facile fabricating methods and excellent performances, are still urgent needs. In this work, a novel electromechanical bimorph actuator constituted by a graphene layer and a PVDF layer, is fabricated through a simple yet versatile solution approach. The bimorph actuator can deflect toward the graphene side under electrical stimulus, due to the differences in coefficient of thermal expansion between the two layers and the converse piezoelectric effect and electrostrictive property of the PVDF layer. Under low voltage stimulus, the actuator (length: 20 mm, width: 3 mm) can generate large actuation motion with a maximum deflection of about 14.0 mm within 0.262 s and produce high actuation stress (more than 312.7 MPa/g). The bimorph actuator also can display reversible swing behavior with long cycle life under high frequencies. on this basis, a fish-like robot that can swim at the speed of 5.02 mm/s is designed and demonstrated. The designed graphene-PVDF bimorph actuator exhibits the overall novel performance compared with many other electromechanical avtuators, and may contribute to the practical actuation applications of graphene-based materials at a macro scale.

  7. Graphene Ink Laminate Structures on Poly(vinylidene difluoride) (PVDF) for Pyroelectric Thermal Energy Harvesting and Waste Heat Recovery.

    PubMed

    Zabek, Daniel; Seunarine, Kris; Spacie, Chris; Bowen, Chris

    2017-03-15

    Thermal energy can be effectively converted into electricity using pyroelectrics, which act as small scale power generator and energy harvesters providing nanowatts to milliwatts of electrical power. In this paper, a novel pyroelectric harvester based on free-standing poly(vinylidene difluoride) (PVDF) was manufactured that exploits the high thermal radiation absorbance of a screen printed graphene ink electrode structure to facilitate the conversion of the available thermal radiation energy into electrical energy. The use of interconnected graphene nanoplatelets (GNPs) as an electrode enable high thermal radiation absorbance and high electrical conductivity along with the ease of deposition using a screen print technique. For the asymmetric structure, the pyroelectric open-circuit voltage and closed-circuit current were measured, and the harvested electrical energy was stored in an external capacitor. For the graphene ink/PVDF/aluminum system the closed circuit pyroelectric current improves by 7.5 times, the open circuit voltage by 3.4 times, and the harvested energy by 25 times compared to a standard aluminum/PVDF/aluminum system electrode design, with a peak energy density of 1.13 μJ/cm(3). For the pyroelectric device employed in this work, a complete manufacturing process and device characterization of these structures are reported along with the thermal conductivity of the graphene ink. The material combination presented here provides a new approach for delivering smart materials and structures, wireless technologies, and Internet of Things (IoT) devices.

  8. A new application of PVDF line-focus transducers on measuring dispersion curves of a layered medium

    NASA Astrophysics Data System (ADS)

    Lee, Yung-Chun; Ko, Shin-Pin

    2000-05-01

    In the past few years, PVDF line-focus acoustic transducers have been proven to be a useful and convenient tool for accurately measuring surface wave velocity. The transducer is very easy to construct and the measurement system can be readily established with conventional ultrasonic instruments. In this investigation, however, the capability of PVDF line-focus transducers will be further extended to the measurement of dispersion relation of surface acoustic waves of a layered medium. To achieve this, a number of line-focus transducers are first fabricated with PVDF films of various thickness so that they can operate at different frequencies. Experimental testing on these transducers shows that surface acoustic waves of frequency ranging from 2 MHz to 20 MHz can be effectively generated and detected. For the determination of surface wave velocity as a function of frequency, a new method of processing the measured waveforms during a z-direction defocusing measurements is developed. A mathematical model is given to explain how this method works. With the transducers and the analyzing method, the surface wave dispersion relation of a layer/substrate configuration have been experimentally determined. Samples include thick polymeric films as well as metal films deposited on glass, aluminum, and silicon crystal. Possibility of determining material properties of the layers from the measured dispersion curves will be discussed.

  9. High-Energy-Density Polymer Nanocomposites Composed of Newly Structured One-Dimensional BaTiO3@Al2O3 Nanofibers.

    PubMed

    Pan, Zhongbin; Yao, Lingmin; Zhai, Jiwei; Fu, Dezhou; Shen, Bo; Wang, Haitao

    2017-02-01

    Flexible electrostatic capacitors are potentially applicable in modern electrical and electric power systems. In this study, flexible nanocomposites containing newly structured one-dimensional (1D) BaTiO3@Al2O3 nanofibers (BT@AO NFs) and the ferroelectric polymer poly(vinylidene fluoride) (PVDF) matrix were prepared and systematically studied. The 1D BT@AO NFs, where BaTiO3 nanoparticles (BT NPs) were embedded and homogeneously dispersed into the AO nanofibers, were successfully synthesized via an improved electrospinning technique. The additional AO layer, which has moderating dielectric constant, was introduced between BT NPs and PVDF matrixes. To improve the compatibility and distributional homogeneity of the nanofiller/matrix, dopamine was coated onto the nanofiller. The results show that the energy density due to high dielectric polarization is about 10.58 J cm(-3) at 420 MV m(-1) and the fast charge-discharge time is 0.126 μs of 3.6 vol % BT@AO-DA NFs/PVDF nanocomposite. A finite element simulation of the electric-field and electric current density distribution revealed that the novel-structured 1D BT@AO-DA NFs significantly improved the dielectric performance of the nanocomposites. The large extractable energy density and high dielectric breakdown strength suggest the potential applications of the BT@AO-DA NFs/PVDF nanocomposite films in electrostatic capacitors and embedded devices.

  10. Carbon-Fiber Reinforced Plastic Passive Composite Damper by Use of Piezoelectric Polymer/Ceramic

    NASA Astrophysics Data System (ADS)

    Tanimoto, Toshio

    2002-11-01

    In this study, the passive damping of carbon-fiber reinforced plastic (CFRP) cantilever beams is examined using (1) interleaving of viscoelastic thermoplastic films, (2) piezoelectric polymer (PVDF) film interlayers and (3) surface-bonded piezoelectric ceramics. Introducing polyethylene-based film interlayers between composite plies resulted in a significant increase in the vibration loss factor. It is also shown that the vibration damping of CFRP laminates can be improved passively by means of PVDF film interlayers and resistively shunted, surface-bonded piezoelectric ceramic, PbZrO3-PbTiO3 (PZT) sheets. This paper also discusses the enhanced vibration damping of CFRP laminates with dispersed PZT particle interlayers. All these damping methods, interleaving of thermoplastic films, interlayers of PVDF films or dispersed PZT particles between composite plies, and resistively shunted, surface-bonded PZT sheets, can be jointly used to improve the damping of CFRP laminates/structures. The use of CFRP beams in combination with several damping concepts discussed here is promising for application in structures where light weight and improved vibration damping are desired.

  11. Characterization of UV-cured gel polymer electrolytes for rechargeable lithium batteries

    NASA Astrophysics Data System (ADS)

    Song, Min-Kyu; Cho, Jin-Yeon; Cho, Byung Won; Rhee, Hee-Woo

    Novel ultraviolet (UV)-cured gel polymer electrolytes based on polyethyleneglycol diacrylate (PEGDA) oligomer and polyvinylidene fluoride (PVdF) are prepared and characterized. UV-curing of PEGDA oligomer containing PVdF and ethylene carbonate (EC)-based liquid electrolyte yields chemically and physically cross-linked PEGDA/PVdF blend gel electrolytes. PEGDA/PVdF blend films show much higher mechanical properties and electrolyte liquid retention than pure PEGDA film. The ionic conductivity ( σ) of a PEGDA/PVdF (5/5) blend electrolyte reaches about 4 mS cm -1 at ambient temperature and is as high as 1 mS cm -1 at 0 °C. All the blend electrolytes are electrochemically stable up to 4.6 V versus Li/Li +. The cation transference number ( t+) measured by dc micropolarization exceeds 0.5 at room temperature. Li/(PEGDA/PVdF)/LiCoO 2 cells ( 2 cm×2 cm) retains >91% of its initial discharge capacity after 50 cycles at the C/3 rate (2 mA cm -2) and delivers about 70% of full capacity with an average load voltage of 3.6 V at the C/1 rate. Cell performance is stable up to 80 °C because PVdF chains might be stabilized by entanglement with the chemically cross-linked PEGDA network structure.

  12. Molecular Dynamics Modeling of Dielectric Polarization and Ferroelectricity in Poly(vinylidene fluoride) and Related Polymers

    NASA Astrophysics Data System (ADS)

    Calame, Jeffrey

    Molecular dynamics studies of the dielectric polarization response of a constrained bond length and bond angle, united-atom-based model of lamellar crystals of poly(vinylidene fluoride) (PVDF) are reported. Classical ferroelectricity is observed in PVDF, and when variations in the basic PVDF-like interaction parameters are allowed, a transition between classical and relaxor ferroelectricity is found to depend systematically on the polymer repeat unit dipole moment and on the united atom radius of the non-CH2 functional group. The effects of step and ramp electric field reversal are studied. A complicated sequence of reorientation processes occurs over a wide range of time scales, including a weak, temperature-independent response of 1-2 ps duration associated with local torsional motion, followed by a slow-rising delay regime lasting 10s of ns or longer that involves trans-gauche (TG) transitions in the amorphous phase. After the delay, a large-amplitude primary reorientation occurs over a relatively short additional duration (0.1 to 2 ns), which is due to rotation of large sub-segments in the crystalline phase with few TG transitions. The overall sequence concludes with a slow terminal rise lasting several 100s of ns involving an improvement in crystalline order. Work supported by the U.S. Office of Naval Research.

  13. Star Polymers.

    PubMed

    Ren, Jing M; McKenzie, Thomas G; Fu, Qiang; Wong, Edgar H H; Xu, Jiangtao; An, Zesheng; Shanmugam, Sivaprakash; Davis, Thomas P; Boyer, Cyrille; Qiao, Greg G

    2016-06-22

    Recent advances in controlled/living polymerization techniques and highly efficient coupling chemistries have enabled the facile synthesis of complex polymer architectures with controlled dimensions and functionality. As an example, star polymers consist of many linear polymers fused at a central point with a large number of chain end functionalities. Owing to this exclusive structure, star polymers exhibit some remarkable characteristics and properties unattainable by simple linear polymers. Hence, they constitute a unique class of technologically important nanomaterials that have been utilized or are currently under audition for many applications in life sciences and nanotechnologies. This article first provides a comprehensive summary of synthetic strategies towards star polymers, then reviews the latest developments in the synthesis and characterization methods of star macromolecules, and lastly outlines emerging applications and current commercial use of star-shaped polymers. The aim of this work is to promote star polymer research, generate new avenues of scientific investigation, and provide contemporary perspectives on chemical innovation that may expedite the commercialization of new star nanomaterials. We envision in the not-too-distant future star polymers will play an increasingly important role in materials science and nanotechnology in both academic and industrial settings.

  14. Polymer Chemistry

    NASA Technical Reports Server (NTRS)

    Williams, Martha; Roberson, Luke; Caraccio, Anne

    2010-01-01

    This viewgraph presentation describes new technologies in polymer and material chemistry that benefits NASA programs and missions. The topics include: 1) What are Polymers?; 2) History of Polymer Chemistry; 3) Composites/Materials Development at KSC; 4) Why Wiring; 5) Next Generation Wiring Materials; 6) Wire System Materials and Integration; 7) Self-Healing Wire Repair; 8) Smart Wiring Summary; 9) Fire and Polymers; 10) Aerogel Technology; 11) Aerogel Composites; 12) Aerogels for Oil Remediation; 13) KSC's Solution; 14) Chemochromic Hydrogen Sensors; 15) STS-130 and 131 Operations; 16) HyperPigment; 17) Antimicrobial Materials; 18) Conductive Inks Formulations for Multiple Applications; and 19) Testing and Processing Equipment.

  15. Low Voltage Electrowetting on Ferroelectric PVDF-HFP Insulator with Highly Tunable Contact Angle Range.

    PubMed

    Sawane, Yogesh B; Ogale, Satishchandra B; Banpurkar, Arun G

    2016-09-14

    We demonstrate a consistent electrowetting response on ferroelectric poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) insulator covered with a thin Teflon AF layer. This bilayer exhibits a factor of 3 enhancement in the contact angle modulation compared to that of conventional single-layered Teflon AF dielectric. On the basis of the proposed model the enhancement is attributed to the high value of effective dielectric constant (εeff ≈ 6) of the bilayer. Furthermore, the bilayer dielectric exhibits a hysteresis-free contact angle modulation over many AC voltage cycles. But the contact angle modulation for DC voltage shows a hysteresis because of the field-induced residual polarization in the ferroelectric layer. Finally, we show that a thin bilayer exhibits contact angle modulation of Δθ (U) ≈ 60° at merely 15 V amplitude of AC voltage indicating a potential dielectric for practical low voltage electrowetting applications. A proof of concept confirms electrowetting based rapid mixing of a fluorescent dye in aqueous glycerol solution for 15 V AC signal.

  16. Analysis of possibility of applying the PVDF foil in industrial vibration sensors

    NASA Astrophysics Data System (ADS)

    Wróbel, A.

    2015-11-01

    There are many machines using the piezoelectric effects. Systems with smart materials are often used because they have high potential applications for example transducers can be applied to receive required characteristic of projected system. Every engineer and designer know how important it is properly mathematical model and method of the analysis. Also it is important to consider all parameters of analyzed system for example glue layer between elements. Geometrical and material parameters has a significant impact on the characteristics of the all system's components because the omission of the influence of one of them results in inaccuracy in the analysis of the system. In article the modeling and testing of vibrating systems with piezoelectric ceramic materials transducers used as actuators and vibration dampers. The method of analysis of the vibrating sensor systems will be presented, mathematical model, and characteristics, to determine the influence of the system's properties on these characteristics. Main scientific point of the project is to analyze and demonstrate possibility of applying new construction with the PVDF foil or any other belonging to a group of smart materials in industrial sensors. Currently, the vibration level sensors are used by practically all manufacturers of piezoelectric ceramic plates to generate and detect the vibration of the fork.

  17. A novel bioinspired PVDF micro/nano hair receptor for a robot sensing system.

    PubMed

    Li, Fei; Liu, Weiting; Stefanini, Cesare; Fu, Xin; Dario, Paolo

    2010-01-01

    This paper describes the concept and design of a novel artificial hair receptor for the sensing system of micro intelligent robots such as a cricket-like jumping mini robot. The concept is inspired from the natural hair receptor of animals, also called cilium or filiform hair by different research groups, which is usually used as a vibration receptor or a flow detector by insects, mammals and fishes. The suspended fiber model is firstly built and the influence of scaling down is analyzed theoretically. The design of this artificial hair receptor is based on aligned suspended PVDF (polyvinylidene fluoride) fibers, manufactures with a novel method called thermo-direct drawing technique, and aligned suspended submicron diameter fibers are thus successfully fabricated on a flexible Kapton. In the post process step, some key problems such as separated electrodes deposition along with the fiber drawing direction and poling of micro/nano fibers to impart them with good piezoeffective activity have been presented. The preliminary validation experiments show that the artificial hair receptor has a reliable response with good sensibility to external pressure variation and, medium flow as well as its prospects in the application on sensing system of mini/micro bio-robots.

  18. Optimized anisotropic magnetoelectric response of Fe61.6Co16.4Si10.8B11.2/PVDF/Fe61.6Co16.4Si10.8B11.2 laminates for AC/DC magnetic field sensing

    NASA Astrophysics Data System (ADS)

    Reis, S.; Silva, M. P.; Castro, N.; Correia, V.; Gutierrez, J.; Lasheras, A.; Lanceros-Mendez, S.; Martins, P.

    2016-05-01

    The anisotropic magnetoelectric (ME) effect on a Fe61.6Co16.4Si10.8B11.2/PVDF Fe61.6Co16.4Si10.8B11.2 laminate composite has been used for the development of a magnetic field sensor able to detect both the magnitude and direction of AC and DC magnetic fields. The accuracy (99% for both AC and DC sensors), linearity (92% for the DC sensor and 99% for the AC sensor) and reproducibility (99% for both sensors) indicate the suitability of the sensor for applications. Furthermore, the sensitivity of the Fe61.6Co16.4Si10.8B11.2/PVDF/Fe61.6Co16.4Si10.8B11.2 anisotropic magnetic sensor—15 and 1400 mV Oe-1 for the DC and AC fields, respectively—are the highest reported in the literature for polymer-based ME materials. Such features, combined with its flexibility, versatility, light weight, low cost and low-temperature fabrication, lead to the suitability of the developed sensor for use in magnetic sensor applications.

  19. Polymers & People

    ERIC Educational Resources Information Center

    Lentz, Linda; Robinson, Thomas; Martin, Elizabeth; Miller, Mary; Ashburn, Norma

    2004-01-01

    Each Tuesday during the fall of 2002, teams of high school students from three South Carolina counties conducted a four-hour polymer institute for their peers. In less than two months, over 300 students visited the Charleston County Public Library in Charleston, South Carolina, to explore DNA, nylon, rubber, gluep, and other polymers. Teams of…

  20. EDITORIAL: Electroactive polymer materials

    NASA Astrophysics Data System (ADS)

    Bar-Cohen, Yoseph; Kim, Kwang J.; Ryeol Choi, Hyouk; Madden, John D. W.

    2007-04-01

    . Turning EAP materials into actuators-of-choice requires a well established infrastructure. This involves improving the understanding of the basic principles that drive the various EAP materials. It is also necessary to develop a comprehensive material science, as well as effective electro-mechanics analytical tools and material processing techniques. Efforts are underway to study the parameters that control EAP electro-activation force and deformation and many successes have been reported. The processes of synthesizing, fabricating, electroding, shaping and handling are being refined to maximize the actuation capability and robustness of EAP materials. Methods of reliably characterizing the response of these materials are being developed and efforts are being made to establish a database with documented material properties in order to support design engineers who are considering the use of these materials. Grand challenge for the development of EAP-actuated robotics. The technology of artificial muscles is still in its emerging stages but the increased resources, growing number of investigators conducting research related to EAP, and improved collaboration among developers, users and sponsors are leading to rapid advances in this field. In 1999, in an effort to promote worldwide development towards the realization of the potential of EAP materials, Yoseph Bar-Cohen posed an arm-wrestling challenge (http://ndeaa.jpl.nasa.gov/nasa-nde/lommas/eap/EAP-armwrestling.htm). A graphic rendering of this challenge is illustrated in the above figure. In posing this challenge, he is seeking to see an EAP-activated robotic arm win against a human in a wrestling match in order to provide a gauge of the level of advances in the development of these materials. Success in wrestling against humans will enable capabilities that are currently considered impossible. It would allow applying EAP materials to improve many aspects of our life where some of the possibilities include effective

  1. A Highly Aromatic and Sulfonated Ionomer for High Elastic Modulus Ionic Polymer Membrane Micro-Actuators

    DTIC Science & Technology

    2012-05-01

    Novel biomimetic actuator based on SPEEK and PVDF Sensors Actuators B 143 357–64 [15] Liu S, Montazami R, Liu Y, Jain V, Lin M, Zhou X, Heflin J R and...membrane swelled with ionic liquids Polymer 52 540–6 [20] Liu Y, Liu S, Lin J, Wang D, Jain V, Montazami R, Heflin J R, Li J, Madsen L and Zhang Q M...6 [35] Liu S, Montazami R, Liu Y, Jain V, Lin M, Heflin J R and Zhang Q M 2009 Layer-by-layer self-assembled conductor network composites in ionic

  2. The influence of self-assembly behavior of nanoparticles on the dielectric polymer composites

    SciTech Connect

    Lu, Xin; Li, Weiping Wang, Tingting; Jiang, Long; Luo, Laihui; Hua, Dayin; Zhu, Yuejin

    2013-11-15

    To clearify the influence of the distribution of the conductive nanoparticles on the dielectric properties of the corresponding polymer composites, the microstructure and dielectric character of the composites based on the oleic acid modified ferroferric oxide and polyvinylidene fluoride (PVDF) polymer have been studied experimentally. It is found that these composites exhibit a normal percolative phase transition over the filler content from insulator to conductor, consistent with the classical percolation theory. However, when the percentage of fillers is at a certain value which is below the percolation threshold, these nanoparticles can assemble into a special porous structure in the PVDF matrix, associated with the enhancement of dielectric constant at low frequency. In addition, the controllable dispersion of conducting nanoparticles in a polymer matrix can prevent premature agglomeration at low filling fractions and avoid the appearance of anomalously early percolation. Therefore, the self-assembly behavior of nanoparticles can be beneficial to preparation of the high dielectric constant and low loss composites for the application of electric energy storage.

  3. Morphological, Thermal, Electrical and Electromechanical Properties of Polyvinylidene Fluoride (PVDF)-Functionalized Carbon Nanotube Composites (Preprint)

    DTIC Science & Technology

    2012-03-01

    FUNCTIONALIZED CARBON NANOTUBE COMPOSITES (PREPRINT) Varrla Eswaraiah, Krishnan Balasubramaniam, and Sundara Ramaprabhu Indian Institute of Technology...composite and carbon nanotubes are embedded within and in between the microspheres. As the concentration of carbon nanotubes increases in the polymer, end...wt % of carbon nanotubes , nearly 25°C of onset decomposition temperature is achieved. DSC manifests the existence of polymer crystalline nature in

  4. Polymer - Ceramic Composites.

    DTIC Science & Technology

    1988-04-01

    characteristic properties of our composite films are then compared with those of Piezel, a commercially available composite, manufactured by the Daikin Industry...S obtained on PIEZEL (composite of PZT and PVDF copolymer, supplied by Daikin Industries Limited of Japan) are also presented. 1% % .... . ,,, ,,,,~m

  5. Muscle-like actuators? A comparison between three electroactive polymers

    NASA Astrophysics Data System (ADS)

    Meijer, Kenneth; Rosenthal, Marc S.; Full, Robert J.

    2001-07-01

    Muscles fulfill several functions within an animal's body. During locomotion they propel and control the limbs in unstructured environments. Therefore, the functional workspace of muscle needs to be represented by variables describing energy management (i.e. power output, efficiency) as well as control aspects (i.e. stiffness, damping). Muscles in the animal kingdom vary greatly with respect to those variables. To study if ElectroActive Polymer's (EAP) can be considered as artificial muscles we are making a direct comparison between the contractile properties of EAP's and biological muscle. We have measured the functional workspace of EAP actuators using the same setup and techniques that we use to test biological muscle. We evaluated the properties of three different EAP materials; the acrylic and silicone dielectric elastomers developed at SRI International and the high-energy electron-irradiated co-polymers (p(VDF-TrFE)) developed at the MRL laboratory at Penn State University. Initial results indicate that the EAP materials partly capture the functional workspace of natural muscle and sometimes even exceed the capabilities of muscle. Based on the data we have collected it seems that both EAP technologies have characteristics that could qualify them as artificial muscles.

  6. Effect of IX dosing on polypropylene and PVDF membrane fouling control.

    PubMed

    Myat, Darli Theint; Mergen, Max; Zhao, Oliver; Stewart, Matthew B; Orbell, John D; Merle, Tony; Croué, Jean-Philippe; Gray, Stephen

    2013-07-01

    The performance of ion exchange (IX) resin for organics removal from wastewater was assessed using advanced characterisation techniques for varying doses of IX. Organic characterisation using liquid chromatography with a photodiode array (PDA) and fluorescence spectroscopy (Method A), and UV254, organic carbon and organic nitrogen detectors (Method B), was undertaken on wastewater before and after magnetic IX treatment. Results showed partial removal of the biopolymer fraction at high IX doses. With increasing concentration of IX, evidence for nitrogen-containing compounds such as proteins and amino acids disappeared from the LC-OND chromatogram, complementary to the fluorescence response. A greater fluorescence response of tryptophan-like proteins (278 nm/343 nm) for low IX concentrations was consistent with aggregation of tryptophan-like compounds into larger aggregates, either by self-aggregation or with polysaccharides. Recycling of IX resin through multiple adsorption steps without regeneration maintained the high level of humics removal but there was no continued removal of biopolymer. Subsequent membrane filtration of the IX treated waters resulted in complex fouling trends. Filtration tests with either polypropylene (PP) or polyvinylidene fluoride (PVDF) membranes showed higher rates of initial fouling following treatment with high IX doses (10 mL/L) compared to filtration of untreated water, while treatment with lower IX doses resulted in decreased fouling rates relative to the untreated water. However, at longer filtration times the rate of fouling of IX treated waters was lower than untreated water and the relative fouling rates corresponded to the amount of biopolymer material in the feed. It was proposed that the mode of fouling changed from pore constriction during the initial filtration period to filter cake build up at longer filtration times. The organic composition strongly influenced the rate of fouling during the initial filtration period due to

  7. Adsorption characteristics of Ni(II) onto MA-DTPA/PVDF chelating membrane.

    PubMed

    Zhao, Xiaodan; Song, Laizhou; Fu, Jie; Tang, Pei; Liu, Feng

    2011-05-30

    The melamine-diethylenetriaminepentaacetic acid/polyvinylidene fluoride (MA-DTPA/PVDF) chelating membrane bearing polyaminecarboxylate groups was prepared for the removal of Ni(II) from wastewater effluents. The membrane was characterized by SEM, (13)C NMR and FTIR techniques. Quantitative adsorption experiments were performed in view of pH, contact time, temperature, the presence of Ca(II) and lactic acid as the controlling parameters. Adsorption kinetics and equilibrium were examined regarding the single Ni(II) system, binary Ni(II) and Ca(II) system and nickel-lactic acid complexes system. The desorption efficiency was also evaluated, and the adsorption mechanism was suggested based on experimental data. The results show that the sorption kinetics fit well to Lagergren second-order equation and the isotherms can be well described by Langmuir model. At 298 K, the second-order rate constant is calculated to be 4.171, 11.39, 6.203 cm(2)/(mg min) and the equilibrium uptake is 0.0264, 0.0211 and 0.0216 mg/cm(2) in the aforementioned three systems. The distribution coefficient of Ni(II) slowly decreases from 4.27 to 2.72, and the separation factor (f(Ni(II)/Ca(II))) increases from 3.10 to 8.46 when the initial Ca(II) concentration varies from 20 to 200mg/L. This reveals the chelating membrane shows more affinity for Ni(II) than Ca(II) ions. In the studied range of lactic acid concentration, Ni(II) uptake decreases with the maximum ratio of 10%. Chemical bonding (chelation) dominates in the adsorption process, and the negative ΔG° and ΔH° indicate the spontaneous and exothermic nature of adsorption.

