Investigation of ionic conduction in PEO-PVDF based blend polymer electrolytes

NASA Astrophysics Data System (ADS)

Patla, Subir Kumar; Ray, Ruma; Asokan, K.; Karmakar, Sanat

2018-03-01

We investigate the effect of blend host polymer on solid polymer electrolyte (SPE) films doped with ammonium iodide (NH4I) salt using a variety of experimental techniques. Structural studies on the composite SPEs show that the blending of Poly(ethylene oxide) (PEO)-Poly(vinylidene fluoride) (PVDF) polymers in a suitable ratio enhances the amorphous fraction of the polymer matrix and facilitates fast ion conduction through it. We observe that the addition of a small amount of PVDF in the PEO host polymer enhances the ion - polymer interaction leading to more ion dissociation. As a result, the effective number of mobile charge carriers within the polymer matrix increases. Systematic investigation in these blend SPEs shows that the maximum conductivity (1.01 × 10-3 S/cm) is obtained for PEO - rich (80 wt. % PEO, 20 wt. % PVDF) composites at 35 wt. % NH4I concentration at room temperature. Interestingly, at higher salt concentrations (above 35 wt. %), the conductivity is found to decrease in this system. The reduction of conductivity at higher salt concentrations is the consequence of decrease in the carrier concentration due to the formation of an ion pair and ion aggregates. PVDF-rich compositions (20 wt. % PEO and 80 wt. % PVDF), on the other hand, show a very complex porous microstructure. We also observe a much lower ionic conductivity (maximum ˜ 10-6 S/cm at 15 wt. % salt) in these composite systems relative to PEO-rich composites.

Fundamental Studies of Low Velocity Impact Resistance of Graphite Fiber Reinforced Polymer Matrix Composites. Ph.D. Thesis

NASA Technical Reports Server (NTRS)

Bowles, K. J.

1985-01-01

A study was conducted to relate the impact resistance of graphite fiber reinforced composites with matrix properties through gaining an understanding of the basic mechanics involved in the deformation and fracture process, and the effect of the polymer matrix structure on these mechanisms. It was found that the resin matrix structure influences the composite impact resistance in at least two ways. The integration of flexibilizers into the polymer chain structure tends to reduce the T sub g and the mechanical properties of the polymer. The reduction in the mechanical properties of the matrix does not enhance the composite impact resistance because it allows matrix controlled failure to initiate impact damage. It was found that when the instrumented dropweight impact tester is used as a means for assessing resin toughness, the resin toughness is enhanced by the ability of the clamped specimen to deflect enough to produce sufficient membrane action to support a significant amount of the load. The results of this study indicate that crossplied composite impact resistance is very much dependent on the matrix mechanical properties.

Tailorable drug capacity of dexamethasone-loaded conducting polymer matrix

NASA Astrophysics Data System (ADS)

Krukiewicz, K.

2018-05-01

The unique properties of conducting polymers, which are in the same time biocompatible and electrically responsive materials, make them perfect candidates for controlled drug release systems. In this study, the electrically-triggered controlled release system based on dexamethasone-loaded poly (3, 4-ethylenedioxypyrrole) (PEDOP) matrix is described. It is shown that the electropolymerization conditions can facilitate or suppress the formation of PEDOP/Dex matrix, as well as they can have the effect on its electrochemical performance. The release experiments performed in three different modes show that the drug capacity of PEDOP matrix increases with the increase in Dex concentration in the step of matrix synthesis, and higher Dex concentrations make it easier to control the amount of Dex released in an electrically-triggered mode. These results confirm the importance of the careful optimization of immobilization conditions to maximize drug capacity of matrix and maintain its electrochemical properties.

Acid-doped polymer nanofiber framework: Three-dimensional proton conductive network for high-performance fuel cells

NASA Astrophysics Data System (ADS)

Tanaka, Manabu; Takeda, Yasushi; Wakiya, Takeru; Wakamoto, Yuta; Harigaya, Kaori; Ito, Tatsunori; Tarao, Takashi; Kawakami, Hiroyoshi

2017-02-01

High-performance polymer electrolyte membranes (PEMs) with excellent proton conductivity, gas barrier property, and membrane stability are desired for future fuel cells. Here we report the development of PEMs based on our proposed new concept "Nanofiber Framework (NfF)." The NfF composite membranes composed of phytic acid-doped polybenzimidazole nanofibers (PBINf) and Nafion matrix show higher proton conductivity than the recast-Nafion membrane without nanofibers. A series of analyses reveal the formation of three-dimensional network nanostructures to conduct protons and water effectively through acid-condensed layers at the interface of PBINf and Nafion matrix. In addition, the NfF composite membrane achieves high gas barrier property and distinguished membrane stability. The fuel cell performance by the NfF composite membrane, which enables ultra-thin membranes with their thickness less than 5 μm, is superior to that by the recast-Nafion membrane, especially at low relative humidity. Such NfF-based high-performance PEM will be accomplished not only by the Nafion matrix used in this study but also by other polymer electrolyte matrices for future PEFCs.

Metallized Nanotube Polymer Composite (MNPC) and Methods for Making Same

NASA Technical Reports Server (NTRS)

Harrison, Joycelyn S. (Inventor); Lowther, Sharon E. (Inventor); Lillehei, Peter T. (Inventor); Park, Cheol (Inventor); Taylor, Larry (Inventor); Kang, Jin Ho (Inventor); Nazem, Negin (Inventor); Kim, Jae-Woo (Inventor); Sauti, Godfrey (Inventor)

2017-01-01

A novel method to develop highly conductive functional materials which can effectively shield various electromagnetic effects (EMEs) and harmful radiations. Metallized nanotube polymer composites (MNPC) are composed of a lightweight polymer matrix, superstrong nanotubes (NT), and functional nanoparticle inclusions. MNPC is prepared by supercritical fluid infusion of various metal precursors (Au, Pt, Fe, and Ni salts), incorporated simultaneously or sequentially, into a solid NT-polymer composite followed by thermal reduction. The infused metal precursor tends to diffuse toward the nanotube surface preferentially as well as the surfaces of the NT-polymer matrix, and is reduced to form nanometer-scale metal particles or metal coatings. The conductivity of the MNPC increases with the metallization, which provides better shielding capabilities against various EMEs and radiations by reflecting and absorbing EM waves more efficiently. Furthermore, the supercritical fluid infusion process aids to improve the toughness of the composite films significantly regardless of the existence of metal.

Dispersion and Mechanical Properties of Carbon Nanotube/Polymer Composites via Melt Compounding

NASA Astrophysics Data System (ADS)

Gorga, Russell; Cohen, Robert

2003-03-01

This work is focused on the fabrication of carbon nanotube/ polymer composites via melt compounding. The main objective of this work is to realize the outstanding properties of carbon nanotubes (high modulus, high thermal and electrical conductivity, elastic buckling) at the macroscopic level by blending carbon nanotubes into a polymer matrix. The challenge lies in dispersing these one dimensional nanoparticles in the polymer matrix. Dispersion of the nanotubes in the composites is analyzed via transmission and scanning electron microscopy. Mechanical properties as well as electrical and thermal conductivity are measured as a function of nanotube loading, orientation, and extrusion conditions. Multi-wall nanotube loadings in the range of 1 and 10 wtconcave-downward departures from the linear stress-strain behavior of the unmodified polymer below 5observations are discussed in the context of possible deformation mechanisms for the nanotube composites.

A solid state actuator based on polypyrrole (PPy) and a solid electrolyte NBR working in air

NASA Astrophysics Data System (ADS)

Cho, Misuk; Nam, Jaedo; Choi, Hyouk Ryeol; Koo, Jachoon; Lee, Youngkwan

2005-05-01

The solid polymer electrolyte based conducting polymer actuator was presented. In the preparation of acutuator module, an ionic liquid impregnated a synthetic rubber (NBR) and PPy were used as a solid polymer electrolyte and conducting polymer, respectively. An ionic liquid, 1-butyl-3-methylimidazolium bis (trifluoromethyl sulfonyl)imide (BMITFSI) is gradually dispersed into the NBR film and the conducting polymer, PPy was synthesized on the surface of NBR. The ionic conductivity of new type solid polymer electrolyte as a function of the immersion time was investigated. The cyclic voltammetry responsed and the redox switching dynamics of PEDOT in NBR matrix were studied. The displacement of the actuator was measured by laser beam.

Matrix-assisted laser desorption/ionization mass spectrometric analysis of poly(3,4-ethylenedioxythiophene) in solid-state dye-sensitized solar cells: comparison of in situ photoelectrochemical polymerization in aqueous micellar and organic media.

PubMed

Zhang, Jinbao; Ellis, Hanna; Yang, Lei; Johansson, Erik M J; Boschloo, Gerrit; Vlachopoulos, Nick; Hagfeldt, Anders; Bergquist, Jonas; Shevchenko, Denys

2015-04-07

Solid-state dye-sensitized solar cells (sDSCs) are devoid of such issues as electrolyte evaporation or leakage and electrode corrosion, which are typical for traditional liquid electrolyte-based DSCs. Poly(3,4-ethylenedioxythiophene) (PEDOT) is one of the most popular and efficient p-type conducting polymers that are used in sDSCs as a solid-state hole-transporting material. The most convenient way to deposit this insoluble polymer into the dye-sensitized mesoporous working electrode is in situ photoelectrochemical polymerization. Apparently, the structure and the physicochemical properties of the generated conducting polymer, which determine the photovoltaic performance of the corresponding solar cell, can be significantly affected by the preparation conditions. Therefore, a simple and fast analytical method that can reveal information on polymer chain length, possible chemical modifications, and impurities is strongly required for the rapid development of efficient solar energy-converting devices. In this contribution, we applied matrix-assisted laser desorption/ionization mass spectrometry (MALDI MS) for the analysis of PEDOT directly on sDSCs. It was found that the PEDOT generated in aqueous micellar medium possesses relatively shorter polymeric chains than the PEDOT deposited from an organic medium. Furthermore, the micellar electrolyte promotes a transformation of one of the thiophene terminal units to thiophenone. The introduction of a carbonyl group into the PEDOT molecule impedes the growth of the polymer chain and reduces the conductivity of the final polymer film. Both the simplicity of sample preparation (only application of the organic matrix onto the solar cell is needed) and the rapidity of analysis hold the promise of making MALDI MS an essential tool for the physicochemical characterization of conducting polymer-based sDSCs.

Solid electrolytes

DOEpatents

Abraham, Kuzhikalail M.; Alamgir, Mohamed

1993-06-15

This invention pertains to Li ion (Li.sup.+) conductive solid polymer electrolytes composed of solvates of Li salts immobilized (encapsulated) in a solid organic polymer matrix. In particular, this invention relates to solid polymer electrolytes derived by immobilizing complexes (solvates) formed between a Li salt such as LiAsF.sub.6, LiCF.sub.3 SO.sub.3 or LiClO.sub.4 and a mixture of aprotic organic solvents having high dielectric constants such as ethylene carbonate (EC) (dielectric constant=89.6) and propylene carbonate (PC) (dielectric constant=64.4) in a polymer matrix such as polyacrylonitrile, poly(tetraethylene glycol diacrylate), or poly(vinyl pyrrolidinone).

Modeling the Role of Bulk and Surface Characteristics of Carbon Fiber on Thermal Conductance across the Carbon Fiber/Matrix Interface (Postprint)

DTIC Science & Technology

2015-11-09

Osguthorpe, D. J.; Wolff, J.; Genest, M.; Hagler, A. T. Structure and Energetics of Ligand Binding to Proteins: Escherichia Coli Dihydrofolate...available at DOI: 10.1021/acsami.5b08591 14. ABSTRACT (Maximum 200 words) The rapid heating of carbon-fiber-reinforced polymer matrix composites leads ...polymer matrix composites leads to complex thermophysical interactions which not only are dependent on the thermal properties of the constituents and

Electrical percolation in graphene–polymer composites

NASA Astrophysics Data System (ADS)

Marsden, A. J.; Papageorgiou, D. G.; Vallés, C.; Liscio, A.; Palermo, V.; Bissett, M. A.; Young, R. J.; Kinloch, I. A.

2018-07-01

Electrically conductive composites comprising polymers and graphene are extremely versatile and have a wide range of potential applications. The conductivity of these composites depends on the choice of polymer matrix, the type of graphene filler, the processing methodology, and any post-production treatments. In this review, we discuss the progress in graphene–polymer composites for electrical applications. Graphene filler types are reviewed, the progress in modelling these composites is outlined, the current optimal composites are presented, and the example of strain sensors is used to demonstrate their application.

Electrically conductive, optically transparent polymer/carbon nanotube composites

NASA Technical Reports Server (NTRS)

Smith, Jr., Joseph G. (Inventor); Connell, John W. (Inventor); Ounaies, Zoubeida (Inventor); Park, Cheol (Inventor); Harrison, Joycelyn S. (Inventor); Watson, Kent A. (Inventor)

2011-01-01

The present invention is directed to the effective dispersion of carbon nanotubes (CNTs) into polymer matrices. The nanocomposites are prepared using polymer matrices and exhibit a unique combination of properties, most notably, high retention of optical transparency in the visible range (i.e., 400-800 nm), electrical conductivity, and high thermal stability. By appropriate selection of the matrix resin, additional properties such as vacuum ultraviolet radiation resistance, atomic oxygen resistance, high glass transition (T.sub.g) temperatures, and excellent toughness can be attained. The resulting nanocomposites can be used to fabricate or formulate a variety of articles such as coatings on a variety of substrates, films, foams, fibers, threads, adhesives and fiber coated prepreg. The properties of the nanocomposites can be adjusted by selection of the polymer matrix and CNT to fabricate articles that possess high optical transparency and antistatic behavior.

Gold nanoparticle-polymer nanocomposites synthesized by room temperature atmospheric pressure plasma and their potential for fuel cell electrocatalytic application

PubMed Central

Zhang, Ri-Chao; Sun, Dan; Zhang, Ruirui; Lin, Wen-Feng; Macias-Montero, Manuel; Patel, Jenish; Askari, Sadegh; McDonald, Calum; Mariotti, Davide; Maguire, Paul

2017-01-01

Conductive polymers have been increasingly used as fuel cell catalyst support due to their electrical conductivity, large surface areas and stability. The incorporation of metal nanoparticles into a polymer matrix can effectively increase the specific surface area of these materials and hence improve the catalytic efficiency. In this work, a nanoparticle loaded conductive polymer nanocomposite was obtained by a one-step synthesis approach based on room temperature direct current plasma-liquid interaction. Gold nanoparticles were directly synthesized from HAuCl4 precursor in poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS). The resulting AuNPs/PEDOT:PSS nanocomposites were subsequently characterized under a practical alkaline direct ethanol fuel cell operation condition for its potential application as an electrocatalyst. Results show that AuNPs sizes within the PEDOT:PSS matrix are dependent on the plasma treatment time and precursor concentration, which in turn affect the nanocomposites electrical conductivity and their catalytic performance. Under certain synthesis conditions, unique nanoscale AuNPs/PEDOT:PSS core-shell structures could also be produced, indicating the interaction at the AuNPs/polymer interface. The enhanced catalytic activity shown by AuNPs/PEDOT:PSS has been attributed to the effective electron transfer and reactive species diffusion through the porous polymer network, as well as the synergistic interfacial interaction at the metal/polymer and metal/metal interfaces. PMID:28436454

Gold nanoparticle-polymer nanocomposites synthesized by room temperature atmospheric pressure plasma and their potential for fuel cell electrocatalytic application

NASA Astrophysics Data System (ADS)

Zhang, Ri-Chao; Sun, Dan; Zhang, Ruirui; Lin, Wen-Feng; Macias-Montero, Manuel; Patel, Jenish; Askari, Sadegh; McDonald, Calum; Mariotti, Davide; Maguire, Paul

2017-04-01

Conductive polymers have been increasingly used as fuel cell catalyst support due to their electrical conductivity, large surface areas and stability. The incorporation of metal nanoparticles into a polymer matrix can effectively increase the specific surface area of these materials and hence improve the catalytic efficiency. In this work, a nanoparticle loaded conductive polymer nanocomposite was obtained by a one-step synthesis approach based on room temperature direct current plasma-liquid interaction. Gold nanoparticles were directly synthesized from HAuCl4 precursor in poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS). The resulting AuNPs/PEDOT:PSS nanocomposites were subsequently characterized under a practical alkaline direct ethanol fuel cell operation condition for its potential application as an electrocatalyst. Results show that AuNPs sizes within the PEDOT:PSS matrix are dependent on the plasma treatment time and precursor concentration, which in turn affect the nanocomposites electrical conductivity and their catalytic performance. Under certain synthesis conditions, unique nanoscale AuNPs/PEDOT:PSS core-shell structures could also be produced, indicating the interaction at the AuNPs/polymer interface. The enhanced catalytic activity shown by AuNPs/PEDOT:PSS has been attributed to the effective electron transfer and reactive species diffusion through the porous polymer network, as well as the synergistic interfacial interaction at the metal/polymer and metal/metal interfaces.

Effects of vacancy defects on the interfacial shear strength of carbon nanotube reinforced polymer composite.

PubMed

Chowdhury, Sanjib Chandra; Okabe, Tomonaga; Nishikawa, Masaaki

2010-02-01

We investigate the effects of the vacancy defects (i.e., missing atoms) in carbon nanotubes (CNTs) on the interfacial shear strength (ISS) of the CNT-polyethylene composite with the molecular dynamics simulation. In the simulation, the crystalline polyethylene matrix is set up in a hexagonal array with the polymer chains parallel to the CNT axis. Vacancy defects in the CNT are introduced by removing the corresponding atoms from the pristine CNT (i.e., CNT without any defect). Three patterns of vacancy defects with three different sizes are considered. Two types of interfaces, with and without cross-links between the CNT and the matrix are also considered here. Polyethylene chains are used as cross-links between the CNT and the matrix. The Brenner potential is used for the carbon-carbon interaction in the CNT, while the polymer is modeled by a united-atom potential. The nonbonded van der Waals interaction between the CNT and the polymer matrix and within the polymer matrix itself is modeled with the Lennard-Jones potential. To determine the ISS, we conduct the CNT pull-out from the polymer matrix and the ISS has been estimated with the change of total potential energy of the CNT-polymer system. The simulation results reveal that the vacancy defects significantly influence the ISS. Moreover, the simulation clarifies that CNT breakage occurs during the pull-out process for large size vacancy defect which ultimately reduces the reinforcement.

Lowering the Percolation Threshold of Conductive Composites Using Particulate Polymer Microstructure

NASA Astrophysics Data System (ADS)

Grunlan, Jaime; Gerberich, William; Francis, Lorraine

2000-03-01

In an effort to lower the percolation threshold of carbon black-filled polymer composites, various polymer microstructures were examined. Composites were prepared using polyvinyl acetate (PVAc) latex, PVAc water-dispersible powder and polyvinylpyrrolidone (PVP) solution as the matrix starting material. Composites prepared using the particulate microstructures showed a significantly lowered percolation threshold relative to an equivalently prepared composite using the PVP solution. The PVAc latex-based composites has a percolation threshold of 3 volthe PVP solution-based composite yielded a percolation threshold near 15 voloccupied by polymer particles, the particulate matrix-based composites create a segregated CB network at low filler concentration.

Solid polymer electrolyte lithium batteries

DOEpatents

Alamgir, M.; Abraham, K.M.

1993-10-12

This invention pertains to Lithium batteries using Li ion (Li[sup +]) conductive solid polymer electrolytes composed of solvates of Li salts immobilized in a solid organic polymer matrix. In particular, this invention relates to Li batteries using solid polymer electrolytes derived by immobilizing solvates formed between a Li salt and an aprotic organic solvent (or mixture of such solvents) in poly(vinyl chloride). 3 figures.

Solid polymer electrolyte lithium batteries

DOEpatents

Alamgir, Mohamed; Abraham, Kuzhikalail M.

1993-01-01

This invention pertains to Lithium batteries using Li ion (Li.sup.+) conductive solid polymer electrolytes composed of solvates of Li salts immobilized in a solid organic polymer matrix. In particular, this invention relates to Li batteries using solid polymer electrolytes derived by immobilizing solvates formed between a Li salt and an aprotic organic solvent (or mixture of such solvents) in poly(vinyl chloride).

Conducting nanotubes or nanostructures based composites, method of making them and applications

NASA Technical Reports Server (NTRS)

Gupta, Mool C. (Inventor); Yang, Yonglai (Inventor); Dudley, Kenneth L. (Inventor); Lawrence, Roland W. (Inventor)

2013-01-01

An electromagnetic interference (EMI) shielding material includes a matrix of a dielectric or partially conducting polymer, such as foamed polystyrene, with carbon nanotubes or other nanostructures dispersed therein in sufficient concentration to make the material electrically conducting. The composite is formed by dispersing the nanotube material in a solvent in which the dielectric or partially conducting polymer is soluble and mixing the resulting suspension with the dielectric or partially conducting polymer. A foaming agent can be added to produce a lightweight foamed material. An organometallic compound can be added to enhance the conductivity further by decomposition into a metal phase.

Ion conduction in high ion content PEO-based ionomers

NASA Astrophysics Data System (ADS)

Caldwell, David, II; Maranas, Janna

Solid Polymer Electrolytes (SPEs) can enable the design of batteries that are safer and have higher capacity than batteries with traditional volatile organic electrolytes. The current limitation for SPEs is their low conductivity, resulting from a conduction mechanism strongly coupled to the dynamics of the polymer host matrix. Our previous work indicated the possibility of a conduction mechanism through the use of ion aggregates. In order to investigate this mechanism, we performed a series of molecular dynamics simulations of PEO-based ionomers at high ion content. Our results indicate that conduction through ion aggregates are partially decoupled from polymer dynamics and could enable the development of higher conductive SPEs.

The optical and electrical properties of graphene oxide with water-soluble conjugated polymer composites by radiation.

PubMed

Jungo, Seung Tae; Oh, Seung-Hwan; Kim, Hyun Bin; Jeun, Joon-Pyo; Lee, Bum-Jae; Kang, Phil-Hyun

2013-11-01

In order to overcome the difficulty of dispersion and low conductivity in composite containing graphene, graphene oxide (GO) has been used instead of neat graphene. And the GO treated by radiation, could give improved conductivity of the GO-containing polymer composite. In this study, fluorene based water-soluble conjugated polymer (WPF-6-oxy-F) was introduced in GO solution to investigate the change of optical and electrical properties through radiation process. UV-Vis absorption of irradiated WPF-6-oxy-F-GO composite was red shifted and I(D)/I(G) ratio of Raman spectra decreased. XPS analysis showed that C-N bonds was formed after the irradiation and confirmed the increased bonds between the GO and the water-soluble conjugated polymer matrix. From the AFM and XPS analysis, it was found that the water-soluble conjugated polymer matrix was stacked between the modified GO in the morphology of irradiated WPF-6-oxy-F-GO composite was increased after gamma ray irradiation up to 10(-2) S/cm.

Electrically conductive, optically transparent polymer/carbon nanotube composites and process for preparation thereof

NASA Technical Reports Server (NTRS)

Watson, Kent A. (Inventor); Connell, John W. (Inventor); Harrison, Joycelyn S. (Inventor); Park, Cheol (Inventor); Ounaies, Zoubeida (Inventor); Smith, Joseph G. (Inventor)

2009-01-01

The present invention is directed to the effective dispersion of carbon nanotubes (CNTs) into polymer matrices. The nanocomposites are prepared using polymer matrices and exhibit a unique combination of properties, most notably, high retention of optical transparency in the visible range (i.e., 400 800 nm), electrical conductivity, and high thermal stability. By appropriate selection of the matrix resin, additional properties such as vacuum ultraviolet radiation resistance, atomic oxygen resistance, high glass transition (T.sub.g) temperatures, and excellent toughness can be attained. The resulting nanocomposites can be used to fabricate or formulate a variety of articles such as coatings on a variety of substrates, films, foams, fibers, threads, adhesives and fiber coated prepreg. The properties of the nanocomposites can be adjusted by selection of the polymer matrix and CNT to fabricate articles that possess high optical transparency and antistatic behavior.

Electrically Conductive, Optically Transparent Polymer/Carbon Nanotube Composites and Process for Preparation Thereof

NASA Technical Reports Server (NTRS)

Park, Cheol (Inventor); Connell, John W. (Inventor); Smith, Joseph G. (Inventor); Harrison, Joycelyn S. (Inventor); Watson, Kent A. (Inventor); Ounaies, Zoubeida (Inventor)

2011-01-01

The present invention is directed to the effective dispersion of carbon nanotubes (CNTs) into polymer matrices. The nanocomposites are prepared using polymer matrices and exhibit a unique combination of properties, most notably, high retention of optical transparency in the visible range (i.e., 400-800 nm), electrical conductivity, and high thermal stability. By appropriate selection of the matrix resin, additional properties such as vacuum ultraviolet radiation resistance, atomic oxygen resistance, high glass transition (T.sub.g) temperatures, and excellent toughness can be attained. The resulting nanocomposites can be used to fabricate or formulate a variety of articles such as coatings on a variety of substrates, films, foams, fibers, threads, adhesives and fiber coated prepreg. The properties of the nanocomposites can be adjusted by selection of the polymer matrix and CNT to fabricate articles that possess high optical transparency and antistatic behavior.