  8. Fabrication of a self-sensing electroactive polymer bimorph actuator based on polyvinylidene fluoride and its electrostrictive terpolymer

    NASA Astrophysics Data System (ADS)

    Engel, Leeya; Van Volkinburg, Kyle R.; Ben-David, Moti; Washington, Gregory N.; Krylov, Slava; Shacham-Diamand, Yosi

    2016-04-01

    In this paper, we report on the fabrication of a self-sensing electroactive polymer cantilevered bimorph beam actuator and its frequency response. Tip deflections of the beam, induced by applying an AC signal across ferroelectric relaxor polyvinylidene fluoride-trifluoroethylene chlorotrifluoroethylene (P(VDF-TrFE-CTFE)), reached a magnitude of 350μm under a field of ~55MV/m and were recorded externally using a laser Doppler vibrometer (LDV). Deflections were determined simultaneously by applying a sensing model to the voltage measured across the bimorph's integrated layer of piezoelectric polymer polyvinylidene fluoride (PVDF). The sensing model treats the structure as a simple Euler- Bernoulli cantilevered beam with two distributed active elements represented through the use of generalized functions and offers a method through which real time tip deflection can be measured without the need for external visualization. When not being used as a sensing element, the PVDF layer can provide an additional means for actuation of the beam via the converse piezoelectric effect, resulting in bidirectional control of the beam's deflections. Integration of flexible sensing elements together with modeling of the electroactive polymer beam can benefit the developing field of polymer microactuators which have applications in soft robotics as "smart" prosthetics/implants, haptic displays, tools for less invasive surgery, and sensing.

  9. High-sensitivity gas phase sequence analysis of proteins and peptides on PVDF membranes using short cycle times.

    PubMed

    Reim, D F; Speicher, D W

    1993-10-01

    An optimized sequencer program with a cycle time of 38 min which is specifically tailored for analysis using polyvinylidene difluoride (PVDF) membranes has been developed. The program was developed using a pulsed liquid-phase instrument which was converted to gas-phase acid delivery. Gas-phase acid delivery minimized sample extraction from PVDF membranes and improved tryptophan yields in at least some cases. Other modifications which contributed to reliable high sensitivity sequencer performance included use of a Blott cartridge, substitution of ethyl acetate:heptane (1:1, v/v) instead of butyl chloride as the extraction solvent, use of a modified 100-microliters injection loop with an internal restrictor to reliably inject nearly 90% of the sample, and an HPLC gradient which resolved tryptophan from diphenylurea. These shortened cycle times were achieved at the conventional gas-phase reaction temperature. A slight increase in lag or carryover at prolines was compensated by reduced background from nonspecific acid cleavage which facilitated extended and/or high sensitivity sequencing of large proteins. Reproducible high initial and repetitive cycle yields were obtained with a wide range of experimental peptides which were electroblotted from either 1D or 2D polyacrylamide gels onto high retention PVDF membranes. Initial yields of the majority of the experimental samples analyzed with this program were less than 5 pmol. In addition, most samples with initial yields below 1-2 pmol yielded sufficient sequence information to identify the protein by comparison to protein sequence data-bases or to design oligonucleotide probes.

  10. Exploring the synergetic effects of graphene oxide (GO) and polyvinylpyrrodione (PVP) on poly(vinylylidenefluoride) (PVDF) ultrafiltration membrane performance

    NASA Astrophysics Data System (ADS)

    Chang, Xiaojing; Wang, Zhenxing; Quan, Shuai; Xu, Yanchao; Jiang, Zaixing; Shao, Lu

    2014-10-01

    Membrane surface and cross-sectional morphology created during membrane formation is one of the most essential factors determining membrane separation performance. However, the complicated interactions between added nanoparticles and additives influencing membrane morphology and performance during building membrane architectures had been generally neglected. In this study, asymmetric PVDF composite ultrafiltration (UF) membranes containing graphene oxides (GO) were prepared by using N-methyl pyrrolidone (NMP) as solvent and polyvinylpyrrodione (PVP) as the pore forming reagent. In the first time, the effects of mutual interactions between GO and PVP on membranes surface compositions, morphology and performance were investigated in detail. The variation in chemical properties of different membranes and hydrogen bonds in the membrane containing GO and PVP were confirmed by X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy-attenuated total reflectance (FTIR-ATR). Atomic force microscopy (AFM), scanning electron microscopy (SEM), and contact angle (CA) were utilized to clarify the synergetic effects of GO and PVP on morphologies and surface hydrophilicity of membranes. Besides, water flux, bovine serum albumin (BSA) rejection and attenuate coefficient were also determined to investigate filtration performance of various membranes. Compared with pure PVDF membrane, the comprehensive performance of PVDF/GO/PVP membrane has been obviously improved. The surface hydrophilicity and anti-fouling performance were enhanced by the synergistic effects of incorporated GO and PVP. When the PVP content was 0.25 wt.% and the GO content was 0.5 wt.%, the optimized performance can be obtained due to the formation of hydrogen bonds between GO and PVP.

  11. Structural evolution during mechanical deformation in high-barrier PVDF-TFE/PET multilayer films using in situ X-ray techniques.

    PubMed

    Jordan, Alex M; Lenart, William R; Carr, Joel M; Baer, Eric; Korley, Lashanda T J

    2014-03-26

    Poly(vinylidene fluoride-co-tetrafluoroethylene) (PVDF-TFE) is confined between alternating layers of poly(ethylene terephthalate) (PET) utilizing a unique multilayer processing technology, in which PVDF-TFE and PET are melt-processed in a continuous fashion. Postprocessing techniques including biaxial orientation and melt recrystallization were used to tune the crystal orientation of the PVDF-TFE layers, as well as achieve crystallinity in the PET layers through strain-induced crystallization and thermal annealing during the melt recrystallization step. A volume additive model was used to extract the effect of crystal orientation within the PVDF-TFE layers and revealed a significant enhancement in the modulus from 730 MPa in the as-extruded state (isotropic) to 840 MPa in the biaxially oriented state (on-edge) to 2230 MPa in the melt-recrystallized state (in-plane). Subsequently, in situ wide-angle X-ray scattering was used to observe the crystal structure evolution during uniaxial deformation in both the as-extruded and melt-recrystallized states. It is observed that the low-temperature ferroelectric PVDF-TFE crystal phase in the as-extruded state exhibits equatorial sharpening of the 110 and 200 crystal peaks during deformation, quantified using the Hermans orientation function, while in the melt-recrystallized state, an overall increase in the crystallinity occurs during deformation. Thus, we correlated the mechanical response (strain hardening) of the films to these respective evolved crystal structures and highlighted the ability to tailor mechanical response. With a better understanding of the structural evolution during deformation, it is possible to more fully characterize the structural response to handling during use of the high-barrier PVDF-TFE/PET multilayer films as commercial dielectrics and packaging materials.

  12. Guar gum: Structural and electrochemical characterization of natural polymer based binder for silicon-carbon composite rechargeable Li-ion battery anodes

    NASA Astrophysics Data System (ADS)

    Kuruba, Ramalinga; Datta, Moni Kanchan; Damodaran, Krishnan; Jampani, Prashanth H.; Gattu, Bharat; Patel, Prasad P.; Shanthi, Pavithra M.; Damle, Sameer; Kumta, Prashant N.

    2015-12-01

    Long term cyclability of a composite Li-ion anode electrode comprised of 82 wt.% Si/C lithium ion active material along with 8 wt.% polymeric binder and 10 wt.% Super P conductive carbon black has been studied utilizing polymeric binders exhibiting different elastic/tensile moduli and tensile yield strengths. Accordingly, electrochemically active Si/C composite synthesized by high energy mechanical milling (HEMM), exhibiting reversible specific capacities of ∼780 mAh/g and ∼600 mAh/g at charge/discharge rates of ∼50 mA/g and ∼200 mA/g, respectively were selected as the Li-ion active anode. Polyvinylidene fluoride (PVDF) and purified guar gum (PGG) with reported elastic moduli ∼1000 MPa and ∼3200 MPa, respectively were selected as the binders. Results show that the composite electrode (Si/C + binder + conducting carbon) comprising the higher elastic modulus binder (PGG) exhibits better long term cyclability contrasted with PVDF. 1H-NMR analysis of the polymer before and after cycling shows structural degradation/deformation of the low elastic modulus PVDF, whereas the high elastic modulus PGG binder shows no permanent structural deformation or damage. The results presented herein thus suggest that PGG based polymers exhibiting high elastic modulus are a promising class of binders with the desired mechanical integrity needed for enduring the colossal volume expansion stresses of Si/C based composite anodes.

  13. Organometallic Polymers.

    ERIC Educational Resources Information Center

    Carraher, Charles E., Jr.

    1981-01-01

    Reactions utilized to incorporate a metal-containing moiety into a polymer chain (addition, condensation, and coordination) are considered, emphasizing that these reactions also apply to smaller molecules. (JN)

  14. Polymer flooding

    SciTech Connect

    Littmann, W.

    1988-01-01

    This book covers all aspects of polymer flooding, an enhanced oil recovery method using water soluble polymers to increase the viscosity of flood water, for the displacement of crude oil from porous reservoir rocks. Although this method is becoming increasingly important, there is very little literature available for the engineer wishing to embark on such a project. In the past, polymer flooding was mainly the subject of research. The results of this research are spread over a vast number of single publications, making it difficult for someone who has not kept up-to-date with developments during the last 10-15 years to judge the suitability of polymer flooding to a particular field case. This book tries to fill that gap. An indispensable book for reservoir engineers, production engineers and lab. technicians within the petroleum industry.

  15. Polymers All Around You!

    ERIC Educational Resources Information Center

    Gertz, Susan

    Background information on natural polymers, synthetic polymers, and the properties of polymers is presented as an introduction to this curriculum guide. Details are provided on the use of polymer products in consumer goods, polymer recycling, polymer densities, the making of a polymer such as GLUEP, polyvinyl alcohol, dissolving plastics, polymers…

  16. Preparation and characterization of poly(vinylidene fluoride): A high dielectric performance nano-composite for electrical storage

    NASA Astrophysics Data System (ADS)

    Abdalla, S.; Obaid, A.; Al-Marzouki, F. M.

    We have prepared films of polymer nano-composite (PNC) of poly[vinylidene-fluoride] (PVDF) and bismuth vanadate (BiVO4) nanoparticles. The α and γ electro-active phases were detected, and the addition of BiVO4 drastically increases the formation of the α-phase. Addition of BiVO4 produces up to 98% of electro-active phases. Robust electrostatic interactions arise between charges at the BiVO4-surfaces, and differences in electron affinity between CH2 and CF2 groups created dielectric dipoles. The addition of BiVO4 has not only enhanced the formation of the electrically active phases but also makes each dipole in the phase has its specific characteristics for example its own relaxation time. The AC-electrical permittivity showed that the dielectric constant of 10%wt- BiVO4 nanoparticles in PVDF has a value 44 ε0, which is four times more than the dielectric constant of the as-prepared PVDF films. These data show the importance of these polymers as easy, flexible, and durable energy storage materials.

  17. Anti-inflammatory polymer electrodes for glial scar treatment: bringing the conceptual idea to future results.

    PubMed

    Asplund, Maria; Boehler, Christian; Stieglitz, Thomas

    2014-01-01

    Conducting polymer films offer a convenient route for the functionalization of implantable microelectrodes without compromising their performance as excellent recording units. A micron thick coating, deposited on the surface of a regular metallic electrode, can elute anti-inflammatory drugs for the treatment of glial scarring as well as growth factors for the support of surrounding neurons. Electro-activation of the polymer drives the release of the substance and should ideally provide a reliable method for controlling quantity and timing of release. Driving signals in the form of a constant potential (CP), a slow redox sweep or a fast pulse are all represented in literature. Few studies present such release in vivo from actual recording and stimulating microelectronic devices. It is essential to bridge the gap between studies based on release in vitro, and the intended application, which would mean release into living and highly delicate tissue. In the biological setting, signals are limited both by available electronics and by the biological safety. Driving signals must not be harmful to tissue and also not activate the tissue in an uncontrolled manner. This review aims at shedding more light on how to select appropriate driving parameters for the polymer electrodes for the in vivo setting. It brings together information regarding activation thresholds for neurons, as well as injury thresholds, and puts this into context with what is known about efficient driving of release from conducting polymer films.

  18. Polyethylene oxide-polytetrahydrofurane-PEDOT conducting interpenetrating polymer networks for high speed actuators

    NASA Astrophysics Data System (ADS)

    Plesse, C.; Khaldi, A.; Wang, Q.; Cattan, E.; Teyssié, D.; Chevrot, C.; Vidal, F.

    2011-12-01

    In recent years, numerous studies on electro-active polymer (EAP) actuators have been reported. One promising technology is the elaboration of electronic conducting polymer-based actuators with interpenetrating polymer network (IPNs) architecture. In this study, the synthesis and characterisation of conducting IPNs for actuator applications is described. The IPNs are synthesised from polyethylene oxide (PEO) and polytetrahydrofurane (PTHF) networks in which the conducting polymer (poly(3,4-ethylenedioxythiophene)) is incorporated. In a first step, PEO/PTHF IPNs were prepared via an 'in situ' process using poly(ethylene glycol) methacrylate and dimethacrylate and hydroxytelechelic PTHF as starting materials. The IPN mechanical properties were examined by DMA and tensile strength tests. N-ethylmethylimidazolium bis(trifluoromethanesulfonyl)imide (EMITFSI) swollen PEO/PTHF IPNs show ionic conductivities up to 10-3 S cm-1 at 30 °C. In a second step, the conducting IPN actuators were prepared by oxidative polymerisation of 3,4-ethylenedioxithiophene (EDOT) using FeCl3 as an oxidising agent within the PEO/PTHF IPN host matrix. The frequency response performance of the bending conducting IPN actuator was then evaluated. The resulting actuator exhibits a mechanical resonance frequency of up to 125 Hz with 0.75% strain for an applied potential of ± 5 V.

  19. Characterization and anti-fouling performance of nano-Al₂O₃/PVDF membrane for Songhua river raw water filtration.

    PubMed

    Yu, S L; Shi, W X; Lu, Y; Yang, J X

    2011-01-01

    Polyvinylidene fluoride (PVDF) flat ultrafiltration membranes modified by nano-sized alumina (Al₂O₃) particles were prepared by phase inversion process and their properties and anti-fouling performances were examined. The influence of three types of natural organic matters on the modified membrane fouling was also studied. Raw water was taken from two different locations, i.e., Harbin and Zhaoyuan, of Songhua River. Dissolved organic compounds in the raw water were fractionated using XAD resins into three fractions, i.e., hydrophobic fraction, transphilic fraction, and hydrophilic fraction (HPI). The three adsorbed compounds were further eluted and dissolved into distilled water respectively to prepare the feed for the fouling tests. All solutions were adjusted to a concentration of 10.6 mg C/L, which equals to the total organic carbon (TOC) of the raw water. Results show that the addition of nano-Al₂O₃ particulars did not affect the inherent traits of the PVDF membranes, however, its surface hydrophilic properties were improved significantly with the addition of nanoparticles and anti-fouling performance was enhanced as well. The HPIs in the Songhua River were the main foulant, causing more fouling to membrane than hydrophobic and transphilic matters.

  20. Multilayered carbon nanotube/polymer composite based thermoelectric fabrics.

    PubMed

    Hewitt, Corey A; Kaiser, Alan B; Roth, Siegmar; Craps, Matt; Czerw, Richard; Carroll, David L

    2012-03-14

    Thermoelectrics are materials capable of the solid-state conversion between thermal and electrical energy. Carbon nanotube/polymer composite thin films are known to exhibit thermoelectric effects, however, have a low figure of merit (ZT) of 0.02. In this work, we demonstrate individual composite films of multiwalled carbon nanotubes (MWNT)/polyvinylidene fluoride (PVDF) that are layered into multiple element modules that resemble a felt fabric. The thermoelectric voltage generated by these fabrics is the sum of contributions from each layer, resulting in increased power output. Since these fabrics have the potential to be cheaper, lighter, and more easily processed than the commonly used thermoelectric bismuth telluride, the overall performance of the fabric shows promise as a realistic alternative in a number of applications such as portable lightweight electronics.

  1. In vitro biofilms formation on polymer matrix composites

    NASA Astrophysics Data System (ADS)

    Stodolak, E.; Paluszkiewicz, C.; Błażewicz, M.; Kotela, I.

    2009-04-01

    Aim of this work was a surface modification and characterisation of composite membrane materials destined for regeneration of damaged bone tissue. The materials consisted of stable, hydrophobic PTFE-PVDF-PP polymer and resorbable, hydrophilic biopolymer fibres made of sodium alginate (NaAlg). The fibres were washed-out with water to create open porosity in the membranes, and part of the dissolved sodium alginate deposited on the composite surface. Distribution of a biopolymer layer modifying the composite surface was investigated with FT-IR method. FT-IR reflection (ATR) and transmission techniques revealed that the surface modification had a domain-type character. The deposited sodium alginate modified physicochemical properties of the membrane i.e., lowered the wetting angle, and increased the surface free energy. Such surface characteristics may be advantageous for cells adhesion and proliferation process in in vitro and in vivo conditions.

  2. Mechanism of high dielectric performance of polymer composites induced by BaTiO3-supporting Ag hybrid fillers

    NASA Astrophysics Data System (ADS)

    Fang, Fang; Yang, Wenhu; Yu, Shuhui; Luo, Suibin; Sun, Rong

    2014-03-01

    BaTiO3-supporting Ag hybrid particles (BT-Ag) with varied fraction of Ag were synthesized by reducing silver nitrate in the glycol solution containing BaTiO3 (BT) suspensions. The Ag nano particles with a size of about 20 nm were discretely grown on the surface of the BT. The dielectric performance of the composites containing the BT-Ag as fillers in the matrix of polyvinylidene fluoride (PVDF) was investigated. The relative permittivity (ɛr) of the BT-Ag/PVDF composites increased prominently with the increase of BT-Ag loading amount, and the typical conductive path of the conductor/polymer system was not observed even with a high loading of BT-Ag. The ɛr at 100 Hz for the three BT-(0.31, 0.49, 0.61)Ag/PVDF composites at room temperature were 283, 350, and 783, respectively. The ɛr of the composites was enhanced by more than 3 times compared with that of the composite containing untreated BT nanoparticles at frequencies over 1 kHz and the loss tangent (tan δ) was less than 0.1 which should be attributed to the low conductivity of the composites. Theoretical calculations based on the effective medium percolation theory model and series-parallel model suggested that the enhanced permittivity of BT-Ag/PVDF composites should arise from the ultrahigh permittivity of BT-Ag fillers, which was over 104 and associated with the content of Ag deposited on the surface of BT.

  3. Multifunctional Nano-engineered Polymer Surfaces with Enhanced Mechanical Resistance and Superhydrophobicity

    PubMed Central

    Hernández, Jaime J.; Monclús, Miguel A.; Navarro-Baena, Iván; Viela, Felipe; Molina-Aldareguia, Jon M.; Rodríguez, Isabel

    2017-01-01

    This paper presents a multifunctional polymer surface that provides superhydrophobicity and self–cleaning functions together with an enhancement in mechanical and electrical performance. These functionalities are produced by nanoimprinting high aspect ratio pillar arrays on polymeric matrix incorporating functional reinforcing elements. Two distinct matrix-filler systems are investigated specifically, Carbon Nanotube reinforced Polystyrene (CNT-PS) and Reduced Graphene Oxide reinforced Polyvinylidene Difluoride (RGO-PVDF). Mechanical characterization of the topographies by quantitative nanoindentation and nanoscratch tests are performed to evidence a considerable increase in stiffness, Young’s modulus and critical failure load with respect to the pristine polymers. The improvement on the mechanical properties is rationalized in terms of effective dispersion and penetration of the fillers into the imprinted structures as determined by confocal Raman and SEM studies. In addition, an increase in the degree of crystallization for the PVDF-RGO imprinted nanocomposite possibly accounts for the larger enhancement observed. Improvement of the mechanical ruggedness of functional textured surfaces with appropriate fillers will enable the implementation of multifunctional nanotextured materials in real applications. PMID:28262672

  4. Multifunctional Nano-engineered Polymer Surfaces with Enhanced Mechanical Resistance and Superhydrophobicity

    NASA Astrophysics Data System (ADS)

    Hernández, Jaime J.; Monclús, Miguel A.; Navarro-Baena, Iván; Viela, Felipe; Molina-Aldareguia, Jon M.; Rodríguez, Isabel

    2017-03-01

    This paper presents a multifunctional polymer surface that provides superhydrophobicity and self–cleaning functions together with an enhancement in mechanical and electrical performance. These functionalities are produced by nanoimprinting high aspect ratio pillar arrays on polymeric matrix incorporating functional reinforcing elements. Two distinct matrix-filler systems are investigated specifically, Carbon Nanotube reinforced Polystyrene (CNT-PS) and Reduced Graphene Oxide reinforced Polyvinylidene Difluoride (RGO-PVDF). Mechanical characterization of the topographies by quantitative nanoindentation and nanoscratch tests are performed to evidence a considerable increase in stiffness, Young’s modulus and critical failure load with respect to the pristine polymers. The improvement on the mechanical properties is rationalized in terms of effective dispersion and penetration of the fillers into the imprinted structures as determined by confocal Raman and SEM studies. In addition, an increase in the degree of crystallization for the PVDF-RGO imprinted nanocomposite possibly accounts for the larger enhancement observed. Improvement of the mechanical ruggedness of functional textured surfaces with appropriate fillers will enable the implementation of multifunctional nanotextured materials in real applications.

  5. Tuning the microwave absorption through engineered nanostructures in co-continuous polymer blends

    NASA Astrophysics Data System (ADS)

    Prasanna Kar, Goutam; Biswas, Sourav; Bose, Suryasarathi

    2016-06-01

    Herein, we report tailor-made properties by dispersing nanostructured materials in a co-continuous polymer blend (PVDF/ABS) that is capable of shielding electromagnetic (EM) radiation. To accomplish this, lossy materials were employed like multi-walled carbon nanotubes (MWNTs), and barium titanate (BT), (which exhibit relaxation losses in the microwave frequency domain) and ferrites (like Fe3O4). To improve the state of dispersion, the MWNTs were non-covalently modified using 3,4,9,10-perylenetetracarboxylic dianhydride (PTCD) via π-π stacking, and for effective shielding the MWNTs were conjugated with either BT or Fe3O4 nanoparticles through suitable modifications. The hybrid nanoparticles were selectively localized in the PVDF phase, governed by its polarity, and exhibited excellent microwave attenuation. In order to gain insight into the dielectric and magnetic attributes, the microwave parameters were assessed systematically. Taken together, our results uncover polymer blend as a promising candidate for designing lightweight, thermally stable microwave absorber materials.

  6. Optoelectronic and acoustic properties and their interfacial durability of GnP/PVDF/GnP composite actuators with nano-structural control

    NASA Astrophysics Data System (ADS)

    Park, Joung-Man; Kwon, Dong-Jun; Wang, Zuo-Jia; Gu, Ga-Young; DeVries, Lawrence

    2013-03-01

    Nano- and hetero-structures of carbon nanotube (CNT), indium tin oxide (ITO), and Graphene nano Platelet (GnP) can control significantly piezoelectric and optoelectronic properties in Microelectromechanical Systems (MEMS) as acoustic actuators. Interfacial durability and electrical properties of CNT, ITO or GnP coated poly(vinylidene fluoride) (PVDF) nanocomposites were investigated for use in acoustic actuator applications. The GnP coated PVDF nanocomposite exhibited better electrical conductivity than either CNT or ITO, due to the unique electrical properties of GnP. GnP nanocomposite coatings also exhibited good acoustical properties. Contact angle, surface energy, work of adhesion, and spreading coefficient measurements were used to explore the interfacial adhesion durability between neat CNT (or plasma treated CNT) and plasma treated PVDF. The acoustic actuation performance of GnP coated PVDF nanocomposites were investigated for different radii of curvature and different coating conditions, using a sound level meter. GnP is considered to be a more appropriate acoustic actuator than either CNT or ITO because of its characteristic electrical properties. A radius of curvature of about 15 degrees was established as being most appropriate. Sound characteristics differed with varying coating thicknesses. The results of this study suggest that it should be possible to manufacture transparent actuators with good sound quality.

  7. Non-activation ZnO array as a buffering layer to fabricate strongly adhesive metal-organic framework/PVDF hollow fiber membranes.

    PubMed

    Li, Wanbin; Meng, Qin; Li, Xiaonian; Zhang, Congyang; Fan, Zheng; Zhang, Guoliang

    2014-09-04

    A non-activation (NA) ZnO array is directly grown on a PVDF hollow fiber membrane. The defect-free MOF layers can be synthesized easily on the NA-ZnO array without any activation procedure. The array and MOF layers are strongly adhered to the hollow fiber membrane. The prepared ZIF membranes exhibit excellent gas separation performances.

  8. Antimocrobial Polymer

    DOEpatents

    McDonald, William F.; Huang, Zhi-Heng; Wright, Stacy C.

    2005-09-06

    A polymeric composition having antimicrobial properties and a process for rendering the surface of a substrate antimicrobial are disclosed. The composition comprises a crosslinked chemical combination of (i) a polymer having amino group-containing side chains along a backbone forming the polymer, (ii) an antimicrobial agent selected from quaternary ammonium compounds, gentian violet compounds, substituted or unsubstituted phenols, biguanide compounds, iodine compounds, and mixtures thereof, and (iii) a crosslinking agent containing functional groups capable of reacting with the amino groups. In one embodiment, the polymer is a polyamide formed from a maleic anhydride or maleic acid ester monomer and alkylamines thereby producing a polyamide having amino substituted alkyl chains on one side of the polyamide backbone; the crosslinking agent is a phosphine having the general formula (A)3P wherein A is hydroxyalkyl; and the antimicrobial agent is chlorhexidine, dimethylchlorophenol, cetyl pyridinium chloride, gentian violet, triclosan, thymol, iodine, and mixtures thereof.

  9. Antimicrobial Polymer

    DOEpatents

    McDonald, William F.; Wright, Stacy C.; Taylor, Andrew C.

    2004-09-28

    A polymeric composition having antimicrobial properties and a process for rendering the surface of a substrate antimicrobial are disclosed. The polymeric composition comprises a crosslinked chemical combination of (i) a polymer having amino group-containing side chains along a backbone forming the polymer, (ii) an antimicrobial agent selected from metals, metal alloys, metal salts, metal complexes and mixtures thereof, and (iii) a crosslinking agent containing functional groups capable of reacting with the amino groups. In one example embodiment, the polymer is a polyamide formed from a maleic anhydride or maleic acid ester monomer and alkylamines thereby producing a polyamide having amino substituted alkyl chains on one side of the polyamide backbone; the crosslinking agent is a phosphine having the general formula (A).sub.3 P wherein A is hydroxyalkyl; and the metallic antimicrobial agent is selected from chelated silver ions, silver metal, chelated copper ions, copper metal, chelated zinc ions, zinc metal and mixtures thereof.

  10. Polymer inflation

    NASA Astrophysics Data System (ADS)

    Hassan, Syed Moeez; Husain, Viqar; Seahra, Sanjeev S.

    2015-03-01

    We consider the semiclassical dynamics of a free massive scalar field in a homogeneous and isotropic cosmological spacetime. The scalar field is quantized using the polymer quantization method assuming that it is described by a Gaussian coherent state. For quadratic potentials, the semiclassical equations of motion yield a universe that has an early "polymer inflation" phase which is generic and almost exactly de Sitter, followed by an epoch of slow-roll inflation. We compute polymer corrections to the slow-roll formalism, and discuss the probability of inflation in this model using a physical Hamiltonian arising from time gauge fixing. We also show how in this model, it is possible to obtain a significant amount of slow-roll inflation from sub-Planckian initial data, hence circumventing some of the criticisms of standard scenarios. These results show the extent to which a quantum gravity motivated quantization method affects early universe dynamics.

  11. An Electrochemical NO₂ Sensor Based on Ionic Liquid: Influence of the Morphology of the Polymer Electrolyte on Sensor Sensitivity.

    PubMed

    Kuberský, Petr; Altšmíd, Jakub; Hamáček, Aleš; Nešpůrek, Stanislav; Zmeškal, Oldřich

    2015-11-11

    A systematic study was carried out to investigate the effect of ionic liquid in solid polymer electrolyte (SPE) and its layer morphology on the characteristics of an electrochemical amperometric nitrogen dioxide sensor. Five different ionic liquids were immobilized into a solid polymer electrolyte and key sensor parameters (sensitivity, response/recovery times, hysteresis and limit of detection) were characterized. The study revealed that the sensor based on 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([EMIM][N(Tf)2]) showed the best sensitivity, fast response/recovery times, and low sensor response hysteresis. The working electrode, deposited from water-based carbon nanotube ink, was prepared by aerosol-jet printing technology. It was observed that the thermal treatment and crystallinity of poly(vinylidene fluoride) (PVDF) in the solid polymer electrolyte influenced the sensitivity. Picture analysis of the morphology of the SPE layer based on [EMIM][N(Tf)2] ionic liquid treated under different conditions suggests that the sensor sensitivity strongly depends on the fractal dimension of PVDF spherical objects in SPE. Their deformation, e.g., due to crowding, leads to a decrease in sensor sensitivity.

  12. Multiscale implications of stress-induced ionic polymer transducer sensing

    NASA Astrophysics Data System (ADS)

    Zangrilli, Ursula Therese

    Ionic Polymer Transducers (IPTs) can act as both actuators and sensors. As actuators, the energy density values are much better than PZT or PVDF materials. As sensors, IPTs are extraordinarily sensitive and have the potential to be used in any mode of deformation. However, application of IPT sensors is limited because of a lack of understanding of their fundamental physics. In this work, the main focus will be to explore and develop a better understanding of how IPTs function with respect to shear deformation. In turn, the results developed here will improve upon the state of understanding of IPT sensors in general and potentially expand meaningful application opportunities. Because IPT active response is a multiscale phenomenon, this study adopts a multiscale modeling framework. Of interest are the interplay among the polymeric backbone of the ionic polymer, the diluent present in the hydrophilic regions of the polymer and the interspersed electrode particulate. To begin, this work improves upon a past multiscale modeling framework for the polymer backbone based upon Rotational Isomeric State Theory such that the effects of material anisotropy may be considered. This is potentially significant in light of the polymer manufacturing process. These modeling results are then incorporated into a model of the diluent movement within the ionic transport regions of the IPT. The electrical current predictions are based upon streaming potential theories. Finally, this model incorporates viscoelastic behavior in order to develop a better understanding of the coupling of these two systems (the polymer and the diluent) and how this coupling influence affects the expected current output over time.

  13. Effect of poly(ethylene oxide) on ionic conductivity and electrochemical properties of poly(vinylidenefluoride) based polymer gel electrolytes prepared by electrospinning for lithium ion batteries

    NASA Astrophysics Data System (ADS)

    Prasanth, Raghavan; Shubha, Nageswaran; Hng, Huey Hoon; Srinivasan, Madhavi

    2014-01-01

    Effect of poly(ethylene oxide) on the electrochemical properties of polymer electrolyte based on electrospun, non-woven membrane of PVdF is demonstrated. Electrospinning process parameters are controlled to get a fibrous membrane consisting of bead-free, uniformly dispersed thin fibers with diameter in the range of 1.5-1.9 μm. The membrane with good mechanical strength and porosity exhibits high uptake when activated with the liquid electrolyte of lithium salt in a mixture of organic solvents. The polymer gel electrolyte shows ionic conductivity of 4.9 × 10-3 S cm-1 at room temperature. Electrochemical performance of the polymer gel electrolyte is evaluated in Li/polymer electrolyte/LiFePO4 coin cell. Good performance with low capacity fading on charge-discharge cycling is demonstrated.

  14. Antimicrobial polymers.

    PubMed

    Jain, Anjali; Duvvuri, L Sailaja; Farah, Shady; Beyth, Nurit; Domb, Abraham J; Khan, Wahid

    2014-12-01

    Better health is basic requirement of human being, but the rapid growth of harmful pathogens and their serious health effects pose a significant challenge to modern science. Infections by pathogenic microorganisms are of great concern in many fields such as medical devices, drugs, hospital surfaces/furniture, dental restoration, surgery equipment, health care products, and hygienic applications (e.g., water purification systems, textiles, food packaging and storage, major or domestic appliances etc.) Antimicrobial polymers are the materials having the capability to kill/inhibit the growth of microbes on their surface or surrounding environment. Recently, they gained considerable interest for both academic research and industry and were found to be better than their small molecular counterparts in terms of enhanced efficacy, reduced toxicity, minimized environmental problems, resistance, and prolonged lifetime. Hence, efforts have focused on the development of antimicrobial polymers with all desired characters for optimum activity. In this Review, an overview of different antimicrobial polymers, their mechanism of action, factors affecting antimicrobial activity, and application in various fields are given. Recent advances and the current clinical status of these polymers are also discussed.

  15. Polymer solutions

    DOEpatents

    Krawczyk, Gerhard Erich; Miller, Kevin Michael

    2011-07-26

    There is provided a method of making a polymer solution comprising polymerizing one or more monomer in a solvent, wherein said monomer comprises one or more ethylenically unsaturated monomer that is a multi-functional Michael donor, and wherein said solvent comprises 40% or more by weight, based on the weight of said solvent, one or more multi-functional Michael donor.

  16. Polymer/inorganic nanocomposites with tailored hierarchical structure as advanced dielectric materials

    SciTech Connect

    Manias, Evangelos; Randall, Clive; Tomer, Vivek; Polyzos, Georgios

    2012-01-01

    Most advances and commercial successes of polymer/inorganic nanocomposites rely only on the dispersion of nanoparticles in a polymer matrix. Such approaches leave untapped opportunities where performance can be improved by controlling the larger length-scale structures. Here, we review selected examples where the hierarchical structure (from millimeter to nanometer) is tailored to control the transport properties of the materials, giving rise to marked property enhancements, relevant to dielectric materials for power capacitors. These examples address composite structures that are self-assembled, both at the nm and the micron scales, and, thus, can be produced using standard industrial practices. Specifically, polyethylene (PE) blends or poly(vinylidene fluoride) (PVDF) copolymers are reinforced with nanofillers; these composites are designed with high filler orientation, which yielded marked improvements in electric-field breakdown strength and, consequently, large improvements in their recoverable energy densities.

  17. Understanding Controls on Wetting at Fluorinated Polyhedral Oligomeric Silsesquioxane/Polymer Surfaces.

    PubMed

    Ye, Yi; Tian, Ming; Zhang, Chen; Du, Zhongjie; Mi, Jianguo

    2016-01-12

    Fluorinated polyhedral oligomeric silsesquioxane (F-POSS) nanoparticles have been widely used to enhance the hydrophobicity or oleophobicity of polymer films via constructing the specific micro/nanoscale roughness. In this work, we study the oleophobicity of pure and F-POSS-decorated poly(vinylidene fluoride) (PVDF) and poly(methyl methacrylate) (PMMA) films using a dynamic density functional theory approach. The role of nanoparticle size and coverage and the chemical features of F-POSS and the polymer film in the wetting behavior of diiodomethane droplets has been integrated to the remaining ratio of surface potential to quantitatively characterize the corner effect. It is shown that, on the basis of universal force field parameters, the theoretically predicted contact angles are in general agreement with the available experimental data.

  18. Annealing effect on the dielectric response of novel polymer/nano-quasicrystalline composites

    NASA Astrophysics Data System (ADS)

    Venkatesh, Ch.; Rao, V. V.

    2013-06-01

    In the earlier paper (Ch. Venkatesh et al. Solid State Comm., 2010), a dielectric percolation has been reported in composites of nano-quasicrystalline (nQc) Al-Cu-Fe (filler) and polyvinylidene fluoride (PVDF) (matrix). Though a high value of dielectric constant is observed near to the percolation threshold, these composites show higher dielectric loss values at lower frequencies. An effect of annealing has been investigated on the same composites which lead to decrement in dielectric loss values appreciably. The low dielectric loss values have been attributed due to the formation of thick grain boundaries in polymer matrix which completely surrounds the nQc cluster that weakens the effective tunneling of charge carriers near the filler-polymer interfacial region. Finally, a dielectric constant of 500 with tanδ<1 at 1 KHz is observed which may make the composite useful for low loss capacitive applications.

  19. Review on the properties of the ferrorelaxor polymers and some new recent developments

    NASA Astrophysics Data System (ADS)

    Bauer, François

    2012-06-01

    It has been found that by introducing defects into the P(VDF-TrFE) copolymers, it is possible to convert the polymer from a normal ferroelectric to a relaxor ferroelectric. A new class of ferroelectric polymers, i.e., the terpolymers of P(VDF-TrFE-CFE) or of P(VDF-TrFE-CTFE), was developed from the normal ferroelectric PVDF-TrFE polymer by employing proper defect modifications which eliminate detrimental effects associated with a normal first order F-P transition while maintaining high material responses. Relevant studies show that this class of electroactive polymers offers unique properties in comparison with other ferroelectric polymers. The syntheses of these relaxor ferroelectric polymers have been done by a combination of the suspension polymerization process and an oxygen-activated initiator at a temperature of 40°C. Films from cast solution can be made in different lengths and thicknesses. Stretching of these films increases the performance as well as the mechanical properties. These relaxor-ferroelectric terpolymers P(VDF-TrFE-CFE), P(VDF-TrFE-CTFE) are multifunctional, i.e., electrostrictive material, dielectric for electric energy storage. The terpolymer exhibits high electrostrictive strain (>7%) with relatively high modulus (>0.4 GPa). Examples of devices applications using unimorphe systems are presented. Micropump and Optical device concerning a liquid-filled varifocal lens on a chip are described.

  20. Stiffness characterisation of microcantilevers based on conducting polymers

    NASA Astrophysics Data System (ADS)

    Alici, Gursel; Higgins, Michael J.

    2008-12-01

    The object of this paper is to characterise the stiffness of microfabricated cantilevers consisting of two electroactive polymer (polypyrrole (PPy)) layers, and two gold layers with a negligible thickness and a layer of porous polyvinylidene fluoride (PVDF), which serves as a backing layer and electrolyte storage tank. This composite cantilever structure is used as polymer actuators or famously known as artificial muscles when tailored appropriately. The polymer microactuators considered in this study, which were fabricated using a laser ablation technique, could operate both in aqueous and non-aqueous media. The stiffness characterization of the microactuators is critical to assess their suitability to numerous applications including the micromanipulation of living cells, bio-analytical nanosystems, datastorage, labon- chip, microvalve, microswitch, microshutter, cantilever light modulators, micro-optical instrumentation, artificial muscles for micro and macro robotic sytems and similar. The stiffness measurement method followed in this study is a static deflection measurement method, using an atomic force microscope (AFM). The stiffness constants of the microactuators while they were in passive (no electrochemical activation) and active (electrochemically activated) states were measured separately, and their statistical comparison was provided. The possible error sources for the stiffness measurement method are elaborated.

  1. Thin polymer etalon arrays for high-resolution photoacoustic imaging

    PubMed Central

    Hou, Yang; Huang, Sheng-Wen; Ashkenazi, Shai; Witte, Russell; O’Donnell, Matthew

    2009-01-01

    Thin polymer etalons are demonstrated as high-frequency ultrasound sensors for three-dimensional (3-D) high-resolution photoacoustic imaging. The etalon, a Fabry-Perot optical resonator, consists of a thin polymer slab sandwiched between two gold layers. It is probed with a scanning continuous-wave (CW) laser for ultrasound array detection. Detection bandwidth of a 20-μm-diam array element exceeds 50 MHz, and the ultrasound sensitivity is comparable to polyvinylidene fluoride (PVDF) equivalents of similar size. In a typical photoacoustic imaging setup, a pulsed laser beam illuminates the imaging target, where optical energy is absorbed and acoustic waves are generated through the thermoelastic effect. An ultrasound detection array is formed by scanning the probing laser beam on the etalon surface in either a 1-D or a 2-D configuration, which produces 2-D or 3-D images, respectively. Axial and lateral resolutions have been demonstrated to be better than 20 μm. Detailed characterizations of the optical and acoustical properties of the etalon, as well as photoacoustic imaging results, suggest that thin polymer etalon arrays can be used as ultrasound detectors for 3-D high-resolution photoacoustic imaging applications. PMID:19123679

  2. Thermal Vapor Deposition and Characterization of Polymer-Ceramic Nanoparticle Composite Thin Films and Capacitors

    NASA Astrophysics Data System (ADS)

    Ewen, Crystal L.

    Thin films composed of the polymer polyvinylidene uoride (PVDF) and the ceramic nanoparticle titanium dioxide (TiO2) were fabricated via thermal vapor deposition. The goal of this research was to improve the amount of TiO2 deposited by varying the temperature and deposition time, to obtain more accurate thickness measurements, and to improve on the electrical properties. The electrical properties analyzed in this study were the dielectric constant, capacitance, breakdown strength and energy density of the capacitors. A starting mixture of PVDF, TiO2, and dimethylformamide (DMF) was prepared prior to deposition, where DMF was used only as a solvent. The elemental composition of the films was determined with energy dispersive x-ray spectroscopy (EDS) using a scanning electron microscope (SEM). Elemental mapping of the films shows that the nanoparticles are homogeneously distributed in the polymer. The ideal initial concentrations (which yield the largest TiO2 concentration) of PVDF and TiO2 were determined to be 83% and 17% respectively by weight. The highest weight percent of Ti was 32.4%, which was made with a deposition temperature of 474°C (corresponding to a current of 27 A) and deposition time of 13 minutes. Thefilm thickness was measured by combining EDS and ImageJ to be 243--46 nm. Parallel plate capacitors were fabricated by combining thermal vapor deposition for the dielectric and sputter coating for the electrodes. For the electrodes, the parallel plates are gold palladium (AuPd) with PVDF:TiO2 as the dielectric. The AuPd electrodes were deposited via sputter coating. Each electrode was sputtered for 100s, which yielded a thickness of 33 nm. The dielectric constant was determined experimentally to be 10.8 and estimated using the Maxwell-Garnett effective medium approximation to be 13.1. The capacitance of these capacitors averaged 30--2 nF. The breakdown voltage of the capacitor was 25--4 V, which corresponds to a breakdown strength of 103 MV/m. Lastly

  3. MOFabric: Electrospun Nanofiber Mats from PVDF/UiO-66-NH2 for Chemical Protection and Decontamination.

    PubMed

    Lu, Annie Xi; McEntee, Monica; Browe, Matthew A; Hall, Morgan G; DeCoste, Jared B; Peterson, Gregory W

    2017-04-05

    Textiles capable of capture and detoxification of toxic chemicals, such as chemical-warfare agents (CWAs), are of high interest. Some metal-organic frameworks (MOFs) exhibit superior reactivity toward CWAs. However, it remains a challenge to integrate powder MOFs into engineered materials like textiles, while retaining functionalities like crystallinity, adsorptivity, and reactivity. Here, we present a simple method of electrospinning UiO-66-NH2, a zirconium MOF, with polyvinylidene fluoride (PVDF). The electrospun composite, which we refer to as "MOFabric", exhibits comparable crystal patterns, surface area, chlorine uptake, and simulant hydrolysis to powder UiO-66-NH2. The MOFabric is also capable of breaking down GD (O-pinacolyl methylphosphonofluoridae) faster than powder UiO-66-NH2. Half-life of GD monitored by solid-state NMR for MOFabric is 131 min versus 315 min on powder UiO-66-NH2.

  4. Ternary systems based on PVDF, BaTiO{sub 3} and MWCNTs: Fabrication, characterization, electromagnetic simulation

    SciTech Connect

    Cacciotti, Ilaria; Valentini, Manlio; Nanni, Francesca

    2015-03-10

    In this work, ternary bulk systems based on polyvinylidene fluoride (PVDF), synthesised barium titanate (BaTiO{sub 3}, BT) nanopowder and multi walled carbon nanotubes (MWCNTs) were fabricated by film stacking technique, starting from solvent cast films. The main purpose was to investigate the influence of BT and MWCNTs addition to the polymeric matrix on its microstructural and dielectrical properties. In order to achieve it, different BT concentrations, ranging between the 60 and 75 %wt, were tested, whereas a MWCNTs content of 2 %wt was maintained constant. The morphology was studied by observation at scanning electron microscopy (SEM), the microstructure and crystalline phases investigated by X-Ray diffraction (XRD) and Fourier transform infrared (FT-IR) spectroscopy, and the electromagnetic properties measured in the microwave region (8-12 GHz). The electromagnetic response of the investigated bulk systems was also simulated as function of the sample thickness.

  5. Wave Propagation in Polymers, Part II

    NASA Astrophysics Data System (ADS)

    Newlander, David C.; Charest, Jacques A.; Lilly, Martin D.; Eisler, Robert D.

    1999-06-01

    Work reported in a previous study (Wave Propagations in Polymers, Part I, J.A. Charest, M.D. Lilly, 44th ARA Meeting Munich, Germany Sept. 17-20, 1993) discussed gas gun plane wave impact work and the measurements of stress wave profiles in Polycarbonate at around 2 kbars. The wave profiles were obtained using combined carbon and PVDF thin film stress gauges. The results showed amplitude attenuation and dispersion effects which were neither expected nor predictable from available hydrocode models. The data have been revisited using a modified material model and the PUFF74 computer code. These new wave profile calculations show remarkable agreement with the previous experiments in Polycarbonate. The model treats the material as viscoelastic-plastic using methods developed by Bade (Dynamic Response Model for PMMA, W. L. Bade, AVCO Systems Division, TR K500-74-WLB-204, Oct. 1, 1974). The measured and calculated results are quite different from those exhibited by PMMA at similar impact conditions. This work is expected to further our understanding of the processes that control wave propagation in highly-compressible and viscoelastic/viscoplastic media. It is also expected to provide clues on the effects of high strain rates on properties such as the modulus of elasticity, strength, and material loading behavior.

  6. Surface characteristics of a self-polymerized dopamine coating deposited on hydrophobic polymer films.

    PubMed

    Jiang, Jinhong; Zhu, Liping; Zhu, Lijing; Zhu, Baoku; Xu, Youyi

    2011-12-06

    This study aims to explore the fundamental surface characteristics of polydopamine (pDA)-coated hydrophobic polymer films. A poly(vinylidene fluoride) (PVDF) film was surface modified by dip coating in an aqueous solution of dopamine on the basis of its self-polymerization and strong adhesion feature. The self-polymerization and deposition rates of dopamine on film surfaces increased with increasing temperature as evaluated by both spectroscopic ellipsometry and scanning electronic microscopy (SEM). Changes in the surface morphologies of pDA-coated films as well as the size and shape of pDA particles in the solution were also investigated by SEM, atomic force microscopy (AFM), and transmission electron microscopy (TEM). The surface roughness and surface free energy of pDA-modified films were mainly affected by the reaction temperature and showed only a slight dependence on the reaction time and concentration of the dopamine solution. Additionally, three other typical hydrophobic polymer films of polytetrafluoroethylene (PTFE), poly(ethylene terephthalate) (PET), and polyimide (PI) were also modified by the same procedure. The lyophilicity (liquid affinity) and surface free energy of these polymer films were enhanced significantly after being coated with pDA, as were those of PVDF films. It is indicated that the deposition behavior of pDA is not strongly dependent on the nature of the substrates. This information provides us with not only a better understanding of biologically inspired surface chemistry for pDA coatings but also effective strategies for exploiting the properties of dopamine to create novel functional polymer materials.

  7. Thermal conductivity and multiferroics of electroactive polymers and polymer composites

    NASA Astrophysics Data System (ADS)

    Jin, Jiezhu

    /m˙K, greatly affected by the phonon-phonon scattering and phonon boundary scattering. When the films are thicker than 130 nm, heat capacity also plays an important role in thermal conduction in polyaniline. The same technique is extended to measure the electrical and thermal conductivity of 55 nm thick polyaniline thin films doped with different levels of camphorsulfonic acid. Results indicate that the effect of the doping level (camphorsulfonic acid/polyaniline ratio) is more pronounced on electrical conductivity than on thermal conductivity, thereby greatly affecting their ratio that determines the thermoelectric efficiency. At the 60% doping level, polyaniline thin film exhibits the maximum electrical and thermal conductivity due to the formation of mostly delocalized polaron structures. It is suggested that polarons are the charge carriers responsible for the electrical conduction, while phonons play a dominant role in the heat conduction in doped polyaniline thin films. Multiferroic materials combine unusual elastic, magnetic and electric properties, and have promising applications in many areas, such as sensors, transducers and read/write memory devices. For strain-mediated multiferroic ME composites, their ME effect are generated as a product property of the piezoelectric phase and magnetostrictive phase. In this dissertation, new multiferroic composites are developed and presented. One of them is based on chain-end cross-linked ferroelectric poly(vinylidene fluoride-co-trifluoroethylene) (PVDF-TrFE). With a low dc bias magnetic field, the ME coefficient of this composite is 17.7 V/cm Oe at non-resonance and 383 V/cm Oe at resonance, well above the reported ME voltage coefficient of polymer based ME composite in current literature. ME composite based on poly(vinylidene fluoride-co-hexafluoropropylene) P(VDF-HFP) are also developed in this dissertation. Crystalline beta phase structure in P(VDF-HFP) is produced by uniaxially stretching of pre-melted and quenched films

  8. Modeling of the time-dependent strain response of electroactive NCC-PEO and PVDF composites

    NASA Astrophysics Data System (ADS)

    Bass, Patrick S.; Blue, Lauchlin; Zhang, Lin; Li, Mi; Cheng, Z.-Y.; Tu, Maobing

    2015-04-01

    Ionic electroactive polymers have been widely studied, wherein the electrically induced ionic motion generates an actuation response. The electromechanical bending observed in these polymers is due to the size difference between two types of ions which results in an unequal expansion and contraction between the two sides. Nanocrystalline cellulose (NCC) is a biodegradable, renewable, and inexpensive biomass derivative. Poly(ethylene oxide) (PEO) is also biodegradable and a well-known solid-state electrolyte capable of having both cations and anions diffuse through its matrix under an applied electric field. In this study, NCC is mixed with the PEO to make 0-3 composites with increased Young's modulus and improved actuation performance. Experimental results showed that the time-dependent strain response for these composites followed an Arrhenius behavior. Using the Stokes- Einstein model, the flux of the ions within in the polymer matrix were defined as charged, spherical particles moving through a viscous medium with low Reynold's number. This new approach makes it possible to calculate parameters that may otherwise have been difficult or impossible to obtain. In this work, calculations for these properties, such as: apparent ionic diffusion coefficient, ionic velocity, and the dynamic viscosity of the matrix material are analyzed and presented. For example, the parameters for PEO-NCC composites doped with 5.0 wt.% lithium were calculated to be 3.58e-10 cm2/s, 102 nm/s, and 275 Poise, respectively. Electroactive polyvinylidene fluoride films were also synthesized for comparison and refinement of the introduced model.

  9. Advanced Polymer

    NASA Technical Reports Server (NTRS)

    1992-01-01

    In the mid-1980's, Langley developed a polyimide sulfone, combining desirable properties of two classes of polymers. Composites and other products made from polyimide sulfone can be used with solvents and corrosive fluids, are light weight, low cost and can be easily fabricated for a wide range of industrial uses. High Technology Systems, Inc. obtained a license for the polymer and was awarded a Small Business Innovation Research (SBIR) contract for development in a powder form. Although its principal use is as a matrix resin for composites, the material can also be used as a high temperature structural adhesive for aircraft structures and as a coating for protection from heat and radiation for electronic components.

  10. Theoretical Polymers.

    DTIC Science & Technology

    1976-10-07

    for the correlation length of 3/4, while 0.72 is observed. Then followed several talks on the expansion coefficient a, the virial coefficients and...calculation of the virial coefficient and c~2. These quantities can be considered merely a testing ground for the use of this method to polymer...the second viria]. coefficient , A2, to be zero and the intrinsic viscosity dependent on~VW for polystyrene mole-cular weights between 33,000 and one

  11. Phthalocyanine polymers

    NASA Technical Reports Server (NTRS)

    Achar, B. N.; Fohlen, G. M.; Parker, J. A. (Inventor)

    1985-01-01

    A method of forming 4,4',4'',4''' -tetraamino phthalocyanines involves reducing 4,4',4'',4''' -tetranitro phthalocyanines, polymerizing the metal tetraamino phthalocyanines with a tetracarboxylic dianhydride (preferably aromatic) or copolymerizing with a tetracarboxylic dianhydride and a diamine (preferably also aromatic) to produce amic acids which are then dehydrocyclized to imides. Thermally and oxidatively stable polymers result which form tough, flexible films, varnishes, adhesives, and fibers.

  12. Periodic Polymers

    NASA Astrophysics Data System (ADS)

    Thomas, Edwin

    2013-03-01

    Periodic polymers can be made by self assembly, directed self assembly and by photolithography. Such materials provide a versatile platform for 1, 2 and 3D periodic nano-micro scale composites with either dielectric or impedance contrast or both, and these can serve for example, as photonic and or phononic crystals for electromagnetic and elastic waves as well as mechanical frames/trusses. Compared to electromagnetic waves, elastic waves are both less complex (longitudinal modes in fluids) and more complex (longitudinal, transverse in-plane and transverse out-of-plane modes in solids). Engineering of the dispersion relation between wave frequency w and wave vector, k enables the opening of band gaps in the density of modes and detailed shaping of w(k). Band gaps can be opened by Bragg scattering, anti-crossing of bands and discrete shape resonances. Current interest is in our group focuses using design - modeling, fabrication and measurement of polymer-based periodic materials for applications as tunable optics and control of phonon flow. Several examples will be described including the design of structures for multispectral band gaps for elastic waves to alter the phonon density of states, the creation of block polymer and bicontinuous metal-carbon nanoframes for structures that are robust against ballistic projectiles and quasi-crystalline solid/fluid structures that can steer shock waves.

  13. Hybrid materials and polymer electrolytes for electrochromic device applications.

    PubMed

    Thakur, Vijay Kumar; Ding, Guoqiang; Ma, Jan; Lee, Pooi See; Lu, Xuehong

    2012-08-08

    Electrochromic (EC) materials and polymer electrolytes are the most imperative and active components in an electrochromic device (ECD). EC materials are able to reversibly change their light absorption properties in a certain wavelength range via redox reactions stimulated by low direct current (dc) potentials of the order of a fraction of volts to a few volts. The redox switching may result in a change in color of the EC materials owing to the generation of new or changes in absorption band in visible region, infrared or even microwave region. In ECDs the electrochromic layers need to be incorporated with supportive components such as electrical contacts and ion conducting electrolytes. The electrolytes play an indispensable role as the prime ionic conduction medium between the electrodes of the EC materials. The expected applications of the electrochromism in numerous fields such as reflective-type display and smart windows/mirrors make these materials of prime importance. In this article we have reviewed several examples from our research work as well as from other researchers' work, describing the recent advancements on the materials that exhibit visible electrochromism and polymer electrolytes for electrochromic devices. The first part of the review is centered on nanostructured inorganic and conjugated polymer-based organic-inorganic hybrid EC materials. The emphasis has been to correlate the structures, morphologies and interfacial interactions of the EC materials to their electronic and ionic properties that influence the EC properties with unique advantages. The second part illustrates the perspectives of polymer electrolytes in electrochromic applications with emphasis on poly (ethylene oxide) (PEO), poly (methyl methacrylate) (PMMA) and polyvinylidene difluoride (PVDF) based polymer electrolytes. The requirements and approaches to optimize the formulation of electrolytes for feasible electrochromic devices have been delineated.