Electrically Conductive, Optically Transparent Polymer/Carbon Nanotube Composites and Process for Preparation Thereof

NASA Technical Reports Server (NTRS)

Park, Cheol (Inventor); Watson, A. (Inventor); Ounales, Zoubeida (Inventor); Connell, John W. (Inventor); Smith, Joseph G. (Inventor); Harrison, Joycelyn S. (Inventor)

2009-01-01

The present invention is directed to the effective dispersion of carbon nanotubes (CNTs) into polymer matrices. The nanocomposites are prepared using polymer matrices and exhibit a unique combination of properties, most notably, high retention of optical transparency in the visible range (i.e., 400-800 nm), electrical conductivity, and high thermal stability. By appropriate selection of the matrix resin, additional properties such as vacuum ultraviolet radiation resistance, atomic oxygen resistance, high glass transition (T(sub g)) temperatures, and excellent toughness can be attained. The resulting nanocomposites can be used to fabricate or formulate a variety of articles such as coatings on a variety of substrates, films, foams, fibers, threads, adhesives and fiber coated prepreg. The properties of the nanocomposites can be adjusted hy selection of the polymer matrix and CNT to fabricate articles that possess high optical transparency and antistatic behavior.

Conductivity and properties of polysiloxane-polyether cluster-LiTFSI networks as hybrid polymer electrolytes

NASA Astrophysics Data System (ADS)

Boaretto, Nicola; Joost, Christine; Seyfried, Mona; Vezzù, Keti; Di Noto, Vito

2016-09-01

This report describes the synthesis and the properties of a series of polymer electrolytes, composed of a hybrid inorganic-organic matrix doped with LiTFSI. The matrix is based on ring-like oligo-siloxane clusters, bearing pendant, partially cross-linked, polyether chains. The dependency of the thermo-mechanic and of the transport properties on several structural parameters, such as polyether chains' length, cross-linkers' concentration, and salt concentration is studied. Altogether, the materials show good thermo-mechanical and electrochemical stabilities, with conductivities reaching, at best, 8·10-5 S cm-1 at 30 °C. In conclusion, the cell performances of one representative sample are shown. The scope of this report is to analyze the correlations between structure and properties in networked and hybrid polymer electrolytes. This could help the design of optimized polymer electrolytes for application in lithium metal batteries.

Preparation, characterization, and surface conductivity of nanocomposites with hollow graphitic carbon nanospheres as fillers in polymethylmethacrylate matrix

NASA Astrophysics Data System (ADS)

Zhang, Cheng; Gao, Qingshan; Zhou, Bing; Bhargava, Gaurang

2017-08-01

Hollow graphitized carbon nanosphere (CNS) materials with inner diameter of 20 to 50 nm and shell thickness of 10 15 nm were synthesized from the polymerization of resorcinol (R) and formaldehyde (F) in the presence of a well-characterized iron polymeric complex (IPC). The CNS with unique nanostructures was used to fabricate CNS-polymer composites by dispersing CNS as fillers in the polymer matrix. Aggregation of CNS in polymer composites is usually a challenging issue. In this work, we employed in situ polymerization method and melt-mixing method to fabricate CNS-polymethylmethacrylate (PMMA) composites and compared their difference in terms of CNS dispersion in the composites and surface electrical conductivity. Four probes technique was utilized to measure the surface electrical conductivity of the CNS-PMMA composites. The measurements on four points and four silver painted lines on the thin film of CNS-PMMA composites were compared. The in situ polymerization method was found more efficient for better CNS dispersion in PMMA matrix and lower percolation conductivity threshold compared to the melt-mixing method. The enhanced electrical conductivity for CNS-PMMA composites may be attributed to the stronger covalent CNS-PMMA bonding between the surface functional groups and the MMA moieties.

Effect of nanochitosan and succinonitrile on the AC ionic conductivity of plasticized nanocomposite solid polymer electrolytes (PNCSPE)

NASA Astrophysics Data System (ADS)

Karuppasamy, K.; Vani, C. Vijil; Nichelson, A.; Balakumar, S.; Shajan, X. Sahaya

2013-06-01

In the present study, the filler chitosan was converted into nanochitosan by ionotropic gelation method. Plasticized nanocomposite solid polymer electrolytes (PNCSPE) composed of poly ethylene oxide as host polymer, LiBOB (lithium bis(oxalatoborate)) as salt, SN as plasticizer and nanochitosan as filler were prepared by membrane hot-press technique. Succinonitrile and nanochitosan incorporation in PEO-LiBOB matrix enhanced the room temperature ionic conductivity. The highest ionic conductivities were found to be in the order of 10-3.2 S/cm.

Novel polymer composite having diamond particles and boron nitride platelets for thermal management of electric vehicle motors

NASA Astrophysics Data System (ADS)

Nakajima, Anri; Shoji, Atsushi; Yonemori, Kei; Seo, Nobuhide

2016-02-01

Thermal conductivities of silicone matrix polymers including fillers of diamond particles and/or hexagonal boron nitride (h-BN) platelets were systematically investigated in an attempt to find a thermal interface material (TIM) having high isotropic thermal conductivity and high electrical insulating ability to enable efficient heat dissipation from the motor coil ends of electric vehicles. The TIM with mixed fillers of diamond particles and h-BN platelets had a maximum thermal conductivity of 6.1 W m-1 K-1 that was almost isotropic. This is the highest value among the thermal conductivities of TIMs with silicone matrix polymer reported to date. The mechanism behind the thermal conductivity of the TIMs was also examined from the viewpoint of the change in the number of thermally conductive networks and/or a decrease in the thermal resistivity of junctions of neighboring diamond particles through the incorporation of h-BN platelets. The TIMs developed in this study will make it possible to manage the heat of electric motors and will help to popularize electric vehicles.

Nanocrystal-polymer nanocomposite electrochromic device

DOEpatents

Milliron, Delia; Runnerstrom, Evan; Helms, Brett; Llordes, Anna; Buonsanti, Raffaella; Garcia, Guillermo

2015-12-08

Described is an electrochromic nanocomposite film comprising a solid matrix of an oxide based material, the solid matrix comprising a plurality of transparent conducting oxide (TCO) nanostructures dispersed in the solid matrix and a lithium salt dispersed in the solid matrix. Also described is a near infrared nanostructured electrochromic device having a functional layer comprising the electrochromic nanocomposite film.

Preparation and crystalline studies of PVDF hybrid composites

NASA Astrophysics Data System (ADS)

Chethan P., B.; Renukappa, N. M.; Sanjeev, Ganesh

2018-04-01

The conducting polymer composites have become increasingly important for electrical and electronic applications due to their flexibility, easy of processing, high strength and low cost. A flexible conducting polymer hybrid composite was prepared by melt mixing of nickel coated multi-walled carbon nanotubes (Ni-MWNT) and graphitized carbon nanofibres (GCNF) in Polyvinylidene fluoride (PVDF) matrix. The crystalline structures of the nano composites were studied by X-ray diffraction (XRD) method and showed characteristic peaks at 17.7°, 18.5°, 20° and 26.7° of 2θ. The β phase crystalline nature of the composite films, degree of crystallinity, melting temperature and crystallization behavior of the hybrid composites were studied using appropriate characterization techniques. The filler in the insulating polymer matrix plays crucial role to improve the crystallinity of the composites.

Processable high temperature resistant polymer matrix materials

NASA Technical Reports Server (NTRS)

Serafini, T. T.

1975-01-01

A review is presented of studies conducted with addition-cured polyimides, giving particular attention to an improved method involving in situ polymerization of monomer reactants (PMR) on the surface of the reinforcing fibers. The studies show that the PMR approach provides a powerful method for fabricating high performance polymer matrix composites. Significant advantages of the PMR approach are related to the superior high temperature properties of the obtained material, lower cost, greater safety, and processing versatility.

Role of succinonitrile in improving ionic conductivity of sodium-ion conductive polymer electrolyte

NASA Astrophysics Data System (ADS)

Nair, Manjula G.; Mohapatra, Saumya R.

2018-05-01

Sodium ion conducting solid polymer electrolytes were prepared using poly (ethylene oxide) (PEO) as polymer matrix, sodium perchlorate (NaClO4) as salt and succinonitrile (SN) as a plasticizer by solution casting technique. By blending a plastic crystal such as succinonitrile (SN) with PEO-NaClO4 electrolyte system, we aimed at improving the ionic conductivity by weakening the ether oxygen-Na+ interactions. The XRD and FTIR studies revealed structural and micro-structural changes in the blended electrolytes which aids in improving ionic conductivity. Also, DSC measurements showed improved segmental motion in the blended polymer electrolytes due to plasticizing effect of SN. The maximum ionic conductivity observed at room temperature is 1.13×10-5 S cm-1 merely for 7 wt. % of SN, which is one order higher than pure polymer-salt complex. The thermo-gravimetric analysis (TGA) suggests that blending of SN with polymer electrolyte had no detrimental effect on its thermal stability.

Polymer-mediated tunneling transport between carbon nanotubes in nanocomposites.

PubMed

Derosa, Pedro A; Michalak, Tyler

2014-05-01

Electron transport in nanocomposites has attracted a good deal of attention for some time now; furthermore, the ability to control its characteristics is a necessary step in the design of multifunctional materials. When conductive nanostructures (for example carbon nanotubes) are inserted in a non-conductive matrix, electron transport below the percolation threshold is dominated by tunneling and thus the conductive characteristics of the composite depends heavily on the characteristics of the tunneling currents between nanoinserts. A parameter-free approach to study tunneling transport between carbon nanotubes across a polymer matrix is presented. The calculation is done with a combination of Density Functional Theory and Green functions (an approach heavily used in molecular electronics) which is shown here to be effective in this non-resonant transport condition. The results show that the method can effectively capture the effect of a dielectric layer in tunneling transport. The current is found to exponentially decrease with the size of the gap for both vacuum and polymer, and that the polymer layer lowers the tunneling barrier enhancing tunneling conduction. For a polyacrylonitrile matrix, a four-fold decrease in the tunneling constant, compared to tunneling in vacuum, is observed, a result that is consistent with available information. The method is very versatile as any DFT functional (or any other quantum mechanics method) can be used and thus the most accurate method for each particular system can be chosen. Furthermore as more methods become available, the calculations can be revised and improved. This approach can be used to design functional materials for fine-tunning the tunneling transport, for instance, the effect of modifying the nanoinsert-matrix interface (for example, by adding functional groups to carbon nanotubes) can be captured and the comparative performance of each interface predicted by simulation.

Electric Field Activated Shape Memory Polymer Composite

NASA Technical Reports Server (NTRS)

Kang, Jin Ho (Inventor); Turner, Travis L. (Inventor); Siochi, Emilie J. (Inventor); Penner, Ronald K. (Inventor)

2017-01-01

Provided is an electrically activated shape memory polymer composite capable of thermal shape reformation using electric power to heat the composite through its matrix glass transition temperature. The composite includes an adaptable polymer matrix component using a diglycidyl ether resin, at least one substantially well-dispersed conductive or magnetic nano-filler component, and at least one elastic, laminated layer. Also provided are methods of preparing the composite and methods of activating the composite. A shape reformation of the composite is triggered by applying an electric field at DC and/or at a frequency above about 1.mu.Hz for a sufficient time.

Polymer Composite Containing Carbon Nanotubes and their Applications.

PubMed

Park, Sung-Hoon; Bae, Joonwon

2017-07-10

Carbon nanotubes (CNTs) are attractive nanostructures in this regard, primarily due to their high aspect ratio coupled with high thermal and electrical conductivities. Consequently, CNT polymer composites have been extensively investigated for various applications, owing to their light weight and processibility. However, there have been several issues affecting the utilization of CNTs, such as aggregation (bundling) which leads to a non-uniform dispersion and poor interfacial bonding of the CNTs with the polymer, resulting in variation in composite performance, along with the additional issue of high cost of CNTs. In this article, recent research and patents for polymer composites containing carbon nanomaterial are presented and summarized. In addition, a rationale for optimally designed carbon nanotube polymer composites and their applications are suggested. Above the electrical percolation threshold, a transition from insulator to conductor occurs. The percolation threshold values of CNT composite are dependent on filler shape, intrinsic properties of filler, type of polymer, CNT dispersion condition and so on. Different values of percolation threshold CNT polymer composites have been summarized. The difference in percolation threshold and conductivity of CNT composites could be explained by the degree of effective interactions between nanotubes and polymer matrix. The reaction between surface functional groups of CNTs and polymer could contribute to better dispersion of CNTs in polymer matrix. Consequently, it increased the number of electrical networks of CNTs in polymer, resulting in an enhancement of composite conductivity. In addition, to exfoliate nanotubes from heavy bundles, ultrasonication with proper solvent and three roll milling processes were used. Potential reactions of covalent bonding between functionalized CNTs and polymer were suggested based on the above rationale. Through the use of CNT functionalization, high aspect ratio CNTs, and proper fabrication, uniform dispersion of nanotubes in polymer can be achieved leading to considerable improvement in electrical conductivity and electromagnetic interference (EMI) shielding properties. Copyright© Bentham Science Publishers; For any queries, please email at epub@benthamscience.org.

Prospects for using carbon-carbon composites for EMI shielding

NASA Technical Reports Server (NTRS)

Gaier, James R.

1990-01-01

Since pyrolyzed carbon has a higher electrical conductivity than most polymers, carbon-carbon composites would be expected to have higher electromagnetic interference (EMI) shielding ability than polymeric resin composites. A rule of mixtures model of composite conductivity was used to calculate the effect on EMI shielding of substituting a pyrolyzed carbon matrix for a polymeric matrix. It was found that the improvements were small, no more than about 2 percent for the lowest conductivity fibers (ex-rayon) and less than 0.2 percent for the highest conductivity fibers (vapor grown carbon fibers). The structure of the rule of mixtures is such that the matrix conductivity would only be important in those cases where it is much higher than the fiber conductivity, as in metal matrix composites.

Polyaniline-CuO hybrid nanocomposite with enhanced electrical conductivity

NASA Astrophysics Data System (ADS)

de Souza, Vânia S.; da Frota, Hidembergue O.; Sanches, Edgar A.

2018-02-01

A hybrid nanocomposite based on a polymer matrix constituted of Polyaniline Emeraldine-salt form (PANI-ES) reinforced by copper oxide II (CuO) particles was obtained by in situ polymerization. Structural, morphological and electrical properties of the pure materials and nanocomposite form were investigated. The presence of CuO particles in the nanocomposite material affected the natural alignment of the polymer chains. XRD technique allowed the visualization of the polymer amorphization in the nanocomposite form, suggesting an interaction between both phases. The FTIR spectra confirmed this molecular interaction due to the blue shift of the characteristic absorption peaks of PANI-ES in the nanocomposite form. SEM images revealed that the polymer nanofiber morphology was no longer observed in the nanocomposite. The CuO spherical particles are randomly dispersed in the polymer matrix. The density functional theory plus the Coulomb interaction method revealed a charge transfer from PANI to CuO slab. Moreover, the density of states (DOS) has revealed that the nanocomposite behaves as a metal. In agreement, the electrical conductivity showed an increase of 60% in the nanocomposite material.

A bio-material: mechanical behaviour of LDPE-Al2O3-TiO2

NASA Astrophysics Data System (ADS)

Dhabale, R.; Jatti, V. S.

2016-09-01

Polymer composites are prominent candidate for polymeric bio-composites due to its low cost, high strength and ease of manufacturing. However, they suffer from low mechanical properties such as high wear rate and low hardness. In view of this, present study focuses on the synthesis of hybrid bio polymer matrix composites using low density polyethylene as matrix material with reinforcing material namely, alumina and titanium oxide. The samples were fabricated as per ASTM standard by varying the percentage of reinforcing particles using injection moulding machine. Various tests namely, tensile, flexural, impact, hardness, wear, SEM and corrosion were conducted on the prepared samples. On the basis of the experimental results, it can be concluded that injection moulding process can fabricate defect free cast samples. Polymer matrix composites of 70%LDPE +10% TiO2 +20% Al2O3 composition is biocompatible and a good candidate for biomaterial. Thus based on the inference of this study the above polymer matrix composite is suitable for orthopaedic applications and can be applied on hard and soft tissues of implantable materials in a human body.

Polymer-based materials to be used as the active element in microsensors: a scanning force microscopy study

PubMed

Porter; Eastman; Pace; Bradley

2000-09-01

Polymer-based materials can be incorporated as the active sensing elements in chemiresistor devices. Most of these devices take advantage of the fact that certain polymers will swell when exposed to gaseous analytes. To measure this response, a conducting material such as carbon black is incorporated within the nonconducting polymer matrix. In response to analytes, polymer swelling results in a measurable change in the conductivity of the polymer/carbon composite material. Arrays of these sensors may be used in conjunction with pattern recognition techniques for purposes of analyte recognition and quantification. We have used the technique of scanning force microscopy (SFM) to investigate microstructural changes in carbon-polymer composites formed from the polymers poly (isobutylene) (PIB), poly (vinyl alcohol) (PVA), and poly (ethylene-vinyl acetate) (PEVA) when exposed to the analytes hexane, toluene, water, ethanol, and acetone. Using phase-contrast imaging (PI), changes in the carbon nanoparticle distribution on the surface of the polymer matrix are measured as the polymers are exposed to the analytes in vapor phase. In some but not all cases, the changes were reversible (at the scale of the SFM measurements) upon removal of the analyte vapor. In this paper, we also describe a new type of microsensor based on piezoresistive microcantilever technology. With these new devices, polymeric volume changes accompanying exposure to analyte vapor are measured directly by a piezoresistive microcantilever in direct contact with the polymer. These devices may offer a number of advantages over standard chemiresistor-based sensors.

Broadband Dielectric Spectroscopy and Quasi-Elastic Neutron Scattering on Single-Ion Polymer Conductors

NASA Astrophysics Data System (ADS)

Soles, Christopher; Peng, Hua-Gen; Page, Kirt; Snyder, Chad; Pandy, Ashoutosh; Jeong, Youmi; Runt, James; NIST Collaboration; Pennsylvania Collaboration

2011-03-01

The application of solid polymer electrolytes in rechargeable batteries has not been fully realized after decades of research due to its low conductivity. Dramatic increases of the ion conductivity are needed and this progress requires the understanding of conduction mechanism. We address this topic in two fronts, namely, the effect of plasticizer additives and geometric confinement on the charge transfer mechanism. To this end, we combine broadband dielectric spectroscopy (BDS) to characterize the ion mobility and quasi-elastic neutron scattering (QENS) to quantify segmental motion on a single-ion model polymer electrolyte. Deuterated small molecules were used as plasticizers so that the segmental motion of the polymer electrolyte could be monitored by QENS to understand the mechanism behind the increased conductivity. Anodic aluminum oxide (AAO) membranes with well defined channel sizes are used as the matrix to study the transport of ions solvated in a 1D polymer electrolyte.

TOPICAL REVIEW: Monitoring of polymer melt processing

NASA Astrophysics Data System (ADS)

Alig, Ingo; Steinhoff, Bernd; Lellinger, Dirk

2010-06-01

The paper reviews the state-of-the-art of in-line and on-line monitoring during polymer melt processing by compounding, extrusion and injection moulding. Different spectroscopic and scattering techniques as well as conductivity and viscosity measurements are reviewed and compared concerning their potential for different process applications. In addition to information on chemical composition and state of the process, the in situ detection of morphology, which is of specific interest for multiphase polymer systems such as polymer composites and polymer blends, is described in detail. For these systems, the product properties strongly depend on the phase or filler morphology created during processing. Examples for optical (UV/vis, NIR) and ultrasonic attenuation spectra recorded during extrusion are given, which were found to be sensitive to the chemical composition as well as to size and degree of dispersion of micro or nanofillers in the polymer matrix. By small-angle light scattering experiments, process-induced structures were detected in blends of incompatible polymers during compounding. Using conductivity measurements during extrusion, the influence of processing conditions on the electrical conductivity of polymer melts with conductive fillers (carbon black or carbon nanotubes) was monitored.

Polymer functionalized single-walled carbon nanotube composites and semi-fluorinated quaternary ammonium polymer colloids and coatings

NASA Astrophysics Data System (ADS)

Paul, Abhijit

Scope and Method of Study: Current study focused on understanding of "wetting" and "dewetting" phenomena between surfaces of single-walled carbon nanotubes (SWCNT) which are lightly grafted with polymer chains by reversible-deactivation radical polymerization, when they are mixed with matrix chains of the same architecture as grafts. Effects of grafts to matrix chain lengths on SWCNT dispersion in matrix polymers were studied by measuring electrical conductivity, glass transition temperature, and storage and loss moduli of nanocomposites. Another area of work was to design semi-fluorinated copolymers with core-shell morphology by emulsion polymerization, study their catalytic activities for hydrolyses of Paraoxon, a toxic insecticide, in the forms of both colloidal dispersions and films, and to characterize the surfaces of the films by atomic force microscopy and by dynamic contact angle measurements. Findings and Conclusions: The glass transition temperature ( Tg) of polystyrene (PS) filled with SWCNT grafted with PS of different lengths increased from 99 to 109 °C at 6 wt% of SWCNT followed by a plateau. The heat capacity (DeltaCp ) at Tg continued to decrease only for the smallest chain length grafted PS nanocomposites. SWCNT/PS nanocomposites had low electrical conductivity and showed no percolation threshold due to the thick polymer coatings. A key finding was that the SWCNT surface can accommodate only a fixed numbers of styrene units. Similar results on change in Tg were obtained for SWCNT/PMMA nanocomposites when molecular weight of matrix (Mmatrix) ≥ molecular weight of grafts (Mgraft). No change in DeltaCp was observed for SWCNT/PMMA nanocomposites. "Wetting" to "dewetting" occurred Mmatrix/ Mgraft ≈ 1. For Mmatrix > Mgraft, electrical conductivity of nanocomposites reached the value of 10-9 S cm-1 at 1.0 wt% nanotube loading and had percolation threshold of electrical conductivity at ˜0.25 wt% SWCNT. Raman and UV-vis-NIR data confirmed that grafting methods have little effect on inherent electronic properties of SWCNT. A key observation was that the behavior of polymer-SWCNT composites is analogous to polymer thin films containing two different lengths of chemically same polymers. On the other hand, semifluorinated copolymers had hydrophobic and lipophilic properties similar to homopolymers of poly(perfluoroalkyl methacrylates), but were not active in detoxification of Paraoxon. Therefore, semi-fluorinated latexes can either act as phase transfer catalysts for hydrolysis of organophosporous compounds or repel the compound, but cannot do both.

Anisotropic thermal conductive MWCNT/polymer composites prepared with an immiscible PS/LDPE blend.

PubMed

Kwon, Younghwan

2014-08-01

This study focuses on MWCNT/polymer composites with flexible, anisotropic heat transporting properties. For this study, an immiscible polymer blend of MWCNT/PS and LDPE (13.5:86.5 v:v) were used as a template. MWCNT/PS composites were first prepared by a solution process, and then melt-blended with LDPE using a brabender mixer. For achieving an alignment of MWCNT/PS in LDPE matrix, the blends of MWCNT/PS and LDPE were continuously treated under a fixed shear rate of 10 s(-1) at 210 °C. With partial extraction of PS in the aligned blends, FE-SEM images of the aligned blends revealed morphology of MWCNT in the PS/LDPE matrix, indicating local distribution of MWCNT selectively inside PS, where PS was elongated parallel to shear direction in LDPE matrix. The prepared MWCNT/PS and LDPE blends showed an anisotropic heat transporting behavior with anisotropic ratio of thermal conductivity (AR = λx/λz) up to 1.330 at 10 wt% of MWCNT in PS (equivalent to 1.50 wt% of MWCNT in PS/LDPE).

Electroconductive PET/SWNT Films by Solution Casting

NASA Technical Reports Server (NTRS)

Steinert, Brian W.; Dean, Derrick R.

2008-01-01

The market for electrically conductive polymers is rapidly growing, and an emerging pathway for attaining these materials is via polymer-carbon nanotube (CNT) nanocomposites, because of the superior properties of CNTs. Due to their excellent electrical properties and anisotropic magnetic susceptibility, we expect CNTs could be easily aligned to maximize their effectiveness in imparting electrical conductivity to the polymer matrix. Single-walled carbon nanotubes (SWNT) were dispersed in a polyethylene terephthalate (PET) matrix by solution blending then cast onto a glass substrate to create thin, flexible films. Various SWNT loading concentrations were implemented (0.5, 1.0, and 3.0 wt.%) to study the effect of additive density. The processing method was repeated to produce films in the presence of magnetic fields (3 and 9.4 Tesla). The SWNTs showed a high susceptibility to the magnetic field and were effectively aligned in the PET matrix. The alignment was characterized with Raman spectroscopy. Impedance spectroscopy was utilized to study the electrical behavior of the films. Concentration and dispersion seemed to play very important roles in improving electrical conductivity, while alignment played a secondary and less significant role. The most interesting result proved to be the effect of a magnetic field during processing. It appears that a magnetic field may improve dispersion of unmodified SWNTs, which seems to be more important than alignment. It was concluded that SWNTs offer a good option as conductive, nucleating filler for electroconductive polymer applications, and the utilization of a magnetic field may prove to be a novel method for CNT dispersion that could lead to improved nanocomposite materials.