  14. Inorganic-organic composite solid polymer electrolytes

    SciTech Connect

    Abraham, K.M.; Koch, V.R.; Blakley, T.J.

    2000-04-01

    Inorganic-organic composite solid polymer electrolytes (CSPEs) have been prepared from the poly(ethylene oxide) (PEO)-like electrolytes of the general formula polyvinylidene fluoride-hexafluoropropylene (PVdF-HFP)-PEO{sub n}-LiX and Li{sup +}-conducting ceramic powders. In the PEO-like electrolytes, PVdF-HFP is the copolymer of PVdF and HFP, PEO{sub n} is a nonvolatile oligomeric polyethylene oxide of {approximately}400 g/mol molecular weight, and LiX is lithium bis(trifluoroethylsulfonyl)imide. Two types of inorganic oxide ceramic powders were used: a highly Li{sup +}-conducting material of the composition 14 mol % Li{sub 2}O-9Al{sub 2}O{sub 3}-38TiO{sub 2}-39P{sub 2}O{sub 5}, and the poorly Li{sup +}-conducting Li-silicates Li{sub 4{minus}x}M{sub x}SiO{sub 4} where M is Ca or Mg and x is 0 or 0.05. The composite electrolytes can be prepared as thin membranes in which the Li{sup +} conductivity and good mechanical strength of the Li{sup +}-conducting inorganic ceramics are complemented by the structural flexibility and high conductivity of organic polymer electrolytes. Excellent electrochemical and thermal stabilities have been demonstrated for the electrolyte films. Li//composite electrolyte//LiCoO{sub 2} rechargeable cells have been fabricated and cycled at room temperature and 50 C.

  15. Preparation of a durable superhydrophobic membrane by electrospinning poly (vinylidene fluoride) (PVDF) mixed with epoxy-siloxane modified SiO2 nanoparticles: a possible route to superhydrophobic surfaces with low water sliding angle and high water contact angle.

    PubMed

    Wang, Shuai; Li, Yapeng; Fei, Xiaoliang; Sun, Mingda; Zhang, Chaoqun; Li, Yaoxian; Yang, Qingbiao; Hong, Xia

    2011-07-15

    A durable superhydrophobic surface with low water sliding angle (SA) and high water contact angle (CA) was obtained by electrospinning poly (vinylidene fluoride) (PVDF) which was mixed with epoxy-siloxane modified SiO(2) nanoparticles. To increase the roughness, modified SiO(2) nanoparticles were introduced into PVDF precursor solution. Then in the electrospinning process, nano-sized SiO(2) particles irregularly inlayed (it could also be regard as self-assembly) in the surface of the micro-sized PVDF mini-islands so as to form a dual-scale structure. This structure was responsible for the superhydrophobicity and self-cleaning property. In addition, epoxy-siloxane copolymer was used to modify the surface of SiO(2) nanoparticles so that the SiO(2) nanoparticles could stick to the surface of the micro-sized PVDF mini-islands. Through the underwater immersion test, the SiO(2) nanoparticles cannot be separated from PVDF easily so as to achieve the effect of durability. We chiefly explore the surface wettability and the relationship between the mass ratio of modified SiO(2) nanoparticles/PVDF and the CA, SA of electrospun mat. As the content of modified SiO(2) nanoparticles increased, the value of CA increased, ranging from 145.6° to 161.2°, and the water SA decreased to 2.17°, apparently indicating that the membrane we fabricated has a perfect effect of superhydrophobicity.

  16. Ferroelectric polymer-based nanocomposites: Towards multiferroic materials

    NASA Astrophysics Data System (ADS)

    Andrew, Jennifer S.

    This dissertation describes new routes towards magnetic-ferroelectric materials, leading to new materials for multiferroic applications. Multiferroic materials exhibit both ferromagnetic and ferroelectric properties, which tend to be mutually exclusive in single-phase materials. Therefore, composite materials are the obvious approach to realizing a material with both a high electric permittivity and high magnetic permeability. In composite systems the magnetoelectric effect arises from a mechanical coupling between a magnetostrictive and a piezoelectric phase. In order to enhance this coupling the interfacial area between the two phases should be maximized. This can be accomplished with nanoparticles, which have a large surface to volume ratio. This work begins with the synthesis of ferrimagnetic (MFe2O 4, M=Ni, Ni0.5Zn0.5, Co) and ferroelectric (BaTiO 3) nanoparticles. Aqueous coprecipitation routes produced superparamagnetic ferrite nanoparticles with an average diameter of 8-10 nanometers. Nanometer sized particles of barium titanate were also produced, but they were cubic and therefore do not exhibit ferroelectric behavior. We then developed routes to form nanoparticle-nanoparticle composites by controlling their stability in solution and therefore their final assembly into magnetic-dielectric nanocomposites. We also developed novel magnetic-ferroelectric composites by filling a ferroelectric polymer with magnetic and dielectric nanoparticles. Polyvinylidene difluoride (PVDF) fibers as well as fibers with continuously dispersed ferrite (Ni0.5Zn0.5Fe2O4) nanoparticles were prepared by electrospinning from dimethyl formamide (DMF) solutions. The effects of the electrospinning processing conditions and nanoparticle loading on the fiber morphology, crystallinity, and the crystalline structure of PVDF were examined. Magnetic and dielectric measurements were also performed. Electrospinning provides a simple technique to form PVDF in the ferroelectric beta

  17. Creep-Fatigue Relationsihps in Electroactive Polymer Systems and Predicted Effects in an Actuator Design

    NASA Technical Reports Server (NTRS)

    Vinogradov, Aleksandra M.; Ihlefeld, Curtis M.; Henslee, Issac

    2009-01-01

    The paper concerns the time-dependent behavior of electroactive polymers (EAP) and their use in advanced intelligent structures for space exploration. Innovative actuator design for low weight and low power valves required in small plants planned for use on the moon for chemical analysis is discussed. It is shown that in-depth understanding of cyclic loading effects observed through accelerated creep rates due to creep-fatigue interaction in polymers is critical in terms of proper functioning of EAP based actuator devices. In the paper, an overview of experimental results concerning the creep properties and cyclic creep response of a thin film piezoelectric polymer polyvinylidene fluoride (PVDF) is presented. The development of a constitutive creep-fatigue interaction model to predict the durability and service life of electroactive polymers is discussed. A novel method is proposed to predict damage accumulation and fatigue life of polymers under oyclic loading conditions in the presence of creep. The study provides a basis for ongoing research initiatives at the NASA Kennedy Space Center in the pursuit of new technologies using EAP as active elements for lunar exploration systems.

  18. Encapsulation of ionic electroactive polymers: reducing the interaction with environment

    NASA Astrophysics Data System (ADS)

    Jaakson, P.; Aabloo, A.; Tamm, T.

    2016-04-01

    Ionic electro-active polymer (iEAP) actuators are composite materials that change their mechanical properties in response to external electrical stimulus. The interest in these devices is mainly driven by their capability to generate biomimetic movements, and their potential use in soft robotics. The driving voltage of an iEAP-actuator (0.5… 3 V) is at least an order of magnitude lower than that needed for other types of electroactive polymers. To apply iEAP-actuators in potential real-world applications, the capability of operating in different environments (open air, different solvents) must be available. In their natural form, the iEAP-actuators are capable of interacting with the surrounding environment (evaporation of solvent from the electrolyte solution, ion or solvent exchange, humidity effects), therefore, for prevention of unpredictable behavior of the actuator and the contamination of the environment, encapsulation of the actuator is needed. The environmental contamination aspect of the encapsulation material is substantial when selecting an applicable encapsulant. The suitable encapsulant should form thin films, be light in weight, elastic, fit tightly, low cost, and easily reproducible. The main goal of the present study is to identify and evaluate the best potential encapsulation techniques for iEAPactuators. Various techniques like thin film on liquid coating, dip coating, hot pressing, hot rolling; and several materials like polydimethylsiloxane, polyurethane, nitrocellulose, paraffin-composite-films were investigated. The advantages and disadvantages of the combinations of the above mentioned techniques and materials are discussed. Successfully encapsulated iEAP-actuators gained durability and were stably operable for long periods of time under ambient conditions. The encapsulation process also increased the stability of the iEAP-actuator by minimizing the environment effects. This makes controlling iEAP-actuators more straight-forward and

  19. Dual layer hollow fiber PVDF ultra-filtration membranes containing Ag nano-particle loaded zeolite with longer term anti-bacterial capacity in salt water.

    PubMed

    Shi, Huyan; Xue, Lixin; Gao, Ailin; Zhou, Qingbo

    2016-01-01

    Dual layer polyvinylidene fluoride (PVDF), antibacterial, hollow fiber, ultra-filtration composite membranes with antibacterial particles (silver (Ag) nano-particles loaded zeolite (Z-Ag)) in the outer layer were prepared with high water flux and desired pore sizes. The amounts of Ag(+) released from the composite membranes, freshly made and stored in water and salt solution, were measured. The result indicated that dual layer PVDF antibacterial hollow fiber containing Z-Ag (M-1-Ag) still possessed the ability of continuous release of Ag(+) even after exposure to water with high ionic content, showing a longer term resistance to bacterial adhesion and antibacterial activity than membrane doped with Z-Ag(+) (M-1). Results from an anti-adhesion and bacteria killing test with Escherichia coli supported that the antibacterial efficiency of dual hollow fiber PVDF membranes with Z-Ag was much higher than those with Z-Ag(+) after long time storage in water or exposure to phosphate buffered saline (PBS) solution. This novel hollow fiber membrane may find applications in constructing sea water pretreatment devices with long term antifouling capability for the desalination processes.

  20. Simultaneous enhancement in mechanical strength, electrical conductivity, and electromagnetic shielding properties in PVDF-ABS blends containing PMMA wrapped multiwall carbon nanotubes.

    PubMed

    Kar, Goutam Prasanna; Biswas, Sourav; Bose, Suryasarathi

    2015-06-14

    A unique approach was adopted to drive the multiwall carbon nanotubes (MWNTs) to the interface of immiscible PVDF-ABS blends by wrapping the nanotubes with a mutually miscible homopolymer (PMMA). A tailor made interface with an improved stress transfer was achieved in the blends with PMMA wrapped MWNTs. This manifested in an impressive 108% increment in the tensile strength and 48% increment in the Young's modulus with 3 wt% PMMA wrapped MWNTs in striking contrast to the neat blends. As the PMMA wrapped MWNTs localized at the interface of PVDF-ABS blends, the electrical conductivity could be tuned with respect to only MWNTs, which were selectively localized in the PVDF phase, driven by thermodynamics. The electromagnetic shielding properties were assessed using a vector network analyser in a broad range of frequency, X-band (8-12 GHz) and Ku-band (12-18 GHz). Interestingly, enhanced EM shielding was achieved by this unique approach. The blends with only MWNTs shielded the EM waves mostly by reflection however, the blends with PMMA wrapped MWNTs (3 wt%) shielded mostly by absorption (62%). This study opens new avenues in designing materials, which show simultaneous improvement in mechanical, electrical conductivity and EM shielding properties.

  1. Interpretations of Polymer-Polymer Miscibility.

    ERIC Educational Resources Information Center

    Olabisi, Olagoke

    1981-01-01

    Discusses various aspects of polymeric mixtures, mixtures of structurally different homopolymers, copolymers, terpolymers, and the like. Defines concepts of polymer-polymer miscibility from practical and theoretical viewpoints, and ways of predicting such miscibility. (JN)

  2. Study of a novel porous gel polymer electrolyte based on thermoplastic polyurethane/poly(vinylidene fluoride-co-hexafluoropropylene) by electrospinning technique

    NASA Astrophysics Data System (ADS)

    Zhou, Ling; Cao, Qi; Jing, Bo; Wang, Xianyou; Tang, Xiaoli; Wu, Na

    2014-10-01

    A novel electrospun gel polymer electrolyte (GPE) consisting of thermoplastic polyurethane (TPU) and poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) is prepared and investigated. Its characteristics are investigated by scanning electron microscopy (SEM), thermal analysis (TGA). The GPE shows a maximum ionic conductivity of 4.1 × 10-3 S cm-1 with electrochemical stability up to 5.5 V versus Li+/Li at room temperature. In addition, it shows a first charge-discharge capacity of 168.8 mAh g-1 when the gel polymer electrolyte (GPE) is evaluated in a Li/PE/LiFePO4 cell under 0.1 C-rate at the first cycle. What's more, there is microscale attenuation (1%) in the 30 cycles of charge and discharge tests. The TPU/PVDF-HFP membrane has a high tensile strength (8.4 ± 0.3 MPa) and elongation at break (118.7 ± 0.2)%. With the outstanding electrochemical and mechanical performance, it is very suitable for application in polymer lithium ion batteries.

  3. Nonvolatile flexible organic bistable devices fabricated utilizing CdSe/ZnS nanoparticles embedded in a conducting poly N-vinylcarbazole polymer layer

    NASA Astrophysics Data System (ADS)

    Son, Dong-Ick; Kim, Ji-Hwan; Park, Dong-Hee; Choi, Won Kook; Li, Fushan; Ham, Jung Hun; Kim, Tae Whan

    2008-02-01

    The bistable effects of CdSe/ZnS nanoparticles embedded in a conducting poly N-vinylcarbazole (PVK) polymer layer by using flexible poly-vinylidene difluoride (PVDF) and polyethylene terephthalate (PET) substrates were investigated. Transmission electron microscopy (TEM) images revealed that CdSe/ZnS nanoparticles were formed inside the PVK polymer layer. Current-voltage (I-V) measurement on the Al/[CdSe/ZnS nanoparticles+ PVK]/ITO/PVDF and Al/[CdSe/ZnS nanoparticles+ PVK ]/ITO/PET structures at 300 K showed a nonvolatile electrical bistability behavior with a flat-band voltage shift due to the existence of the CdSe/ZnS nanoparticles, indicative of trapping, storing and emission of charges in the electronic states of the CdSe nanoparticles. A bistable behavior for the fabricated organic bistable device (OBD) structures is described on the basis of the I-V results. These results indicate that OBDs fabricated by embedding inorganic CdSe/ZnS nanoparticles in a conducting polymer matrix on flexible substrates are prospects for potential applications in flexible nonvolatile flash memory devices.

  4. Composite gel polymer electrolyte for lithium ion batteries

    NASA Astrophysics Data System (ADS)

    Naderi, Roya

    Composite gel polymer electrolyte (CGPE) films, consisting of poly (vinylidene fluoride-hexafluoropropylene) (PVdF-HFP) as the membrane, DMF and PC as solvent and plasticizing agent, mixture of charge modified TiO2 and SiO 2 nano particles as ionic conductors, and LiClO4+LiPF 6 as lithium salts were fabricated. Following the work done by Li et al., CGPE was coated on an O2-plasma treated trilayer polypropylene-polyethylene-polypropylene membrane separator using solution casting technique in order to improve the adhesive properties of gel polymer electrolyte to the separator membrane and its respective ionic conductivity due to decreasing the bulk resistance. In acidic CGPE with, the mixture of acid treated TiO2 and neutral SiO2 nano particles played the role of the charge modified nano fillers with enhanced hydroxyl groups. Likely, the mixture of neutral TiO 2 nano particles with basic SiO2 prepared through the hydrolization of tetraethyl orthosilicate (TEOS) provided a more basic environment due to the residues of NH4OH (Ammonium hydroxide) catalyst. The O2 plasma treated separator was coated with the solution of PVDF-HFP: modified nano fillers: Organic solvents with the mixture ratio of 0.1:0.01:1. After the evaporation of the organic solvents, the dried coated separator was soaked in PC-LiClO4+LiPF6 in EC: DMC:DEC (4:2:4 in volume) solution (300% wt. of PVDF-HFP) to form the final CGPE. Lim et al. has reported the enhanced ionic conductivity of 9.78*10-5 Scm-1 in an acidic composite polystyrene-Al2O3 solid electrolyte system with compared to that of basic and neutral in which the ionic conductivity undergoes an ion hopping process in solid interface rather than a segmental movement of ions through the plasticized polymer chain . Half-cells with graphite anode and Li metal as reference electrode were then assembled and the electrochemical measurements and morphology examinations were successfully carried out. Half cells demonstrated a considerable change in their

  5. Tapered Bottlebrush Polymers: A New Polymer Architecture

    DTIC Science & Technology

    2015-07-30

    length of the backbone polymer . This type of covalent, cone- shaped polymer may have applications in supersoft elastomeric materials and as...rate of polymerization must be as high as possible for the synthesis of precise tapered bottlebrush polymers . An example of the kinetics data obtained... polymers with anchor group 1 allow for faster polymerization . MM Name k p (10 -3 L * mol -1 * s -1 ) t1/2 (s) krel 1S 3k 11 ± 2 68 ± 20

  6. In situ ceramic fillers of electrospun thermoplastic polyurethane/poly(vinylidene fluoride) based gel polymer electrolytes for Li-ion batteries

    NASA Astrophysics Data System (ADS)

    Wu, Na; Cao, Qi; Wang, Xianyou; Li, Sheng; Li, Xiaoyun; Deng, Huayang

    Gel polymer electrolyte films based on thermoplastic polyurethane (TPU)/poly(vinylidene fluoride) (PVdF) with and without in situ ceramic fillers (SiO 2 and TiO 2) are prepared by electrospinning 9 wt% polymer solution at room temperature. The electrospun TPU-PVdF blending membrane with 3% in situ TiO 2 shows a highest ionic conductivity of 4.8 × 10 -3 S cm -1 with electrochemical stability up to 5.4 V versus Li +/Li at room temperature and has a high tensile strength (8.7 ± 0.3 MPa) and % elongation at break (110.3 ± 0.2). With the superior electrochemical and mechanical performance, it is very suitable for application in polymer lithium ion batteries.

  7. Ti1-xAgx electrodes deposited on polymer based sensors

    NASA Astrophysics Data System (ADS)

    Marques, S. M.; Manninen, N. K.; Ferdov, Stanislav; Lanceros-Mendez, S.; Carvalho, S.

    2014-10-01

    Piezoelectric materials are interesting for the development of sensors and actuators for biomedical applications in areas such as smart prosthesis, implantable biosensors and biomechanical signal monitoring, among others. For acquiring or applying the electrical signal from/to the piezoelectric material, suitable electrodes can be produced from Ti based coatings with tailored multifunctional properties: conductivity and antibacterial characteristics through Ag inclusions. This work reports on Ti1-xAgx electrodes with different Ag/Ti atomic ratios deposited by dc and pulsed magnetron sputtering at room temperature on poly(vinylidene fluoride), PVDF. The X-ray diffraction (XRD) results revealed that the deposition conditions preserve the polymer structure and suggested the presence of crystalline Tiβ phase in pure titanium coating and fcc-Ag phase in pure silver coating. According to the results obtained from scanning electron microscopy (SEM) analysis, the coatings are homogeneous and no clusters were found; since β-PVDF is anisotropic, the deposited coatings replicate the underlying substrate surface. Sheet resistivity values show a typical behavior of a binary alloy system, with low resistivity values for coatings of zone 1 (Ti rich) and zone 3 (Ag rich) and a slightly higher resistivity values in zone 2. The piezoelectricity of the different samples show similar values.

  8. Generalized Ferroelectricity in the Mesomorphic Phase of Nylon Polymers

    NASA Astrophysics Data System (ADS)

    Zhang, Zhongbo; Zhu, Lei; Litt, Morton

    Novel ferroelectric polymers, featured by narrow electric displacement-electric (D-E) hysteresis loop, are attractive for electric energy storage applications due to their high dielectric constant and low loss property. Currently, only poly(vinylidene fluoride) (PVDF)-based copolymers (e-beamed) and terpolymers show novel ferroelectric behavior. It is desired to achieve novel ferroelectricity in other polymers such as nylons by carefully modifying the chemical and crystal structures. In this presentation, isomorphic crystals are successfully achieved by copolymerization of nylon 11 and nylon 12 with different compositions. In this way, both chemical and structural defects (i.e., dangling amide groups and kinked bonds) are introduced into the mesomorphic phase. As a consequence, hydrogen bonding interaction is successfully weakened and thus enhanced ferroelectricity with higher maximum polarization and better polarizability is obtained. In addition, for the purpose of further disturbing the mesomorphic phase and pinning effect, partially methylated nylon copolymers are synthesized. With the help of N-methylation of amide groups, the methylated nylon copolymers show relatively narrow hysteresis loops, suggesting the pinning effect from the N-methylated amide moieties.

  9. Pressure-assisted synthesis of HKUST-1 thin film on polymer hollow fiber at room temperature toward gas separation.

    PubMed

    Mao, Yiyin; Li, Junwei; Cao, Wei; Ying, Yulong; Sun, Luwei; Peng, Xinsheng

    2014-03-26

    The scalable fabrication of continuous and defect-free metal-organic framework (MOF) films on the surface of polymeric hollow fibers, departing from ceramic supported or dense composite membranes, is a huge challenge. The critical way is to reduce the growth temperature of MOFs in aqueous or ethanol solvents. In the present work, a pressure-assisted room temperature growth strategy was carried out to fabricate continuous and well-intergrown HKUST-1 films on a polymer hollow fiber by using solid copper hydroxide nanostrands as the copper source within 40 min. These HKUST-1 films/polyvinylidenefluoride (PVDF) hollow fiber composite membranes exhibit good separation performance for binary gases with selectivity 116% higher than Knudsen values via both inside-out and outside-in modes. This provides a new way to enable for scale-up preparation of HKUST-1/polymer hollow fiber membranes, due to its superior economic and ecological advantages.

  10. An Ionic-Polymer-Metallic Composite Actuator for Reconfigurable Antennas in Mobile Devices

    PubMed Central

    Lin, Yi-Chen; Yu, Chung-Yi; Li, Chung-Min; Liu, Chin-Heng; Chen, Jiun-Peng; Chu, Tah-Hsiung; Su, Guo-Dung John

    2014-01-01

    In this paper, a new application of an electro-active-polymer for a radio frequency (RF) switch is presented. We used an ionic polymer metallic composite (IPMC) switch to change the operating frequency of an inverted-F antenna. This switch is light in weight, small in volume, and low in cost. In addition, the IPMC is suitable for mobile devices because of its driving voltage of 3 volts and thickness of 200 μm. The IPMC acts as a normally-on switch to control the operating frequency of a reconfigurable antenna in mobile phones. We experimentally demonstrated by network analysis that the IPMC switch could shift its operating frequency from 1.1 to 2.1 GHz, with return losses of than −10 dB at both frequencies. To minimize electrolysis and maximize the operation time in air, propylene carbonate electrolyte with lithium perchlorate (LiClO4) was applied inside the IPMC. The results showed that when the IPMC was actuated over three months at 3.5 V, the tip displacement fell by less than 10%. Therefore, an IPMC actuator is a promising choice for application to a reconfigurable antenna. PMID:24399156

  11. An ionic-polymer-metallic composite actuator for reconfigurable antennas in mobile devices.

    PubMed

    Lin, Yi-Chen; Yu, Chung-Yi; Li, Chung-Min; Liu, Chin-Heng; Chen, Jiun-Peng; Chu, Tah-Hsiung; Su, Guo-Dung John

    2014-01-06

    In this paper, a new application of an electro-active-polymer for a radio frequency (RF) switch is presented. We used an ionic polymer metallic composite (IPMC) switch to change the operating frequency of an inverted-F antenna. This switch is light in weight, small in volume, and low in cost. In addition, the IPMC is suitable for mobile devices because of its driving voltage of 3 volts and thickness of 200 μm. The IPMC acts as a normally-on switch to control the operating frequency of a reconfigurable antenna in mobile phones. We experimentally demonstrated by network analysis that the IPMC switch could shift its operating frequency from 1.1 to 2.1 GHz, with return losses of than -10 dB at both frequencies. To minimize electrolysis and maximize the operation time in air, propylene carbonate electrolyte with lithium perchlorate (LiClO₄) was applied inside the IPMC. The results showed that when the IPMC was actuated over three months at 3.5 V, the tip displacement fell by less than 10%. Therefore, an IPMC actuator is a promising choice for application to a reconfigurable antenna.

  12. A preliminary discourse on adhesion of nanofibers derived from electrospun polymers

    NASA Astrophysics Data System (ADS)

    Chen, Pei

    To bio-mimic gecko's foot hair, which possess high adhesion strength and can be re- usable for lifetime, fibrous membranes are fabricated by electrospinning to provide sufficient adhesion energy. Shaft-loaded blister test (SLBT) is firstly used to measure the work of adhesion between electrospun membrane and rigid substrate. Poly(vinylidene fluoride) (PVDF) were electrospun with an average fiber diameter of 333+/-59 nm. Commercial cardboard with inorganic coating was used to provide a model substrate for adhesion tests. In SLBT, the elastic response PVDF was analyzed and its adhesion energy measured. FEA model with cohesive layer is developed to evaluate the experiment results. The results show SLBT presented a viable methodology for evaluating the adhesion energy of electrospun polymer fabrics. Electrospun membranes with different fiber diameter are tested for their distinctive adhesion property. Five sets of PVDF membranes with different fiber diameters (from 201 +/- 86 nm to 2724 +/- 587 nm) are electrospun for size effect evaluation. Obtaining testing results from SLBT adhesion test, adhesion energy ranges from 258.83 +/- 43.54 mJ/m2 to 8.06 +/- 0.71 mJ/m2. Significant size effect is observed, and electrospun membrane composing from finer fibers possesses greater adhesion energy. Thickness effect is also evaluated. By stacking multiple layers of electrospun membrane together, membrane samples with different thickness are produced. Test results illustrate thick membrane trends to debond easier than thin membrane. After considering the characteristic of electrospun membrane, the effect of substrate is also evaluated. One approach is made by substituting SiC substrates with different roughness for cardboard substrate. The grit size of the SiC substrates varies from 5 mum to 68 mum. A correlation between adhesion energy and mean peak and valley roughness (Rz) is established from mechanical interlocking theory. The other approach is comparing adhesion energies if

  13. From commodity polymers to functional polymers.

    PubMed

    Xiang, Tao; Wang, Ling-Ren; Ma, Lang; Han, Zhi-Yuan; Wang, Rui; Cheng, Chong; Xia, Yi; Qin, Hui; Zhao, Chang-Sheng

    2014-04-08

    Functional polymers bear specified chemical groups, and have specified physical, chemical, biological, pharmacological, or other uses. To adjust the properties while keeping material usage low, a method for direct synthesis of functional polymers is indispensable. Here we show that various functional polymers can be synthesized by in situ cross-linked polymerization/copolymerization. We demonstrate that the polymers synthesized by the facile method using different functional monomers own outstanding pH-sensitivity and pH-reversibility, antifouling property, antibacterial, and anticoagulant property. Our study opens a route for the functionalization of commodity polymers, which lead to important advances in polymeric materials applications.

  14. From Commodity Polymers to Functional Polymers

    PubMed Central

    Xiang, Tao; Wang, Ling-Ren; Ma, Lang; Han, Zhi-Yuan; Wang, Rui; Cheng, Chong; Xia, Yi; Qin, Hui; Zhao, Chang-Sheng

    2014-01-01

    Functional polymers bear specified chemical groups, and have specified physical, chemical, biological, pharmacological, or other uses. To adjust the properties while keeping material usage low, a method for direct synthesis of functional polymers is indispensable. Here we show that various functional polymers can be synthesized by in situ cross-linked polymerization/copolymerization. We demonstrate that the polymers synthesized by the facile method using different functional monomers own outstanding pH-sensitivity and pH-reversibility, antifouling property, antibacterial, and anticoagulant property. Our study opens a route for the functionalization of commodity polymers, which lead to important advances in polymeric materials applications. PMID:24710333

  15. Double-layer PVDF transducer and V(z) measurement system for measuring leaky Lamb waves in a piezoelectric plate.

    PubMed

    Lee, Yung-Chun; Kuo, Shi Hoa

    2007-03-01

    This paper presents a new experimental measurement method for leaky Lamb waves propagating in a piezoelectric plate immersed in a conductive fluid. The measurement system is a low-frequency version of lens-less acoustic microscopy which has been developed based on a line-focus double-layer PVDF transducer. The transducer and its defocusing measurement system can perform V(z) measurements on a sample plate immersed in a fluid, and therefore can obtain the leaky Lamb wave velocities with high accuracy. An X-cut LiNbO(3) plate is investigated with this experimental measurement system to find out its fluid-loading effects, especially the conductive loading effects by water of various conductivities. Angular dependence of this conductive loading effect along different propagating directions on the X-cut LiNbO(3) plate is measured. It is found out the conductive loading effects are strongly dependent on the piezoelectric coupling factor. Theoretical calculations based on partial wave theory have also been carried out and compared with experimental data. Good agreements have been observed.

  16. Investigation of Shock-Induced Chemical Reactions in Mo-Si Powder Mixtures Using Instrumented Experiments with PVDF Stress Gauges

    SciTech Connect

    Vandersall, K S; Thadhani, N N

    2001-05-29

    Shock-induced chemical reactions in {approx}58% dense Mo+2Si powder mixtures were investigated using time-resolved instrumented experiments, employing PVDF-piezoelectric stress gauges placed at the front and rear surfaces of the powders to measure the input and propagated stresses, and wave speed through the powder mixture. Experiments performed on the powders at input stresses less than 4 GPa, showed characteristics of powder densification and dispersed propagated wave stress profiles with rise time > {approx}40 nanoseconds. At input stress between 4-6 GPa, the powder mixtures showed a sharp rise time (<{approx}10 ns) of propagated wave profile and an expanded state of products revealing evidence of shock-induced chemical reaction. At input stresses greater than 6 GPa, the powder mixtures showed a slower propagated-stress-wave rise time and transition to a low-compressibility (melt) state indicating lack of shock-induced reaction. The results illustrate that premature melting of Si, at input stresses less than the crush-strength of the powder mixtures, restricts mixing between reactants and inhibits ''shock-induced'' reaction initiation.

  17. Rapid prototyping of all-solution-processed multi-lengthscale electrodes using polymer-induced thin film wrinkling

    NASA Astrophysics Data System (ADS)

    Gabardo, Christine M.; Adams-McGavin, Robert C.; Fung, Barnabas C.; Mahoney, Eric J.; Fang, Qiyin; Soleymani, Leyla

    2017-02-01

    Three-dimensional electrodes that are controllable over multiple lengthscales are very important for use in bioanalytical systems that integrate solid-phase devices with solution-phase samples. Here we present a fabrication method based on all-solution-processing and thin film wrinkling using smart polymers that is ideal for rapid prototyping of tunable three-dimensional electrodes and is extendable to large volume manufacturing. Although all-solution-processing is an attractive alternative to vapor-based techniques for low-cost manufacturing of electrodes, it often results in films suffering from low conductivity and poor substrate adhesion. These limitations are addressed here by using a smart polymer to create a conformal layer of overlapping wrinkles on the substrate to shorten the current path and embed the conductor onto the polymer layer. The structural evolution of these wrinkled electrodes, deposited by electroless deposition onto a nanoparticle seed layer, is studied at varying deposition times to understand its effects on structural parameters such as porosity, wrinkle wavelength and height. Furthermore, the effect of structural parameters on functional properties such as electro-active surface area and surface-enhanced Raman scattering is investigated. It is found that wrinkling of electroless-deposited thin films can be used to reduce sheet resistance, increase surface area, and enhance the surface-enhanced Raman scattering signal.

  18. Rapid prototyping of all-solution-processed multi-lengthscale electrodes using polymer-induced thin film wrinkling.

    PubMed

    Gabardo, Christine M; Adams-McGavin, Robert C; Fung, Barnabas C; Mahoney, Eric J; Fang, Qiyin; Soleymani, Leyla

    2017-02-13

    Three-dimensional electrodes that are controllable over multiple lengthscales are very important for use in bioanalytical systems that integrate solid-phase devices with solution-phase samples. Here we present a fabrication method based on all-solution-processing and thin film wrinkling using smart polymers that is ideal for rapid prototyping of tunable three-dimensional electrodes and is extendable to large volume manufacturing. Although all-solution-processing is an attractive alternative to vapor-based techniques for low-cost manufacturing of electrodes, it often results in films suffering from low conductivity and poor substrate adhesion. These limitations are addressed here by using a smart polymer to create a conformal layer of overlapping wrinkles on the substrate to shorten the current path and embed the conductor onto the polymer layer. The structural evolution of these wrinkled electrodes, deposited by electroless deposition onto a nanoparticle seed layer, is studied at varying deposition times to understand its effects on structural parameters such as porosity, wrinkle wavelength and height. Furthermore, the effect of structural parameters on functional properties such as electro-active surface area and surface-enhanced Raman scattering is investigated. It is found that wrinkling of electroless-deposited thin films can be used to reduce sheet resistance, increase surface area, and enhance the surface-enhanced Raman scattering signal.

  19. Rapid prototyping of all-solution-processed multi-lengthscale electrodes using polymer-induced thin film wrinkling

    PubMed Central

    Gabardo, Christine M.; Adams-McGavin, Robert C.; Fung, Barnabas C.; Mahoney, Eric J.; Fang, Qiyin; Soleymani, Leyla

    2017-01-01

    Three-dimensional electrodes that are controllable over multiple lengthscales are very important for use in bioanalytical systems that integrate solid-phase devices with solution-phase samples. Here we present a fabrication method based on all-solution-processing and thin film wrinkling using smart polymers that is ideal for rapid prototyping of tunable three-dimensional electrodes and is extendable to large volume manufacturing. Although all-solution-processing is an attractive alternative to vapor-based techniques for low-cost manufacturing of electrodes, it often results in films suffering from low conductivity and poor substrate adhesion. These limitations are addressed here by using a smart polymer to create a conformal layer of overlapping wrinkles on the substrate to shorten the current path and embed the conductor onto the polymer layer. The structural evolution of these wrinkled electrodes, deposited by electroless deposition onto a nanoparticle seed layer, is studied at varying deposition times to understand its effects on structural parameters such as porosity, wrinkle wavelength and height. Furthermore, the effect of structural parameters on functional properties such as electro-active surface area and surface-enhanced Raman scattering is investigated. It is found that wrinkling of electroless-deposited thin films can be used to reduce sheet resistance, increase surface area, and enhance the surface-enhanced Raman scattering signal. PMID:28211898

  20. High Energy Density Polymer Film Capacitors

    DTIC Science & Technology

    2006-10-01

    are formed by vapor deposition of multifunctional acrylate monomers that are deposited on the PVDF as a thin liquid film and are cross linked using...the world. Vacuum Depositing Inc. American Thin Films Vapor Technologies Inc. 1294 Old Fern Valley Road 2010 East Hennepin Ave. Boulder Tech Center...78 5.5.1 Capacitors Values, Voltage Breakdown, and Energy Density ................ 79 APPENDIX A PVDF AND PET FILMS

  1. Shape memory polymers

    DOEpatents

    Wilson, Thomas S.; Bearinger, Jane P.

    2015-06-09

    New shape memory polymer compositions, methods for synthesizing new shape memory polymers, and apparatus comprising an actuator and a shape memory polymer wherein the shape memory polymer comprises at least a portion of the actuator. A shape memory polymer comprising a polymer composition which physically forms a network structure wherein the polymer composition has shape-memory behavior and can be formed into a permanent primary shape, re-formed into a stable secondary shape, and controllably actuated to recover the permanent primary shape. Polymers have optimal aliphatic network structures due to minimization of dangling chains by using monomers that are symmetrical and that have matching amine and hydroxyl groups providing polymers and polymer foams with clarity, tight (narrow temperature range) single transitions, and high shape recovery and recovery force that are especially useful for implanting in the human body.

  2. Lowest of AC-DC power output for electrostrictive polymers energy harvesting systems

    NASA Astrophysics Data System (ADS)

    Meddad, Mounir; Eddiai, Adil; Hajjaji, Abdelowahed; Guyomar, Daniel; Belkhiat, Saad; Boughaleb, Yahia; Chérif, Aida

    2013-11-01

    Advances in technology led to the development of electronic circuits and sensors with extremely low electricity consumption. At the same time, structural health monitoring, technology and intelligent integrated systems created a need for wireless sensors in hard to reach places in aerospace vehicles and large civil engineering structures. Powering sensors with energy harvesters eliminates the need to replace batteries on a regular basis. Scientists have been forced to search for new power source that are able to harvested energy from their surrounding environment (sunlight, temperature gradients etc.). Electrostrictive polymer belonging to the family of electro-active polymers, offer unique properties for the electromechanical transducer technology has been of particular interest over the last few years in order to replace conventional techniques such as those based on piezoelectric or electromagnetic, these materials are highly attractive for their low-density, with large strain capability that can be as high as two orders of magnitude greater than the striction-limited, rigid and fragile electroactive ceramics. Electrostrictive polymers sensors respond to vibration with an ac output signal, one of the most important objectives of the electronic interface is to realize the required AC-DC conversion. The goal of this paper is to design an active, high efficiency power doubler converter for electrostrictive polymers exclusively uses a fraction of the harvested energy to supply its active devices. The simulation results show that it is possible to obtain a maximum efficiency of the AC-DC converter equal to 80%. Premiliminary experimental measurements were performed and the results obtained are in good agreement with simulations.

  3. Effect of Dipolar Orientational Polarization on Electronic Conductivity in Ferroelectric Polymer Electrets

    NASA Astrophysics Data System (ADS)

    Yang, Lianyun; Zhu, Lei

    2014-03-01

    The leakage current, ion migration, and dipolar orientational polarization are major losses in ferroelectric polymers. The loss from the leakage current originates from electronic conduction and its behavior could be significantly affected by the internal electric field, which is induced by the dipolar orientational polarization. In this work, the leakage current in the corona charged PVDF electrets is studied under different external electric fields. Under low applied electric field, when no or very few dipoles could flip, the conductivity from the leakage direct current increases upon increasing the electric field. Under higher electric field, the aligned dipole-induced internal field would prevent the electrons from going through so that the conductivity decreases. After all the dipoles are aligned with the external electric field, the conductivity can increase again. This study will help us better understand the interplay between electronic conduction and dipolar orientation in ferroelectric materials.

  4. Flexible ferroelectric polymer devices based on inkjet-printed electrodes from nanosilver ink

    NASA Astrophysics Data System (ADS)

    Lü, Zhaoyue; Pu, Tiansong; Huang, Yaopeng; Meng, Xiangjian; Xu, Haisheng

    2015-02-01

    High-quality silver (Ag) patterns were inkjet-printed with nanosilver ink on a flexible polyethylene terephthalate (PET) substrate. All-solution-processed flexible ferroelectric polymer devices that use inkjet-printed Ag to create their bottom and top electrodes were demonstrated. The active layer, a poly (vinylidene fluoride-trifluoroethylene) (PVDF-TrFE) thin film, was spin-coated from solution. The devices have a remanent polarization of 8.03 μC cm-2 and a coercive field of 68.5 MV m-1, which is comparable to the device with evaporated-Ti electrodes on a silicon substrate. Based on the results presented in this paper, mass production of flexible ferroelectric devices is predictable.

  5. Polymer Functionalized Nanoparticles in Polymer Nanocomposites

    NASA Astrophysics Data System (ADS)

    Jayaraman, Arthi

    2013-03-01

    Significant interest has grown around the ability to control spatial arrangement of nanoparticles in a polymer nanocomposite to engineer materials with target properties. Past work has shown that one could achieve controlled assembly of nanoparticles in the polymer matrix by functionalizing nanoparticle surfaces with homopolymers. This talk will focus on our recent work using Polymer Reference Interaction Site Model (PRISM) theory and Monte Carlo simulations and GPU-based molecular dynamics simulations to specifically understand how heterogeneity in the polymer functionalization in the form of a) copolymers with varying monomer chemistry and monomer sequence, and b) polydispersity in homopolymer grafts can tune effective interactions between functionalized nanoparticles, and the assembly of functionalized nanoparticles.

  6. Lipid-absorbing Polymers

    NASA Technical Reports Server (NTRS)

    Marsh, H. E., Jr.; Wallace, C. J.

    1973-01-01

    The removal of bile acids and cholesterol by polymeric absorption is discussed in terms of micelle-polymer interaction. The results obtained with a polymer composed of 75 parts PEO and 25 parts PB plus curing ingredients show an absorption of 305 to 309%, based on original polymer weight. Particle size effects on absorption rate are analyzed. It is concluded that crosslinked polyethylene oxide polymers will absorb water, crosslinked polybutadiene polymers will absorb lipids; neither polymer will absorb appreciable amounts of lipids from micellar solutions of lipids in water.

  7. Designing and synthesis of a polymer matrix piezoelectric composite for energy harvesting

    NASA Astrophysics Data System (ADS)

    Biswal, Asutya Kumar; Das, Satyabati; Roy, Amritendu

    2017-02-01

    Now a day, a large variety of electronic and network devices require small yet steady power supply for operation. Traditionally, these devices are battery operated and the batteries are periodically charged for continuous operation. Often, the devices are so located that supply of power to recharge the batteries becomes challenging. Electrical energy harvesting by means of principle of piezoelectricity could be a viable solution to the above problem by means of providing a permanent power source. In this regard, piezoelectric lead zirconium titanate (PZT) was found to be a potential material. However, poor mechanical properties (brittleness) of bulk ceramic materials have been a concern for energy harvesting by means of mechanical motion (footsteps). In the present work, Pb(Zr 0.52 Ti 0.48)1‑x NbxO 3 at x=0.05 was prepared by conventional solid state synthesis route. XRD and SEM analyses were performed for structural characterization. PZT powders were found to be in single phase with tetragonal symmetry without any trace of a second phase. To render the required mechanical properties (flexibility), in the present work, we designed a polymer matrix ceramic composite without much compromising the piezoelectric properties. We prepared composite thick films of lead zirconium titanate (PZT) ceramic in poly vinylidene fluoride (PVDF) polymer matrix with varied composition of PZT from 10-50 vol %. The study of surface morphology by scanning electron microscope (SEM) shows good degree of dispersion of PZT in PVDF matrix. Ferroelectric characteristics of the composite films were studied by measuring the polarization-electric field hysteresis loops. Generated output voltage and current from the composite films are found to be approximately 0.35 volt and 4 nA, respectively.

  8. A novel high-performance gel polymer electrolyte membrane basing on electrospinning technique for lithium rechargeable batteries

    NASA Astrophysics Data System (ADS)

    Wu, Na; Cao, Qi; Wang, Xianyou; Li, Xiaoyun; Deng, Huayang

    2011-10-01

    Nonwoven films of composites of thermoplastic polyurethane (TPU) with different proportion of poly(vinylidene fluoride) (PVdF) (80, 50 and 20%, w/w) are prepared by electrospinning 9 wt% polymer solution at room temperature. Then the gel polymer electrolytes (GPEs) are prepared by soaking the electrospun TPU-PVdF blending membranes in 1 M LiClO4/ethylene carbonate (EC)/propylene carbonate (PC) for 1 h. The gel polymer electrolyte (GPE) shows a maximum ionic conductivity of 3.2 × 10-3 S cm-1 at room temperature and electrochemical stability up to 5.0 V versus Li+/Li for the 50:50 blend ratio of TPU:PVdF system. At the first cycle, it shows a first charge-discharge capacity of 168.9 mAh g-1 when the gel polymer electrolyte (GPE) is evaluated in a Li/PE/lithium iron phosphate (LiFePO4) cell at 0.1 C-rate at 25 °C. TPU-PVdF (50:50, w/w) based gel polymer electrolyte is observed much more suitable than the composite films with other ratios for high-performance lithium rechargeable batteries.

  9. The Measurement of Temperature Gradients in a Soft Tissue Phantom using PVDF arrays: A Simulation Case Using the Finite Element Method (FEM)

    NASA Astrophysics Data System (ADS)

    Acevedo, Pedro; Vázquez, Mónica; Durán, Joel; Petrearce, Rodolfo

    A simulation case is presented using the Finite Element Method (FEM) to simulate the performance of PVDF arrays to measure temperature gradients through the determination of phase shifts, i.e. time shifts of the waveform of the echo due to a change in the speed of propagation of ultrasound as a result of a change in temperature, they can be interpreted as phase shifts in the frequency domain. Making it possible to determine the change in temperature from the phase shifts; in a medium of propagation previously characterized.

  10. Playing with Polymers.

    ERIC Educational Resources Information Center

    Chemecology, 1997

    1997-01-01

    Presents an activity that enables students to gain a better understanding of the importance of polymers. Students perform an experiment in which polymer chains of polyvinyl acetate form crosslinks. Includes background information and discussion questions. (DDR)

  11. Polymer composites containing nanotubes

    NASA Technical Reports Server (NTRS)

    Bley, Richard A. (Inventor)

    2008-01-01

    The present invention relates to polymer composite materials containing carbon nanotubes, particularly to those containing singled-walled nanotubes. The invention provides a polymer composite comprising one or more base polymers, one or more functionalized m-phenylenevinylene-2,5-disubstituted-p-phenylenevinylene polymers and carbon nanotubes. The invention also relates to functionalized m-phenylenevinylene-2,5-disubstituted-p-phenylenevinylene polymers, particularly to m-phenylenevinylene-2,5-disubstituted-p-phenylenevinylene polymers having side chain functionalization, and more particularly to m-phenylenevinylene-2,5-disubstituted-p-phenylenevinylene polymers having olefin side chains and alkyl epoxy side chains. The invention further relates to methods of making polymer composites comprising carbon nanotubes.

  12. Polymer Fluid Dynamics.

    ERIC Educational Resources Information Center

    Bird, R. Byron

    1980-01-01

    Problems in polymer fluid dynamics are described, including development of constitutive equations, rheometry, kinetic theory, flow visualization, heat transfer studies, flows with phase change, two-phase flow, polymer unit operations, and drag reduction. (JN)

  13. Introduction to Polymer Chemistry.

    ERIC Educational Resources Information Center

    Harris, Frank W.

    1981-01-01

    Reviews the physical and chemical properties of polymers and the two major methods of polymer synthesis: addition (chain, chain-growth, or chain-reaction), and condensation (step-growth or step-reaction) polymerization. (JN)

  14. Mechanical Properties of Polymers.

    ERIC Educational Resources Information Center

    Aklonis, J. J.

    1981-01-01

    Mechanical properties (stress-strain relationships) of polymers are reviewed, taking into account both time and temperature factors. Topics include modulus-temperature behavior of polymers, time dependence, time-temperature correspondence, and mechanical models. (JN)

  15. ALUMINUM-CONTAINING POLYMERS

    DTIC Science & Technology

    ALUMINUM COMPOUNDS, *ORGANOMETALLIC COMPOUNDS, *POLYMERIZATION, *POLYMERS, ACRYLIC RESINS, ALKYL RADICALS, CARBOXYLIC ACIDS, COPOLYMERIZATION, LIGHT TRANSMISSION, STABILITY, STYRENES, TRANSPARENT PANELS.

  16. Dendritic polyurea polymers.

    PubMed

    Tuerp, David; Bruchmann, Bernd

    2015-01-01

    Dendritic polymers, subsuming dendrimers as well as hyperbranched or highly branched polymers are well established in the field of polymer chemistry. This review article focuses on urea based dendritic polymers and summarizes their synthetic routes through both isocyanate and isocyanate-free processes. Furthermore, this article highlights applications where dendritic polyureas show their specific chemical and physical potential. For these purposes scientific publications as well as patent literature are investigated to generate a comprehensive overview on this topic.

  17. Engineered Protein Polymers

    DTIC Science & Technology

    2010-05-31

    of each pure polymer, we plan to combine the various polymer solutions in different ratios to tune the composition and physico-chemical properties...protein materials as vehicles for storage and delivery of small molecules. Each protein polymer under concentrations for particle formation ( vida

  18. Synthetic hydrophilic polymers

    NASA Astrophysics Data System (ADS)

    Rajasekharan Pillai, V. N.; Mutter, Manfred

    1981-11-01

    Synthetic hydrophilic polymers find promising applications in pharmacology, biotechnology and chemistry. The biocompatibility, biodegradability and pharmacological activity of these polymers depend much on their hydrophilic nature. This article summarizes the recent developments in the utilization of the different classes of these hydrophilic polymers as pharmacologically active agents, for enzyme modification and as catalysts and supports for chemical reactions.

  19. Dynamic covalent polymers.

    PubMed

    García, Fátima; Smulders, Maarten M J

    2016-11-15

    This Highlight presents an overview of the rapidly growing field of dynamic covalent polymers. This class of polymers combines intrinsic reversibility with the robustness of covalent bonds, thus enabling formation of mechanically stable, polymer-based materials that are responsive to external stimuli. It will be discussed how the inherent dynamic nature of the dynamic covalent bonds on the molecular level can be translated to the macroscopic level of the polymer, giving access to a range of applications, such as stimuli-responsive or self-healing materials. A primary distinction will be made based on the type of dynamic covalent bond employed, while a secondary distinction will be based on the consideration whether the dynamic covalent bond is used in the main chain of the polymer or whether it is used to allow side chain modification of the polymer. Emphasis will be on the chemistry of the dynamic covalent bonds present in the polymer, in particular in relation to how the specific (dynamic) features of the bond impart functionality to the polymer material, and to the conditions under which this dynamic behavior is manifested. © 2016 The Authors. Journal of Polymer Science Part A: Polymer Chemistry Published by Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016, 54, 3551-3577.

  20. Fire-safe polymers and polymer composites

    NASA Astrophysics Data System (ADS)

    Zhang, Huiqing

    The intrinsic relationships between polymer structure, composition and fire behavior have been explored to develop new fire-safe polymeric materials. Different experimental techniques, especially three milligram-scale methods---pyrolysis-combustion flow calorimetry (PCFC), simultaneous thermal analysis (STA) and pyrolysis GC/MS---have been combined to fully characterize the thermal decomposition and flammability of polymers and polymer composites. Thermal stability, mass loss rate, char yield and properties of decomposition volatiles were found to be the most important parameters in determining polymer flammability. Most polymers decompose by either an unzipping or a random chain scission mechanism with an endothermic decomposition of 100--900 J/g. Aromatic or heteroaromatic rings, conjugated double or triple bonds and heteroatoms such as halogens, N, O, S, P and Si are the basic structural units for fire-resistant polymers. The flammability of polymers can also be successfully estimated by combining pyrolysis GC/MS results or chemical structures with TGA results. The thermal decomposition and flammability of two groups of inherently fire-resistant polymers---poly(hydroxyamide) (PHA) and its derivatives, and bisphenol C (BPC II) polyarylates---have been systematically studied. PHA and most of its derivatives have extremely low heat release rates and very high char yields upon combustion. PHA and its halogen derivatives can completely cyclize into quasi-polybenzoxazole (PBO) structures at low temperatures. However, the methoxy and phosphate derivatives show a very different behavior during decomposition and combustion. Molecular modeling shows that the formation of an enol intermediate is the rate-determining step in the thermal cyclization of PHA. BPC II-polyarylate is another extremely flame-resistant polymer. It can be used as an efficient flame-retardant agent in copolymers and blends. From PCFC results, the total heat of combustion of these copolymers or blends

  1. Magnetodielectric effect in trilayered Co65Fe35B20/PVDF/Co65Fe35B20 composite materials. Prediction and measurement for tunable microwave applications

    NASA Astrophysics Data System (ADS)

    Rasoanoavy, F.; Laur, V.; De Blasi, S.; Lezaca, J.; Quéffélec, P.; Garello, K.; Viala, B.

    2010-05-01

    The variation in the permeability of a multilayered polyvinylidene fluoride/CoFeB (piezoelectric/magnetostrictive) composite material under the action of a dc voltage is demonstrated. The driven-voltage permeability is first predicted using a finite element method-based multiphysics calculation. The simulation allows us to determine a magnetic anisotropy field of 45 Oe induced in the ferromagnetic layers by the mechanical coupling between magnetostrictive and piezoelectric layers due to the applied dc voltage. A variation of 30% for the permeability of the ferromagnetic layers is then measured using a radiofrequency permeameter and under the application of a dc voltage of 15 V applied on the ferromagnetic layers, which also act as electrodes for the bias of the polyvinylidene fluoride (PVDF). An additional measurement of the trilayered structure under the application of a dc magnetic field is finally performed to evaluate the magnetic field needed to get a 30% variation in the magnetic layers permeability in order to compare this value to the one predicted by multiphysics calculation. These experimental results are in good agreement with calculations and are very encouraging for the application of the CoFeB/PVDF/CoFeB composite material to ensure the tunability of microwave devices (filters, phase shifters, antennas, etc.)

  2. Facile surface glycosylation of PVDF microporous membrane via direct surface-initiated AGET ATRP and improvement of antifouling property and biocompatibility

    NASA Astrophysics Data System (ADS)

    Yuan, Jing; Meng, Jian-qiang; Kang, Yin-lin; Du, Qi-yun; Zhang, Yu-feng

    2012-01-01

    This paper describes a facile and novel approach for the surface glycosylation of poly(vinylidene difluoride) (PVDF) microporous membrane. A glycopolymer poly(D-gluconamidoethyl methacrylate) (PGAMA) was tethered onto the membrane surface via activators generated by electron transfer atom transfer radical polymerization (AGET ATRP) directly initiated from the PVDF surface. Chemical changes of membrane surface were characterized by Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS). It was revealed that PGAMA was successfully grafted onto the membrane surface and its grafting density can be modulated in a wide range up to 2.4 μmol/cm2. The effects of glycosylation on membrane morphology, flux and surface hydrophilicity were investigated. Field emission scanning electron microscopy (FESEM) results indicated shrinkage of the surface pore diameters and the growth of the glycopolymer layer on the membrane surface. The static water contact angle (WCA) of the membrane surface decreased from 110° to 30.4° with the increase of grafting density, indicating that the PGAMA grafts dramatically improved the surface hydrophilicity. The protein adsorption and platelets adhesion experiments indicated that the grafted PGAMA could effectively improve the membrane antifouling property and biocompatibility.