Preparation of Conductive Polymer Graphite (PG) Composites

NASA Astrophysics Data System (ADS)

Munirah Abdullah, Nur; Saddam Kamarudin, M.; Rus, Anika Zafiah M.; Abdullah, M. F. L.

2017-08-01

The preparation of conductive polymer graphite (PG) composites thin film is described. The thickness of the PG composites due to slip casting method was set approximately ~0.1 mm. The optical microscope (OM) and fourier transform infra-red spectroscopy (FTIR) has been operated to distinguish the structure-property relationships scheme of PG composites. It shows that the graphite is homogenously dispersed in polymer matrix composites. The electrical characteristics of the PG composite were measured at room temperature and the electrical conductivity (σ) was discovered with respect of its resistivity (Ω). By achieving conductivity of 103 S/m, it is proven that at certain graphite weight loading (PG20, PG25 and PG30) attributes to electron pathway in PG composites.

Preparation and Properties of Nanocomposites Prepared From Shortened, Functionalized Single-Walled Carbon Nanotubes

NASA Technical Reports Server (NTRS)

Smith, J. G., Jr.; Delozier, D. M.; Watson, K. A.; Connell, J. W.; Yu, Aiping; Haddon, R. C.; Bekyarova, E.

2006-01-01

As part of a continuing materials development activity, low color space environmentally stable polymeric materials that possess sufficient electrical conductivity for electrostatic charge dissipation (ESD) have been investigated. One method of incorporating sufficient electrical conductivity for ESD without detrimental effects on other polymer properties of interest (i.e., optical and thermo-optical) is through the incorporation of single-walled carbon nanotubes (SWNTs). However, SWNTs are difficult to fully disperse in the polymer matrix. One means of improving dispersion is by shortening and functionalizing SWNTs. While this improves dispersion, other properties (i.e., electrical) of the SWNTs can be affected which can in turn alter the final nanocomposite properties. Additionally, functionalization of the polymer matrix can also influence nanocomposite properties obtained from shortened, functionalized SWNTs. The preparation and characterization of nanocomposites fabricated from a polyimide, both functionalized and unfunctionalized, and shortened, functionalized SWNTs will be presented.

Mechanical Behavior of a Hi-Nicalon(tm)/SiC Composite Having a Polycarbosilane Derived Matrix

NASA Technical Reports Server (NTRS)

Hurwitz, Frances I.; Calomino, Anthony M.; McCue, Terry R.

1999-01-01

Polymer infiltration of a rigidized preform, followed by pyrolysis to convert the polymer to a ceramic, potentially offers a lower cost alternative to CVD. It also offers more moderate temperature requirements than melt infiltration approaches, which should minimize potential fiber damage during processing. However, polymer infiltration and pyrolysis results in a more microcracked matrix. Preliminary mechanical property characterization, including elevated temperature (1204 C) tensile, 500 h stress rupture behavior and low cycle fatigue, was conducted on Hi-Nicalon (TM)/Si-C-(O) composites having a dual layer BN/SiC interface and a matrix derived by impregnation and pyrolysis of allylhydridopolycarbosilane (AHPCS). Microstructural evaluation of failure surfaces and of polished transverse and longitudinal cross sections of the failed specimens was used to identify predominant failure mechanisms. In stress rupture testing at 1093 C, the failure was interface dominated, while at 1204 C in both stress rupture and two hour hold/fatigue tests failure was matrix dominated, resulting in specimen delamination.

Synthesis and characterization of hybrid nanocomposites as highly-efficient conducting CH4 gas sensor.

PubMed

Aldalbahi, Ali; Feng, Peter; Alhokbany, Norah; Al-Farraj, Eida; Alshehri, Saad M; Ahamad, Tansir

2017-02-15

Functionalized (MWCNTs-COOH), non-functionalized multiwalled carbon nanotubes (MWCNTs) and polyaniline (PANI) based conducting nanocomposites (PANI/polymer/MWCNTs and PANI/polymer/MWCNTs-COOH) have been prepared in polymer matrix. The prepared nanocomposites were characterized via FTIR, TGA, Raman spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray diffraction (XRD). It was observed that the prepared conducting nanocomposites show excellent sensing performances toward CH 4 at room temperature and both the response and recovery time were recorded at around 5s, respectively, at the room. The PANI/polymer/MWCNTs based detector had quicker/shorter response time (<1s), as well as higher sensitivity (3.1%) than that of the PANI/polymer/MWCNTs-COOH based detector. This was attributed to nonconductive -COOH that results in a poor sensitivity of PANI/polymer/MWCNTs-COOH-based prototype. The PANI/polymer/MWCNTs-COOH nanocomposites show almost 10 time higher sensitivity at higher temperature (60°C) than that at room temperature. Copyright © 2016. Published by Elsevier B.V.

Multi-Functional Carbon Fibre Composites using Carbon Nanotubes as an Alternative to Polymer Sizing

PubMed Central

Pozegic, T. R.; Anguita, J. V.; Hamerton, I.; Jayawardena, K. D. G. I.; Chen, J-S.; Stolojan, V.; Ballocchi, P.; Walsh, R.; Silva, S. R. P.

2016-01-01

Carbon fibre reinforced polymers (CFRP) were introduced to the aerospace, automobile and civil engineering industries for their high strength and low weight. A key feature of CFRP is the polymer sizing - a coating applied to the surface of the carbon fibres to assist handling, improve the interfacial adhesion between fibre and polymer matrix and allow this matrix to wet-out the carbon fibres. In this paper, we introduce an alternative material to the polymer sizing, namely carbon nanotubes (CNTs) on the carbon fibres, which in addition imparts electrical and thermal functionality. High quality CNTs are grown at a high density as a result of a 35 nm aluminium interlayer which has previously been shown to minimise diffusion of the catalyst in the carbon fibre substrate. A CNT modified-CFRP show 300%, 450% and 230% improvements in the electrical conductivity on the ‘surface’, ‘through-thickness’ and ‘volume’ directions, respectively. Furthermore, through-thickness thermal conductivity calculations reveal a 107% increase. These improvements suggest the potential of a direct replacement for lightning strike solutions and to enhance the efficiency of current de-icing solutions employed in the aerospace industry. PMID:27876858

Multi-Functional Carbon Fibre Composites using Carbon Nanotubes as an Alternative to Polymer Sizing

NASA Astrophysics Data System (ADS)

Pozegic, T. R.; Anguita, J. V.; Hamerton, I.; Jayawardena, K. D. G. I.; Chen, J.-S.; Stolojan, V.; Ballocchi, P.; Walsh, R.; Silva, S. R. P.

2016-11-01

Carbon fibre reinforced polymers (CFRP) were introduced to the aerospace, automobile and civil engineering industries for their high strength and low weight. A key feature of CFRP is the polymer sizing - a coating applied to the surface of the carbon fibres to assist handling, improve the interfacial adhesion between fibre and polymer matrix and allow this matrix to wet-out the carbon fibres. In this paper, we introduce an alternative material to the polymer sizing, namely carbon nanotubes (CNTs) on the carbon fibres, which in addition imparts electrical and thermal functionality. High quality CNTs are grown at a high density as a result of a 35 nm aluminium interlayer which has previously been shown to minimise diffusion of the catalyst in the carbon fibre substrate. A CNT modified-CFRP show 300%, 450% and 230% improvements in the electrical conductivity on the ‘surface’, ‘through-thickness’ and ‘volume’ directions, respectively. Furthermore, through-thickness thermal conductivity calculations reveal a 107% increase. These improvements suggest the potential of a direct replacement for lightning strike solutions and to enhance the efficiency of current de-icing solutions employed in the aerospace industry.

Multi-Functional Carbon Fibre Composites using Carbon Nanotubes as an Alternative to Polymer Sizing.

PubMed

Pozegic, T R; Anguita, J V; Hamerton, I; Jayawardena, K D G I; Chen, J-S; Stolojan, V; Ballocchi, P; Walsh, R; Silva, S R P

2016-11-23

Carbon fibre reinforced polymers (CFRP) were introduced to the aerospace, automobile and civil engineering industries for their high strength and low weight. A key feature of CFRP is the polymer sizing - a coating applied to the surface of the carbon fibres to assist handling, improve the interfacial adhesion between fibre and polymer matrix and allow this matrix to wet-out the carbon fibres. In this paper, we introduce an alternative material to the polymer sizing, namely carbon nanotubes (CNTs) on the carbon fibres, which in addition imparts electrical and thermal functionality. High quality CNTs are grown at a high density as a result of a 35 nm aluminium interlayer which has previously been shown to minimise diffusion of the catalyst in the carbon fibre substrate. A CNT modified-CFRP show 300%, 450% and 230% improvements in the electrical conductivity on the 'surface', 'through-thickness' and 'volume' directions, respectively. Furthermore, through-thickness thermal conductivity calculations reveal a 107% increase. These improvements suggest the potential of a direct replacement for lightning strike solutions and to enhance the efficiency of current de-icing solutions employed in the aerospace industry.

Carbon nanotube-polymer nanocomposite infrared sensor.

PubMed

Pradhan, Basudev; Setyowati, Kristina; Liu, Haiying; Waldeck, David H; Chen, Jian

2008-04-01

The infrared photoresponse in the electrical conductivity of single-walled carbon nanotubes (SWNTs) is dramatically enhanced by embedding SWNTs in an electrically and thermally insulating polymer matrix. The conductivity change in a 5 wt % SWNT-polycarbonate nanocomposite is significant (4.26%) and sharp upon infrared illumination in the air at room temperature. While the thermal effect predominates in the infrared photoresponse of a pure SWNT film, the photoeffect predominates in the infrared photoresponse of SWNT-polycarbonate nanocomposites.

High cation transport polymer electrolyte

DOEpatents

Gerald, II, Rex E.; Rathke, Jerome W [Homer Glen, IL; Klingler, Robert J [Westmont, IL

2007-06-05

A solid state ion conducting electrolyte and a battery incorporating same. The electrolyte includes a polymer matrix with an alkali metal salt dissolved therein, the salt having an anion with a long or branched chain having not less than 5 carbon or silicon atoms therein. The polymer is preferably a polyether and the salt anion is preferably an alkyl or silyl moiety of from 5 to about 150 carbon/silicon atoms.

Review paper: progress in the field of conducting polymers for tissue engineering applications.

PubMed

Bendrea, Anca-Dana; Cianga, Luminita; Cianga, Ioan

2011-07-01

This review focuses on one of the most exciting applications area of conjugated conducting polymers, which is tissue engineering. Strategies used for the biocompatibility improvement of this class of polymers (including biomolecules' entrapment or covalent grafting) and also the integrated novel technologies for smart scaffolds generation such as micropatterning, electrospinning, self-assembling are emphasized. These processing alternatives afford the electroconducting polymers nanostructures, the most appropriate forms of the materials that closely mimic the critical features of the natural extracellular matrix. Due to their capability to electronically control a range of physical and chemical properties, conducting polymers such as polyaniline, polypyrrole, and polythiophene and/or their derivatives and composites provide compatible substrates which promote cell growth, adhesion, and proliferation at the polymer-tissue interface through electrical stimulation. The activities of different types of cells on these materials are also presented in detail. Specific cell responses depend on polymers surface characteristics like roughness, surface free energy, topography, chemistry, charge, and other properties as electrical conductivity or mechanical actuation, which depend on the employed synthesis conditions. The biological functions of cells can be dramatically enhanced by biomaterials with controlled organizations at the nanometer scale and in the case of conducting polymers, by the electrical stimulation. The advantages of using biocompatible nanostructures of conducting polymers (nanofibers, nanotubes, nanoparticles, and nanofilaments) in tissue engineering are also highlighted.

Implementation of Laminate Theory Into Strain Rate Dependent Micromechanics Analysis of Polymer Matrix Composites

NASA Technical Reports Server (NTRS)

Goldberg, Robert K.

2000-01-01

A research program is in progress to develop strain rate dependent deformation and failure models for the analysis of polymer matrix composites subject to impact loads. Previously, strain rate dependent inelastic constitutive equations developed to model the polymer matrix were implemented into a mechanics of materials based micromechanics method. In the current work, the computation of the effective inelastic strain in the micromechanics model was modified to fully incorporate the Poisson effect. The micromechanics equations were also combined with classical laminate theory to enable the analysis of symmetric multilayered laminates subject to in-plane loading. A quasi-incremental trapezoidal integration method was implemented to integrate the constitutive equations within the laminate theory. Verification studies were conducted using an AS4/PEEK composite using a variety of laminate configurations and strain rates. The predicted results compared well with experimentally obtained values.

Thermo-oxidative stability studies of PMR-15 polymer matrix composites reinforced with various fibers

NASA Technical Reports Server (NTRS)

Bowles, Kenneth J.

1990-01-01

An experimental study was conducted to measure the thermo-oxidative stability of PMR-15 polymer matrix composites reinforced with various fibers and to observe differences in the way they degrade in air. The fibers that were studied included graphite and the thermally stable Nicalon and Nextel ceramic fibers. Weight loss rates for the different composites were assessed as a function of mechanical properties, specimen geometry, fiber sizing, and interfacial bond strength. Differences were observed in rates of weight loss, matrix cracking, geometry dependency, and fiber-sizing effects. It was shown that Celion 6000 fiber-reinforced composites do not exhibit a straight-line Arrhenius relationship at temperatures above 316 C.

Novel patternable and conducting metal-polymer nanocomposites: a step towards advanced mutlifunctional materials

NASA Astrophysics Data System (ADS)

Rodríguez-Cantó, Pedro J.; Martínez-Marco, Mariluz; Abargues, Rafael; Latorre-Garrido, Victor; Martínez-Pastor, Juan P.

2013-03-01

In this work, we present a novel patternable conducting nanocomposite containing gold nanoparticles. Here, the in-situ polymerization of 3T is carried out using HAuCl4 as oxidizing agent inside PMMA as host matrix. During the bake step, the gold salt is also reduced from Au(III) to Au(0) generating Au nanoparticles in the interpenetrating polymer network (IPN) system. We found that this novel multifunctional resist shows electrical conductivity and plasmonic properties as well as potential patterning capability provided by the host matrix. The resulting nanocomposite has been investigated by TEM and UV-Vis spectroscopy. Electrical characterization was also conducted for different concentration of 3T and Au(III) following a characteristic percolation behaviour. Conductivities values from 10-5 to 10 S/cm were successfully obtained depending on the IPN formulation. Moreover, The Au nanoparticles generated exhibited a localized surface plasmon resonance at around 520 nm. This synthetic approach is of potential application to modify the conductivity of numerous insulating polymers and synthesize Au nanoparticles preserving to some extent their physical and chemical properties. In addition, combination of optical properties (Plasmonics), electrical, and lithographic capability in the same material allows for the design of materials with novel functionalities and provides the basis for next generation devices.

Enhanced electrical conductivity of poly(methyl methacrylate) filled with graphene and in situ synthesized gold nanoparticles

NASA Astrophysics Data System (ADS)

Feng, Jie; Athanassiou, Athanassia; Bonaccorso, Francesco; Fragouli, Despina

2018-06-01

The improvement of the electrical conductivity of polymers by incorporating graphene has been intensively studied in recent years. To further boost the electrical conductivity, blending third-party additives into the polymer/graphene systems has been demonstrated as a viable strategy. Herein, we propose a simple route to increase the electrical conductivity of poly(methyl methacrylate) (PMMA)/graphene nanoplatelet (GnP) composites, by the in situ synthesis of gold nanoparticles directly into the solid film. In particular, PMMA, GnPs and a gold precursor are solution blended to form the composite films. The subsequent heat-induced formation of gold nanoparticles directly in the solid state film, cause the significant decrease of the percolation threshold of GnPs loading, from 3% to 1% by weight in the composite. This is attributed to the preferential formation of the gold nanoparticles onto the GnPs, with synergistic effects beneficial for the improvement of the electrical conductivity. The formation procedure of the gold nanoparticles, and their arrangement into the composite matrix are studied. We demonstrate that following this straightforward process it is possible to form nanocomposites able to conduct efficiently electric current even at low graphene loadings preserving at the same time the mechanical properties of the polymer matrix.

Study of Swift Heavy Ion Modified Conducting Polymer Composites for Application as Gas Sensor

PubMed Central

Srivastava, Alok; Singh, Virendra; Dhand, Chetna; Kaur, Manindar; Singh, Tejvir; Witte, Karin; Scherer, Ulrich W.

2006-01-01

A polyaniline-based conducting composite was prepared by oxidative polymerisation of aniline in a polyvinylchloride (PVC) matrix. The coherent free standing thin films of the composite were prepared by a solution casting method. The polyvinyl chloride-polyaniline composites exposed to 120 MeV ions of silicon with total ion fluence ranging from 1011 to 1013 ions/cm2, were observed to be more sensitive towards ammonia gas than the unirradiated composite. The response time of the irradiated composites was observed to be comparably shorter. We report for the first time the application of swift heavy ion modified insulating polymer conducting polymer (IPCP) composites for sensing of ammonia gas.

Electrochromic conductive polymer fuses for hybrid organic/inorganic semiconductor memories

NASA Astrophysics Data System (ADS)

Möller, Sven; Forrest, Stephen R.; Perlov, Craig; Jackson, Warren; Taussig, Carl

2003-12-01

We demonstrate a nonvolatile, write-once-read-many-times (WORM) memory device employing a hybrid organic/inorganic semiconductor architecture consisting of thin film p-i-n silicon diode on a stainless steel substrate integrated in series with a conductive polymer fuse. The nonlinearity of the silicon diodes enables a passive matrix memory architecture, while the conductive polyethylenedioxythiophene:polystyrene sulfonic acid polymer serves as a reliable switch with fuse-like behavior for data storage. The polymer can be switched at ˜2 μs, resulting in a permanent decrease of conductivity of the memory pixel by up to a factor of 103. The switching mechanism is primarily due to a current and thermally dependent redox reaction in the polymer, limited by the double injection of both holes and electrons. The switched device performance does not degrade after many thousand read cycles in ambient at room temperature. Our results suggest that low cost, organic/inorganic WORM memories are feasible for light weight, high density, robust, and fast archival storage applications.

Synthetic biodegradable functional polymers for tissue engineering: a brief review.

PubMed

BaoLin, Guo; Ma, Peter X

2014-04-01

Scaffolds play a crucial role in tissue engineering. Biodegradable polymers with great processing flexibility are the predominant scaffolding materials. Synthetic biodegradable polymers with well-defined structure and without immunological concerns associated with naturally derived polymers are widely used in tissue engineering. The synthetic biodegradable polymers that are widely used in tissue engineering, including polyesters, polyanhydrides, polyphosphazenes, polyurethane, and poly (glycerol sebacate) are summarized in this article. New developments in conducting polymers, photoresponsive polymers, amino-acid-based polymers, enzymatically degradable polymers, and peptide-activated polymers are also discussed. In addition to chemical functionalization, the scaffold designs that mimic the nano and micro features of the extracellular matrix (ECM) are presented as well, and composite and nanocomposite scaffolds are also reviewed.

Effect of two hydrophobic polymers on the release of gliclazide from their matrix tablets.

PubMed

Hussain, Talib; Saeed, Tariq; Mumtaz, Ahmad M; Javaid, Zeeshan; Abbas, Khizar; Awais, Azeema; Idrees, Hafiz Arfat

2013-01-01

Gliclazide is an oral hypoglycemic agent, indicated in non insulin dependent diabetes mellitus and in patients with diabetic retinopathy. It has good tolerability and is a short acting sulfonyl urea that requires large dose to maintain the blood glucose level. So development of a sustained release formulation of gliclazide (GLZ) is required for better patient compliance. This study was conducted to assess the effects of different drug polymer ratios on the release profile of gliclazide from the matrix. Oral matrix tablets of gliclazide were prepared by hot melt method, using pure and blended mixture of glyceryl monostearate (GMS) and stearic acid (SA) in different ratios. In vitro release pattern was studied for 8 h in phosphate buffer media (pH 7.4). Different kinetic models including zero order, first order, Higuchi and Peppas were applied to evaluate drug release behavior. Drug excipient compatibility was evaluated by scanning with DSC and FTIR. Higuchi model was found the most appropriate model for describing the release profile of GLZ and non-Fickian release was found predominant mechanism of drug release. The release of drug from the matrix was greatly controlled by GMS while SA appeared to facilitate the release of drug from matrix tablets. FTIR results showed no chemical interaction between drug and the polymers, and DSC results indicated amorphous state of GLZ and polymers without significant complex formation. The results indicate that matrix tablets of gliclazide using glyceryl monostearate and stearic acid showed marked sustained release properties.

Characterization of conducting cellulose acetate based polymer electrolytes doped with "green" ionic mixture.

PubMed

Ramesh, S; Shanti, R; Morris, Ezra

2013-01-02

Polymer electrolytes were developed by solution casting technique utilizing the materials of cellulose acetate (CA), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) and deep eutectic solvent (DES). The DES is synthesized from the mixture of choline chloride and urea of 1:2 ratios. The increasing DES content well plasticizes the CA:LiTFSI:DES matrix and gradually improves the ionic conductivity and chemical integrity. The highest conducting sample was identified for the composition of CA:LiTFSI:DES (28 wt.%:12 wt.%:60 wt.%), which has the greatest ability to retain the room temperature ionic conductivity over the entire 30 days of storage time. The changes in FTIR cage peaks upon varying the DES content in CA:LiTFSI:DES prove the complexation. This complexation results in the collapse of CA matrix crystallinity, observed from the reduced intensity of XRD diffraction peaks. The DES-plasticized sample is found to be more heat-stable compared to pure CA. Nevertheless, the addition of DES diminishes the CA:LiTFSI matrix's heat-resistivity but at the minimum addition the thermal stability is enhanced. Copyright © 2012 Elsevier Ltd. All rights reserved.

Graphite Nanoreinforcements for Aerospace Nanocomposites

NASA Technical Reports Server (NTRS)

Drzal, Lawrence T.

2005-01-01

New advances in the reinforcement of polymer matrix composite materials are critical for advancement of the aerospace industry. Reinforcements are required to have good mechanical and thermal properties, large aspect ratio, excellent adhesion to the matrix, and cost effectiveness. To fulfill the requirements, nanocomposites in which the matrix is filled with nanoscopic reinforcing phases having dimensions typically in the range of 1nm to 100 nm show considerably higher strength and modulus with far lower reinforcement content than their conventional counterparts. Graphite is a layered material whose layers have dimensions in the nanometer range and are held together by weak Van der Waals forces. Once these layers are exfoliated and dispersed in a polymer matrix as nano platelets, they have large aspect ratios. Graphite has an elastic modulus that is equal to the stiffest carbon fiber and 10-15 times that of other inorganic reinforcements, and it is also electrically and thermally conductive. If the appropriate surface treatment can be found for graphite, its exfoliation and dispersion in a polymer matrix will result in a composite with excellent mechanical properties, superior thermal stability, and very good electrical and thermal properties at very low reinforcement loadings.

Composite Solid Electrolyte Containing Li+- Conducting Fibers

NASA Technical Reports Server (NTRS)

Appleby, A. John; Wang, Chunsheng; Zhang, Xiangwu

2006-01-01

Improved composite solid polymer electrolytes (CSPEs) are being developed for use in lithium-ion power cells. The matrix components of these composites, like those of some prior CSPEs, are high-molecular-weight dielectric polymers [generally based on polyethylene oxide (PEO)]. The filler components of these composites are continuous, highly-Li(+)-conductive, inorganic fibers. PEO-based polymers alone would be suitable for use as solid electrolytes, were it not for the fact that their room-temperature Li(+)-ion conductivities lie in the range between 10(exp -6) and 10(exp -8) S/cm, too low for practical applications. In a prior approach to formulating a CSPE, one utilizes nonconductive nanoscale inorganic filler particles to increase the interfacial stability of the conductive phase. The filler particles also trap some electrolyte impurities. The achievable increase in conductivity is limited by the nonconductive nature of the filler particles.

Polymer-Nanoparticle Composites: From Synthesis to Modern Applications

PubMed Central

Hanemann, Thomas; Szabó, Dorothée Vinga

2010-01-01

The addition of inorganic spherical nanoparticles to polymers allows the modification of the polymers physical properties as well as the implementation of new features in the polymer matrix. This review article covers considerations on special features of inorganic nanoparticles, the most important synthesis methods for ceramic nanoparticles and nanocomposites, nanoparticle surface modification, and composite formation, including drawbacks. Classical nanocomposite properties, as thermomechanical, dielectric, conductive, magnetic, as well as optical properties, will be summarized. Finally, typical existing and potential applications will be shown with the focus on new and innovative applications, like in energy storage systems.