  3. Real-Time Deflection Monitoring for Milling of a Thin-Walled Workpiece by Using PVDF Thin-Film Sensors with a Cantilevered Beam as a Case Study

    PubMed Central

    Luo, Ming; Liu, Dongsheng; Luo, Huan

    2016-01-01

    Thin-walled workpieces, such as aero-engine blisks and casings, are usually made of hard-to-cut materials. The wall thickness is very small and it is easy to deflect during milling process under dynamic cutting forces, leading to inaccurate workpiece dimensions and poor surface integrity. To understand the workpiece deflection behavior in a machining process, a new real-time nonintrusive method for deflection monitoring is presented, and a detailed analysis of workpiece deflection for different machining stages of the whole machining process is discussed. The thin-film polyvinylidene fluoride (PVDF) sensor is attached to the non-machining surface of the workpiece to copy the deflection excited by the dynamic cutting force. The relationship between the input deflection and the output voltage of the monitoring system is calibrated by testing. Monitored workpiece deflection results show that the workpiece experiences obvious vibration during the cutter entering the workpiece stage, and vibration during the machining process can be easily tracked by monitoring the deflection of the workpiece. During the cutter exiting the workpiece stage, the workpiece experiences forced vibration firstly, and free vibration exists until the amplitude reduces to zero after the cutter exits the workpiece. Machining results confirmed the suitability of the deflection monitoring system for machining thin-walled workpieces with the application of PVDF sensors. PMID:27626424

  4. Real-Time Deflection Monitoring for Milling of a Thin-Walled Workpiece by Using PVDF Thin-Film Sensors with a Cantilevered Beam as a Case Study.

    PubMed

    Luo, Ming; Liu, Dongsheng; Luo, Huan

    2016-09-10

    Thin-walled workpieces, such as aero-engine blisks and casings, are usually made of hard-to-cut materials. The wall thickness is very small and it is easy to deflect during milling process under dynamic cutting forces, leading to inaccurate workpiece dimensions and poor surface integrity. To understand the workpiece deflection behavior in a machining process, a new real-time nonintrusive method for deflection monitoring is presented, and a detailed analysis of workpiece deflection for different machining stages of the whole machining process is discussed. The thin-film polyvinylidene fluoride (PVDF) sensor is attached to the non-machining surface of the workpiece to copy the deflection excited by the dynamic cutting force. The relationship between the input deflection and the output voltage of the monitoring system is calibrated by testing. Monitored workpiece deflection results show that the workpiece experiences obvious vibration during the cutter entering the workpiece stage, and vibration during the machining process can be easily tracked by monitoring the deflection of the workpiece. During the cutter exiting the workpiece stage, the workpiece experiences forced vibration firstly, and free vibration exists until the amplitude reduces to zero after the cutter exits the workpiece. Machining results confirmed the suitability of the deflection monitoring system for machining thin-walled workpieces with the application of PVDF sensors.

  5. Critical insights into the effect of shear on in situ reduction of graphene oxide in PVDF: assessing by rheo-dielectric measurements

    NASA Astrophysics Data System (ADS)

    Sharma, Maya; Madras, Giridhar; Bose, Suryasarathi

    2016-06-01

    In situ reduction of graphene oxide (GO) during the preparation of conducting polymeric nanocomposites has been explored recently. In this study, the in situ reduction of GO in poly (vinylidene fluoride) (PVDF) under different conditions like quiescent, high and low shear, pre-shear has been investigated in detail. To accomplish this, PVDF/GO composites were prepared by both melt and solution blending. The bulk electrical conductivity of melt mixed composites, which had undergone extensive shear during preparation, was monitored by a rheo-dielectric setup and compared with the composites which experienced low shear. In addition, the bulk electric conductivity was also measured in situ for the composites that had undergone quiescent compositing. Comprehensive characterization of the composites reveals that GO is in situ reducing under all processes but the improvement in conductivity is dependent on the adopted process. Compression molded samples, which were annealed for 45 min, showed highest melt conductivity among all the adopted processes. The intense shearing of composites at high temperature in melt extrusion led to re-stacking of graphene sheets and resulted in decreased bulk electrical conductivity. Surprisingly, melt conductivity decreases with shear and time in all composites. This study can help in understanding the reduction of GO during intense shearing of composites.

  6. Stochastic analysis of motor-control stability, polymer based force sensing, and optical stimulation as a preventive measure for falls

    NASA Astrophysics Data System (ADS)

    Landrock, Clinton K.

    Falls are the leading cause of all external injuries. Outcomes of falls include the leading cause of traumatic brain injury and bone fractures, and high direct medical costs in the billions of dollars. This work focused on developing three areas of enabling component technology to be used in postural control monitoring tools targeting the mitigation of falls. The first was an analysis tool based on stochastic fractal analysis to reliably measure levels of motor control. The second focus was on thin film wearable pressure sensors capable of relaying data for the first tool. The third was new thin film advanced optics for improving phototherapy devices targeting postural control disorders. Two populations, athletes and elderly, were studied against control groups. The results of these studies clearly show that monitoring postural stability in at-risk groups can be achieved reliably, and an integrated wearable system can be envisioned for both monitoring and treatment purposes. Keywords: electro-active polymer, ionic polymer-metal composite, postural control, motor control, fall prevention, sports medicine, fractal analysis, physiological signals, wearable sensors, phototherapy, photobiomodulation, nano-optics.

  7. Nanoporous polymer electrolyte

    SciTech Connect

    Elliott, Brian; Nguyen, Vinh

    2012-04-24

    A nanoporous polymer electrolyte and methods for making the polymer electrolyte are disclosed. The polymer electrolyte comprises a crosslinked self-assembly of a polymerizable salt surfactant, wherein the crosslinked self-assembly includes nanopores and wherein the crosslinked self-assembly has a conductivity of at least 1.0.times.10.sup.-6 S/cm at 25.degree. C. The method of making a polymer electrolyte comprises providing a polymerizable salt surfactant. The method further comprises crosslinking the polymerizable salt surfactant to form a nanoporous polymer electrolyte.

  8. Characterisation and Modelling of Meshed Electrodes on Free Standing Polyvilylidene Difluoride (PVDF) Films for Enhanced Pyroelectric Energy Harvesting.

    PubMed

    Zabek, Daniel; Taylor, John; Bowen, Chris

    2016-09-05

    Flexible pyroelectric energy generators provide unique features for harvesting temperature fluctuations which can be effectively enhanced using meshed electrodes that improve thermal conduction, convection and radiation into the pyroelectric. In this paper, thermal radiation energy is continuously harvested with pyroelectric free standing Polyvilylidene Difluoride (PVDF) films over a large number of heat heat cycles using a novel micro-sized symmetrical patterned meshed electrode. It is shown that, for the meshed electrode geometries considered in this work, the polarisation-field (P-E), current-field (I-E) characteristics and device capacitance are unaffected since the fringing fields were generally small; this is verified using numerical simulations and comparison with experimental measurements. The use of meshed electrodes has been shown to significantly improve both the open circuit voltage (16 V to 59 V) and closed-circuit current (9 nA to 32 nA). The pyroelectric alternating current (AC) is rectified for direct current (DC) storage and 30% reduction in capacitor charging time is achieved by using the optimum meshed electrodes. The use of meshed electrodes on ferroelectric materials provides an innovative route to improve their performance in applications such as wearable devices, novel flexible sensors and large scale pyroelectric energy harvesters.hese instructions give you guidelines for preparing papers for IEEE Transactions and Journals. Use this document as a template if you are using Microsoft Word 6.0 or later. Otherwise, use this document as an instruction set. The electronic file of your paper will be formatted further at IEEE. Paper titles should be written in uppercase and lowercase letters, not all uppercase. Avoid writing long formulas with subscripts in the title; short formulas that identify the elements are fine (e.g., "Nd-Fe-B"). Do not write "(Invited)" in the title. Full names of authors are preferred in the author field, but are not

  9. Dynamic covalent polymers

    PubMed Central

    García, Fátima

    2016-01-01

    ABSTRACT This Highlight presents an overview of the rapidly growing field of dynamic covalent polymers. This class of polymers combines intrinsic reversibility with the robustness of covalent bonds, thus enabling formation of mechanically stable, polymer‐based materials that are responsive to external stimuli. It will be discussed how the inherent dynamic nature of the dynamic covalent bonds on the molecular level can be translated to the macroscopic level of the polymer, giving access to a range of applications, such as stimuli‐responsive or self‐healing materials. A primary distinction will be made based on the type of dynamic covalent bond employed, while a secondary distinction will be based on the consideration whether the dynamic covalent bond is used in the main chain of the polymer or whether it is used to allow side chain modification of the polymer. Emphasis will be on the chemistry of the dynamic covalent bonds present in the polymer, in particular in relation to how the specific (dynamic) features of the bond impart functionality to the polymer material, and to the conditions under which this dynamic behavior is manifested. © 2016 The Authors. Journal of Polymer Science Part A: Polymer Chemistry Published by Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016, 54, 3551–3577. PMID:27917019

  10. High performance polymer development

    NASA Technical Reports Server (NTRS)

    Hergenrother, Paul M.

    1991-01-01

    The term high performance as applied to polymers is generally associated with polymers that operate at high temperatures. High performance is used to describe polymers that perform at temperatures of 177 C or higher. In addition to temperature, other factors obviously influence the performance of polymers such as thermal cycling, stress level, and environmental effects. Some recent developments at NASA Langley in polyimides, poly(arylene ethers), and acetylenic terminated materials are discussed. The high performance/high temperature polymers discussed are representative of the type of work underway at NASA Langley Research Center. Further improvement in these materials as well as the development of new polymers will provide technology to help meet NASA future needs in high performance/high temperature applications. In addition, because of the combination of properties offered by many of these polymers, they should find use in many other applications.

  11. Conductivity in zeolite-polymer composite membranes for PEMFCs

    NASA Astrophysics Data System (ADS)

    Sancho, T.; Soler, J.; Pina, M. P.

    Structured materials, such as zeolites can be candidates to be used as electrolytes in proton exchange membrane fuel cells (PEMFC) to substitute polymeric membranes, taking advantage of their higher chemical and thermal stability and their specific adsorption properties. The possibility to work at temperatures of nearly 150 °C would make easy the selection of the fuel, decreasing the influence of CO in the catalyst poisoning, and it would also improve the kinetics of the electrochemical reactions involved. In this work, four zeolites and related materials have been studied: mordenite, NaA zeolite, umbite and ETS-10. In special, the influence of relative humidity and temperature have been carefully explored. A conductivity cell was designed and built to measure in cross direction, by using the electrochemical impedance spectroscopy. The experimental system was validated using Nafion ® as a reference material by comparing the results with bibliography data. Samples were prepared by pressing the zeolite powders, with size of 1 μm on average, using polymer PVDF (10 wt.%) as a binder. The results here obtained, in spite of not reaching the absolute values of the Nafion ® ones, show a lower effect of the dehydration phenomenon on the conduction performance in the temperature range studied (from room temperature to 150 °C). This increase of the operation temperature range would give important advantages to the PEMFC. ETS-10 sample shows the best behaviour with respect to conductivity exhibiting an activation energy value comparable with reported for Nafion ® membrane.

  12. Predictive Model of Graphene Based Polymer Nanocomposites: Electrical Performance

    NASA Astrophysics Data System (ADS)

    Manta, Asimina; Gresil, Matthieu; Soutis, Constantinos

    2016-11-01

    In this computational work, a new simulation tool on the graphene/polymer nanocomposites electrical response is developed based on the finite element method (FEM). This approach is built on the multi-scale multi-physics format, consisting of a unit cell and a representative volume element (RVE). The FE methodology is proven to be a reliable and flexible tool on the simulation of the electrical response without inducing the complexity of raw programming codes, while it is able to model any geometry, thus the response of any component. This characteristic is supported by its ability in preliminary stage to predict accurately the percolation threshold of experimental material structures and its sensitivity on the effect of different manufacturing methodologies. Especially, the percolation threshold of two material structures of the same constituents (PVDF/Graphene) prepared with different methods was predicted highlighting the effect of the material preparation on the filler distribution, percolation probability and percolation threshold. The assumption of the random filler distribution was proven to be efficient on modelling material structures obtained by solution methods, while the through-the -thickness normal particle distribution was more appropriate for nanocomposites constructed by film hot-pressing. Moreover, the parametrical analysis examine the effect of each parameter on the variables of the percolation law. These graphs could be used as a preliminary design tool for more effective material system manufacturing.

  13. Predictive Model of Graphene Based Polymer Nanocomposites: Electrical Performance

    NASA Astrophysics Data System (ADS)

    Manta, Asimina; Gresil, Matthieu; Soutis, Constantinos

    2017-04-01

    In this computational work, a new simulation tool on the graphene/polymer nanocomposites electrical response is developed based on the finite element method (FEM). This approach is built on the multi-scale multi-physics format, consisting of a unit cell and a representative volume element (RVE). The FE methodology is proven to be a reliable and flexible tool on the simulation of the electrical response without inducing the complexity of raw programming codes, while it is able to model any geometry, thus the response of any component. This characteristic is supported by its ability in preliminary stage to predict accurately the percolation threshold of experimental material structures and its sensitivity on the effect of different manufacturing methodologies. Especially, the percolation threshold of two material structures of the same constituents (PVDF/Graphene) prepared with different methods was predicted highlighting the effect of the material preparation on the filler distribution, percolation probability and percolation threshold. The assumption of the random filler distribution was proven to be efficient on modelling material structures obtained by solution methods, while the through-the -thickness normal particle distribution was more appropriate for nanocomposites constructed by film hot-pressing. Moreover, the parametrical analysis examine the effect of each parameter on the variables of the percolation law. These graphs could be used as a preliminary design tool for more effective material system manufacturing.

  14. PVDF-HFP/ether-modified polysiloxane membranes obtained via airbrush spraying as active separators for application in lithium ion batteries.

    PubMed

    Seidel, S M; Jeschke, S; Vettikuzha, P; Wiemhöfer, H-D

    2015-08-04

    Improved hybrid polymer electrolyte membranes are introduced based on ether-modified polysiloxanes and poly(vinylidene fluoride-co-hexafluoropropylene) yielding a safe separator membrane, which is able to be sprayed directly onto lithium ion battery active materials, with an active role for enhanced ion transport.

  15. From electrode charges on dielectric elastomers to trapped charges and electric dipoles in electrets and ferroelectrets: fundamental and applications-relevant aspects of diversity in electroactive polymers

    NASA Astrophysics Data System (ADS)

    Gerhard, Reimund

    2016-04-01

    Some recent developments in the areas of soft and basically incompressible electro-electrets (dielectric elastomers) with large strains, of anisotropic polymer ferro- or piezo-electrets with quasi-ferroelectric behavior, of moleculardipole electrets with significant ferro-, pyro- and piezo-electricity, and of space-charge polymer electrets with locally stabilised charges are described. Such materials may be applied, e.g., in soft actuators, energy harvesters and flexible and stretchable sensors for devices such as artificial muscles, electrically controllable refractive and diffractive optics, flexible pyroelectric detectors, motion and displacement sensors, earphones and microphones, ultrasonic transducers, air filters, radiation dosimeters, etc. The performance of dielectric elastomers for actuator, energy-harvester and sensor applications relies on a high relative permittivity and a low elastic modulus. High densities of electric charges in the electrodes are required in order to provide large Maxwell stresses or high energy densities. Significant amounts of localised or trapped charges, as well as electric dipoles from pairs of charges, lead to useful electro-mechanical and mechano-electrical effects (or inverse and direct piezoelectricity, respectively) if they are properly arranged in dielectric materials with extremely low conductivities. Space-charge electret films and ferroelectret systems should exhibit thermal and long-term stability of the trapped charges within the respective materials. Ferroelectric polymers and other polar polymers show useful piezo- and pyroelectric properties if their polymer-chain conformations allow for parallel packing of the molecular dipoles. Space-charge and molecular-dipole electrets are widely applied, e.g. in microphones, air filters, radiation dosimeters, ultrasonic transducers, etc. Basically, the performance of all electro-active polymers relies on the attraction (and repulsion) of electric charges and thus directly on

  16. A robust, highly stretchable supramolecular polymer conductive hydrogel with self-healability and thermo-processability

    NASA Astrophysics Data System (ADS)

    Wu, Qian; Wei, Junjie; Xu, Bing; Liu, Xinhua; Wang, Hongbo; Wang, Wei; Wang, Qigang; Liu, Wenguang

    2017-01-01

    Dual amide hydrogen bond crosslinked and strengthened high strength supramolecular polymer conductive hydrogels were fabricated by simply in situ doping poly (N-acryloyl glycinamide-co-2-acrylamide-2-methylpropanesulfonic) (PNAGA-PAMPS) hydrogels with PEDOT/PSS. The nonswellable conductive hydrogels in PBS demonstrated high mechanical performances—0.22–0.58 MPa tensile strength, 1.02–7.62 MPa compressive strength, and 817–1709% breaking strain. The doping of PEDOT/PSS could significantly improve the specific conductivities of the hydrogels. Cyclic heating and cooling could lead to reversible sol-gel transition and self-healability due to the dynamic breakup and reconstruction of hydrogen bonds. The mending hydrogels recovered not only the mechanical properties, but also conductivities very well. These supramolecular conductive hydrogels could be designed into arbitrary shapes with 3D printing technique, and further, printable electrode can be obtained by blending activated charcoal powder with PNAGA-PAMPS/PEDOT/PSS hydrogel under melting state. The fabricated supercapacitor via the conducting hydrogel electrodes possessed high capacitive performances. These cytocompatible conductive hydrogels have a great potential to be used as electro-active and electrical biomaterials.

  17. A robust, highly stretchable supramolecular polymer conductive hydrogel with self-healability and thermo-processability

    PubMed Central

    Wu, Qian; Wei, Junjie; Xu, Bing; Liu, Xinhua; Wang, Hongbo; Wang, Wei; Wang, Qigang; Liu, Wenguang

    2017-01-01

    Dual amide hydrogen bond crosslinked and strengthened high strength supramolecular polymer conductive hydrogels were fabricated by simply in situ doping poly (N-acryloyl glycinamide-co-2-acrylamide-2-methylpropanesulfonic) (PNAGA-PAMPS) hydrogels with PEDOT/PSS. The nonswellable conductive hydrogels in PBS demonstrated high mechanical performances—0.22–0.58 MPa tensile strength, 1.02–7.62 MPa compressive strength, and 817–1709% breaking strain. The doping of PEDOT/PSS could significantly improve the specific conductivities of the hydrogels. Cyclic heating and cooling could lead to reversible sol-gel transition and self-healability due to the dynamic breakup and reconstruction of hydrogen bonds. The mending hydrogels recovered not only the mechanical properties, but also conductivities very well. These supramolecular conductive hydrogels could be designed into arbitrary shapes with 3D printing technique, and further, printable electrode can be obtained by blending activated charcoal powder with PNAGA-PAMPS/PEDOT/PSS hydrogel under melting state. The fabricated supercapacitor via the conducting hydrogel electrodes possessed high capacitive performances. These cytocompatible conductive hydrogels have a great potential to be used as electro-active and electrical biomaterials. PMID:28134283

  18. A robust, highly stretchable supramolecular polymer conductive hydrogel with self-healability and thermo-processability.

    PubMed

    Wu, Qian; Wei, Junjie; Xu, Bing; Liu, Xinhua; Wang, Hongbo; Wang, Wei; Wang, Qigang; Liu, Wenguang

    2017-01-30

    Dual amide hydrogen bond crosslinked and strengthened high strength supramolecular polymer conductive hydrogels were fabricated by simply in situ doping poly (N-acryloyl glycinamide-co-2-acrylamide-2-methylpropanesulfonic) (PNAGA-PAMPS) hydrogels with PEDOT/PSS. The nonswellable conductive hydrogels in PBS demonstrated high mechanical performances-0.22-0.58 MPa tensile strength, 1.02-7.62 MPa compressive strength, and 817-1709% breaking strain. The doping of PEDOT/PSS could significantly improve the specific conductivities of the hydrogels. Cyclic heating and cooling could lead to reversible sol-gel transition and self-healability due to the dynamic breakup and reconstruction of hydrogen bonds. The mending hydrogels recovered not only the mechanical properties, but also conductivities very well. These supramolecular conductive hydrogels could be designed into arbitrary shapes with 3D printing technique, and further, printable electrode can be obtained by blending activated charcoal powder with PNAGA-PAMPS/PEDOT/PSS hydrogel under melting state. The fabricated supercapacitor via the conducting hydrogel electrodes possessed high capacitive performances. These cytocompatible conductive hydrogels have a great potential to be used as electro-active and electrical biomaterials.

  19. Structural design of flexible Au electrode to enable shape memory polymer for electrical actuation

    NASA Astrophysics Data System (ADS)

    Lu, Haibao; Lei, Ming; Zhao, Chao; Xu, Ben; Leng, Jinsong; Fu, Y. Q.

    2015-04-01

    An effective resistive Joule heating approach was conducted to improve the electrical actuation and shape-recovery performance of a shape memory polymer (SMP) nanocomposite. Two types of gold (Au) film patterns were deposited to be used as electrodes to drive thermal-responsive SMPs and achieve a uniform temperature distribution during electro-activated shape recovery. Furthermore, the sensing capability of the Au electrode to both mechanical and thermal stimuli applied to the SMP nanocomposite was experimentally investigated and theoretically analyzed. It was found that the change in the electrical resistance of the Au electrode could be used as an indication of shape-recovery performance. The linear response of the electrical resistance to strain was identified mainly due to the opening/closing of microcracks and their propagations in the Au electrodes during out-of-plane deformations. With an increment of thermomechanical bending cycles, the electrical resistance was increased exponentially, but it returned back to the original reading when the SMP nanocomposite returned back to its permanent shape. Finally, the flexible Au electrode enabled the actuation of the SMP nanocomposite under an electric voltage of 13.4 V, with an improved shape-recovery performance and temperature distribution.

  20. Electrostatic processing of polymers and polymer composites

    NASA Astrophysics Data System (ADS)

    Sanders, Elliot Howard

    2005-11-01

    Polymers are a broad class of molecules whose use in modern life is undeniable ranging from automobile parts to pharmaceuticals. One method applicable to polymer material production is known as electrostatic processing which includes electrospraying, used to produce films or microparticles, and electrospinning, which can be used to produce fibers or non-woven materials. Electrostatic processing typically results in products with droplet or fiber diameters on the micron or nanometer scale. We have sought to develop novel polymeric materials and composites using electrostatic processing. The end uses of these materials were diverse, and included controlled release of drugs, microencapsulation of proteins and enzymes, provision of molecular cues for directed cell growth, hydronium ion transport, and electrically conductive polymer and catalytically active composites. We have successfully demonstrated that electrostatic processing can be used to produce a wide variety of functionally active polymer based materials with significant commercial, medical, and scientific potential.

  1. Fabrication of Si negative electrodes for Li-ion batteries (LIBs) using cross-linked polymer binders

    PubMed Central

    Jang, Suk-Yong; Han, Sien-Ho

    2016-01-01

    Currently, Si as an active material for LIBs has been attracting much attention due to its high theoretical specific capacity (3572 mAh g−1). However, a disadvantage when using a Si negative electrode for LIBs is the abrupt drop of its capabilities during the cycling process. Therefore, there have been a few studies of polymers such as poly(vinylidene fluoride) (PVdF), carboxymethyl cellulose (CMC), styrene butadiene rubber (SBR) and polyacrylic acid (PAA) given that the robust structure of a polymeric binder to LIBs anodes is a promising means by which to enhance the performance of high-capacity anodes. These studies essentially focused mainly on modifying of the linear-polymer component or on copolymers dissolved in solvents. Cross-linking polymers as a binder may be preferred due to their good scratch resistance, excellent chemical resistance and high levels of adhesion and resilience. However, because these types of polymers (with a rigid structure and cross-linking points) are also insoluble in general organic solvents, applying these types in this capacity is virtually impossible. PMID:27991497

  2. Fabrication of Si negative electrodes for Li-ion batteries (LIBs) using cross-linked polymer binders

    NASA Astrophysics Data System (ADS)

    Jang, Suk-Yong; Han, Sien-Ho

    2016-12-01

    Currently, Si as an active material for LIBs has been attracting much attention due to its high theoretical specific capacity (3572 mAh g‑1). However, a disadvantage when using a Si negative electrode for LIBs is the abrupt drop of its capabilities during the cycling process. Therefore, there have been a few studies of polymers such as poly(vinylidene fluoride) (PVdF), carboxymethyl cellulose (CMC), styrene butadiene rubber (SBR) and polyacrylic acid (PAA) given that the robust structure of a polymeric binder to LIBs anodes is a promising means by which to enhance the performance of high-capacity anodes. These studies essentially focused mainly on modifying of the linear-polymer component or on copolymers dissolved in solvents. Cross-linking polymers as a binder may be preferred due to their good scratch resistance, excellent chemical resistance and high levels of adhesion and resilience. However, because these types of polymers (with a rigid structure and cross-linking points) are also insoluble in general organic solvents, applying these types in this capacity is virtually impossible.

  3. Frontiers in polymer chemistry.

    PubMed

    Schlüter, A Dieter

    2013-01-01

    The article shows how the initial concept of Staudinger on linear macromolecules was expanded topologically by increasing the cross-section diameter of polymer chains and by introducing sheet polymers with planar rather than the commonly known linear repeat units. The two concrete projects addressed are the synthesis of dendronized and of two-dimensional polymers. It is explained how these novel macromolecules were achieved and which obstacles had to be overcome but also where these frontiers in polymer chemistry might lead to new insights in polymer science in general and novel applications in particular. The article also provides insights into analytical issues because both target macromolecules are in an extraordinarily high molar mass range and contrast/sensitivity issues can turn rather serious in particular for the two-dimensional polymers.

  4. CO2 -Responsive polymers.

    PubMed

    Lin, Shaojian; Theato, Patrick

    2013-07-25

    This Review focuses on the recent progress in the area of CO2 -responsive polymers and provides detailed descriptions of these existing examples. CO2 -responsive polymers can be categorized into three types based on their CO2 -responsive groups: amidine, amine, and carboxyl groups. Compared with traditional temperature, pH, or light stimuli-responsive polymers, CO2 -responsive polymers provide the advantage to use CO2 as a "green" trigger as well as to capture CO2 directly from air. In addition, the current challenges of CO2 -responsive polymers are discussed and the different solution methods are compared. Noteworthy, CO2 -responsive polymers are considered to have a prosperous future in various scientific areas.

  5. Thermally conductive polymers

    NASA Technical Reports Server (NTRS)

    Byrd, N. R.; Jenkins, R. K.; Lister, J. L. (Inventor)

    1971-01-01

    A thermally conductive polymer is provided having physical and chemical properties suited to use as a medium for potting electrical components. The polymer is prepared from hydroquinone, phenol, and formaldehyde, by conventional procedures employed for the preparation of phenol-formaldehyde resins. While the proportions of the monomers can be varied, a preferred polymer is formed from the monomers in a 1:1:2.4 molar or ratio of hydroquinone:phenol:formaldehyde.

  6. High Performance Polymers

    NASA Technical Reports Server (NTRS)

    Venumbaka, Sreenivasulu R.; Cassidy, Patrick E.

    2003-01-01

    This report summarizes results from research on high performance polymers. The research areas proposed in this report include: 1) Effort to improve the synthesis and to understand and replicate the dielectric behavior of 6HC17-PEK; 2) Continue preparation and evaluation of flexible, low dielectric silicon- and fluorine- containing polymers with improved toughness; and 3) Synthesis and characterization of high performance polymers containing the spirodilactam moiety.

  7. Predictive aging of polymers

    NASA Technical Reports Server (NTRS)

    Cuddihy, Edward F. (Inventor); Willis, Paul B. (Inventor)

    1990-01-01

    A method of predicting aging of polymers operates by heating a polymer in the outdoors to an elevated temperature until a change of property is induced. The test is conducted at a plurality of temperatures to establish a linear Arrhenius plot which is extrapolated to predict the induction period for failure of the polymer at ambient temperature. An Outdoor Photo Thermal Aging Reactor (OPTAR) is also described including a heatable platen for receiving a sheet of polymer, means to heat the platen and switching means such as a photoelectric switch for turning off the heater during dark periods.

  8. Predictive aging of polymers

    NASA Technical Reports Server (NTRS)

    Cuddihy, Edward F. (Inventor); Willis, Paul B. (Inventor)

    1989-01-01

    A method of predicting aging of polymers operates by heating a polymer in the outdoors to an elevated temperature until a change of property is induced. The test is conducted at a plurality of temperatures to establish a linear Arrhenius plot which is extrapolated to predict the induction period for failure of the polymer at ambient temperature. An Outdoor Photo Thermal Aging Reactor (OPTAR) is also described including a heatable platen for receiving a sheet of polymer, means to heat the platen, and switching means such as a photoelectric switch for turning off the heater during dark periods.

  9. Microstructure Development in Polymers.

    DTIC Science & Technology

    1981-05-12

    J. S. Lin, R. W. Hendricks, J. Petermann , and R. M. Gohil, J. Polymer Sci., Polym. Phys. Ed., 19, 609 (1981). 8. J. Petermann , J. M. Schultz, R. M...Gohil, R. W. Hendricks, and J. S. Lin, submitted to Polymer. 9. J. Rau, R. M. Gohil, J. Petermann , and J. M. Schultz, Colloid & Polymer Sci., 259, 241...1981). 10. J. Petermann , J. M. Schultz, R. W. Hendricks, and J. S. Lin, J. Mater. Sci., 16, 265 (1981). 11. K. M. Gupte, Ph.D. Dissertation, Univ. of

  10. Polymers for engineering applications

    SciTech Connect

    Seymour, R.B.

    1987-01-01

    This book provides an introduction to the world of engineering plastics. It discusses the polymers, their properties strengths and limitations. There are 11 chapters, organized so that each chapter builds on the knowledge of the previous material. Coverage includes important polymer concepts, such as molecular structure, bonding, morphology and molecular weight, and polymer properties, such as thermal expansion, thermal transition, electrical properties and viscoelasticity. Details are provided on methods of processing fabrication and on specific families of polymers. The general-purpose polymers are discussed, such as natural and synthetic rubbers, rayon, acrylic and alkyd coatings, polyethylene, polystyrene and polyvinyl chloride (PVC). There's information on high-performance polymers - fibers, elastomers, and coatings. A thorough explanation of the characteristics and qualities of nylons, polyesters, polyimides, neoprene, silicones, polyurethanes and other polymers is given in the same section. Functional polymers with special properties, such as photoconductivity, electric conductivity, piezoelectricity, light sensitivity, and ion exchange; and polymers that are superior to general-purpose plastics, such as ABS, filled polypropylene, and glass-reinforced plastics, are also covered.

  11. Adhesion of Polymer Vesicles

    NASA Astrophysics Data System (ADS)

    Lin, John J.; Bates, Frank S.; Hammer, Daniel A.; Silas, James A.

    2005-07-01

    The adhesion and bending modulus of polybutadiene-poly(ethylene oxide) block copolymer vesicles made from a bidisperse mixture of polymers is measured using micropipette aspiration. The adhesion energy between biotinylated vesicles and avidin beads is modeled by incorporating the extension of the adhesive ligands above the surface brush of the vesicle according to the blob model of bidisperse polymer mixtures of Komura and Safran assuming the polymer brush at the surface of the vesicle is compact. The same model accurately reproduces the scaling of the bending modulus with polymer composition.

  12. Highly Sensitive and Multifunctional Tactile Sensor Using Free-standing ZnO/PVDF Thin Film with Graphene Electrodes for Pressure and Temperature Monitoring

    PubMed Central

    Lee, James S.; Shin, Keun-Young; Cheong, Oug Jae; Kim, Jae Hyun; Jang, Jyongsik

    2015-01-01

    We demonstrate an 80-μm-thick film (which is around 15% of the thickness of the human epidermis), which is a highly sensitive hybrid functional gauge sensor, and was fabricated from poly(vinylidene fluoride) (PVDF) and ZnO nanostructures with graphene electrodes. Using this film, we were able to simultaneously measure pressure and temperature in real time. The pressure was monitored from the change in the electrical resistance via the piezoresistance of the material, and the temperature was inferred based on the recovery time of the signal. Our thin film system enabled us to detect changes in pressure as small as 10 Pa which is pressure detection limit was 103-fold lower than the minimum level required for artificial skin, and to detect temperatures in the range 20–120°C. PMID:25601479

  13. Binary Polymer Brushes of Strongly Immiscible Polymers.

    PubMed

    Chu, Elza; Babar, Tashnia; Bruist, Michael F; Sidorenko, Alexander

    2015-06-17

    The phenomenon of microphase separation is an example of self-assembly in soft matter and has been observed in block copolymers (BCPs) and similar materials (i.e., supramolecular assemblies (SMAs) and homo/block copolymer blends (HBCs)). In this study, we use microphase separation to construct responsive polymer brushes that collapse to generate periodic surfaces. This is achieved by a chemical reaction between the minor block (10%, poly(4-vinylpyridine)) of the block copolymer and a substrate. The major block of polystyrene (PS) forms mosaic-like arrays of grafted patches that are 10-20 nm in size. Depending on the nature of the assembly (SMA, HBC, or neat BCP) and annealing method (exposure to vapors of different solvents or heating above the glass transition temperature), a range of "mosaic" brushes with different parameters can be obtained. Successive grafting of a secondary polymer (polyacrylamide, PAAm) results in the fabrication of binary polymer brushes (BPBs). Upon being exposed to specific selective solvents, BPBs may adopt different conformations. The surface tension and adhesion of the binary brush are governed by the polymer occupying the top stratum. The "mosaic" brush approach allows for a combination of strongly immiscible polymers in one brush. This facilitates substantial contrast in the surface properties upon switching, previously only possible for substrates composed of predetermined nanostructures. We also demonstrate a possible application of such PS/PAAm brushes in a tunable bioadhesion-bioadhesive (PS on top) or nonbioadhesive (PAAm on top) surface as revealed by Escherichia coli bacterial seeding.

  14. Triclosan antimicrobial polymers

    PubMed Central

    Petersen, Richard C.

    2016-01-01

    Triclosan antimicrobial molecular fluctuating energies of nonbonding electron pairs for the oxygen atom by ether bond rotations are reviewed with conformational computational chemistry analyses. Subsequent understanding of triclosan alternating ether bond rotations is able to help explain several material properties in Polymer Science. Unique bond rotation entanglements between triclosan and the polymer chains increase both the mechanical properties of polymer toughness and strength that are enhanced even better through secondary bonding relationships. Further, polymer blend compatibilization is considered due to similar molecular relationships and polarities. With compatibilization of triclosan in polymers a more uniform stability for nonpolar triclosan in the polymer solid state is retained by the antimicrobial for extremely low release with minimum solubility into aqueous solution. As a result, triclosan is projected for long extended lifetimes as an antimicrobial polymer additive. Further, triclosan rapid alternating ether bond rotations disrupt secondary bonding between chain monomers in the resin state to reduce viscosity and enhance polymer blending. Thus, triclosan is considered for a polymer additive with multiple properties to be an antimicrobial with additional benefits as a nonpolar toughening agent and a hydrophobic wetting agent. The triclosan material relationships with alternating ether bond rotations are described through a complete different form of medium by comparisons with known antimicrobial properties that upset bacterial cell membranes through rapid fluctuating mechanomolecular energies. Also, triclosan bond entanglements with secondary bonding can produce structural defects in weak bacterial lipid membranes requiring pliability that can then interfere with cell division. Regarding applications with polymers, triclosan can be incorporated by mixing into a resin system before cure, melt mixed with thermoplastic polymers that set on cooling

  15. Modifying glass fiber surface with grafting acrylamide by UV-grafting copolymerization for preparation of glass fiber reinforced PVDF composite membrane.

    PubMed

    Luo, Nan; Zhong, Hui; Yang, Min; Yuan, Xing; Fan, Yaobo

    2016-01-01

    Experimental design and response surface methodology (RSM) were used to optimize the modification of conditions for glass surface grafting with acrylamide (AM) monomer for preparation of a glass fiber reinforced poly(vinylidene fluoride) (PVDF) composite membrane (GFRP-CM). The factors considered for experimental design were the UV (ultraviolet)-irradiation time, the concentrations of the initiator and solvent, and the kinds and concentrations of the silane coupling agent. The optimum operating conditions determined were UV-irradiation time of 25 min, an initiator concentration of 0-0.25 wt.%, solvent of N-Dimethylacetamide (DMAC), and silane coupling agent KH570 with a concentration of 7 wt.%. The obtained optimal parameters were located in the valid region and the experimental confirmation tests conducted showed good accordance between predicted and experimental values. Under these optimal conditions, the water absorption of the grafted modified glass fiber was improved from 13.6% to 23%; the tensile strength was enhanced and the peeling strength of the glass fiber reinforced PVDF composite membrane was improved by 23.7% and 32.6% with an AM concentration at 1 wt.% and 2 wt.%. The surface composition and microstructure of AM grafted glass fiber were studied via several techniques including Field Emission Scanning Electron Microscopy (FESEM), Fourier transform infrared spectroscopy-attenuated total reflectance (FTIR-ATR) and energy dispersive X-ray spectroscopy (EDX). The analysis of the EDX and FTIR-ATR results confirmed that the AM was grafted to the glass fiber successfully by detecting and proving the existence of nitrogen atoms in the GFRP-CM.

  16. In Vitro Evaluation of Biocompatibility of Uncoated Thermally Reduced Graphene and Carbon Nanotube-Loaded PVDF Membranes with Adult Neural Stem Cell-Derived Neurons and Glia.

    PubMed

    Defteralı, Çağla; Verdejo, Raquel; Majeed, Shahid; Boschetti-de-Fierro, Adriana; Méndez-Gómez, Héctor R; Díaz-Guerra, Eva; Fierro, Daniel; Buhr, Kristian; Abetz, Clarissa; Martínez-Murillo, Ricardo; Vuluga, Daniela; Alexandre, Michaël; Thomassin, Jean-Michel; Detrembleur, Christophe; Jérôme, Christine; Abetz, Volker; López-Manchado, Miguel Ángel; Vicario-Abejón, Carlos

    2016-01-01

    Graphene, graphene-based nanomaterials (GBNs), and carbon nanotubes (CNTs) are being investigated as potential substrates for the growth of neural cells. However, in most in vitro studies, the cells were seeded on these materials coated with various proteins implying that the observed effects on the cells could not solely be attributed to the GBN and CNT properties. Here, we studied the biocompatibility of uncoated thermally reduced graphene (TRG) and poly(vinylidene fluoride) (PVDF) membranes loaded with multi-walled CNTs (MWCNTs) using neural stem cells isolated from the adult mouse olfactory bulb (termed aOBSCs). When aOBSCs were induced to differentiate on coverslips treated with TRG or control materials (polyethyleneimine-PEI and polyornithine plus fibronectin-PLO/F) in a serum-free medium, neurons, astrocytes, and oligodendrocytes were generated in all conditions, indicating that TRG permits the multi-lineage differentiation of aOBSCs. However, the total number of cells was reduced on both PEI and TRG. In a serum-containing medium, aOBSC-derived neurons and oligodendrocytes grown on TRG were more numerous than in controls; the neurons developed synaptic boutons and oligodendrocytes were more branched. In contrast, neurons growing on PVDF membranes had reduced neurite branching, and on MWCNTs-loaded membranes oligodendrocytes were lower in numbers than in controls. Overall, these findings indicate that uncoated TRG may be biocompatible with the generation, differentiation, and maturation of aOBSC-derived neurons and glial cells, implying a potential use for TRG to study functional neuronal networks.

  17. In Vitro Evaluation of Biocompatibility of Uncoated Thermally Reduced Graphene and Carbon Nanotube-Loaded PVDF Membranes with Adult Neural Stem Cell-Derived Neurons and Glia

    PubMed Central

    Defteralı, Çağla; Verdejo, Raquel; Majeed, Shahid; Boschetti-de-Fierro, Adriana; Méndez-Gómez, Héctor R.; Díaz-Guerra, Eva; Fierro, Daniel; Buhr, Kristian; Abetz, Clarissa; Martínez-Murillo, Ricardo; Vuluga, Daniela; Alexandre, Michaël; Thomassin, Jean-Michel; Detrembleur, Christophe; Jérôme, Christine; Abetz, Volker; López-Manchado, Miguel Ángel; Vicario-Abejón, Carlos

    2016-01-01

    Graphene, graphene-based nanomaterials (GBNs), and carbon nanotubes (CNTs) are being investigated as potential substrates for the growth of neural cells. However, in most in vitro studies, the cells were seeded on these materials coated with various proteins implying that the observed effects on the cells could not solely be attributed to the GBN and CNT properties. Here, we studied the biocompatibility of uncoated thermally reduced graphene (TRG) and poly(vinylidene fluoride) (PVDF) membranes loaded with multi-walled CNTs (MWCNTs) using neural stem cells isolated from the adult mouse olfactory bulb (termed aOBSCs). When aOBSCs were induced to differentiate on coverslips treated with TRG or control materials (polyethyleneimine-PEI and polyornithine plus fibronectin-PLO/F) in a serum-free medium, neurons, astrocytes, and oligodendrocytes were generated in all conditions, indicating that TRG permits the multi-lineage differentiation of aOBSCs. However, the total number of cells was reduced on both PEI and TRG. In a serum-containing medium, aOBSC-derived neurons and oligodendrocytes grown on TRG were more numerous than in controls; the neurons developed synaptic boutons and oligodendrocytes were more branched. In contrast, neurons growing on PVDF membranes had reduced neurite branching, and on MWCNTs-loaded membranes oligodendrocytes were lower in numbers than in controls. Overall, these findings indicate that uncoated TRG may be biocompatible with the generation, differentiation, and maturation of aOBSC-derived neurons and glial cells, implying a potential use for TRG to study functional neuronal networks. PMID:27999773

  18. Influence of membrane structure on the operating current densities of non-aqueous redox flow batteries: Organic-inorganic composite membranes based on a semi-interpenetrating polymer network

    NASA Astrophysics Data System (ADS)

    Shin, Sung-Hee; Kim, Yekyung; Yun, Sung-Hyun; Maurya, Sandip; Moon, Seung-Hyeon

    2015-11-01

    We develop three types of organic-inorganic composite membranes based on a semi-interpenetrating polymer network (SIPN) to explore the effects of membrane structure on the possible operating current densities of a non-aqueous redox flow battery (RFB) system. Poly(vinylidene fluoride) (PVdF) is selected as a supporting polymer matrix for improving the chemical and thermal stability of the organic-inorganic composite membranes. We also introduce silica nanoparticles (5 wt% of PVdF) into the membranes to ensure the low crossover of active species. The fabrication of SIPN through the addition of glycidyl methacrylate, 4-vinylpyridine, or N-vinylcarbazole enables control of the membrane structure. Depending on monomer type, the membrane structure is determined to be either aliphatic or aromatic in terms of chemical properties and either dense or porous in terms of physical properties. These chemical and physical structures affect the electrochemical properties that correspond to charge/discharge performance and to the range of possible operating current densities. An important requirement is to examine charge/discharge performance at the possible range of operating current densities by using various membrane structures. This requirement is discussed in relation to a proposed design strategy for non-aqueous RFB membranes.

  19. Polymer based tunneling sensor

    NASA Technical Reports Server (NTRS)

    Cui, Tianhong (Inventor); Wang, Jing (Inventor); Zhao, Yongjun (Inventor)

    2006-01-01

    A process for fabricating a polymer based circuit by the following steps. A mold of a design is formed through a lithography process. The design is transferred to a polymer substrate through a hot embossing process. A metal layer is then deposited over at least part of said design and at least one electrical lead is connected to said metal layer.

  20. Melons are Branched Polymers

    NASA Astrophysics Data System (ADS)

    Gurau, Razvan; Ryan, James P.

    2014-11-01

    Melonic graphs constitute the family of graphs arising at leading order in the 1/N expansion of tensor models. They were shown to lead to a continuum phase, reminiscent of branched polymers. We show here that they are in fact precisely branched polymers, that is, they possess Hausdorff dimension 2 and spectral dimension 4/3.

  1. Advanced Polymer Network Structures

    DTIC Science & Technology

    2016-02-01

    13. SUPPLEMENTARY NOTES 14. ABSTRACT Polymer networks and gels are important classes of materials for defense applications . In an effort to......it is no longer needed. Do not return it to the originator. ARL-TR-7612 ● FEB 2016 US Army Research Laboratory Advanced Polymer

  2. Polymers Are Everywhere.

    ERIC Educational Resources Information Center

    Seymour, Raymond B.

    1988-01-01

    Describes the history of the human understanding of polymers from alchemy to modern times. Discusses renaissance chemistry, polymers in the nineteenth century, synthetic elastomers, thermoplastic elastomers, fibers, coatings, adhesives, derivatives of natural rubber, thermosets, step-reaction, and chain polymerization. (CW)

  3. Radioluminescent polymer lights

    SciTech Connect

    Jensen, G.A.; Nelson, D.A.; Molton, P.M.

    1990-09-01

    The preparation of radioluminescent light sources where the tritium is located on the aryl-ring in a polymer has been demonstrated with deuterium/tritium substitution. This report discusses tests, results, and future applications of radioluminescent polymers. 10 refs. (FI)

  4. Stability of polydopamine and poly(DOPA) melanin-like films on the surface of polymer membranes under strongly acidic and alkaline conditions.

    PubMed

    Wei, Houliang; Ren, Jun; Han, Bo; Xu, Li; Han, Lulu; Jia, Lingyun

    2013-10-01

    This study investigated the stability of polydopamine and poly(3,4-dihydroxyphenylalanine) (poly(DOPA)) melanin-like films on the surface of polymer substrates. Three polymer membranes, polypropylene (PP), poly(vinylidenefluoride) (PVDF) and nylon, were modified with polydopamine or poly(DOPA), and then immersed in 0.1M HCl or NaOH, followed by UV-vis spectrometry analysis to detect the presence of film detachment. The results showed that the outer parts of both polydopamine and poly(DOPA) films were detached, probably due to electrostatic repulsion between the polymers within the film, when the modified membranes were washed in HCl or NaOH solution. These two films were more stable in strongly acidic solution, but the stability of poly(DOPA) film was better than that of polydopamine film. Compared to the films on the surface of PVDF or nylon membrane, films on PP surface showed the lowest stability, possibly because of the hydrophobic property of PP. The process of film detachment was analyzed by GPC, which showed that unreacted dopamine or DOPA monomers were still present in the freshly formed films. The unreacted monomers, as well as polydopamine or poly(DOPA) that were incorporated in the film via noncovalent interactions, became detached when the film was exposed to strongly acidic or alkaline solution. Oxidation of freshly formed films could significantly enhance their stability. The results therefore provide us with a better understanding of the stability of melanin-like films, and allow us to develop an effective strategy for constructing stable films.

  5. Polymers at membranes

    NASA Astrophysics Data System (ADS)

    Breidenich, Markus

    2000-11-01

    The surface of biological cells consists of a lipid membrane and a large amount of various proteins and polymers, which are embedded in the membrane or attached to it. We investigate how membranes are influenced by polymers, which are anchored to the membrane by one end. The entropic pressure exerted by the polymer induces a curvature, which bends the membrane away from the polymer. The resulting membrane shape profile is a cone in the vicinity of the anchor segment and a catenoid far away from it. The perturbative calculations are confirmed by Monte-Carlo simulations. An additional attractive interaction between polymer and membrane reduces the entropically induced curvature. In the limit of strong adsorption, the polymer is localized directly on the membrane surface and does not induce any pressure, i.e. the membrane curvature vanishes. If the polymer is not anchored directly on the membrane surface, but in a non-vanishing anchoring distance, the membrane bends towards the polymer for strong adsorption. In the last part of the thesis, we study membranes under the influence of non-anchored polymers in solution. In the limit of pure steric interactions between the membrane and free polymers, the membrane curves towards the polymers (in contrast to the case of anchored polymers). In the limit of strong adsorption the membrane bends away from the polymers. Die Oberfläche biologischer Zellen besteht aus einer Lipidmembran und einer Vielzahl von Proteinen und Polymeren, die in die Membran eingebaut sind. Die Beeinflussung der Membran durch Polymere, die mit einem Ende an der Membran verankert sind, wird im Rahmen dieser Arbeit anhand eines vereinfachten biomimetischen Systems studiert. Der entropische Druck, den das Polymer durch Stöße auf die Membran ausübt, führt dazu, dass sich die Membran vom Polymer weg krümmt. Die resultierende Membranform ist ein Kegel in der Nähe des Ankers und ein Katenoid in grossem Abstand vom Ankerpunkt. Monte Carlo-Simulationen best

  6. Polymer Crystallization under Confinement

    NASA Astrophysics Data System (ADS)

    Floudas, George

    Recent efforts indicated that polymer crystallization under confinement can be substantially different from the bulk. This can have important technological applications for the design of polymeric nanofibers with tunable mechanical strength, processability and optical clarity. However, the question of how, why and when polymers crystallize under confinement is not fully answered. Important studies of polymer crystallization confined to droplets and within the spherical nanodomains of block copolymers emphasized the interplay between heterogeneous and homogeneous nucleation. Herein we report on recent studies1-5 of polymer crystallization under hard confinement provided by model self-ordered AAO nanopores. Important open questions here are on the type of nucleation (homogeneous vs. heterogeneous), the size of critical nucleus, the crystal orientation and the possibility to control the overall crystallinity. Providing answers to these questions is of technological relevance for the understanding of nanocomposites containing semicrystalline polymers. In collaboration with Y. Suzuki, H. Duran, M. Steinhart, H.-J. Butt.

  7. Rapid Polymer Sequencer

    NASA Technical Reports Server (NTRS)

    Stolc, Viktor (Inventor); Brock, Mathew W. (Inventor)

    2011-01-01

    Method and system for rapid and accurate determination of each of a sequence of unknown polymer components, such as nucleic acid components. A self-assembling monolayer of a selected substance is optionally provided on an interior surface of a pipette tip, and the interior surface is immersed in a selected liquid. A selected electrical field is impressed in a longitudinal or transverse direction at the tip, a polymer sequence is passed through the tip, and a change in an electrical current signal is measured as each polymer component passes through the tip. Each measured change in electrical current signals is compared with a database of reference signals, with each reference signal identified with a polymer component, to identify the unknown polymer component. The tip preferably has a pore inner diameter of no more than about 40 nm and is prepared by heating and pulling a very small section of a glass tubing.

  8. Porous polymer media

    DOEpatents

    Shepodd, Timothy J.

    2002-01-01

    Highly crosslinked monolithic porous polymer materials for chromatographic applications. By using solvent compositions that provide not only for polymerization of acrylate monomers in such a fashion that a porous polymer network is formed prior to phase separation but also for exchanging the polymerization solvent for a running buffer using electroosmotic flow, the need for high pressure purging is eliminated. The polymer materials have been shown to be an effective capillary electrochromatographic separations medium at lower field strengths than conventional polymer media. Further, because of their highly crosslinked nature these polymer materials are structurally stable in a wide range of organic and aqueous solvents and over a pH range of 2-12.

  9. Non-resonant Mie scattering: Emergent optical properties of core-shell polymer nanowires

    PubMed Central

    Khudiyev, Tural; Huseyinoglu, Ersin; Bayindir, Mehmet

    2014-01-01

    We provide the in-depth characterization of light-polymer nanowire interactions in the context of an effective Mie scattering regime associated with low refractive index materials. Properties of this regime sharply contrast with these of resonant Mie scattering, and involve the formation of strictly forward-scattered and coupling-free optical fields in the vicinity of core-shell polymer nanowires. Scattering from these optical fields is shown to be non-resonant in nature and independent from incident polarization. In order to demonstrate the potential utility of this scattering regime in one-dimensional (1D) polymeric nanostructures, we fabricate polycarbonate (PC) - polyvinylidene difluoride (PVDF) core-shell nanowires using a novel iterative thermal drawing process that yields uniform and indefinitely long core-shell nanostructures. These nanowires are successfully engineered for novel nanophotonics applications, including size-dependent structural coloration, efficient light capture on thin-film solar cells, optical nano-sensors with ultrahigh sensitivity and a mask-free photolithography method suitable for the straightforward production of 1D nanopatterns. PMID:24714206

  10. Flexible thin-film battery based on solid-like ionic liquid-polymer electrolyte

    NASA Astrophysics Data System (ADS)

    Li, Qin; Ardebili, Haleh

    2016-01-01

    The development of high-performance flexible batteries is imperative for several contemporary applications including flexible electronics, wearable sensors and implantable medical devices. However, traditional organic liquid-based electrolytes are not ideal for flexible batteries due to their inherent safety and stability issues. In this study, a non-volatile, non-flammable and safe ionic liquid (IL)-based polymer electrolyte film with solid-like feature is fabricated and incorporated in a flexible lithium ion battery. The ionic liquid is 1-Ethyl-3-methylimidazolium dicyanamide (EMIMDCA) and the polymer is composed of poly(vinylidene fluoride-co-hexafluoropropene) (PVDF-HFP). The electrolyte exhibits good thermal stability (i.e. no weight loss up to 300 °C) and relatively high ionic conductivity (6 × 10-4 S cm-1). The flexible thin-film lithium ion battery based on solid-like electrolyte film is encapsulated using a thermal-lamination process and demonstrates excellent electrochemical performance, in both flat and bent configurations.