Anhydrous state proton and lithium ion conducting solid polymer electrolytes based on sulfonated bisphenol-A-poly(arylene ethers)

NASA Astrophysics Data System (ADS)

Guha Thakurta, Soma

Sulfonated polymer based solid polymer electrolytes (SPEs) have received considerable interest in recent years because of their wide variety of applications particularly in fuel cells, batteries, supercapacitors, and electrochromic devices. The present research was focused on three interrelated subtopics. First, two different bisphenol-A-poly(arylene ethers), polyetherimide (PEI) and polysulfone (PSU) were sulfonated by a post sulfonation method to various degrees of sulfonation, and their thermal and mechanical properties were examined. The effects of poly(arylene ether) chemical structure, reaction time, concentration, and types of sulfonating agents on sulfonation reaction were investigated. It was found that deactivation of bisphenol A unit caused by the electron withdrawing imide, retarded the sulfonation of PEI compared to PSU. Sulfonation conducted with a high concentration of sulfonating agent and/or prolonged reaction time exhibited evidence of degradation at the isopropylidene unit. The degradation occurred through the same mechanistic pathway with the two different sulfonating agents, chlorosulfonic acid (CSA) and trimethylsilyl chlorosulfonate (TMSCS). The degradation was faster with CSA than its silyl ester, TMSCS, and was evident even at low acid concentration. Second, novel anhydrous proton conducting solid polymer electrolytes (SPEs) were prepared by the incorporation of 1H-1,2,4-triazole (Taz) as a proton solvent in sulfonated polyetherimide (SPEI) matrix. The size, shape, and state of dispersion (crystal morphology) of triazole crystals in SPEI were examined as a function of degree of sulfonation and triazole concentration. Increasing sulfonic acid content caused reduction of triazole crystallite size, hence the depression of melting temperature and their uniform distribution throughout the sulfonated polymer matrix. The increased rate of structure diffusion within the smaller size crystals due to the improved molecular mobility contributed significantly to the anhydrous state proton conductivity. Third, a new category of single lithium ion conducting SPEs was developed by crosslinking a polyether epoxy, poly(ethylene glycol)diglicidyl ether (PEGDGE) (lithium ion solvent), in sulfonated polysulfone (SPSU) matrix. The effects of degree of sulfonation and electrolyte composition on ionic conductivity, thermal, and tensile properties of SPEs were investigated. It was found that ion-dipole interactions between lithium sulfonate (SO3Li) and PEGDGE were responsible for the reduction in size of the dispersed epoxy phase and increased thermal stability. Lithium sulfonate promoted compatibilization and also caused improvement in elongation at break. A low molecular weight electrolyte salt, lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) was further dissolved in PEGDGE phase prior to its crosslinking in SPSU matrix, and the ionic conductivity and thermal properties were evaluated as a function of doping level. The ionic conductivity showed remarkable improvement compared to the undoped system.

Unusually conductive carbon-inherently conducting polymer (ICP) composites: Synthesis and characterization

NASA Astrophysics Data System (ADS)

Bourdo, Shawn Edward

Two groups of materials that have recently come to the forefront of research initiatives are carbon allotropes, especially nanotubes, and conducting polymers-more specifically inherently conducting polymers. The terms conducting polymers and inherently conducting polymers sometimes are used interchangeably without fully acknowledging a major difference in these terms. Conducting polymers (CPs) and inherently conducting polymers (ICPs) are both polymeric materials that conduct electricity, but the difference lies in how each of these materials conducts electricity. For CPs of the past, an electrically conductive filler such as metal particles, carbon black, or graphite would be blended into a polymer (insulator) allowing for the CP to carry an electric current. An ICP conducts electricity due to the intrinsic nature of its chemical structure. The two materials at the center of this research are graphite and polyaniline. For the first time, a composite between carbon allotropes (graphite) and an inherently conducting polymer (PANI) has exhibited an electrical conductivity greater than either of the two components. Both components have a plethora of potential applications and therefore the further investigation could lead to use of these composites in any number of technologies. Touted applications that use either conductive carbons or ICPs exist in a wide range of fields, including electromagnetic interference (EMI) shielding, radar evasion, low power rechargeable batteries, electrostatic dissipation (ESD) for anti-static textiles, electronic devices, light emitting diodes (LEDs), corrosion prevention, gas sensors, super capacitors, photovoltaic cells, and resistive heating. The main motivation for this research has been to investigate the connection between an observed increase in conductivity and structure of composites. Two main findings have resulted from the research as related to the observed increase in conductivity. The first was the structural evidence from Raman spectroscopy, X-ray diffraction, and thermal analysis suggesting a more crystalline graphite matrix due to intimate interactions with PANI that resulted in a charge transfer. Confirmation of charge transfer was observed through magnetic susceptibility, electron paramagnetic resonance, and temperature dependent electrical conductivity studies.

Underlying Physics of Conductive Polymer Composites and Force Sensing Resistors (FSRs) under Static Loading Conditions

PubMed Central

2017-01-01

Conductive polymer composites are manufactured by randomly dispersing conductive particles along an insulating polymer matrix. Several authors have attempted to model the piezoresistive response of conductive polymer composites. However, all the proposed models rely upon experimental measurements of the electrical resistance at rest state. Similarly, the models available in literature assume a voltage-independent resistance and a stress-independent area for tunneling conduction. With the aim of developing and validating a more comprehensive model, a test bench capable of exerting controlled forces has been developed. Commercially available sensors—which are manufactured from conductive polymer composites—have been tested at different voltages and stresses, and a model has been derived on the basis of equations for the quantum tunneling conduction through thin insulating film layers. The resistance contribution from the contact resistance has been included in the model together with the resistance contribution from the conductive particles. The proposed model embraces a voltage-dependent behavior for the composite resistance, and a stress-dependent behavior for the tunneling conduction area. The proposed model is capable of predicting sensor current based upon information from the sourcing voltage and the applied stress. This study uses a physical (non-phenomenological) approach for all the phenomena discussed here. PMID:28906467

The effect of filler parameters on the healing of thermal conductivity and mechanical properties of a thermal interface material based on a self-healable organic-inorganic polymer matrix

NASA Astrophysics Data System (ADS)

Zhong, Nan; Garcia, Santiago J.; van der Zwaag, Sybrand

2016-08-01

Thermal interface materials (TIMs) are widely used in all kinds of electronic devices to handle the heat dissipation and the mechanical anchoring of the heat producing component. The aging of TIMs may lead to delamination and internal crack formation causing a loss of heat transfer and mechanical integrity both leading to premature device failure. In the present work, a novel TIM system based on a self-healing organic-inorganic polymer matrix filled with spherical glass beads is presented which is capable of healing both the thermal conductivity and the mechanical properties upon thermal activation. The effect of particle volume concentration (PVC) and particle size on tensile strength and thermal conductivity healing behavior is investigated. The results show that a higher PVC increases the mechanical property but decreases mechanical healing. For the same PVC, bigger particles lead to lower mechanical properties but higher thermal conductivities and higher mechanical healing efficiencies.

High aspect ratio template and method for producing same

NASA Technical Reports Server (NTRS)

Sakamoto, Jeff S. (Inventor); Weiss, James R. (Inventor); Fleurial, Jean-Pierre (Inventor); Kisor, Adam (Inventor); Tuszynski, Mark (Inventor); Stokols, Shula (Inventor); Holt, Todd Edward (Inventor); Welker, David James (Inventor); Breckon, Christopher David (Inventor)

2010-01-01

Millimeter to nano-scale structures manufactured using a multi-component polymer fiber matrix are disclosed. The use of dissimilar polymers allows the selective dissolution of the polymers at various stages of the manufacturing process. In one application, biocompatible matrixes may be formed with long pore length and small pore size. The manufacturing process begins with a first polymer fiber arranged in a matrix formed by a second polymer fiber. End caps may be attached to provide structural support and the polymer fiber matrix selectively dissolved away leaving only the long polymer fibers. These may be exposed to another product, such as a biocompatible gel to form a biocompatible matrix. The polymer fibers may then be selectively dissolved leaving only a biocompatible gel scaffold with the pores formed by the dissolved polymer fibers.

Polyimide matrix resins for up to 700 deg F service

NASA Technical Reports Server (NTRS)

Jones, R. J.; Chang, G. E.; Powell, S. H.; Green, H. E.

1985-01-01

TRW is in the process of data accumulation that strongly indicates that incorporation of the perfluorsisopropylidene linkage in molecular structures other than those employed in DU Pont's NR-150B polyimides likewise yield polymers demonstrating extremely high thermo-oxidative stability. Polyimide synthetic and characterization studies conducted to date on new polymers incorporating the perfluoroisopropylidene linkage are presented and discussed.

Ultrasonic Assessment of Impact-Induced Damage and Microcracking in Polymer Matrix Composites

NASA Technical Reports Server (NTRS)

Liaw, Benjamin; Zeichner, Glenn; Liu, Yanxiong; Bowles, Kenneth J. (Technical Monitor)

2000-01-01

The main objective of this NASA FAR project is to conduct ultrasonic assessment of impact-induced damage and microcracking in polymer matrix composites at various temperatures. It is believed that the proposed study of impact damage assessment on polymer matrix composites will benefit several NASA's missions and current interests, such as ballistic impact testing of composite fan containment and high strain rate deformation modeling of polymer matrix composites. Currently, impact-induced delamination and fracture in 6061-T6 aluminum/cast acrylic sandwich plates adhered by epoxy were generated in an instrumented drop-weight impact machine. Although only a small dent was produced on the aluminum side when a hemispherical penetrator tup was dropped onto it from a couple of inches, a large ring of delamination at the interface was observed. The delamination damage was often accompanied by severe shattering in the acrylic substratum. Damage patterns in the acrylic layer include radial and ring cracks and, together with delamination at the interface, may cause peeling-off of acrylic material from the sandwich plate. Theory of stress-wave propagation can be used to explain these damage patterns. The impact tests were conducted at various temperatures. The results also show clearly that temperature effect is very important in impact damage. For pure cast acrylic nil-ductile transition (NDT) occurs between 185-195 F Excessive impact energy was dissipated into fracture energy when tested at temperature below this range or through plastic deformation when tested at temperature above the NDT temperature. Results from this study will be used as baseline data for studying fiber-metal laminates, such as GLARE and ARALL for advanced aeronautical and astronautical applications.

Conductivity of gel polymer electrolytes doped with solutions of phosphonic acid or protic ionic liquids

NASA Astrophysics Data System (ADS)

Shmukler, Liudmila E.; Fadeeva, Yuliya A.; Glushenkova, Ekaterina V.; Nguyen, Van Thuc; Safonova, Liubov P.

2018-04-01

The proton-conducting gel electrolytes (PCGEs) based on PMMA, PVdF or PVdF-HFP doped with solutions of phosphonic acid or ammonium based protic ionic liquids (PILs) in DMF have been synthesized. Rather high values of the conductivity (10-4-10-3 S cm-1) have been reached at low dopant concentrations (up to 1 mol l-1). The influence of the nature of both polymeric matrix and dopant as well as dopant concentration on the conductivity values was discussed. It was established that the dependence of conductivity on the nature of dopant, but not the polymeric matrix, was more pronounced.

Lead selenide quantum dot polymer nanocomposites

NASA Astrophysics Data System (ADS)

Waldron, Dennis L.; Preske, Amanda; Zawodny, Joseph M.; Krauss, Todd D.; Gupta, Mool C.

2015-02-01

Optical absorption and fluorescence properties of PbSe quantum dots (QDs) in an Angstrom Bond AB9093 epoxy polymer matrix to form a nanocomposite were investigated. To the authors’ knowledge, this is the first reported use of AB9093 as a QD matrix material and it was shown to out-perform the more common poly(methyl methacrylate) matrix in terms of preserving the optical properties of the QD, resulting in the first reported quantum yield (QY) for PbSe QDs in a polymer matrix, 26%. The 1-s first excitonic absorption peak of the QDs in a polymer matrix red shifted 65 nm in wavelength compared to QDs in a hexane solution, while the emission peak in the polymer matrix red shifted by 38 nm. The fluorescence QY dropped from 55% in hexane to 26% in the polymer matrix. A time resolved fluorescence study of the QDs showed single exponential lifetimes of 2.34 and 1.34 μs in toluene solution and the polymer matrix respectively.

Nanoparticle/Polymer Nanocomposite Bond Coat or Coating

NASA Technical Reports Server (NTRS)

Miller, Sandi G.

2011-01-01

This innovation addresses the problem of coatings (meant to reduce gas permeation) applied to polymer matrix composites spalling off in service due to incompatibility with the polymer matrix. A bond coat/coating has been created that uses chemically functionalized nanoparticles (either clay or graphene) to create a barrier film that bonds well to the matrix resin, and provides an outstanding barrier to gas permeation. There is interest in applying clay nanoparticles as a coating/bond coat to a polymer matrix composite. Often, nanoclays are chemically functionalized with an organic compound intended to facilitate dispersion of the clay in a matrix. That organic modifier generally degrades at the processing temperature of many high-temperature polymers, rendering the clay useless as a nano-additive to high-temperature polymers. However, this innovation includes the use of organic compounds compatible with hightemperature polymer matrix, and is suitable for nanoclay functionalization, the preparation of that clay into a coating/bondcoat for high-temperature polymers, the use of the clay as a coating for composites that do not have a hightemperature requirement, and a comparable approach to the preparation of graphene coatings/bond coats for polymer matrix composites.

Carbon fiber polymer-matrix structural composites tailored for multifunctionality by filler incorporation

NASA Astrophysics Data System (ADS)

Han, Seungjin

This dissertation provides multifunctional carbon fiber polymer-matrix structural composites for vibration damping, thermal conduction and thermoelectricity. Specifically, (i) it has strengthened and stiffened carbon fiber polymer-matrix structural composites by the incorporation of halloysite nanotubes, carbon nanotubes and silicon carbide whiskers, (ii) it has improved mechanical energy dissipation using carbon fiber polymer-matrix structural composites with filler incorporation, (iii) it has increased the through-thickness thermal conductivity of carbon fiber polymer-matrix composite by curing pressure increase and filler incorporation, and (iv) it has enhanced the thermoelectric behavior of carbon fiber polymer-matrix structural composites. Low-cost natural halloysite nanotubes (0.1 microm diameter) were effective for strengthening and stiffening continuous fiber polymer-matrix composites, as shown for crossply carbon fiber (5 microm diameter, ˜59 vol.%) epoxy-matrix composites under flexure, giving 17% increase in strength, 11% increase in modulus and 21% decrease in ductility. They were less effective than expensive multiwalled carbon nanotubes (0.02 microm diameter), which gave 25% increase in strength, 11% increase in modulus and 14% decrease in ductility. However, they were more effective than expensive silicon carbide whiskers (1 microm diameter), which gave 15% increase in strength, 9% increase in modulus and 20% decrease in ductility. Each filler, at ˜2 vol.%, was incorporated in the composite at every interlaminar interface by fiber prepreg surface modification. The flexural strength increase due to halloysite nanotubes incorporation related to the interlaminar shear strength increase. The measured values of the composite modulus agreed roughly with the calculated values based on the Rule of Mixtures. Continuous carbon fiber composites with enhanced vibration damping under flexure are provided by incorporation of fillers between the laminae. Exfoliated graphite (EG) as a sole filler is more effective than carbon nanotube (SWCNT/MWCNT), halloysite nanotube (HNT) or nanoclay as sole fillers in enhancing the loss tangent, if the curing pressure is 2.0 (not 0.5) MPa. The MWCNT, SiC whisker and halloysite nanotube as sole fillers are effective for increasing the storage modulus. The combined use of a storage-modulus-enhancing filler (CNT, SiC whisker or HNT) and a loss-tangent-enhancing filler (EG or nanoclay) gives the best performance. With EG, HNT and 2.0-MPa curing, the loss modulus is increased by 110%, while the flexural strength is decreased by 14% and the flexural modulus is not affected. With nanoclay, HNT and 0.5-MPa curing, the loss modulus is increased by 96%, while the flexural strength and modulus are essentially not affected. The low through-thickness thermal conductivity limits heat dissipation from continuous carbon fiber polymer-matrix composites. This conductivity is increased by up to 60% by raising the curing pressure from 0.1 to 2.0 MPa and up to 33% by incorporation of a filler (61.5 vol.%) at the interlaminar interface. The thermal resistivity is dominated by the lamina resistivity (which is contributed substantially by the intralaminar fiber--fiber interfacial resistivity), with the interlaminar interface thermal resistivity being unexpectedly negligible. The lamina resistivity and intralaminar fiber-fiber interfacial resistivity are decreased by up to 56% by raising the curing pressure and up to 36% by filler incorporation. Thermoelectric structural materials are potentially attractive for large-scale energy harvesting. Through filler incorporation and unprecedented decoupling of the bulk (laminae) and interfacial (interlaminar interfaces) contributions to the Seebeck voltage (through-thickness Seebeck voltage of a crossply continuous carbon fiber/epoxy composite laminate), this work provides thermoelectric power magnitudes at ˜70°C up to 110, 1670 and 11000 microV/K for the laminate, a lamina and an interlaminar interface respectively. The interface provides an apparent thermoelectric effect due to carrier backflow. The interfacial voltage is opposite in sign from the laminate and lamina voltages and is slightly lower in magnitude than the lamina voltage. The through-thickness thermoelectric behavior of continuous carbon fiber epoxy-matrix structural composites has been greatly improved by the use of tellurium particles (13 vol.% of composite), bismuth telluride particles (2 vol.%) and carbon black (2 vol.%) at the interlaminar interface. The thermoelectric power is increased from 8 to 163 microV/K, while the electrical resistivity is decreased from 0.17 to 0.02 O.cm, the thermal conductivity is decreased from 1.31 to 0.51 W/m.K, and the dimensionless thermoelectric figure of merit ZT at 70°C is increased from 9 x 10-6 to 9 x 10-2. Decrease in the curing pressure from 4.0 to 0.5 MPa decreases ZT slightly, mainly due to the increase in electrical resistivity.

Breakdown of water super-permeation in electrically insulating graphene oxide films: role of dual interlayer spacing.

PubMed

Kavitha, Maheshwari Kavirajan; Sakorikar, Tushar; Vayalamkuzhi, Pramitha; Jaiswal, Manu

2018-08-10

Conventional graphene oxide (GO) is characterized by low sp 2 content in a sp 3 rich matrix, which is responsible both for electrical insulation and water super-permeation. Upon reduction, electrical conduction is achieved at the expense of water permeation ability. Here, we demonstrate that charge conduction and water permeation can be simultaneously restricted in a functionalized form of GO. Gravimetric studies reveal that diffusion of water vapor through a glassy polymer membrane is arrested by loading a hydrophobic form of GO (H-GO) in the polymer matrix, even as such, water inhibition cannot be realized by substantially increasing the thickness of the bare polymer. As an application, the ability of the coating to impede the degradation of methyl ammonium lead iodide films under high humidity conditions is demonstrated. At the same time the H-GO film has a resistance over 10 7 times higher when compared to thermally reduced GO of similar sp 2 fraction. We attribute this unique behavior to the presence of a sub-micron matrix of GO with simultaneous presence of large (∼9.5 Å) and small (∼4.7 Å) interlayer spacing. This leads to disruption of the spatially distributed percolation pathways for electrical charge, and it also serves to block the nanocapillary networks for water molecules.

Processable high temperature resistant polymer matrix materials

NASA Technical Reports Server (NTRS)

Serafini, T. T.

1975-01-01

Studies conducted with addition-type polyimides are reviewed with emphasis on the development of the Polymerization of Monomer Reactants (PMR) approach, in which PMR occurs on the surface of the reinforcing fibers.

Gel polymer electrolyte for lithium-ion batteries comprising cyclic carbonate moieties

NASA Astrophysics Data System (ADS)

Tillmann, S. D.; Isken, P.; Lex-Balducci, A.

2014-12-01

A polymer system based on oligo (ethylene glycol) methyl ether methacrylate (OEGMA) and cyclic carbonate methacrylate (CCMA) was chosen as matrix to realize high-performance gel polymer electrolytes due to the fact that both monomers are able to interact with the liquid electrolyte, thus, retaining it inside the matrix. Additionally, OEGMA enables high flexibility, while CCMA provides mechanical stability. The polymer displays a high thermal stability up to 200 °C and a glass transition temperature below room temperature (5 °C) allowing an easy handling of the obtained films. By immobilizing the liquid electrolyte 1 M LiPF6 in EC:DMC 1:1 w:w in the polymer host a gel polymer electrolyte with a high conductivity of 2.3 mS cm-1 at 25 °C and a stable cycling behavior with high capacities and efficiencies in Li(Ni1/3Co1/3Mn1/3)O2 (NCM)/graphite full cells is obtained. The investigated gel polymer electrolyte is identified as promising electrolyte for lithium-ion batteries, because it combines good electrochemical properties comparable to that of liquid electrolytes with the safety advantage that no leakage of the flammable electrolyte solvents can occur.

Recent Development of Nanomaterial-Doped Conductive Polymers

NASA Astrophysics Data System (ADS)

Asyraf, Mohammad; Anwar, Mahmood; Sheng, Law Ming; Danquah, Michael K.

2017-12-01

Conductive polymers (CPs) have received significant research attention in material engineering for applications in microelectronics, micro-scale sensors, electromagnetic shielding, and micro actuators. Numerous research efforts have been focused on enhancing the conductivity of CPs by doping. Various conductive materials, such as metal nanoparticles and carbon-based nanoparticles, and structures, such as silver nanoparticles and graphene nanosheets, have been converted into polypyrrole and polypyrrole compounds as the precursors to developing hybrids, conjugates, or crystal nodes within the matrix to enhance the various structural properties, particularly the electrical conductivity. This article reviews nanomaterial doping of conductive polymers alongside technological advancements in the development and application of nanomaterial-doped polymeric systems. Emphasis is given to conductive nanomaterials such as nano-silver particles and carbon-based nanoparticles, graphene nano-sheets, fullerene, and carbon nanotubes (CNT) as dopants for polypyrrole-based CPs. The nature of induced electrical properties including electromagnetic absorption, electrical capacitance, and conductivities of polypyrrole systems is also discussed. The prospects and challenges associated with the development and application of CPs are also presented.

Stress-tuned conductor-polymer composite for use in sensors

DOEpatents

Martin, James E; Read, Douglas H

2013-10-22

A method for making a composite polymeric material with electrical conductivity determined by stress-tuning of the conductor-polymer composite, and sensors made with the stress-tuned conductor-polymer composite made by this method. Stress tuning is achieved by mixing a miscible liquid into the polymer precursor solution or by absorbing into the precursor solution a soluble compound from vapor in contact with the polymer precursor solution. The conductor may or may not be ordered by application of a magnetic field. The composite is formed by polymerization with the stress-tuning agent in the polymer matrix. The stress-tuning agent is removed following polymerization to produce a conductor-polymer composite with a stress field that depends on the amount of stress-tuning agent employed.

Novel Materials Containing Single-Wall Carbon Nanotubes Wrapped in Polymer Molecules

NASA Technical Reports Server (NTRS)

Smalley, Richard E.; O'Connell, Michael J.; Smith, Kenneth; Colbert, Daniel T.

2009-01-01

In this design, single-wall carbon nanotubes (SWNTs) have been coated in polymer molecules to create a new type of material that has low electrical conductivity, but still contains individual nanotubes, and small ropes of individual nanotubes, which are themselves good electrical conductors and serve as small conducting rods immersed in an electrically insulating matrix. The polymer is attached through weak chemical forces that are primarily non-covalent in nature, caused primarily through polarization rather than the sharing of valence electrons. Therefore, the electronic structure of the SWNT involved is substantially the same as that of free, individual (and small ropes of) SWNT. Their high conductivity makes the individual nanotubes extremely electrically polarizable, and materials containing these individual, highly polarizable molecules exhibit novel electrical properties including a high dielectric constant.

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.

Assessment of Erosion Resistance of Coated Polymer Matrix Composites for Propulsion Applications

NASA Technical Reports Server (NTRS)

Miyoshi, Kazuhisa; Sutter, James K.; Horan, Richard A.; Naik, Subhash K.; Cupp, Randall J.

2004-01-01

The erosion behavior of tungsten carbide-cobalt (WC-Co) coated and uncoated polymer matrix composites (PMCs) was examined with solid particle impingement using air jets. Erosion tests were conducted with Arizona road dust impinging at 20 degrees, 60 degrees, and 90 degrees angles at a velocity of 229 meters per second at both 294 and 366 K. Noncontact optical profilometry was used to measure the wear volume loss. Results indicate that the WC-Co coating enhanced erosion resistance and reduced erosion wear volume loss by a factor of nearly 2. This should contribute to longer wear lives, reduced related breakdowns, decreased maintenance costs, and increased product reliability.