  11. Polymers pushing Polymers: Polymer Mixtures in Thermodynamic Equilibrium with a Pore.

    PubMed

    Podgornik, R; Hopkins, J; Parsegian, V A; Muthukumar, M

    2012-11-13

    We investigate polymer partitioning from polymer mixtures into nanometer size cavities by formulating an equation of state for a binary polymer mixture assuming that only one (smaller) of the two polymer components can penetrate the cavity. Deriving the partitioning equilibrium equations and solving them numerically allows us to introduce the concept of "polymers-pushing-polymers" for the action of non-penetrating polymers on the partitioning of the penetrating polymers. Polymer partitioning into a pore even within a very simple model of a binary polymer mixture is shown to depend in a complicated way on the composition of the polymer mixture and/or the pore-penetration penalty. This can lead to enhanced as well as diminished partitioning, due to two separate energy scales that we analyse in detail.

  12. Tailoring the interface of an immiscible polymer blend by a mutually miscible homopolymer grafted onto graphene oxide: outstanding mechanical properties.

    PubMed

    Kar, Goutam Prasanna; Biswas, Sourav; Bose, Suryasarathi

    2015-01-21

    A unique strategy was adopted here to improve the compatibility between the components of an immiscible polymer blend and strengthen the interface. PMMA, a mutually miscible polymer to both PVDF and ABS, improved the compatibility between the phases by localizing at the blends interface. This was supported by the core-shell formation with PMMA as the shell and ABS as the core as observed from the SEM micrographs. This phenomenon was strongly contingent on the concentration of PMMA in the blends. This strategy was further extended to localize graphene oxide (GO) sheets at the blends interface by chemically coupling it to PMMA (PMMA-g-GO). A dramatic increment of ca. 84% in the Young's modulus and ca. 124% in the yield strength was observed in the presence of PMMA-g-GO with respect to the neat blends. A simultaneous increment in both the strength and the modulus was observed in the presence of PMMA-g-GO whereas, only addition of GO resulted in a moderate improvement in the yield strength. This study reveals that a mutually miscible polymer can render compatibility between the immiscible pair and can improve the stress transfer at the interface.

  13. Low Dielectric Polymers

    NASA Technical Reports Server (NTRS)

    Venumbaka, Sreenivasulu R.; Cassidy, Patrick E.

    2002-01-01

    This report summarizes results obtained from research funded through Research Cooperative Agreement No. NCC-1-01033-"Low Dielectric Polymers" (from 5/10/01 through 5/09/02). Results are reported in three of the proposed research areas (Tasks 1-3 in the original proposal): (1) Repeat and confirm the preparation and properties of the new alkyl-substituted PEK, 6HC17-PEK, (2) Prepare and evaluate polymers derived from a highly fluorinated monomer, and (3) Prepare and evaluate new silicon and/or fluorine-containing polymers expected to retain useful properties at low temperature.

  14. Elasticity of semiflexible polymers.

    PubMed

    Samuel, Joseph; Sinha, Supurna

    2002-11-01

    We present a method for solving the wormlike chain model for semiflexible polymers to any desired accuracy over the entire range of polymer lengths. Our results are in excellent agreement with recent computer simulations and reproduce important qualitatively interesting features observed in simulations of polymers of intermediate lengths. We also make a number of predictions that can be tested in a variety of concrete experimental realizations. The expected level of finite size fluctuations in force-extension curves is also estimated. This study is relevant to mechanical properties of biological molecules.

  15. Soluble porphyrin polymers

    DOEpatents

    Gust, Jr., John Devens; Liddell, Paul Anthony

    2015-07-07

    Porphyrin polymers of Structure 1, where n is an integer (e.g., 1, 2, 3, 4, 5, or greater) ##STR00001## are synthesized by the method shown in FIGS. 2A and 2B. The porphyrin polymers of Structure 1 are soluble in organic solvents such as 2-MeTHF and the like, and can be synthesized in bulk (i.e., in processes other than electropolymerization). These porphyrin polymers have long excited state lifetimes, making the material suitable as an organic semiconductor for organic electronic devices including transistors and memories, as well as solar cells, sensors, light-emitting devices, and other opto-electronic devices.

  16. Sulfonated polyphenylene polymers

    DOEpatents

    Cornelius, Christopher J.; Fujimoto, Cy H.; Hickner, Michael A.

    2007-11-27

    Improved sulfonated polyphenylene compositions, improved polymer electrolyte membranes and nanocomposites formed there from for use in fuel cells are described herein. The improved compositions, membranes and nanocomposites formed there from overcome limitations of Nafion.RTM. membranes.

  17. Driving magnetic colloidal polymers

    NASA Astrophysics Data System (ADS)

    Dempster, Joshua; Olvera de La Cruz, Monica

    Magnetic colloids are of growing interest for applications such as drug delivery and in vitro tissue growth. Recent experiments have synthesized 1D chains of magnetic colloids into permanent colloidal polymers. We study magnetic colloidal polymers theoretically and computationally under the influence of time-varying external fields and find a rich set of controllable, dynamic conformations. By iterating through a sequence of conformations, these polymers can perform mechanical functions. We discuss possible roles for these polymers beyond those considered for single colloids. This work was supported as part of the Center for Bio-Inspired Energy Science, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Basic Energy Sciences under Award # DE-SC0000989.

  18. Electroactive polymers for sensing

    PubMed Central

    2016-01-01

    Electromechanical coupling in electroactive polymers (EAPs) has been widely applied for actuation and is also being increasingly investigated for sensing chemical and mechanical stimuli. EAPs are a unique class of materials, with low-moduli high-strain capabilities and the ability to conform to surfaces of different shapes. These features make them attractive for applications such as wearable sensors and interfacing with soft tissues. Here, we review the major types of EAPs and their sensing mechanisms. These are divided into two classes depending on the main type of charge carrier: ionic EAPs (such as conducting polymers and ionic polymer–metal composites) and electronic EAPs (such as dielectric elastomers, liquid-crystal polymers and piezoelectric polymers). This review is intended to serve as an introduction to the mechanisms of these materials and as a first step in material selection for both researchers and designers of flexible/bendable devices, biocompatible sensors or even robotic tactile sensing units. PMID:27499846

  19. Covalent polymers of water.

    PubMed

    O'konski, C T

    1970-05-29

    A new covalent structural scheme for water polymers is proposed. The observed properties of "polywater" are related to the structures of the suggested homologous series of molecules. Mechanisms of formation are suggested.

  20. Dendritic Polymers for Theranostics

    PubMed Central

    Ma, Yuan; Mou, Quanbing; Wang, Dali; Zhu, Xinyuan; Yan, Deyue

    2016-01-01

    Dendritic polymers are highly branched polymers with controllable structures, which possess a large population of terminal functional groups, low solution or melt viscosity, and good solubility. Their size, degree of branching and functionality can be adjusted and controlled through the synthetic procedures. These tunable structures correspond to application-related properties, such as biodegradability, biocompatibility, stimuli-responsiveness and self-assembly ability, which are the key points for theranostic applications, including chemotherapeutic theranostics, biotherapeutic theranostics, phototherapeutic theranostics, radiotherapeutic theranostics and combined therapeutic theranostics. Up to now, significant progress has been made for the dendritic polymers in solving some of the fundamental and technical questions toward their theranostic applications. In this review, we briefly summarize how to control the structures of dendritic polymers, the theranostics-related properties derived from their structures and their theranostics-related applications. PMID:27217829

  1. Rechargeable solid polymer electrolyte battery cell

    DOEpatents

    Skotheim, Terji

    1985-01-01

    A rechargeable battery cell comprising first and second electrodes sandwiching a solid polymer electrolyte comprising a layer of a polymer blend of a highly conductive polymer and a solid polymer electrolyte adjacent said polymer blend and a layer of dry solid polymer electrolyte adjacent said layer of polymer blend and said second electrode.

  2. Carbon Nanofiber Reinforced Polymers

    DTIC Science & Technology

    2006-01-01

    2006 2. REPORT TYPE 3. DATES COVERED 00-00-2006 to 00-00-2006 4. TITLE AND SUBTITLE Carbon Nanofiber Reinforced Polymers 5a. CONTRACT NUMBER 5b...REVIEW Carbon Nanofiber Reinforced Polymers J.N. Baucom, A. Rohatgi, W.R. Pogue III, and J.P. Thomas Materials Science and Technology Division...of mass-produced and inexpensive, discontinuous carbon nanofibers to create a percolated fiber network within a polymeric matrix that will result in

  3. Amine terminated bisaspartimide polymer

    NASA Technical Reports Server (NTRS)

    Kumar, D. (Inventor); Fohlen, G. M. (Inventor); Parker, J. A. (Inventor)

    1986-01-01

    Novel amine terminated bisaspartimides are prepared by a Michael-type reaction of an aromatic bismalteimide and an aromatic diamine in an aprotic solvent. These bisaspartimides are thermally polymerized to yield tough, resinous polymers cross-lined through -NH- groups. Such polymers are useful in applications requiring materials with resistance to change at elevated temperatures, e.g., as lightweight laminates with graphite cloth, molding material prepregs, adhesives and insulating material.

  4. Functional Polymer Matrix Fibers

    DTIC Science & Technology

    2007-11-02

    the carbon nanofibers led to the deterioration of the polymeric cellulose structure. Extensive research on the surface treatment of carbon nanofibers...1 November 2003 - 14-Mar-05 4. TITLE AND SUBTITLE 5a. CONTRACT NUMBER FA8655-03-1-3042 Functional Polymer Matrix Fibres 5b. GRANT NUMBER 5c. PROGRAM...MARYLABONE RD LONDON NWl 5TH PERFORMANCE REPORT Project title: Functional polymer matrix fibers Period of performance: 1 November 2003 - 31 October 2004

  5. Polymer optical motherboard technology

    NASA Astrophysics Data System (ADS)

    Keil, N.; Yao, H.; Zawadzki, C.; Grote, N.; Schell, M.

    2008-02-01

    In this paper, different hybridly integrated optical devices including optical multiplexer/ demultiplexer and optical transceivers are described. The devices were made using polymer planar light wave circuit (P2LC) technology. Laser diodes, photodiodes, and thin-film filters have been integrated. Key issues involved in this technology, in particular the coupling between laser diodes and polymer waveguides, and between waveguides and photodiodes and also fibers are discussed.

  6. Cylodextrin Polymer Nitrate

    NASA Technical Reports Server (NTRS)

    Kosowski, Bernard; Ruebner, Anja; Statton, Gary; Robitelle, Danielle; Meyers, Curtis

    2000-01-01

    The development of the use of cyclodextrin nitrates as possible components of insensitive, high-energy energetics is outlined over a time period of 12 years. Four different types of cyclodextrin polymers were synthesized, nitrated, and evaluated regarding their potential use for the military and aerospace community. The synthesis of these novel cyclodextrin polymers and different nitration techniques are shown and the potential of these new materials is discussed.

  7. Polymer Blends. Volume 1

    DTIC Science & Technology

    1992-05-01

    polyimides, thereby potentially leading to a viable, new class of high temperature, thermoformable resins for 371 0C (7000F) applica- tions. The Polymer...PBI/PI systems exhibit miscibility which: - exhibit improved processibility over neat PBI - are thermoformable - have improved mechanical performance...new class of high temperature, thermoformable resins for 3710C (700*F) applications. The Polymer Alloy and Composite Program also established a

  8. High through-plane thermal conduction of graphene nanoflake filled polymer composites melt-processed in an L-shape kinked tube.

    PubMed

    Jung, Haejong; Yu, Seunggun; Bae, Nam-Seok; Cho, Suk Man; Kim, Richard Hahnkee; Cho, Sung Hwan; Hwang, Ihn; Jeong, Beomjin; Ryu, Ji Su; Hwang, Junyeon; Hong, Soon Man; Koo, Chong Min; Park, Cheolmin

    2015-07-22

    Design of materials to be heat-conductive in a preferred direction is a crucial issue for efficient heat dissipation in systems using stacked devices. Here, we demonstrate a facile route to fabricate polymer composites with directional thermal conduction. Our method is based on control of the orientation of fillers with anisotropic heat conduction. Melt-compression of solution-cast poly(vinylidene fluoride) (PVDF) and graphene nanoflake (GNF) films in an L-shape kinked tube yielded a lightweight polymer composite with the surface normal of GNF preferentially aligned perpendicular to the melt-flow direction, giving rise to a directional thermal conductivity of approximately 10 W/mK at 25 vol % with an anisotropic thermal conduction ratio greater than six. The high directional thermal conduction was attributed to the two-dimensional planar shape of GNFs readily adaptable to the molten polymer flow, compared with highly entangled carbon nanotubes and three-dimensional graphite fillers. Furthermore, our composite with its density of approximately 1.5 g/cm(3) was mechanically stable, and its thermal performance was successfully preserved above 100 °C even after multiple heating and cooling cycles. The results indicate that the methodology using an L-shape kinked tube is a new way to achieve polymer composites with highly anisotropic thermal conduction.

  9. Nanoimprinted polymer solar cell.

    PubMed

    Yang, Yi; Mielczarek, Kamil; Aryal, Mukti; Zakhidov, Anvar; Hu, Walter

    2012-04-24

    Among the various organic photovoltaic devices, the conjugated polymer/fullerene approach has drawn the most research interest. The performance of these types of solar cells is greatly determined by the nanoscale morphology of the two components (donor/acceptor) and the molecular orientation/crystallinity in the photoactive layer. A vertically bicontinuous and interdigitized heterojunction between donor and acceptor has been regarded as one of the ideal structures to enable both efficient charge separation and transport. Synergistic control of polymer orientation in the nanostructured heterojunction is also critical to improve the performance of polymer solar cells. Nanoimprint lithography has emerged as a new approach to simultaneously control both the heterojunction morphology and polymer chains in organic photovoltaics. Currently, in the area of nanoimprinted polymer solar cells, much progress has been achieved in the fabrication of nanostructured morphology, control of molecular orientation/crystallinity, deposition of acceptor materials, patterned electrodes, understanding of structure-property correlations, and device performance. This review article summarizes the recent studies on nanoimprinted polymer solar cells and discusses the outstanding challenges and opportunities for future work.

  10. Rapid Polymer Sequencer

    NASA Technical Reports Server (NTRS)

    Stolc, Viktor (Inventor); Brock, Matthew W (Inventor)

    2013-01-01

    Method and system for rapid and accurate determination of each of a sequence of unknown polymer components, such as nucleic acid components. A self-assembling monolayer of a selected substance is optionally provided on an interior surface of a pipette tip, and the interior surface is immersed in a selected liquid. A selected electrical field is impressed in a longitudinal direction, or in a transverse direction, in the tip region, a polymer sequence is passed through the tip region, and a change in an electrical current signal is measured as each polymer component passes through the tip region. Each of the measured changes in electrical current signals is compared with a database of reference electrical change signals, with each reference signal corresponding to an identified polymer component, to identify the unknown polymer component with a reference polymer component. The nanopore preferably has a pore inner diameter of no more than about 40 nm and is prepared by heating and pulling a very small section of a glass tubing.

  11. Polymer and composite polymer slot waveguides

    NASA Astrophysics Data System (ADS)

    Hiltunen, Marianne; Fegadolli, William S.; Lira, Hugo L. R.; Vahimaa, Pasi; Hiltunen, Jussi; Aikio, Sanna; Almeida, Vilson R.; Karioja, Pentti

    2014-05-01

    A fully polymer slot Young interferometer operating at 633 nm wavelength was fabricated by using nanoimprint molding method. The phase response of the interference pattern was measured with several concentrations of glucose-water solutions, utilizing both TE and TM polarization states. The sensor was experimentally found to detect a bulk refractive index change of 6.4×10-6 RIU. Temperature dependency of silicon slot waveguide has been demonstrated to be reduced with composite slot waveguide structure. The slot filled with thermally stable polymer having negative thermo-optic coefficient showed nearly an athermal operation of silicon slot waveguide. Experimental results show that the slot waveguide geometry covered with Ormocomp has thermo-optical coefficient of 6 pm/K.

  12. Precursor polymer compositions comprising polybenzimidazole

    SciTech Connect

    Klaehn, John R.; Peterson, Eric S.; Orme, Christopher J.

    2015-07-14

    Stable, high performance polymer compositions including polybenzimidazole (PBI) and a melamine-formaldehyde polymer, such as methylated, poly(melamine-co-formaldehyde), for forming structures such as films, fibers and bulky structures. The polymer compositions may be formed by combining polybenzimidazole with the melamine-formaldehyde polymer to form a precursor. The polybenzimidazole may be reacted and/or intertwined with the melamine-formaldehyde polymer to form the polymer composition. For example, a stable, free-standing film having a thickness of, for example, between about 5 .mu.m and about 30 .mu.m may be formed from the polymer composition. Such films may be used as gas separation membranes and may be submerged into water for extended periods without crazing and cracking. The polymer composition may also be used as a coating on substrates, such as metal and ceramics, or may be used for spinning fibers. Precursors for forming such polymer compositions are also disclosed.

  13. Optimization of a quasi-solid-state dye-sensitized solar cell employing a nanocrystal-polymer composite electrolyte modified with water and ethanol.

    PubMed

    Yang, Ying; Zhou, Cong-Hua; Xu, Sheng; Zhang, Jing; Wu, Su-Juan; Hu, Hao; Chen, Bo-Lei; Tai, Qi-Dong; Sun, Zheng-Hua; Liu, Wei; Zhao, Xing-Zhong

    2009-03-11

    A quasi-solid-state dye-sensitized solar cell employing a poly(ethylene oxide)-poly(vinylidene fluoride) (PEO-PVDF)/TiO2 gel electrolyte modified by various concentrations of water and ethanol is described. It is shown that the introduction of water and ethanol prevents the crystallization of the polymer matrix, and enhances the free I(-)/I(3)(-) concentration and the networks for ion transportation in the electrolyte, thus leading to an improvement in conductivity. A high energy conversion efficiency of about 5.8% is achieved by controlling the additive concentration in the electrolyte. Optimization of the additive-modified electrolyte performance has been obtained by studying the cross-linking behavior of water and ethanol with Fourier transform infrared (FTIR), differential scanning calorimetry (DSC) and viscosity measurements, and the electrical conduction behavior of the electrolyte with impedance spectra measurements.

  14. Tailored Magnetic and Magnetoelectric Responses of Polymer-Based Composites.

    PubMed

    Martins, P; Kolen'ko, Yu V; Rivas, J; Lanceros-Mendez, S

    2015-07-15

    The manipulation of electric ordering with applied magnetic fields has been realized on magnetoelectric (ME) materials; however, their ME switching is often accompanied by significant hysteresis and coercivity that represents for some applications a severe weakness. To overcome this obstacle, this work focuses on the development of a new type of ME polymer nanocomposites that exhibits a tailored ME response at room temperature. The multiferroic nanocomposites are based on three different ferrite nanoparticles, Zn0.2Mn0.8Fe2O4 (ZMFO), CoFe2O4 (CFO) and Fe3O4 (FO), dispersed in a piezoelectric copolymer poly(vinylindene fluoride-trifluoroethylene) (P(VDF-TrFE)) matrix. No substantial differences were detected in the time-stable piezoelectric response of the composites (∼-28 pC·N(1-)) with distinct ferrite fillers and for the same ferrite content of 10 wt %. Magnetic hysteresis loops from pure ferrite nanopowders showed different magnetic responses. ME results of the nanocomposite films with 10 wt % ferrite content revealed that the ME induced voltage increases with increasing dc magnetic field until a maximum of 6.5 mV·cm(-1)·Oe(1-), at an optimum magnetic field of 0.26 T, and 0.8 mV·cm(-1)·Oe(1-), at an optimum magnetic field of 0.15 T, for the CFO/P(VDF-TrFE) and FO/P(VDF-TrFE) composites, respectively. In contrast, the ME response of ZMFO/P(VDF-TrFE) exposed no hysteresis and high dependence on the ZMFO filler content. Possible innovative applications such as memories and information storage, signal processing, and ME sensors and oscillators have been addressed for such ferrite/PVDF nanocomposites.

  15. Simulations of Polymer Translocation

    NASA Astrophysics Data System (ADS)

    Vocks, H.

    2008-07-01

    Transport of molecules across membranes is an essential mechanism for life processes. These molecules are often long, and the pores in the membranes are too narrow for the molecules to pass through as a single unit. In such circumstances, the molecules have to squeeze -- i.e., translocate -- themselves through the pores. DNA, RNA and proteins are such naturally occuring long molecules in a variety of biological processes. Understandably, the process of translocation has been an active topic of current research: not only because it is a cornerstone of many biological processes, but also due to its relevance for practical applications. Translocation is a complicated process in living organisms -- the presence of chaperone molecules, pH, chemical potential gradients, and assisting molecular motors strongly influence its dynamics. Consequently, the translocation process has been empirically studied in great variety in biological literature. Study of translocation as a biophysical process is more recent. Herein, the polymer is simplified to a sequentially connected string of N monomers as it passes through a narrow pore on a membrane. The quantities of interest are the typical time scale for the polymer to leave a confining cell (the ``escape of a polymer from a vesicle'' time scale), and the typical time scale the polymer spends in the pore (the ``dwell'' time scale) as a function of N and other parameters like membrane thickness, membrane adsorption, electrochemical potential gradient, etc. Our research is focused on computer simulations of translocation. Since our main interest is in the scaling properties, we use a highly simplified description of the translocation process. The polymer is described as a self-avoiding walk on a lattice, and its dynamics consists of single-monomer jumps from one lattice site to another neighboring one. Since we have a very efficient program to simulate such polymer dynamics, which we decribe in Chapter 2, we can perform long

  16. Synthesis of Conductive Nanofillers/Nanofibers and Electrical Properties of their Conductive Polymer Composites

    NASA Astrophysics Data System (ADS)

    Sarvi, Ali

    Thanks to their corrosion resistance, light weight, low cost, and ease of processing, electrically conducting polymer composites (CPCs) have received significant attention for the replacement of metals and inorganic materials for sensors, actuators, supercapacitors, and electromagnetic interference (EMI) shields. In this PhD thesis, high aspect ratio conductive nanofillers namely copper nanowires (CuNWs) and multiwall carbon nanotubes (MWCNTs) were coated with polyaniline (PANi) using solution mixing and in-situ polymerization method, respectively. Transmission electron microscopy (TEM) showed a smooth polyaniline nano-coating between 5--18 nm in thickness on the nanofillers' surface. The coating thickness and; consequently, electrical conductivity was controlled and tuned by polyaniline/aniline concentration in solution. Composites with tunable conductivity may be used as chemisensors, electronic pressure sensors and switches. Coated nanofillers demonstrated better dispersion in polystyrene (PS) and provided lower electrical percolation threshold. Dispersion of nanofillers in PS was investigated using rheological measurements and confirmed with electron micrographs and nano-scale images of CPCs. Polyaniline (PANi), when used as a coating layer, was able to attenuate electromagnetic (EM) waves via absorption and store electrical charges though pseudocapacitance mechanism. The dielectric measurements of MWCNT-PANi/PS composites showed one order of magnitude increase in real electrical permittivity compared to that of MWCNT/PS composites making them suitable for charge storage purposes. Incorporation of PANi also brought a new insight into conductive network formation mechanism in electrospun mats where the orientation of conductive high aspect ratio nanofillers is a major problem. Conductive nanofibers of poly(vinylidene fluoride) (PVDF) filled with coated multiwall carbon nanotubes (MWCNTs) were fabricated using electrospinning. These highly oriented PVDF

  17. Physical properties of immiscible polymers

    NASA Technical Reports Server (NTRS)

    Harris, J. Milton

    1987-01-01

    The demixing of immiscible polymers in low gravity is discussed. Applications of knowledge gained in this research will provide a better understanding of the role of phase segregation in determining the properties of polymer blends made from immiscible polymers. Knowledge will also be gained regarding the purification of biological materials by partitioning between the two liquid phases formed by solution of the polymers polyethylene glycol and dextran in water. Testing of new apparatus for space flight, extension of affinity phase partitioning, refinement of polymer chemistry, and demixing of isopycnic polymer phases in a one gravity environment are discussed.

  18. Jamming of Semiflexible Polymers

    NASA Astrophysics Data System (ADS)

    Hoy, Robert S.

    2017-02-01

    We study jamming in model freely rotating polymers as a function of chain length N and bond angle θ0. The volume fraction at jamming ϕJ(θ0) is minimal for rigid-rodlike chains (θ0=0 ), and increases monotonically with increasing θ0≤π /2 . In contrast to flexible polymers, marginally jammed states of freely rotating polymers are highly hypostatic, even when bond and angle constraints are accounted for. Large-aspect-ratio (small θ0) chains behave comparably to stiff fibers: resistance to large-scale bending plays a major role in their jamming phenomenology. Low-aspect-ratio (large θ0) chains behave more like flexible polymers, but still jam at much lower densities due to the presence of frozen-in three-body correlations corresponding to the fixed bond angles. Long-chain systems jam at lower ϕ and are more hypostatic at jamming than short-chain systems. Implications of these findings for polymer solidification are discussed.

  19. Modelling polymer draft gears

    NASA Astrophysics Data System (ADS)

    Wu, Qing; Yang, Xiangjian; Cole, Colin; Luo, Shihui

    2016-09-01

    This paper developed a new and simple approach to model polymer draft gears. Two types of polymer draft gears were modelled and compared with experimental data. Impact characteristics, in-train characteristics and frequency responses of these polymer draft gears were studied and compared with those of a friction draft gear. The impact simulations show that polymer draft gears can withstand higher impact speeds than the friction draft gear. Longitudinal train dynamics simulations show that polymer draft gears have significantly longer deflections than friction draft gears in normal train operations. The maximum draft gear working velocities are lower than 0.2 m/s, which are significantly lower than the impact velocities during shunting operations. Draft gears' in-train characteristics are similar to their static characteristics but are very different from their impact characteristics; this conclusion has also been reached from frequency response simulations. An analysis of gangway bridge plate failures was also conducted and it was found that they were caused by coupler angling behaviour and long draft gear deflections.

  20. Self reinforcing polymer composites

    SciTech Connect

    Kenig, S.

    1993-12-31

    In the advent of liquid crystalline polymers (LCPs), self reinforcing polymer composites comprising a polymer matrix and an LCP reinforcement, have become a reality. The so called self reinforcement is due to the LCPs orientability characteristics resulting from their rigid molecular backbone and anisotropy structure in the fluid state. Orientation development takes place during melt processing of the LCP composite blends where shear as well as elongational flows occur prior to consolidation to the solid state. By proper flow control anisotropy develops and in-situ composites are obtained. Polymer composites comprising self-reinforcement by LCPs during processing induced flow, were analyzed and studied with respect to their orientation development and resultant mechanical properties. The analysis commenced with the hydrodynamics of immiscible fluids in shear and elongational flows. Based on the analysis, orientation and morphology development in capillary extrusion was studied, using a variety of thermoplastic polymer matrices like amorphous and crystalline polyamides, polycarbonate and polyester in conjunction of a naphthalene based thermotropic LCP. Based on the flow-morphology relationship the amorphous polyamide/LCP composite was further investigated as it exhibited enhanced properties. Laminated composites based on LCP/amorphous polyamide were developed composed of unidirectional extruded and drawn sheets that were subsequently compression molded. Unidirectional, +45/{minus}45 and quasi-isotropic laminates were prepared and analyzed as to their microstructure and mechanical properties.