Lowering the operational temperature of all-solid-state lithium polymer cell with highly conductive and interfacially robust solid polymer electrolytes

NASA Astrophysics Data System (ADS)

Aldalur, Itziar; Martinez-Ibañez, Maria; Piszcz, Michal; Rodriguez-Martinez, Lide M.; Zhang, Heng; Armand, Michel

2018-04-01

Novel solid polymer electrolytes (SPEs), comprising of comb polymer matrix grafted with soft and disordered polyether moieties (Jeffamine®) and lithium bis(fluorosulfonyl)imide (LiFSI) are investigated in all-solid-state lithium metal (Li°) polymer cells. The LiFSI/Jeffamine-based SPEs are fully amorphous at room temperature with glass transitions as low as ca. -55 °C. They show higher ionic conductivities than conventional poly(ethylene oxide) (PEO)-based SPEs at ambient temperature region, and good electrochemical compatibility with Li° electrode. These exceptional properties enable the operational temperature of Li° | LiFePO4 cells to be decreased from an elevated temperature (70 °C) to room temperature. Those results suggest that LiFSI/Jeffamine-based SPEs can be promising electrolyte candidates for developing safe and high performance all-solid-state Li° batteries.

Electrical Conductivity Response of Poly(Phenylene-vinylene)/Zeolite Composites Exposed to Ammonium Nitrate

PubMed Central

Kamonsawas, Jirarat; Sirivat, Anuvat; Niamlang, Sumonman; Hormnirun, Pimpa; Prissanaroon-Ouajai, Walaiporn

2010-01-01

Poly(p-phenylenevinylene) (PPV) was chemically synthesized via the polymerization of p-xylene-bis(tetrahydrothiophenium chloride) monomer and doped with H2SO4. To improve the electrical conductivity sensitivity of the conductive polymer, Zeolites Y (Si/Al = 5.1, 30, 60, 80) were added into the conductive polymer matrix. All composite samples show definite positive responses towards NH4NO3. The electrical conductivity sensitivities of the composite sensors increase linearly with increasing Si/Al ratio: with values of 0.201, 1.37, 2.80 and 3.18, respectively. The interactions between NH4NO3 molecules and the PPV/zeolite composites with respect to the electrical conductivity sensitivity were investigated through the infrared spectroscopy. PMID:22219677

Dielectric, electric and thermal properties of carboxylic functionalized multiwalled carbon nanotubes impregnated polydimethylsiloxane nanocomposite

NASA Astrophysics Data System (ADS)

Sagar, Sadia; Iqbal, Nadeem; Maqsood, Asghari

2013-06-01

The dielectric, electric and thermal properties of carboxylic functionalized multiwalled carbon nanotubes (F-MWCNT) incorporated into the polydimethylsiloxane (PDMS) were evaluated to determine their potential in the field of electronic materials. Carboxylic functionalization of the pristine multi walled carbon tubes (Ps-MWCNT) was confirmed through Fourier transform infrared spectroscopy, X-ray diffraction patterns for both Ps-MWCNTs and F-MWCNTs elaborated that crystalline behavior did not change with carboxylic moieties. Thermogravimetric and differential thermal analyses were performed to elucidate the thermal stability with increasing weight % addition of F-MWCNTs in the polymer matrix. Crystallization/glass transition / melting temperatures were evaluated using differential scanning calorimeter and it was observed that glass transition and crystallization temperatures were diminished while temperatures of first and second melting transitions were progressed with increasing F-MWCNT concentration in the PDMS matrix. Scanning electron microscopy and energy dispersive x-ray spectroscopy were carried out to confirm the morphology, functionalization, and uniform dispersion of F-MWCNTs in the polymer matrix. Electrical resistivity at temperature range (100-300°C), dielectric loss (tanδ) and dielectric parameters (epsilon/ epsilon//) were measured in the frequency range (1MHz-3GHz). The measured data simulate that the aforementioned properties were influenced by increasing filler contents in the polymer matrix because of the high polarization of conductive F-MWCNTs at the reinforcement/polymer interface.

Processing of uranium oxide and silicon carbide based fuel using polymer infiltration and pyrolysis

NASA Astrophysics Data System (ADS)

Singh, Abhishek K.; Zunjarrao, Suraj C.; Singh, Raman P.

2008-09-01

Ceramic composite pellets consisting of uranium oxide, UO 2, contained within a silicon carbide matrix, were fabricated using a novel processing technique based on polymer infiltration and pyrolysis (PIP). In this process, particles of depleted uranium oxide, in the form of U 3O 8, were dispersed in liquid allylhydridopolycarbosilane (AHPCS), and subjected to pyrolysis up to 900 °C under a continuous flow of ultra high purity argon. The pyrolysis of AHPCS, at these temperatures, produced near-stoichiometric amorphous silicon carbide ( a-SiC). Multiple polymer infiltration and pyrolysis (PIP) cycles were performed to minimize open porosity and densify the silicon carbide matrix. Analytical characterization was conducted to investigate chemical interaction between U 3O 8 and SiC. It was observed that U 3O 8 reacted with AHPCS during the very first pyrolysis cycle, and was converted to UO 2. As a result, final composition of the material consisted of UO 2 particles contained in an a-SiC matrix. The physical and mechanical properties were also quantified. It is shown that this processing scheme promotes uniform distribution of uranium fuel source along with a high ceramic yield of the parent matrix.

Reflexive composites: self-healing composite structures

NASA Astrophysics Data System (ADS)

Margraf, Thomas W., Jr.; Barnell, Thomas J.; Havens, Ernie; Hemmelgarn, Christopher D.

2008-03-01

Cornerstone Research Group Inc. has developed reflexive composites achieving increased vehicle survivability through integrated structural awareness and responsiveness to damage. Reflexive composites can sense damage through integrated piezoelectric sensing networks and respond to damage by heating discrete locations to activate the healable polymer matrix in areas of damage. The polymer matrix is a modified thermoset shape memory polymer that heals based on phenomena known as reptation. In theory, the reptation healing phenomena should occur in microseconds; however, during experimentation, it has been observed that to maximize healing and restore up to 85 % of mechanical properties a healing cycle of at least three minutes is required. This paper will focus on work conducted to determine the healing mechanisms at work in CRG's reflexive composites, the optimal healing cycles, and an explanation of the difference between the reptation model and actual healing times.

Organic/Inorganic Polymeric Composites for Heat-Transfer Reduction

NASA Technical Reports Server (NTRS)

Smith, Trent; Williams, Martha

2008-01-01

Organic/inorganic polymeric composite materials have been invented with significant reduction in heat-transfer properties. Measured decreases of 20-50 percent in thermal conductivity versus that of the unmodified polymer matrix have been attained. These novel composite materials also maintain mechanical properties of the unmodified polymer matrix. The present embodiments are applicable, but not limited to: racing applications, aerospace applications, textile industry, electronic applications, military hardware improvements, and even food service industries. One specific application of the polymeric composition is for use in tanks, pipes, valves, structural supports, and components for hot or cold fluid process systems where heat flow through materials is problematic and not desired. With respect to thermal conductivity and physical properties, these materials are superior alternatives to prior composite materials. These materials may prove useful as substitutes for metals in some cryogenic applications. A material of this type can be made from a blend of thermoplastics, elastomers, and appropriate additives and processed on normal polymer processing equipment. The resulting processed organic/inorganic composite can be made into fibers, molded, or otherwise processed into useable articles.

Multi-Length Scale-Enriched Continuum-Level Material Model for Kevlar-Fiber-Reinforced Polymer-Matrix Composites

DTIC Science & Technology

2012-08-03

is unlimited. Multi-Length Scale-Enriched Continuum-Level Material Model for Kevlar ®-Fiber-Reinforced Polymer-Matrix Composites The views, opinions...12211 Research Triangle Park, NC 27709-2211 ballistics, composites, Kevlar , material models, microstructural defects REPORT DOCUMENTATION PAGE 11... Kevlar ®-Fiber-Reinforced Polymer-Matrix Composites Report Title Fiber-reinforced polymer matrix composite materials display quite complex deformation

[Modern polymers in matrix tablets technology].

PubMed

Zimmer, Łukasz; Kasperek, Regina; Poleszak, Ewa

2014-01-01

Matrix tablets are the most popular method of oral drug administration, and polymeric materials have been used broadly in matrix formulations to modify and modulate drug release rate. The main goal of the system is to extend drug release profiles to maintain a constant in vivo plasma drug concentration and a consistent pharmacological effect. Polymeric matrix tablets offer a great potential as oral controlled drug delivery systems. Cellulose derivatives, like hydroxypropyl methylcellulose (HPMC) are often used as matrix formers. However, also other types of polymers can be used for this purpose including: Kollidon SR, acrylic acid polymers such as Eudragits and Carbopols. Nevertheless, polymers of natural origin like: carragens, chitosan and alginates widely used in the food and cosmetics industry are now coming to the fore of pharmaceutical research and are used in matrix tablets technology. Modern polymers allow to obtain matrix tablets by 3D printing, which enables to develop new formulation types. In this paper, the polymers used in matrix tablets technology and examples of their applications were described.

Synthesis, Dielectric, Electrical and Optical characterization of ZnO synthesized by chemical route using polymer precursors

NASA Astrophysics Data System (ADS)

Mishra, Raman; Bajpai, P. K.

2011-11-01

Nano-size ZnO (particle size 7.8 nm) have been prepared from a versatile, efficient and technically simple polymer matrix based precursor solution. The precursor solution constituted of zinc nitrates with polymer PVA in presence of mono-/disaccharides. Annealing the precursor mass at 900 °C single phase zinc oxide nano-particles are obtained. X-ray diffraction analysis confirms hexagonal crystal structure with lattice parameter a = b = 3.261 A0, c = 5.220 A0. The estimated average particle size obtained from XRD data is ≈7.8 nm. The impedance analysis reveals that the grain resistance decreases with increase in temperature as expected for a semi-conducting material. The relaxation is polydispersive and conduction is mainly through grains. Optical properties and AC/DC conduction activation energies are estimated from Arrhenius plots and conduction mechanism is discussed.

Exploratory studies of new avenues to achieve high electromechanical response and high dielectric constant in polymeric materials

NASA Astrophysics Data System (ADS)

Huang, Cheng

High performance soft electronic materials are key elements in advanced electronic devices for broad range applications including capacitors, actuators, artificial muscles and organs, smart materials and structures, microelectromechanical (MEMS) and microfluidic devices, acoustic devices and sensors. This thesis exploits new approaches to improve the electromechanical response and dielectric response of these materials. By making use of novel material phenomena such as large anisotropy in dipolar response in liquid crystals (LCs) and all-organic composites in which high dielectric constant organic solids and conductive polymers are either physically blended into or chemically grafted to a polymer matrix, we demonstrate that high dielectric constant and high electromechanical conversion efficiency comparable to that in ceramic materials can be achieved. Nano-composite approach can also be utilized to improve the performance of the electronic electroactive polymers (EAPs) and composites, for example, exchange coupling between the fillers and matrix with very large dielectric contrast can lead to significantly enhance the dielectric response as well as electromechanical response when the heterogeneity size of the composite is comparable to the exchange length. In addition to the dielectric composites, in which high dielectric constant fillers raise the dielectric constant of composites, conductive percolation can also lead to high dielectric constant in polymeric materials. An all-polymer percolative composite is introduced which exhibits very high dielectric constant (>7,000). The flexible all-polymer composites with a high dielectric constant make it possible to induce a high electromechanical response under a much reduced electric field in the field effect electroactive polymer (EAP) actuators (a strain of 2.65% with an elastic energy density of 0.18 J/cm3 can be achieved under a field of 16 V/mum). Agglomeration of the particles can also be effectively prevented by in situ preparation. High dielectric constant copper phthalocyanine oligomer and conductive polyaniline oligomer were successfully bonded to polyurethane backbone to form fully functionalized nano-phase polymers. Improvement of dispersibility of oligomers in polymer matrix makes the system self-organize the nanocomposites possessing oligomer nanophase (below 30nm) within the fully functionalized polymers. The resulting nanophase polymers significantly enhance the interface effect, which through the exchange coupling raises the dielectric response markedly above that expected from simple mixing rules for dielectric composites. Consequently, these nano-phase polymers offer a high dielectric constant (a dielectric constant near 1,000 at 20 Hz), improve the breakdown field and mechanical properties, and exhibit high electromechanical response. A longitudinal strain of more than -14% can be induced under a much reduced field, 23 V/mum, with an elastic energy density of higher than 1 J/cm3. The elastic modulus is as high as 100MPa, and a transverse strain is 7% under the same field. (Abstract shortened by UMI.)

Patterning methods for polymers in cell and tissue engineering.

PubMed

Kim, Hong Nam; Kang, Do-Hyun; Kim, Min Sung; Jiao, Alex; Kim, Deok-Ho; Suh, Kahp-Yang

2012-06-01

Polymers provide a versatile platform for mimicking various aspects of physiological extracellular matrix properties such as chemical composition, rigidity, and topography for use in cell and tissue engineering applications. In this review, we provide a brief overview of patterning methods of various polymers with a particular focus on biocompatibility and processability. The materials highlighted here are widely used polymers including thermally curable polydimethyl siloxane, ultraviolet-curable polyurethane acrylate and polyethylene glycol, thermo-sensitive poly(N-isopropylacrylamide) and thermoplastic and conductive polymers. We also discuss how micro- and nanofabricated polymeric substrates of tunable elastic modulus can be used to engineer cell and tissue structure and function. Such synergistic effect of topography and rigidity of polymers may be able to contribute to constructing more physiologically relevant microenvironment.

Carbon Nanotube/Space Durable Polymer Nanocomposite Films for Electrostatic Charge Dissipation

NASA Technical Reports Server (NTRS)

Smith, J. G., Jr.; Watson, K. A.; Thompson, C. M.; Connell, J. W.

2002-01-01

Low solar absorptivity, space environmentally stable polymeric materials possessing sufficient electrical conductivity for electrostatic charge dissipation (ESD) are of interest for potential applications on spacecraft as thin film membranes on antennas, solar sails, large lightweight space optics, and second surface mirrors. One method of imparting electrical conductivity while maintaining low solar absorptivity is through the use of single wall carbon nanotubes (SWNTs). However, SWNTs are difficult to disperse. Several preparative methods were employed to disperse SWNTs into the polymer matrix. Several examples possessed electrical conductivity sufficient for ESD. The chemistry, physical, and mechanical properties of the nanocomposite films will be presented.

Synthesis and characterization of conducting polyaniline-copper composites.

PubMed

Liu, Aijie; Bac, Luong Huu; Kim, Ji-Soon; Kim, Byoung-Kee; Kim, Jin-Chun

2013-11-01

Conducting polymer composites have many interesting physical properties and important application potentials. Suitable combinations of metal nanoparticles with conductive polymers can result in composite materials having unique physical and chemical properties that can have wide application potential in diverse areas. In this work, copper nanoparticles were fabricated by electrical explosion of wire (EEW) in solution of polyacrylic acid (PAA) and ethanol. Conductive polyaniline-copper (PANI-Cu) composites have been synthesized by in-situ polymerization of aniline in the fabricated copper suspension. Optical absorption in the UV-visible region of these suspensions was measured in the range of 200-900 nm. Morphology and structure of the composites were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) and Fourier-transform infrared spectra (FTIR). Pure copper nanoparticles were uniformly dispersed into the polymer matrix. Thermal stability of the composites was characterized by thermogravimetric analysis (TGA). Electrical conductivity measurements indicated that the conductivity of the composites was higher than that of pure polyaniline and increased with increasing content of copper.

Curcumin-Eudragit® E PO solid dispersion: A simple and potent method to solve the problems of curcumin.

PubMed

Li, Jinglei; Lee, Il Woo; Shin, Gye Hwa; Chen, Xiguang; Park, Hyun Jin

2015-08-01

Using a simple solution mixing method, curcumin was dispersed in the matrix of Eudragit® E PO polymer. Water solubility of curcumin in curcumin-Eudragit® E PO solid dispersion (Cur@EPO) was greatly increased. Based on the results of several tests, curcumin was demonstrated to exist in the polymer matrix in amorphous state. The interaction between curcumin and the polymer was investigated through Fourier transform infrared spectroscopy and (1)H NMR which implied that OH group of curcumin and carbonyl group of the polymer involved in the H bonding formation. Cur@EPO also provided protection function for curcumin as verified by the pH challenge and UV irradiation test. The pH value influenced curcumin release profile in which sustained release pattern was revealed. Additionally, in vitro transdermal test was conducted to assess the potential of Cur@EPO as a vehicle to deliver curcumin through this alternative administration route. Copyright © 2015 Elsevier B.V. All rights reserved.

The rheology and phase separation kinetics of mixed-matrix membrane dopes

NASA Astrophysics Data System (ADS)

Olanrewaju, Kayode Olaseni

Mixed-matrix hollow fiber membranes are being developed to offer more efficient gas separations applications than what the current technologies allow. Mixed-matrix membranes (MMMs) are membranes in which molecular sieves incorporated in a polymer matrix enhance separation of gas mixtures based on the molecular size difference and/or adsorption properties of the component gases in the molecular sieve. The major challenges encountered in the efficient development of MMMs are associated with some of the paradigm shifts involved in their processing, as compared to pure polymer membranes. For instance, mixed-matrix hollow fiber membranes are prepared by a dry-wet jet spinning method. Efficient large scale processing of hollow fibers by this method requires knowledge of two key process variables: the rheology and kinetics of phase separation of the MMM dopes. Predicting the rheological properties of MMM dopes is not trivial; the presence of particles significantly affects neat polymer membrane dopes. Therefore, the need exists to characterize and develop predictive capabilities for the rheology of MMM dopes. Furthermore, the kinetics of phase separation of polymer solutions is not well understood. In the case of MMM dopes, the kinetics of phase separation are further complicated by the presence of porous particles in a polymer solution. Thus, studies on the phase separation kinetics of polymer solutions and suspensions of zeolite particles in polymer solutions are essential. Therefore, this research thesis aims to study the rheology and phase separation kinetics of mixed-matrix membrane dopes. In our research efforts to develop predictive models for the shear rheology of suspensions of zeolite particles in polymer solutions, it was found that MFI zeolite suspensions have relative viscosities that dramatically exceed the Krieger-Dougherty predictions for hard sphere suspensions. Our investigations showed that the major origin of this discrepancy is the selective absorption of solvent molecules from the suspending polymer solution into the zeolite pores. Consequently, both the viscosity of the polymer solution and the particle contribution to the suspension viscosity are greatly increased. A predictive model for the viscosity of porous zeolite suspensions incorporating a solvent absorption parameter, alpha, into the Krieger-Dougherty model was developed. We experimentally determined the solvent absorption parameter and our results are in good agreement with the theoretical pore volume of MFI particles. In addition, fundamental studies were conducted with spherical nonporous silica suspensions to elucidate the role of colloidal and hydrodynamic forces on the rheology of mixed-matrix membrane dopes. Also in this thesis, details of a novel microfluidic device for measuring the phase separation kinetics of membrane dopes are presented. We have used this device to quantify the phase separation kinetics (PSK) of polymer solutions and MMM dopes upon contact with an array of relevant nonsolvent. For the polymer solution, we found that PSK is governed by the micro-rheological and thermodynamic properties of the polymer solution and nonsolvent. For the MMM dopes, we found that the PSK may increase with increase in particles surface area due to surface diffusion enhancement. In addition, it was found that the dispersed particles alter the thermodynamic properties of the dope based on the hydrophilicity and porosity of the particle.

A Study of the Critical Factors Controlling the Synthesis of Ceramic Matrix Composites from Preceramic Polymers.

DTIC Science & Technology

1988-04-15

physical properties of a polycarbosilane preceramic polymer as a function of temperature to derive synthesis methodology for SiC matrix composites , (2...investigate the role of interface modification in creating tough carbon fiber reinforced SiC matrix composites . RESEARCH PROGRESS Preceramic Polymer ...Classfication) A STUDY OF THE CRITICAL FACTORS CONTROLLING THE SYNTHESIS OF CERAMIC MATRIX COMPOSITES FROM PRECERAMIC POLYMERS 12. PERSONAL AUTHOR(S

Enhancement of the optical, thermal and electrical properties of PEO/PAM:Li polymer electrolyte films doped with Ag nanoparticles

NASA Astrophysics Data System (ADS)

Morsi, M. A.; El-Khodary, Sherif A.; Rajeh, A.

2018-06-01

Both lithium bromide (LiBr) and biosynthesized silver nanoparticles (Ag NPs) with average size 2-30 nm have been incorporated into the polymeric matrix of polyethylene oxide and polyacrylamide (PEO/PAM) blend by the casting method. FT-IR analysis indicates the formation of hydrogen bond between the blend components. Also, LiBr and Ag NPs interact with the functional groups of PEO/PAM matrix. The results of XRD analysis depict the semi-crystalline nature of these polymer samples and the degree of crystallinity is decreased due to the addition process. The values of optical energy gap from UV-Vis. data are decreased from 3.55 eV for blend to 3.26 for the nanocomposite sample in the indirect transition. LiBr/Ag NPs assist the improvement of the thermal stability of the PEO/PAM blend, as evidenced by TGA and DTA techniques. Upon the addition of LiBr and Ag NPs, an improvement for the conductivity, dielectric permittivity (έ) and dielectric loss (ἕ) of PEO/PAM solid polymer electrolytes are observed. It's clear that the improvement of the electrical conductivity and dielectric parameters for PEO/PAM: Li+/Ag NPs polymer electrolyte system makes it as a promising candidate for solid-state Li battery applications.

Polyimide/carbon Nanocomposites

NASA Technical Reports Server (NTRS)

Harris, Frank W.

2003-01-01

The goal of this product is to design and characterize well-defined conductive nanocomposite materials. The materials will be composed of a polymer matrix composed of rigid-backbone polyimides, and will be filled with modified or unmodified multi-walled carbon nanotubes (MWNTs). The ultimate design of this project is to create composite materials with optical clarity and a high conductivity.

Role of interfacial effects in carbon nanotube/epoxy nanocomposite behavior.

PubMed

Pécastaings, G; Delhaès, P; Derré, A; Saadaoui, H; Carmona, F; Cui, S

2004-09-01

The interfacial effects are critical to understand the nanocomposite behavior based on polymer matrices. These effects are dependent upon the morphology of carbon nanotubes, the type of used polymer and the processing technique. Indeed, we show that the different parameters, as the eventual surfactant use, the ultrasonic treatment and shear mixing have to be carefully examined, in particular, for nanotube dispersion and their possible alignment. A series of multiwalled nanotubes (MWNT) have been mixed with a regular epoxy resin under a controlled way to prepare nanocomposites. The influence of nanotube content is examined through helium bulk density, glass transition temperature of the matrix and direct current electrical conductivity measurements. These results, including the value of the percolation threshold, are analyzed in relationship with the mesostructural organization of these nanotubes, which is observed by standard and conductive probe atomic force microscopy (AFM) measurements. The wrapping effect of the organic matrix along the nanotubes is evidenced and analyzed to get a better understanding of the final composite characteristics, in particular, for eventually reinforcing the matrix without covalent bonding.

High Strain Rate Deformation Modeling of a Polymer Matrix Composite. Part 1; Matrix Constitutive Equations

NASA Technical Reports Server (NTRS)

Goldberg, Robert K.; Stouffer, Donald C.

1998-01-01

Recently applications have exposed polymer matrix composite materials to very high strain rate loading conditions, requiring an ability to understand and predict the material behavior under these extreme conditions. In this first paper of a two part report, background information is presented, along with the constitutive equations which will be used to model the rate dependent nonlinear deformation response of the polymer matrix. Strain rate dependent inelastic constitutive models which were originally developed to model the viscoplastic deformation of metals have been adapted to model the nonlinear viscoelastic deformation of polymers. The modified equations were correlated by analyzing the tensile/ compressive response of both 977-2 toughened epoxy matrix and PEEK thermoplastic matrix over a variety of strain rates. For the cases examined, the modified constitutive equations appear to do an adequate job of modeling the polymer deformation response. A second follow-up paper will describe the implementation of the polymer deformation model into a composite micromechanical model, to allow for the modeling of the nonlinear, rate dependent deformation response of polymer matrix composites.

Enhancement in ionic conductivity on solid polymer electrolytes containing large conducting species

DOE Office of Scientific and Technical Information (OSTI.GOV)

Praveen, D.; Damle, Ramakrishna

2016-05-23

Solid Polymer Electrolytes (SPEs) lack better conducting properties at ambient temperatures. Various methods to enhance their ionic conductivity like irradiation with swift heavy ions, γ-rays, swift electrons and quenching at low temperature etc., have been explored in the literature. Among these, one of the oldest methods is incorporation of different conducting species into the polymer matrix and/or addition of nano-sized inert particles into SPEs. Various new salts like LiBr, Mg(ClO{sub 4}){sub 2}, NH{sub 4}I etc., have already been tried in the past with some success. Also various nanoparticles like Al{sub 2}O{sub 3}, TiO{sub 2} etc., have been tried in themore » past. In this article, we have investigated an SPE containing Rubidium as a conducting species. Rubidium has a larger ionic size compared to lithium and sodium ions which have been investigated in the recent past. In the present article, we have investigated the conductivity of large sized conducting species and shown the enhancement in the ionic conductivity by addition of nano-sized inert particles.« less

Properties of Multifunctional Hybrid Carbon Nanotube/Carbon Fiber Polymer Matrix Composites

NASA Technical Reports Server (NTRS)

Cano, Roberto J.; Kang, Jin Ho; Grimsley, Brian W.; Ratcliffe, James G.; Siochi, Emilie J.

2016-01-01

For aircraft primary structures, carbon fiber reinforced polymer (CFRP) composites possess many advantages over conventional aluminum alloys due to their light weight, higher strength- and stiffness-to-weight ratios, and low life-cycle maintenance costs. However, the relatively low electrical and thermal conductivities of CFRP composites fail to provide structural safety in certain operational conditions such as lightning strikes. Carbon nanotubes (CNT) offer the potential to enhance the multi-functionality of composites with improved thermal and electrical conductivity. In this study, hybrid CNT/carbon fiber (CF) polymer composites were fabricated by interleaving layers of CNT sheets with Hexcel® IM7/8852 prepreg. Resin concentrations from 1 wt% to 50 wt% were used to infuse the CNT sheets prior to composite fabrication. The interlaminar properties of the resulting hybrid composites were characterized by mode I and II fracture toughness testing. Fractographical analysis was performed to study the effect of resin concentration. In addition, multi-directional physical properties like thermal conductivity of the orthotropic hybrid polymer composite were evaluated.

Multifunctional polymer nano-composite based superhydrophobic surface

NASA Astrophysics Data System (ADS)

Maitra, Tanmoy; Asthana, Ashish; Buchel, Robert; Tiwari, Manish K.; Poulikakos, Dimos

2014-11-01

Superhydrophobic surfaces become desirable in plethora of applications in engineering fields, automobile industry, construction industries to name a few. Typical fabrication of superhydrophobic surface consists of two steps: first is to create rough morphology on the substrate of interest, followed by coating of low energy molecules. However, typical exception of the above fabrication technique would be direct coating of functional polymer nanocomposites on substrate where superhydrophobicity is needed. Also in this case, the use of different nanoparticles in the polymer matrix can be exploited to impart multi-functional properties to the superhydrophobic coatings. Herein, different carbon nanoparticles like graphene nanoplatelets (GNP), carbon nanotubes (CNT) and carbon black (CB) are used in fluropolymer matrix to prepare superhydrophobic coatings. The multi-functional properties of coatings are enhanced by combining two different carbon fillers in the matrix. The aforementioned superhydrophobic coatings have shown high electrical conductivity and excellent droplet meniscus impalement resistance. Simultaneous superhydrophobic and oleophillic character of the above coating is used to separate mineral oil and water through filtration of their mixture. Swiss National Science Foundation (SNF) Grant 200021_135479.

Ladder polymers for use as high temperature stable resins or coatings

NASA Technical Reports Server (NTRS)

Meador, Mary Ann (Inventor)

1990-01-01

An object of the invention is to synthesize a new class of ladder and partial ladder polymers. In accordance with the invention, the new class of ladder and partial ladder polymers are synthesized by polymerizing a bis-dienophile with a bis-diene. Another object of the invention is to provide a fabricated, electrically conducting, void free composite comprising the new class of the ladder and partial ladder polymers described above. The novelty of the invention relates to a new class of ladder and partial ladder polymers and a process for synthesizing these polymers. These polymers are soluble in common organic solvents and are characterized with a unique dehydration property at temperatures of 300 to 400 C to provide thermo-oxidatively stable pentiptycene units along the polymeric backbone. These polymers are further characterized with high softening points and good thermo-oxidative stability properties. Thus these polymers have potential as processable, matrix resins for high temperature composite applications.

Dielectric breakdown in silica-amorphous polymer nanocomposite films: the role of the polymer matrix.

PubMed

Grabowski, Christopher A; Fillery, Scott P; Westing, Nicholas M; Chi, Changzai; Meth, Jeffrey S; Durstock, Michael F; Vaia, Richard A

2013-06-26

The ultimate energy storage performance of an electrostatic capacitor is determined by the dielectric characteristics of the material separating its conductive electrodes. Polymers are commonly employed due to their processability and high breakdown strength; however, demands for higher energy storage have encouraged investigations of ceramic-polymer composites. Maintaining dielectric strength, and thus minimizing flaw size and heterogeneities, has focused development toward nanocomposite (NC) films; but results lack consistency, potentially due to variations in polymer purity, nanoparticle surface treatments, nanoparticle size, and film morphology. To experimentally establish the dominant factors in broad structure-performance relationships, we compare the dielectric properties for four high-purity amorphous polymer films (polymethyl methacrylate, polystyrene, polyimide, and poly-4-vinylpyridine) incorporating uniformly dispersed silica colloids (up to 45% v/v). Factors known to contribute to premature breakdown-field exclusion and agglomeration-have been mitigated in this experiment to focus on what impact the polymer and polymer-nanoparticle interactions have on breakdown. Our findings indicate that adding colloidal silica to higher breakdown strength amorphous polymers (polymethyl methacrylate and polyimide) causes a reduction in dielectric strength as compared to the neat polymer. Alternatively, low breakdown strength amorphous polymers (poly-4-vinylpyridine and especially polystyrene) with comparable silica dispersion show similar or even improved breakdown strength for 7.5-15% v/v silica. At ∼15% v/v or greater silica content, all the polymer NC films exhibit breakdown at similar electric fields, implying that at these loadings failure becomes independent of polymer matrix and is dominated by silica.

Polymer-Single Wall Carbon Nanotube Composites for Potential Spacecraft Applications

NASA Technical Reports Server (NTRS)

Park, C.; Ounaies, Z.; Watson, K. A.; Pawlowski, K.; Lowther, S. E.; Connell, J. W.; Siochi, E. J.; Harrison, J. S.; St.Clair, T. L.; Bushnell, Dennis M. (Technical Monitor)

2002-01-01

Polymer-single wall carbon nanotube (SWNT) composite films were prepared and characterized as part of an effort to develop polymeric materials with improved combinations of properties for potential use on future spacecraft. Next generation spacecraft will require ultra-lightweight materials that possess specific and unique combinations of properties such as radiation and atomic oxygen resistance, low solar absorptivity, high thermal emissitivity, electrical conductivity, tear resistance, ability to be folded and seamed, and good mechanical properties. The objective of this work is to incorporate sufficient electrical conductivity into space durable polyimides to mitigate static charge build-up. The challenge is to obtain this level of conductivity (10(exp -8) S/cm) without degrading other properties of importance, particularly optical transparency. Several different approaches were attempted to fully disperse the SWNTs into the polymer matrix. These included high shear mixing, sonication, and synthesizing the polymers in the presence of pre-dispersed SWNTs. Acceptable levels of conductivity were obtained at loading levels less than one tenth weight percent SWNT without significantly sacrificing optical properties. Characterization of the nanocomposite films and the effect of SWNT concentration and dispersion on the conductivity, solar absorptivity, thermal emissivity, mechanical and thermal properties were discussed. Fibers and non-woven porous mats of SWNT reinforced polymer nanocomposite were produced using electrospinning.

Composite Materials for Low-Temperature Applications

NASA Technical Reports Server (NTRS)

2008-01-01

Composite materials with improved thermal conductivity and good mechanical strength properties should allow for the design and construction of more thermally efficient components (such as pipes and valves) for use in fluid-processing systems. These materials should have wide application in any number of systems, including ground support equipment (GSE), lunar systems, and flight hardware that need reduced heat transfer. Researchers from the Polymer Science and Technology Laboratory and the Cryogenics Laboratory at Kennedy Space Center were able to develop a new series of composite materials that can meet NASA's needs for lightweight materials/composites for use in fluid systems and also expand the plastic-additive markets. With respect to thermal conductivity and physical properties, these materials are excellent alternatives to prior composite materials and can be used in the aerospace, automotive, military, electronics, food-packaging, and textile markets. One specific application of the polymeric composition is for use in tanks, pipes, valves, structural supports, and components for hot or cold fluid-processing systems where heat flow through materials is a problem to be avoided. These materials can also substitute for metals in cryogenic and other low-temperature applications. These organic/inorganic polymeric composite materials were invented with significant reduction in heat transfer properties. Decreases of 20 to 50 percent in thermal conductivity versus that of the unmodified polymer matrix were measured. These novel composite materials also maintain mechanical properties of the unmodified polymer matrix. These composite materials consist of an inorganic additive combined with a thermoplastic polymer material. The intrinsic, low thermal conductivity of the additive is imparted into the thermoplastic, resulting in a significant reduction in heat transfer over that of the base polymer itself, yet maintaining most of the polymer's original properties. Normal polymer processing techniques can turn these composite materials into unique, custom parts for ground support, Shuttle, and Constellation needs. We fabricated test specimens of the composite and base materials for thermal and mechanical characterization and found that the strength of the composite material at nominal-percentage loading remained relatively unchanged from the base material.

Temperature dependent dielectric properties and ion transportation in solid polymer electrolyte for lithium ion batteries

NASA Astrophysics Data System (ADS)

Sengwa, R. J.; Dhatarwal, Priyanka; Choudhary, Shobhna

2016-05-01

Solid polymer electrolyte (SPE) film consisted of poly(ethylene oxide) (PEO) and poly(methyl methacrylate) (PMMA) blend matrix with lithium tetrafluroborate (LiBF4) as dopant ionic salt and poly(ethylene glycol) (PEG) as plasticizer has been prepared by solution casting method followed by melt pressing. Dielectric properties and ionic conductivity of the SPE film at different temperatures have been determined by dielectric relaxation spectroscopy. It has been observed that the dc ionic conductivity of the SPE film increases with increase of temperature and also the decrease of relaxation time. The temperature dependent relaxation time and ionic conductivity values of the electrolyte are governed by the Arrhenius relation. Correlation observed between dc conductivity and relaxation time confirms that ion transportation occurs with polymer chain segmental dynamics through hopping mechanism. The room temperature ionic conductivity is found to be 4 × 10-6 S cm-1 which suggests the suitability of the SPE film for rechargeable lithium batteries.

Temperature dependent dielectric properties and ion transportation in solid polymer electrolyte for lithium ion batteries

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sengwa, R. J., E-mail: rjsengwa@rediffmail.com; Dhatarwal, Priyanka, E-mail: dhatarwalpriyanka@gmail.com; Choudhary, Shobhna, E-mail: shobhnachoudhary@rediffmail.com

2016-05-06

Solid polymer electrolyte (SPE) film consisted of poly(ethylene oxide) (PEO) and poly(methyl methacrylate) (PMMA) blend matrix with lithium tetrafluroborate (LiBF{sub 4}) as dopant ionic salt and poly(ethylene glycol) (PEG) as plasticizer has been prepared by solution casting method followed by melt pressing. Dielectric properties and ionic conductivity of the SPE film at different temperatures have been determined by dielectric relaxation spectroscopy. It has been observed that the dc ionic conductivity of the SPE film increases with increase of temperature and also the decrease of relaxation time. The temperature dependent relaxation time and ionic conductivity values of the electrolyte are governedmore » by the Arrhenius relation. Correlation observed between dc conductivity and relaxation time confirms that ion transportation occurs with polymer chain segmental dynamics through hopping mechanism. The room temperature ionic conductivity is found to be 4 × 10{sup −6} S cm{sup −1} which suggests the suitability of the SPE film for rechargeable lithium batteries.« less

Studies on surface morphology and electrical conductivity of PEDOT:PSS thin films in presence of gold nanoparticles

NASA Astrophysics Data System (ADS)

Bhowal, Ashim Chandra; Kundu, Sarathi

2018-04-01

PEDOT:PSS is a water soluble conducting polymer consists of positively charged PEDOT and negatively charged PSS. However, this polymer suffers low conductivity problem which restrict its use. In this paper, electrical conductivity of PEDOT:PSS thin films is improved by using charged gold nanoparticles. The nanoparticles used are synthesized using lysozyme protein. The nanoparticles coated with lysozyme protein possess positive zeta potential. In the presence of gold nanoparticles due to electrostatic interaction between positively charged nanoparticles and negatively charged PSS chains, modification takes place in the surface morphology and electrical behaviors of PEDOT:PSS thin films. The changes in the polymer matrix conformations in the presence of nanoparticles are studied by Fourier transformed Infra-red (FTIR) spectroscopy, whereas the surface morphology of prepared thin films before and after interaction with nanoparticles is investigated through atomic force microscopy (AFM). Four probe method is used to measure the variation of electrical conductivity from I-V characteristics curves.

Significantly improved dielectric performances of nanocomposites via loading two-dimensional core-shell structure Bi2Te3@SiO2 nanosheets

NASA Astrophysics Data System (ADS)

Chen, Jianwen; Wang, Xiucai; Yu, Xinmei; Fan, Yun; Duan, Zhikui; Jiang, Yewen; Yang, Faquan; Zhou, Yuexia

2018-07-01

Polymer/semiconductor-insulator nanocomposites can display high dielectric constants with a relatively low dissipation factor under low electric fields, and thus seem to promising for high energy density capacitors. Here, a novel nanocomposite films is developed by loading two-dimensional (2D) core-shell structure Bi2Te3@SiO2 nanosheets in the poly (vinylidene fluoride-hexafluoro propylene) (P(VDF-HFP)) polymer matrix. The 2D Bi2Te3 nanosheets were prepared through simple microwave-assisted method. The experimental results suggesting that the SiO2 shell layer between the fillers and polymer matrix could effectively improve the dielectric constant, dielectric loss, AC conductivity, and breakdown strength of composites films. The composite films load with 10 vol.% 2D Bi2Te3@SiO2 nanosheets exhibits a high dielectric constant of 70.3 at 1 kHz and relatively low dielectric loss of 0.058 at 1 kHz. The finite element simulation of electric field and electric current density distribution revealed that the SiO2 shell layer between the fillers and polymer matrix could effectively improve the energy loss, local electric field strength, and breakdown strength of composite films. Therefore, this work will provide a promising route to achieve high-performance capacitors.

Patterning Methods for Polymers in Cell and Tissue Engineering

PubMed Central

Kim, Hong Nam; Kang, Do-Hyun; Kim, Min Sung; Jiao, Alex; Kim, Deok-Ho; Suh, Kahp-Yang

2017-01-01

Polymers provide a versatile platform for mimicking various aspects of physiological extracellular matrix properties such as chemical composition, rigidity, and topography for use in cell and tissue engineering applications. In this review, we provide a brief overview of patterning methods of various polymers with a particular focus on biocompatibility and processability. The materials highlighted here are widely used polymers including thermally curable polydimethyl siloxane, ultraviolet-curable polyurethane acrylate and polyethylene glycol, thermo-sensitive poly(N-isopropylacrylamide) and thermoplastic and conductive polymers. We also discuss how micro- and nanofabricated polymeric substrates of tunable elastic modulus can be used to engineer cell and tissue structure and function. Such synergistic effect of topography and rigidity of polymers may be able to contribute to constructing more physiologically relevant microenvironment. PMID:22258887

Block copolymers for alkaline fuel cell membrane materials

NASA Astrophysics Data System (ADS)

Li, Yifan

Alkaline fuel cells (AFCs) using anion exchange membranes (AEMs) as electrolyte have recently received considerable attention. AFCs offer some advantages over proton exchange membrane fuel cells, including the potential of non-noble metal (e.g. nickel, silver) catalyst on the cathode, which can dramatically lower the fuel cell cost. The main drawback of traditional AFCs is the use of liquid electrolyte (e.g. aqueous potassium hydroxide), which can result in the formation of carbonate precipitates by reaction with carbon dioxide. AEMs with tethered cations can overcome the precipitates formed in traditional AFCs. Our current research focuses on developing different polymer systems (blend, block, grafted, and crosslinked polymers) in order to understand alkaline fuel cell membrane in many aspects and design optimized anion exchange membranes with better alkaline stability, mechanical integrity and ionic conductivity. A number of distinct materials have been produced and characterized. A polymer blend system comprised of poly(vinylbenzyl chloride)-b-polystyrene (PVBC-b-PS) diblock copolymer, prepared by nitroxide mediated polymerization (NMP), with poly(2,6-dimethyl-1,4-phenylene oxide) (PPO) or brominated PPO was studied for conversion into a blend membrane for AEM. The formation of a miscible blend matrix improved mechanical properties while maintaining high ionic conductivity through formation of phase separated ionic domains. Using anionic polymerization, a polyethylene based block copolymer was designed where the polyethylene-based block copolymer formed bicontinuous morphological structures to enhance the hydroxide conductivity (up to 94 mS/cm at 80 °C) while excellent mechanical properties (strain up to 205%) of the polyethylene block copolymer membrane was observed. A polymer system was designed and characterized with monomethoxy polyethylene glycol (mPEG) as a hydrophilic polymer grafted through substitution of pendent benzyl chloride groups of a PVBC-b-PS. The incorporation of the hydrophilic polymer allows for an investigation of the effect of hydration on ionic conductivity, resulting in the increase in membrane water affinity, enhancement of conductivity and reduced dependence of conductivity on relative humidity. A study of crosslinking of block copolymers was done wherein the crosslinking occurs in the non-matrix phase in order to maintain mechanical properties. The formation of a cationic crosslinked structure improves the mechanical integrity of the membrane in water while showing little deleterious effect on ionic conductivity and mechanical properties.

Effect of Dispersoid on Sulfonium Ionic Liquid Based Gel Polymer Electrolyte for Lithium Secondary Battery.

PubMed

Muthupradeepa, R; Sivakumar, M; Subadevi, R; Suryanarayanan, V; Liu, Wei-Ren

2018-01-01

The present study emphases on the effect of toting of TiO2 filler on the electrochemical enactment of polymer electrolyte containing PVdF-co-HFP(30) + SEt3TFSI(10) + EC/PC(60) + TiO2(x) wt% (Poly (vinylidene fluoride-co-hexafluoropropylene + Triethylsulfoniumbis(trifluoromethylsulfonyl)imide + Ethylene carbonate/Propylene carbonate (1:1 ratio) + Titanium dioxide) for lithium battery applications. Composite electrolytes with different weight percentages of TiO2 were prepared and characterized by different surface analytical, thermal and electrochemical techniques. With gradual increase of the amount of TiO2 upto 6 wt%, broadening of the prominent peak has been noted, suggesting a decrease in the degree of crystallinity upon the addition of TiO2, as revealed by X-ray diffraction (XRD). Raman and FT-IR studies confirm the presence of various functional groups, present in the matrix. The electrolyte with TiO2 (6 wt%) has maximum stability of 460 °C, as confirmed by thermal analysis. Conductivity of the composite polymer electrolytes increases upto 6 wt% of TiO2 (3.42 × 10-3 S/cm at 303 K) and further addition, causes a dip down in conductivity, indicating an improvement in the ionic conductivity and thermal stability with the incorporation of TiO2 filler. Surface morphologic images show the presence of surface and cavity in the polymer matrix, filled with the filler uniformly. Voltammetric studies confirm the electrochemical stability of films upto 4.62 V. Coin cell containing Li anode and LiFePO4 cathode along with polymer electrolyte/6 wt% TiO2 filler, delivers a first discharge capacity of 145 mAh/g with the working voltage of 3.4 V.

Selective and Responsive Nanopore-Filled Membranes

DTIC Science & Technology

2011-03-14

Materials Science and Engineering Poster Competition 15. Chen, H.; Elabd, Y.A. Ionic Liquid Polymers: Electrospinning and Solution Properties. Fall...hydrophilic ionic polymer gels within a hydrophobic polymer host matrix. The specific tasks of this project include (1) synthesizing stimuli...on polymer-polymer nanocomposites of hydrophilic ionic polymer gels within a hydrophobic polymer host matrix. The specific tasks of this project

DOE Office of Scientific and Technical Information (OSTI.GOV)

Arya, Anil; Sharma, Sweety; Sharma, A. L., E-mail: alsharmaiitkgp@gmail.com

Blend polymer electrolytes are prepared for salt concentration (Ö/Li = 4) with the constant ratio (0.5 gm) of PEO and PAN using solution casting technique. The prepared free standing solid polymeric film is characterized by Field Emission Scanning Electron Microscopy (FESEM) which confirms the homogeneous distribution of dissociated salt in blend polymer matrix. After addition of salt the ionic conductivity value is found to be of the order of 7.13 × 10{sup −5} Scm{sup −1} which is three orders higher when compared with pure blend polymer films. The microscopic interaction among the polymer-ion, ion-ion has been confirmed by the Fouriermore » Transform Infrared (FTIR) Spectroscopy. A very fine correlation has been built in the electrical conductivity and FTIR result. On the basis of above finding, a prepared free standing solid polymeric film appears to be appropriate for the energy storage/conversion device applications.« less

Impedance studies of a green blend polymer electrolyte based on PVA and Aloe-vera

NASA Astrophysics Data System (ADS)

Selvalakshmi, S.; Mathavan, T.; Vijaya, N.; Selvasekarapandian, Premalatha, M.; Monisha, S.

2016-05-01

The development of polymer electrolyte materials for energy generating and energy storage devices is a challenge today. A new type of blended green electrolyte based on Poly-vinyl alcohol (PVA) and Aloe-vera has been prepared by solution casting technique. The blending of polymers may lead to the increase in stability due to one polymer portraying itself as a mechanical stiffener and the other as a gelled matrix supported by the other. The prepared blend electrolytes were subjected to Ac impedance studies. It has been found out that the polymer film in which 1 gm of PVA was dissolved in 40 ml of Aloe-vera extract exhibits highest conductivity and its value is 3.08 × 10-4 S cm-1.

Anticorrosion Coatings Based on Assemblies of Superhydrophobic Particles Impregnated with Conductive Oil

DTIC Science & Technology

2016-05-13

silver nanowires synthesized in our group using sol-gel techniques...been demonstrated (Figure 12). The electrical resistance of the coatings should further be decreased Figure 14. High aspect ratio silver nanowires ...the coatings is to use a conductive polymer matrix and disperse high aspect ratio silver nanowires into the coating formulations. The electrical

The electrical conductivities of polyimide and polyimide/Li triflate composites: An a.c. impedance study

NASA Astrophysics Data System (ADS)

Aziz, Nor Diyana Abdul; Kamarulzaman, Norlida; Subban, Ri Hanum Yahaya; Hamzah, Ahmad Sazali; Ahmed, Azni Zain; Osman, Zurina; Rusdi, Roshidah; Kamarudin, Norashikin; Mohalid, Norhanim; Romli, Ahmad Zafir; Shaameri, Zurina

2017-09-01

Polymer electrolytes have been an essential area of research for many decades. One of the reasons was the need to find new electrolyte materials suitable for device applications like solid-state batteries, supercapacitors, fuel cells, etc. with enhanced characteristics. For more than 40 years, polyimide has been known as a super-engineering plastic due to its excellent thermal stability (Tg > 250 °C) and mechanical properties. Therefore, in an effort to develop new polymer electrolytes, polyimide as a polymer matrix was chosen. Composite films of the polymer doped with lithium salt, LiCF3SO3 was prepared. These PI based polymer electrolyte films were investigated by the alternating current (a.c.) impedance spectroscopy method in the temperature range from 300 K to 373 K. It was observed that conductivity increased with the increase of temperature and amount of doping salt. Alternatively, the activation energy (Ea) of the composite films decreased with the increase of the doping salt, LiCF3SO3.

Semi-Interpenetrating Polymer Networks for Enhanced Supercapacitor Electrodes.

PubMed

Fong, Kara D; Wang, Tiesheng; Kim, Hyun-Kyung; Kumar, R Vasant; Smoukov, Stoyan K

2017-09-08

Conducting polymers show great promise as supercapacitor materials due to their high theoretical specific capacitance, low cost, toughness, and flexibility. Poor ion mobility, however, can render active material more than a few tens of nanometers from the surface inaccessible for charge storage, limiting performance. Here, we use semi-interpenetrating networks (sIPNs) of a pseudocapacitive polymer in an ionically conductive polymer matrix to decrease ion diffusion length scales and make virtually all of the active material accessible for charge storage. Our freestanding poly(3,4-ethylenedioxythiophene)/poly(ethylene oxide) (PEDOT/PEO) sIPN films yield simultaneous improvements in three crucial elements of supercapacitor performance: specific capacitance (182 F/g, a 70% increase over that of neat PEDOT), cycling stability (97.5% capacitance retention after 3000 cycles), and flexibility (the electrodes bend to a <200 μm radius of curvature without breaking). Our simple and controllable sIPN fabrication process presents a framework to develop a range of polymer-based interpenetrated materials for high-performance energy storage technologies.

Fabrication of conductive polymer-based nanofiber scaffolds for tissue engineering applications.

PubMed

Gu, Bon Kang; Kim, Min Sup; Kang, Chang Mo; Kim, Jong-Ll; Park, Sang Jun; Kim, Chun-Ho

2014-10-01

Natural and synthetic polymers, in particular those that are conductive, are of great interest in the field of tissue engineering and the pursuit of biomimetic extracellular matrix (ECM) structures for adhesion, proliferation, and differentiation of cells. In the present study, natural chitin and conductive polyaniline (PANi) blended solutions were electrospun to produce biodegradable and conductive biomimetic nanostructured scaffolds. The chitin/PANi (Chi-PANi) nanofibrous materials were characterized using field emission scanning electron microscopy, Fourier transform-infrared spectroscopy, wettability analysis, mechanical testing, and electrical conductivity measurements using a 4-point probe method. The calculated electrical conductivities of the PANi-containing nanofiber scaffolds significantly increased as the amount of PANi increased, reaching 5.21 ± 0.28 x 10(-3) S/cm for 0.3 wt% content of the conducting polymer. In addition, the viability of human mesenchymal stem cells (hMSCs) cultured on the Chi-PANi nanofiber scaffolds in vitro was found to be excellent. These results suggest that the Chi-PANi nanofiber scaffolds have great potential for use in tissue engineering applications that involve electrical stimulation.

Electrically and Thermally Conductive Carbon Fibre Fabric Reinforced Polymer Composites Based on Nanocarbons and an In-situ Polymerizable Cyclic Oligoester.

PubMed

Jang, Ji-Un; Park, Hyeong Cheol; Lee, Hun Su; Khil, Myung-Seob; Kim, Seong Yun

2018-05-16

There is growing interest in carbon fibre fabric reinforced polymer (CFRP) composites based on a thermoplastic matrix, which is easy to rapidly produce, repair or recycle. To expand the applications of thermoplastic CFRP composites, we propose a process for fabricating conductive CFRP composites with improved electrical and thermal conductivities using an in-situ polymerizable and thermoplastic cyclic butylene terephthalate oligomer matrix, which can induce good impregnation of carbon fibres and a high dispersion of nanocarbon fillers. Under optimal processing conditions, the surface resistivity below the order of 10 +10 Ω/sq, which can enable electrostatic powder painting application for automotive outer panels, can be induced with a low nanofiller content of 1 wt%. Furthermore, CFRP composites containing 20 wt% graphene nanoplatelets (GNPs) were found to exhibit an excellent thermal conductivity of 13.7 W/m·K. Incorporating multi-walled carbon nanotubes into CFRP composites is more advantageous for improving electrical conductivity, whereas incorporating GNPs is more beneficial for enhancing thermal conductivity. It is possible to fabricate the developed thermoplastic CFRP composites within 2 min. The proposed composites have sufficient potential for use in automotive outer panels, engine blocks and other mechanical components that require conductive characteristics.

Composite material

DOEpatents

Hutchens, Stacy A [Knoxville, TN; Woodward, Jonathan [Solihull, GB; Evans, Barbara R [Oak Ridge, TN; O'Neill, Hugh M [Knoxville, TN

2012-02-07

A composite biocompatible hydrogel material includes a porous polymer matrix, the polymer matrix including a plurality of pores and providing a Young's modulus of at least 10 GPa. A calcium comprising salt is disposed in at least some of the pores. The porous polymer matrix can comprise cellulose, including bacterial cellulose. The composite can be used as a bone graft material. A method of tissue repair within the body of animals includes the steps of providing a composite biocompatible hydrogel material including a porous polymer matrix, the polymer matrix including a plurality of pores and providing a Young's modulus of at least 10 GPa, and inserting the hydrogel material into cartilage or bone tissue of an animal, wherein the hydrogel material supports cell colonization in vitro for autologous cell seeding.

Development of membranes and a study of their interfaces for rechargeable lithium-air battery

NASA Astrophysics Data System (ADS)

Kumar, Jitendra; Kumar, Binod

This paper describes an investigation with an objective to screen and select high performance membrane materials for a working, rechargeable lithium-air battery. Membrane laminates comprising glass-ceramic (GC) and polymer-ceramic (PC) membranes were assembled, evaluated and analyzed. A superionic conducting GC membrane with a chemical composition of Li 1+ xAl xGe 2- x(PO 4) 3 (x = 0.5) was used. Polymer membranes comprising of PC(BN), PC(AlN), PC(Si 3N 4) and PC(Li 2O) electrochemically coupled the GC membrane with the lithium anode. The cell and membrane laminates were characterized by determining cell conductivity, open circuit voltage and carrier concentration and its mobility. The measurements identified Li 2O and BN as suitable dopants in polymer matrix which catalyzed anodic charge transfer reaction, formed stable SEI layer and provided high lithium ion conductivity.

Formulation and evaluation of controlled release matrix mucoadhesive tablets of domperidone using Salvia plebeian gum

PubMed Central

Arora, Gurpreet; Malik, Karan; Singh, Inderbir; Arora, Sandeep; Rana, Vikas

2011-01-01

The aim of study was to prepare controlled release matrix mucoadhesive tablets of domperidone using Salvia plebeian gum as natural polymer. Tablets were formulated by direct compression technology employing the natural polymer in different concentrations (5, 10, 15 and 20% w/w). The prepared batches were evaluated for drug assay, diameter, thickness, hardness and tensile strength, swelling index, mucoadhesive strength (using texture analyzer) and subjected to in vitro drug release studies. Real-time stability studies were also conducted on prepared batches. In vitro drug release data were fitted in various release kinetic models for studying the mechanism of drug release. Tensile strength was found to increase from 0.808 ± 0.098 to 1.527 ± 0.10 mN/cm2 and mucoadhesive strength increased from 13.673 ± 1.542 to 40.378 ± 2.345 N, with an increase in the polymer concentration from 5 to 20% (A1 to A4). Swelling index was reported to increase with both increase in the concentration of gum and the time duration. The in vitro drug release decreased from 97.76 to 83.4% (A1 to A4) with the increase in polymer concentration. The drug release from the matrix tablets was found to follow zero-order and Higuchi models, indicating the matrix-forming potential of natural polymer. The value of n was found to be between 0.5221 and 0.8992, indicating the involvement of more than one drug release mechanism from the formulation and possibly the combination of both diffusion and erosion. These research findings clearly indicate the potential of S. plebeian gum to be used as binder, release retardant and mucoadhesive natural material in tablet formulations. PMID:22171313

Regenerative peripheral nerve interface viability and signal transduction with an implanted electrode.

PubMed

Kung, Theodore A; Langhals, Nicholas B; Martin, David C; Johnson, Philip J; Cederna, Paul S; Urbanchek, Melanie G

2014-06-01

The regenerative peripheral nerve interface is an internal interface for signal transduction with external electronics of prosthetic limbs; it consists of an electrode and a unit of free muscle that is neurotized by a transected residual peripheral nerve. Adding a conductive polymer coating on electrodes improves electrode conductivity. This study examines regenerative peripheral nerve interface tissue viability and signal fidelity in the presence of an implanted electrode coated or uncoated with a conductive polymer. In a rat model, the extensor digitorum longus muscle was moved as a nonvascularized free tissue transfer and neurotized by the divided peroneal nerve. Either a stainless steel pad electrode (n = 8) or a pad electrode coated with poly(3,4-ethylenedioxythiophene) conductive polymer (PEDOT) (n = 8) was implanted on the muscle transfer and secured with an encircling acellular extracellular matrix. The contralateral muscle served as the control. The free muscle transfers were successfully revascularized and over time reinnervated as evidenced by serial insertional needle electromyography. Compound muscle action potentials were successfully transduced through the regenerative peripheral nerve interface. The conductive polymer coating on the implanted electrode resulted in increased recorded signal amplitude that was observed throughout the course of the study. Histologic examination confirmed axonal sprouting, elongation, and synaptogenesis within regenerative peripheral nerve interface regardless of electrode type. The regenerative peripheral nerve interface remains viable over seven months in the presence of an implanted electrode. Electrodes with and without conductive polymer reliably transduced signals from the regenerative peripheral nerve interface. Electrodes with a conductive polymer coating resulted in recording more of the regenerative peripheral nerve interface signal.

Hydrostatic Stress Effects Incorporated Into the Analysis of the High-Strain-Rate Deformation of Polymer Matrix Composites

NASA Technical Reports Server (NTRS)

Goldberg, Robert K.; Roberts, Gary D.

2003-01-01

Procedures for modeling the effect of high strain rate on composite materials are needed for designing reliable composite engine cases that are lighter than the metal cases in current use. The types of polymer matrix composites that are likely to be used in such an application have a deformation response that is nonlinear and that varies with strain rate. The nonlinearity and strain rate dependence of the composite response is primarily due to the matrix constituent. Therefore, in developing material models to be used in the design of impact-resistant composite engine cases, the deformation of the polymer matrix must be correctly analyzed. However, unlike in metals, the nonlinear response of polymers depends on the hydrostatic stresses, which must be accounted for within an analytical model. An experimental program has been carried out through a university grant with the Ohio State University to obtain tensile and shear deformation data for a representative polymer for strain rates ranging from quasi-static to high rates of several hundred per second. This information has been used at the NASA Glenn Research Center to develop, characterize, and correlate a material model in which the strain rate dependence and nonlinearity (including hydrostatic stress effects) of the polymer are correctly analyzed. To obtain the material data, Glenn s researchers designed and fabricated test specimens of a representative toughened epoxy resin. Quasi-static tests at low strain rates and split Hopkinson bar tests at high strain rates were then conducted at the Ohio State University. The experimental data confirmed the strong effects of strain rate on both the tensile and shear deformation of the polymer. For the analytical model, Glenn researchers modified state variable constitutive equations previously used for the viscoplastic analysis of metals to allow for the analysis of the nonlinear, strain-rate-dependent polymer deformation. Specifically, we accounted for the effects of hydrostatic stresses. An important discovery in the course of this work was that the hydrostatic stress effects varied during the loading process, which needed to be accounted for within the constitutive equations. The model is characterized primarily by shear data, with tensile data used to characterize the hydrostatic stress effects.

Novel Precursor Approached for CMC Derived by Polymer Pyrolysis

DTIC Science & Technology

1994-02-15

to remove signals from probe polymer materials. C. Pyrolysis Methods The conversion of polymeric PMVS to SiC -containing ceramic was studied by... Composite Fabrication Methods Ceramic matrix composites with different matrix compositions were fabricated using the Polymer Impregnation- Pyrolysis (PIP...Pyrolyzed composites were re- infiltrated with the appropriate polymer matrix source under vacuum, and cured in an autoclave under 100 psi overpressure of N2

High rate lithium-sulfur battery enabled by sandwiched single ion conducting polymer electrolyte

PubMed Central

Sun, Yubao; Li, Gai; Lai, Yuanchu; Zeng, Danli; Cheng, Hansong

2016-01-01

Lithium-sulfur batteries are highly promising for electric energy storage with high energy density, abundant resources and low cost. However, the battery technologies have often suffered from a short cycle life and poor rate stability arising from the well-known “polysulfide shuttle” effect. Here, we report a novel cell design by sandwiching a sp3 boron based single ion conducting polymer electrolyte film between two carbon films to fabricate a composite separator for lithium-sulfur batteries. The dense negative charges uniformly distributed in the electrolyte membrane inherently prohibit transport of polysulfide anions formed in the cathode inside the polymer matrix and effectively blocks polysulfide shuttling. A battery assembled with the composite separator exhibits a remarkably long cycle life at high charge/discharge rates. PMID:26898772

Angular selectivity asymmetry of holograms recorded in near infrared sensitive liquid crystal photopolymerizable materials

NASA Astrophysics Data System (ADS)

Harbour, Steven; Galstian, Tigran; Akopyan, Rafik; Galstyan, Artur

2004-08-01

We have experimentally observed and theoretically explained the angular selectivity asymmetry in polymer dispersed liquid crystal holograms. Experiments are conducted in compounds with near infrared sensitivity. The coupled-wave theory is used to describe the diffraction properties of obtained anisotropic holographic gratings. Furthermore, the comparison of theory and experiments provides information about the optical axis direction that is defined by the average molecular orientation of the liquid crystal in the polymer matrix.

Preparation of a DNA matrix via an electrochemically directed copolymerization of pyrrole and oligonucleotides bearing a pyrrole group.

PubMed Central

Livache, T; Roget, A; Dejean, E; Barthet, C; Bidan, G; Téoule, R

1994-01-01

A new methodology for the preparation of addressed DNA matrices is described. The process includes an electrochemically directed copolymerization of pyrrole and oligonucleotides bearing on their 5' end a pyrrole moiety introduced by phosphoramidite chemistry. The electro-controlled synthesis of the copolymer (poly-pyrrole) gives, in one step, a solid conducting film deposited on the surface of an electrode. The resulting polymer consists of pyrrole chains bearing covalently linked oligonucleotide. The polymer growth is limited to the electrode surface, so that it is possible to prepare a DNA matrix on a multiple electrode device by successive copolymerizations. A support bearing four oligonucleotides was used to detect three ras mutations on a synthetic DNA fragment. PMID:8065902

Simulation of bipolar charge transport in nanocomposite polymer films

NASA Astrophysics Data System (ADS)

Lean, Meng H.; Chu, Wei-Ping L.

2015-03-01

This paper describes 3D particle-in-cell simulation of bipolar charge injection and transport through nanocomposite film comprised of ferroelectric ceramic nanofillers in an amorphous polymer matrix. The classical electrical double layer (EDL) model for a monopolar core is extended (eEDL) to represent the nanofiller by replacing it with a dipolar core. Charge injection at the electrodes assumes metal-polymer Schottky emission at low to moderate fields and Fowler-Nordheim tunneling at high fields. Injected particles migrate via field-dependent Poole-Frenkel mobility and recombine with Monte Carlo selection. The simulation algorithm uses a boundary integral equation method for solution of the Poisson equation coupled with a second-order predictor-corrector scheme for robust time integration of the equations of motion. The stability criterion of the explicit algorithm conforms to the Courant-Friedrichs-Levy limit assuring robust and rapid convergence. The model is capable of simulating a wide dynamic range spanning leakage current to pre-breakdown. Simulation results for BaTiO3 nanofiller in amorphous polymer matrix indicate that charge transport behavior depend on nanoparticle polarization with anti-parallel orientation showing the highest leakage conduction and therefore lowest level of charge trapping in the interaction zone. Charge recombination is also highest, at the cost of reduced leakage conduction charge. The eEDL model predicts the meandering pathways of charge particle trajectories.

High aspect ratio template and method for producing same for central and peripheral nerve repair

NASA Technical Reports Server (NTRS)

Sakamoto, Jeff S. (Inventor); Chan, Christina (Inventor); Tuszynski, Mark Henry (Inventor); Mehrotra, Sumit (Inventor); Gros, Thomas (Inventor)

2011-01-01

Millimeter to nano-scale structures manufactured using a multi-component polymer fiber matrix are disclosed. The use of dissimilar polymers allows the selective dissolution of the polymers at various stages of the manufacturing process. In one application, biocompatible matrixes may be formed with long pore length and small pore size. The manufacturing process begins with a first polymer fiber arranged in a matrix formed by a second polymer fiber. End caps may be attached to provide structural support and the polymer fiber matrix selectively dissolved away leaving only the long polymer fibers. These may be exposed to another product, such as a biocompatible gel to form a biocompatible matrix. The polymer fibers may then be selectively dissolved leaving only a biocompatible gel scaffold with the pores formed by the dissolved polymer fibers. The scaffolds may be used in, among other applications, the repair of central and peripheral nerves. Scaffolds for the repair of peripheral nerves may include a reservoir for the sustained release of nerve growth factor. The scaffolds may also include a multifunctional polyelectrolyte layer for the sustained release of nerve growth factor and enhance biocompatibility.

Performance improvement of gel- and solid-state dye-sensitized solar cells by utilization the blending effect of poly (vinylidene fluoride-co-hexafluropropylene) and poly (acrylonitrile-co-vinyl acetate) co-polymers

NASA Astrophysics Data System (ADS)

Venkatesan, Shanmugam; Obadja, Nesia; Chang, Ting-Wei; Chen, Li-Tung; Lee, Yuh-Lang

2014-12-01

Poly (vinylidene fluoride-co-hexafluropropylene) (PVDF-HFP) and poly (acrylonitrile-co-vinyl acetate) (PAN-VA) are used as gelator to prepare gel- and solid-state polymer electrolytes for dye sensitized solar cells (DSSCs) applications. The electrolytes prepared using PVDF-HFP have higher conductivities than those prepared using PAN-VA. In blended polymers, the conductivities of the electrolytes increase with increasing composition of PVDF-HFP; at 75% PVDF-HFP, conductivity of the blended polymer surpassed that of pure polymers. It is also found that the viscosity of the electrolyte prepared by PAN-VA (1.2 kPaS) is much lower than that by PVDF-HFP (11 kPaS). Therefore, increasing PAN-VA composition can decrease the viscosity of the electrolyte, improving the penetration of electrolytes in the TiO2 matrix. By controlling the ratio of PVDF-HFP/PAN-VA, the conductivity and viscosity of the electrolyte can be regulated and an optimal ratio based on the conversion efficiency of the gel- and solid state DSSCs is obtained at the ratio of 3/1. The highest efficiency achieved by the gel- and solid-state cells using the blending polymers are 6.3% and 4.88%, respectively, which are higher than those prepared using pure polymers (5.53% and 4.56%, respectively). The introduction of TiO2 fillers to the solid electrolyte can further increase the cell efficiency to 5.34%.

Optimization and control of dynamic percolationin nanostructured silicon oils

NASA Astrophysics Data System (ADS)

Badard, Mathieu; Combessis, Anthony; Allais, Arnaud; Flandin, Lionel

2017-06-01

The addition of carbonaceous fillers in polymers allows the conception of composites with optimized electrical properties. The conductivity of such material depends of the fillers structuration in matrix, especially the presence of percolated network. The objective of this paper is to understand the main aggregation mechanisms of carbon nanotubes in different media. The structuration of these filler network is probed by the use of electrical and dielectrical measurements. The innovative part of our work lies in the use of liquid matrices, especially silicon oils, to overcome mechanical constraints present in polymers on the one hand and to simplify processing on the other hand. Our work has revealed a filler aggregation over time, well known as dynamic percolation. Conductivity has been modeled as a function of time and filler content from Kirkpatrick equation. The further use of an electrical field led to conductivity enhancement as well as a decrease in percolation threshold. Finally, a study of intrinsic parameters of matrix has shown a strong effect of viscosity and surface tension on nanotubes aggregation. Contribution to the topical issue "Electrical Engineering Symposium (SGE 2016)", edited by Adel Razek

A low switching voltage organic-on-inorganic heterojunction memory element utilizing a conductive polymer fuse on a doped silicon substrate

NASA Astrophysics Data System (ADS)

Smith, Shawn; Forrest, Stephen R.

2004-06-01

We present a simple, nonvolatile, write-once-read-many-times (WORM) memory device utilizing an organic-on-inorganic heterojunction (OI-HJ) diode with a conductive polymer fuse consisting of polyethylene dioxythiophene:polysterene sulfonic acid (PEDOT:PSS) forming one side of the rectifying junction. Current transients are used to change the fuse from a conducting to a nonconducting state to record a logical "1" or "0", while the nonlinearity of the OI-HJ allows for passive matrix memory addressing. The device switches at 2 and 4 V for 50 nm thick PEDOT:PSS films on p-type Si and n-type Si, respectively. This is significantly lower than the switching voltage used in PEDOT:PSS/p-i-n Si memory elements [J. Appl Phys. 94, 7811 (2003)]. The switching results in a permanent reduction of forward-bias current by approximately five orders of magnitude. These results suggest that the OI-HJ structure has potential for use in low-cost passive matrix WORM memories for archival storage applications.

Making molecular balloons in laser-induced explosive boiling of polymer solutions.

PubMed

Leveugle, Elodie; Sellinger, Aaron; Fitz-Gerald, James M; Zhigilei, Leonid V

2007-05-25

The effect of the dynamic molecular rearrangements leading to compositional segregation is revealed in coarse-grained molecular dynamics simulations of short pulse laser interaction with a polymer solution in a volatile matrix. An internal release of matrix vapor at the onset of the explosive boiling of the overheated liquid is capable of pushing polymer molecules to the outskirts of a transient bubble, forming a polymer-rich surface layer enclosing the volatile matrix material. The results explain unexpected "deflated balloon" structures observed in films deposited by the matrix-assisted pulsed laser evaporation technique.

Method of tissue repair using a composite material

DOEpatents

Hutchens, Stacy A.; Woodward, Jonathan; Evans, Barbara R.; O'Neill, Hugh M.

2016-03-01

A composite biocompatible hydrogel material includes a porous polymer matrix, the polymer matrix including a plurality of pores and providing a Young's modulus of at least 10 GPa. A calcium comprising salt is disposed in at least some of the pores. The porous polymer matrix can comprise cellulose, including bacterial cellulose. The composite can be used as a bone graft material. A method of tissue repair within the body of animals includes the steps of providing a composite biocompatible hydrogel material including a porous polymer matrix, the polymer matrix including a plurality of pores and providing a Young's modulus of at least 10 GPa, and inserting the hydrogel material into cartilage or bone tissue of an animal, wherein the hydrogel material supports cell colonization in vitro for autologous cell seeding.

Method of tissue repair using a composite material

DOEpatents

Hutchens, Stacy A; Woodward, Jonathan; Evans, Barbara R; O'Neill, Hugh M

2014-03-18

A composite biocompatible hydrogel material includes a porous polymer matrix, the polymer matrix including a plurality of pores and providing a Young's modulus of at least 10 GPa. A calcium comprising salt is disposed in at least some of the pores. The porous polymer matrix can comprise cellulose, including bacterial cellulose. The composite can be used as a bone graft material. A method of tissue repair within the body of animals includes the steps of providing a composite biocompatible hydrogel material including a porous polymer matrix, the polymer matrix including a plurality of pores and providing a Young's modulus of at least 10 GPa, and inserting the hydrogel material into cartilage or bone tissue of an animal, wherein the hydrogel material supports cell colonization in vitro for autologous cell seeding.

DIRECT ELECTROCHEMICAL IMMUNOSENSOR FOR POLYCHLORINATED BIPHENYLS. (R825323)

EPA Science Inventory

A direct electrochemical immunosensor has been developed for the determination of polychlorinated biphenyls (PCBs) in water. The assay is based on the measurement of the current due to the specific binding between PCB and anti-PCB antibody-immobilized conducting polymer matrix. T...

Mechanisms of charge transport and resistive switching in composite films of semiconducting polymers with nanoparticles of graphene and graphene oxide

NASA Astrophysics Data System (ADS)

Berestennikov, A. S.; Aleshin, A. N.

2017-11-01

We have investigated the effect of the resistive switching in the composite films based on polyfunctional polymers - PVK, PFD and PVC mixed with particles of Gr and GO with the concentration of ˜ 1 - 3 wt.%. We have developed the solution processed hybrid memory structures based on PVK and GO particles composite films. The effect of the resistive switching in Al/PVK(PFD; PVC):Gr(GO)/ITO/PET structures manifests itself as a sharp change of the electrical resistance from a low-conducting state to a relatively high-conducting state when applying a bias to Al-ITO electrodes of ˜ 0.2-0.4 V. It has been established that a sharp conductivity jump characterized by S-shaped current-voltage curves and the presence of their hysteresis occurs upon applying a voltage pulse to the Au/PVK(PFD; PVC):Gr(GO)/ITO/PET structures, with the switching time in the range from 1 to 30 μs. The mechanism of resistive switching associated with the processes of capture and accumulation of charge carriers by Gr(GO) particles introduced into the matrixes of the PVK polymer due to the reduction/oxidation processes. The possible mechanisms of energy transfer between organic and inorganic components in PVK(PFD; PVC):GO(Gr) films causes increase mobility are discussed. Incorporating of Gr (GO) particles into the polymer matrix is a promising route to enhance the performance of hybrid memory structures, as well as it is an effective medium for memory cells.

Heat Rejection Systems Utilizing Composites and Heat Pipes: Design and Performance Testing

NASA Technical Reports Server (NTRS)

Jaworske, Donald A.; Beach, Duane E.; Sanzi, James L.

2007-01-01

Polymer matrix composites offer the promise of reducing the mass and increasing the performance of future heat rejection systems. With lifetimes for heat rejection systems reaching a decade or more in a micrometeoroid environment, use of multiple heat pipes for fault tolerant design is compelling. The combination of polymer matrix composites and heat pipes is of particular interest for heat rejection systems operating on the lunar surface. A technology development effort is under way to study the performance of two radiator demonstration units manufactured with different polymer matrix composite face sheet resin and bonding adhesives, along with different titanium-water heat pipe designs. Common to the two radiator demonstration units is the use of high thermal conductivity fibers in the face sheets and high thermal conductivity graphite saddles within a light weight aluminum honeycomb core. Testing of the radiator demonstration units included thermal vacuum exposure and thermal vacuum exposure with a simulated heat pipe failure. Steady state performance data were obtained at different operating temperatures to identify heat transfer and thermal resistance characteristics. Heat pipe failure was simulated by removing the input power from an individual heat pipe in order to identify the diminished performance characteristics of the entire panel after a micrometeoroid strike. Freeze-thaw performance was also of interest. This paper presents a summary of the two radiator demonstration units manufactured to support this technology development effort along with the thermal performance characteristics obtained to date. Future work will also be discussed.

Pressure sensor using liquid crystals

NASA Technical Reports Server (NTRS)

Parmar, Devendra S. (Inventor); Holmes, Harlan K. (Inventor)

1994-01-01

A pressure sensor includes a liquid crystal positioned between transparent, electrically conductive films (18 and 20), that are biased by a voltage (V) which induces an electric field (E) that causes the liquid crystal to assume a first state of orientation. Application of pressure (P) to a flexible, transparent film (24) causes the conductive film (20) to move closer to or farther from the conductive film (18), thereby causing a change in the electric field (E'(P)) which causes the liquid crystal to assume a second state of orientation. Polarized light (P.sub.1) is directed into the liquid crystal and transmitted or reflected to an analyzer (A or 30). Changes in the state of orientation of the liquid crystal induced by applied pressure (P) result in a different light intensity being detected at the analyzer (A or 30) as a function of the applied pressure (P). In particular embodiments, the liquid crystal is present as droplets (10) in a polymer matrix (12) or in cells (14) in a polymeric or dielectric grid (16) material in the form of a layer (13) between the electrically conductive films (18 and 20). The liquid crystal fills the open wells in the polymer matrix (12) or grid (16) only partially.

Preparation and application of conducting polymer/Ag/clay composite nanoparticles formed by in situ UV-induced dispersion polymerization

PubMed Central

Zang, Limin; Qiu, Jianhui; Yang, Chao; Sakai, Eiichi

2016-01-01

In this work, composite nanoparticles containing polypyrrole, silver and attapulgite (PPy/Ag/ATP) were prepared via UV-induced dispersion polymerization of pyrrole using ATP clay as a templet and silver nitrate as photoinitiator. The effects of ATP concentration on morphology, structure and electrical conductivity were studied. The obtained composite nanoparticles with an interesting beads-on-a-string morphology can be obtained in a short time (10 min), which indicates the preparation method is facile and feasible. To explore the potential applications of the prepared PPy/Ag/ATP composite nanoparticles, they were served as multifunctional filler and blended with poly(butylene succinate) (PBS) matrix to prepare biodegradable composite material. The distribution of fillers in polymer matrix and the interfacial interaction between fillers and PBS were confirmed by scanning electron microscope, elemental mapping and dynamic mechanical analysis. The well dispersed fillers in PBS matrix impart outstanding antibacterial property to the biodegradable composite material as well as enhanced storage modulus due to Ag nanoparticles and ATP clay. The biodegradable composite material also possesses modest surface resistivity (106 ~ 109 Ω/◻). PMID:26839126

Preparation and application of conducting polymer/Ag/clay composite nanoparticles formed by in situ UV-induced dispersion polymerization.

PubMed

Zang, Limin; Qiu, Jianhui; Yang, Chao; Sakai, Eiichi

2016-02-03

In this work, composite nanoparticles containing polypyrrole, silver and attapulgite (PPy/Ag/ATP) were prepared via UV-induced dispersion polymerization of pyrrole using ATP clay as a templet and silver nitrate as photoinitiator. The effects of ATP concentration on morphology, structure and electrical conductivity were studied. The obtained composite nanoparticles with an interesting beads-on-a-string morphology can be obtained in a short time (10 min), which indicates the preparation method is facile and feasible. To explore the potential applications of the prepared PPy/Ag/ATP composite nanoparticles, they were served as multifunctional filler and blended with poly(butylene succinate) (PBS) matrix to prepare biodegradable composite material. The distribution of fillers in polymer matrix and the interfacial interaction between fillers and PBS were confirmed by scanning electron microscope, elemental mapping and dynamic mechanical analysis. The well dispersed fillers in PBS matrix impart outstanding antibacterial property to the biodegradable composite material as well as enhanced storage modulus due to Ag nanoparticles and ATP clay. The biodegradable composite material also possesses modest surface resistivity (10(6)~ 10(9) Ω/◻).

Electrochemical characteristics of Li/LiMn 2O 4 cells using gel polymer electrolytes

NASA Astrophysics Data System (ADS)

Kim, Dong-Won; Ko, Jang-Myoun; Chun, Jong-Han

Gel polymer electrolytes composed of acrylonitrile-methylmethacrylate (AM) copolymer and 1 M LiClO 4-ethylene carbonate (EC)/propylene carbonate (PC) are prepared. The ionic conductivity reaches 1.9×10 -3 S cm -1 in a gel polymer electrolyte with 20 wt.% of AM copolymer and 80 wt.% of LiClO 4-EC/PC at room temperature. These systems showed no solvent exudation from the matrix polymer due to enhanced compatibility between AM copolymer and organic liquid electrolyte. A Li/gel polymer electrolyte/LiMn 2O 4 cell has a reversible capacity of 132 mAh g -1 in the voltage range of 3.0-4.3 V at the C/5 rate and shows good cycling performance with a coulombic efficiency >99%.

Detection of percolating paths in polyhedral segregated network composites using electrostatic force microscopy and conductive atomic force microscopy

NASA Astrophysics Data System (ADS)

Waddell, J.; Ou, R.; Capozzi, C. J.; Gupta, S.; Parker, C. A.; Gerhardt, R. A.; Seal, K.; Kalinin, S. V.; Baddorf, A. P.

2009-12-01

Composite specimens possessing polyhedral segregated network microstructures require a very small amount of nanosize filler, <1 vol %, to reach percolation because percolation occurs by accumulation of the fillers along the edges of the deformed polymer matrix particles. In this paper, electrostatic force microscopy (EFM) and conductive atomic force microscopy (C-AFM) were used to confirm the location of the nanosize fillers and the corresponding percolating paths in polymethyl methacrylate/carbon black composites. The EFM and C-AFM images revealed that the polyhedral polymer particles were coated with filler, primarily on the edges as predicted by the geometric models provided.

1,2-diketones promoted degradation of poly(epsilon-caprolactone)

NASA Astrophysics Data System (ADS)

Danko, Martin; Borska, Katarina; Ragab, Sherif Shaban; Janigova, Ivica; Mosnacek, Jaroslav

2012-07-01

Photochemical reactions of Benzil and Camphorquinone were used for modification of poly(ɛ-caprolactone) polymer films. Photochemistry of dopants was followed by infrared spectroscopy, changes on polymer chains of matrix were followed by gel permeation chromatography. Benzoyl peroxide was efficiently photochemically generated from benzyl in solid polymer matrix in the presence of air. Following decomposition of benzoyl peroxide led to degradation of matrix. Photochemical transformation of benzil in vacuum led to hydrogen abstraction from the polymer chains in higher extent, which resulted to chains recombination and formation of gel. Photochemical transformation of camphorquinone to corresponding camphoric peroxide was not observed. Only decrease of molecular weight of polymer matrix doped with camphorquinone was observed during the irradiation.

Synthesis and characterization of polyaniline coated gold nanocomposites

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zuber, Siti Nurzulaiha Mohd; Kamarun, Dzaraini; Zaki, Hamizah

2015-08-28

Considerable attention has been drawn during the last two decades to prepare nanocomposites consists of conducting polymer and noble metal due to their potential ability to generate a new class of material with novel optical, chemical, electronic or mechanical properties for various applications. In this work, an attempt has been made to synthesize nanocomposite of polyaniline (PANI) coated with gold nanoparticles (AuNPs) chemically with various types of surfactants such as polyvinylpyrrolidone (PVP), and sodium dodecyl sulphate (SDS) which act as stabilizing agents to help in stabilization of the PANI/Gold nanocomposites system. The synthesized nanocomposites were characterized by UV-Visible, field emissionmore » scanning electron microscope (FESEM) and particle size analyzer (PSA). The formation of finger like structure can be seen in the FESEM images when the AuNPs were incorporated into the polymer matrix. The EDX data showed that 18.66% and 12.67% of AuNPs atoms were present in the composite system thus proved the incorporation of AuNPs into the polymer matrix. A small red shift of the absorption peak in the UV-Vis of both PANI/AuNPs composites system may be due to the incorporation of AuNPs in the PANI matrix.« less

Implementation of Improved Transverse Shear Calculations and Higher Order Laminate Theory Into Strain Rate Dependent Analyses of Polymer Matrix Composites

NASA Technical Reports Server (NTRS)

Zhu, Lin-Fa; Kim, Soo; Chattopadhyay, Aditi; Goldberg, Robert K.

2004-01-01

A numerical procedure has been developed to investigate the nonlinear and strain rate dependent deformation response of polymer matrix composite laminated plates under high strain rate impact loadings. A recently developed strength of materials based micromechanics model, incorporating a set of nonlinear, strain rate dependent constitutive equations for the polymer matrix, is extended to account for the transverse shear effects during impact. Four different assumptions of transverse shear deformation are investigated in order to improve the developed strain rate dependent micromechanics model. The validities of these assumptions are investigated using numerical and theoretical approaches. A method to determine through the thickness strain and transverse Poisson's ratio of the composite is developed. The revised micromechanics model is then implemented into a higher order laminated plate theory which is modified to include the effects of inelastic strains. Parametric studies are conducted to investigate the mechanical response of composite plates under high strain rate loadings. Results show the transverse shear stresses cannot be neglected in the impact problem. A significant level of strain rate dependency and material nonlinearity is found in the deformation response of representative composite specimens.

Next generation brain implant coatings and nerve regeneration via novel conductive nanocomposite development.

PubMed

Antoniadou, Eleni V; Ahmad, Rezal K; Jackman, Richard B; Seifalian, Alexander M

2011-01-01

Composite materials based on the coupling of conductive organic polymers and carbon nanotubes have shown that they possess properties of the individual components with a synergistic effect. Multi-wall carbon nanotube (MWCNT)/ polymer composites are hybrid materials that combine numerous mechanical, electrical and chemical properties and thus, constitute ideal biomaterials for a wide range of regenerative medicine applications. Although, complete dispersion of CNT in a polymer matrix has rarely been achieved, in this study we have succeeded high dispersibility of CNT in POSS-PCU and POSS-PCL, novel polymers based on polyprolactone and polycarbonate polyurethane (PCU) and poly(caprolactoneurea)urethane both having incorporated polyhedral oligomeric silsesquioxane (POSS). We report the synthesis and characterization of a novel biomaterial that possesses unique properties of being electrically conducting and thus being capable of electronic interfacing with tissue. To this end, POSS-PCU/MWCNT composite can be used as a biomaterial for the development of nerve guidance channels to promote nerve regeneration and POSS-PCL/MWCNT as a substrate to increase electronic interfacing between neurons and micro-machined electrodes for potential applications in neural probes, prosthetic devices and brain implants.

Effect of bidispersity in grafted chain length on grafted chain conformations and potential of mean force between polymer grafted nanoparticles in a homopolymer matrix.

PubMed

Nair, Nitish; Wentzel, Nathaniel; Jayaraman, Arthi

2011-05-21

In efforts to produce polymeric materials with tailored physical properties, significant interest has grown around the ability to control the spatial organization of nanoparticles in polymer nanocomposites. One way to achieve controlled particle arrangement is by grafting the nanoparticle surface with polymers that are compatible with the matrix, thus manipulating the interfacial interactions between the nanoparticles and the polymer matrix. Previous work has shown that the molecular weight of the grafted polymer, both at high grafting density and low grafting density, plays a key role in dictating the effective inter-particle interactions in a polymer matrix. At high grafting density nanoparticles disperse (aggregate) if the graft molecular weight is higher (lower) than the matrix molecular weight. At low grafting density the longer grafts can better shield the nanoparticle surface from direct particle-particle contacts than the shorter grafts and lead to the dispersion of the grafted particles in the matrix. Despite the importance of graft molecular weight, and evidence of non-trivial effects of polydispersity of chains grafted on flat surfaces, most theoretical work on polymer grafted nanoparticles has only focused on monodisperse grafted chains. In this paper, we focus on how bidispersity in grafted chain lengths affects the grafted chain conformations and inter-particle interactions in an implicit solvent and in a dense homopolymer polymer matrix. We first present the effects of bidispersity on grafted chain conformations in a single polymer grafted particle using purely Monte Carlo (MC) simulations. This is followed by calculations of the potential of mean force (PMF) between two grafted particles in a polymer matrix using a self-consistent Polymer Reference Interaction Site Model theory-Monte Carlo simulation approach. Monte Carlo simulations of a single polymer grafted particle in an implicit solvent show that in the bidisperse polymer grafted particles with an equal number of short and long grafts at low to medium grafting density, the short grafts are in a more coiled up conformation (lower radius of gyration) than their monodisperse counterparts to provide a larger free volume to the longer grafts so they can gain conformational entropy. The longer grafts do not show much difference in conformation from their monodisperse counterparts at low grafting density, but at medium grafting density the longer grafts exhibit less stretched conformations (lower radius of gyration) as compared to their monodisperse counterparts. In the presence of an explicit homopolymer matrix, the longer grafts are more compressed by the matrix homopolymer chains than the short grafts. We observe that the potential of mean force between bidisperse grafted particles has features of the PMF of monodisperse grafted particles with short grafts and monodisperse grafted particles with long grafts. The value of the PMF at contact is governed by the short grafts and values at large inter-particle distances are governed by the longer grafts. Further comparison of the PMF for bidisperse and monodisperse polymer grafted particles in a homopolymer matrix at varying parameters shows that the effects of matrix chain length, matrix packing fraction, grafting density, and particle curvature on the PMF between bidisperse polymer grafted particles are similar to those seen between monodisperse polymer grafted particles. © 2011 American Institute of Physics.

Spectral properties of nanocomposites based on fluorine-containing polymer and gold nanoparticles

NASA Astrophysics Data System (ADS)

Barmina, E. V.; Mel’nik, N. N.; Rakov, I. I.; Ivanov, V. E.; Simakin, A. V.; Gudkov, S. V.; Shafeev, G. A.

2018-04-01

The optical properties of nanocomposites of gold nanoparticles and fluorine-containing polymer have been studied. Gold nanoparticles were obtained by laser ablation of gold or terbium targets in organic solvents. The thus formed colloidal solutions were used to prepare nanocomposites of gold nanoparticles in polymer matrices of transparent and colorless fluorine-containing polymer. The polymer matrix is found to promote aggregation of nanoparticles of metal under study into elongated chains. In turn, metal nanoparticles influence on the polymer matrix. Gold nanoparticles amplify the Raman signal of the polymer matrix. In addition, the Raman spectra of nanocomposites indicate aggregation of disordered carbon around the nanoparticles obtained by laser ablation in organic solvents.

Membrane consisting of polyquaternary amine ion exchange polymer network interpenetrating the chains of thermoplastic matrix polymer

NASA Technical Reports Server (NTRS)

Rembaum, A.; Wallace, C. J. (Inventor)

1978-01-01

An ion exchange membrane was formed from a solution containing dissolved matrix polymer and a set of monomers which are capable of reacting to form a polyquaternary ion exchange material; for example vinyl pyride and a dihalo hydrocarbon. After casting solution and evaporation of the volatile component's, a relatively strong ion exchange membrane was obtained which is capable of removing anions, such as nitrate or chromate from water. The ion exchange polymer forms an interpenetrating network with the chains of the matrix polymer.

Surface functionalization of metal organic frameworks for mixed matrix membranes

DOEpatents

Albenze, Erik; Lartey, Michael; Li, Tao; Luebke, David R.; Nulwala, Hunaid B.; Rosi, Nathaniel L.; Venna, Surendar R.

2017-03-21

Mixed Matrix Membrane (MMM) are composite membranes for gas separation and comprising a quantity of inorganic filler particles, in particular metal organic framework (MOF), dispersed throughout a polymer matrix comprising one or more polymers. This disclosure is directed to MOF functionalized through addition of a pendant functional group to the MOF, in order to improve interaction with a surrounding polymer matrix in a MMM. The improved interaction aids in avoiding defects in the MMM due to incompatible interfaces between the polymer matrix and the MOF particle, in turn increasing the mechanical and gas separation properties of the MMM. The disclosure is also directed to a MMM incorporating the surface functionalized MOF.

Multifunctional Nanotube Polymer Nanocomposites for Aerospace Applications: Adhesion between SWCNT and Polymer Matrix

NASA Technical Reports Server (NTRS)

Park, Cheol; Wise, Kristopher E.; Kang, Jin Ho; Kim, Jae-Woo; Sauti, Godfrey; Lowther, Sharon E.; Lillehei, Peter T.; Smith, Michael W.; Siochi, Emilie J.; Harrison, Joycelyn S.;

Plastic scintillator with effective pulse shape discrimination for neutron and gamma detection

DOEpatents

Zaitseva, Natalia P.; Carman, M Leslie; Cherepy, Nerine; Glenn, Andrew M.; Hamel, Sebastien; Payne, Stephen A.; Rupert, Benjamin L.

2016-04-12

In one embodiment, a scintillator material includes a polymer matrix; and a primary dye in the polymer matrix, the primary dye being a fluorescent dye, the primary dye being present in an amount of 5 wt % or more; wherein the scintillator material exhibits an optical response signature for neutrons that is different than an optical response signature for gamma rays. In another embodiment, a scintillator material includes a polymer matrix; and a primary dye in the polymer matrix, the primary dye being a fluorescent dye, the primary dye being present in an amount greater than 10 wt %.

Effects of functionalization on thermal properties of single-wall and multi-wall carbon nanotube-polymer nanocomposites.

PubMed

Gulotty, Richard; Castellino, Micaela; Jagdale, Pravin; Tagliaferro, Alberto; Balandin, Alexander A

2013-06-25

Carboxylic functionalization (-COOH groups) of carbon nanotubes is known to improve their dispersion properties and increase the electrical conductivity of carbon-nanotube-polymer nanocomposites. We have studied experimentally the effects of this type of functionalization on the thermal conductivity of the nanocomposites. It was found that while even small quantities of carbon nanotubes (~1 wt %) can increase the electrical conductivity, a larger loading fraction (~3 wt %) is required to enhance the thermal conductivity of nanocomposites. Functionalized multi-wall carbon nanotubes performed the best as filler material leading to a simultaneous improvement of the electrical and thermal properties of the composites. Functionalization of the single-wall carbon nanotubes reduced the thermal conductivity enhancement. The observed trends were explained by the fact that while surface functionalization increases the coupling between carbon nanotube and polymer matrix, it also leads to formation of defects, which impede the acoustic phonon transport in the single-wall carbon nanotubes. The obtained results are important for applications of carbon nanotubes and graphene flakes as fillers for improving thermal, electrical and mechanical properties of composites.

Dielectric Properties of Polymer Matrix Composites Prepared from Conductive Polymer Treated Fabrics

DTIC Science & Technology

1992-02-01

JPS 09827 finish. The doping agent used was anthraquinone-2 sulfonic acid. (3) A 5 x 5 S2-glass 24 oz. woven roving with an Owens Corning 463 finish...x- I S2-glass 27 oz. woven roving with an Owens Corning 933 finish, nominally equiv- alent to the JPS 09827 finish. The doping agent used was...were fabricated by laminating the layers of Fabric with wet polyester resin ( Owens Corning E-780) and subsequently processing the com- posites using the

Emerging low-cost LED thermal management materials

NASA Astrophysics Data System (ADS)

Zweben, Carl H.

2004-10-01

As chip size and power levels continue to increase, thermal management, thermal stresses and cost have become key LED packaging issues. Until recently, low-coefficient-of-thermal-expansion (CTE) materials, which are needed to minimize thermal stresses, had thermal conductivities that are no better than those of aluminum alloys, about 200 W/m-K. Copper, which has a higher thermal conductivity (400 W/m-K), also has a high CTE, which can cause severe thermal stresses. We now have over a dozen low-CTE materials with thermal conductivities ranging between 400 and 1700 W/m-K, and almost a score with thermal conductivities at least 50% greater than that of aluminum. Some of these materials are low cost. Others have the potential to be low cost in high volume production. Emphasizing low cost, this paper reviews traditional packaging materials and the six categories of advanced materials: polymer matrix-, metal matrix-, ceramic matrix-, and carbon matrix composites; monolithic carbonaceous materials; and metal-metal composites/alloys. Topics include properties, status, applications, cost and likely future directions of new advanced materials, including carbon nanotubes and inexpensive graphite nanoplatelets.

Novel Transparent Phosphor Conversion Matrix with High Thermal Conductivity for Next Generation Phosphor-Converted LED-based Solid State Lighting

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bockstaller, Michael

The low thermal conductivity of state-of-the-art polymer encapsulants (k ~ 0.15 Wm-1K-1) limits the efficiency and power density of current phosphor conversion light emitting diodes (pc-LEDs). The technical objective of this project was to demonstrate synthesis and processing schemes for the fabrication of polymer hybrid encapsulants with a thermal conductivity exceeding k = 0.4 Wm-1K-1 for LED applications. The ‘hybrid polymer’ approach encompasses the dispersion of high thermal conductivity particle fillers (zinc oxide, ZnO as well as the alpha-polymorph of alumina, Al2O3) within a polysiloxane matrix (poly(dimethylsiloxane), PDMS as well as poly(phenyl methyl siloxane), PPMS) to increase the thermal conductivitymore » while maintaining optical transparency and photothermal stability at levels consistent with LED applications. To accomplish this goal, a novel synthesis method for the fabrication of nanosized ZnO particles was developed and a novel surface chemistry was established to modify the surface of zinc oxide particle fillers and thus to enable their dispersion in poly(dimethyl siloxane) (PDMS) matrix polymers. Molecular dynamics and Mie simulations were used to optimize ligand structure and to enable the concurrent mixing of particles in PDMS/PPMS embedding media while also minimizing the thermal boundary resistance as well as optical scattering of particle fillers. Using this approach the synthesis of PDMS/ZnO hybrid encapsulants exhibiting a thermal conductivity of 0.64 Wm-1K-1 and optical transparency > 0.7 mm-1 was demonstrated. A forming process based on micromolding was developed to demonstrate the forming of particle filled PDMS into film and lens shapes. Photothermal stability testing revealed stability of the materials for approximately 4000 min when exposed to blue light LED (450 nm, 30 W/cm2). One postgraduate and seven graduate students were supported by the project. The research performed within this project led to fifteen publications in peer-reviewed journals and one patent application. The grant stimulated a multi-investigator research collaborations among seven investigators at Carnegie Mellon University to address the challenge of encapsulants in pc-LED applications. The grant also catalyzed the future collaboration between researchers at Carnegie Mellon University and OSRAM Sylvania to address challenges associated with the use if polymers in LED applications.« less

Biopolymer system for permeability modification in porous media

DOE Office of Scientific and Technical Information (OSTI.GOV)

Stepp, A.K.; Bryant, R.S.; Llave, F.M.

1995-12-31

New technologies are needed to reduce the current high rate of well abandonment. Improved sweep efficiency, reservoir conformance, and permeability modification can have a significant impact on oil recovery processes. Microorganisms can be used to selectively plug high-permeability zones to improve sweep efficiency and impart conformance control. Studies of a promising microbial system for polymer production were conducted to evaluate reservoir conditions in which this system would be effective. Factors which can affect microbial growth and polymer production include salinity, pH, temperature, divalent ions, presence of residual oil, and rock matrix. Flask tests and coreflooding experiments were conducted to optimizemore » and evaluate the effectiveness of this system. Nuclear magnetic resonance imaging (NMRI) was used to visualize microbial polymer production in porous media. Changes in fluid distribution within the pore system of the core were detected.« less

Multifunctional and biologically active matrices from multicomponent polymeric solutions

NASA Technical Reports Server (NTRS)

Kiick, Kristi L. (Inventor); Yamaguchi, Nori (Inventor); Rabolt, John (Inventor); Casper, Cheryl (Inventor)

2012-01-01

A functionalized electrospun matrix for the controlled-release of biologically active agents, such as growth factors, is presented. The functionalized matrix comprises a matrix polymer, a compatibilizing polymer and a biomolecule or other small functioning molecule. In certain aspects the electrospun polymer fibers comprise at least one biologically active molecule functionalized with low molecular weight heparin.

Free volume dependence on electrical properties of Poly (styrene co-acrylonitrile)/Nickel oxide polymer nanocomposites

NASA Astrophysics Data System (ADS)

Ningaraju, S.; Hegde, Vinayakaprasanna N.; Prakash, A. P. Gnana; Ravikumar, H. B.

2018-04-01

Polymer nanocomposites of Poly (styrene co-acrylonitrile)/Nickel Oxide (PSAN/NiO) have been prepared. The increased free volume sizes up to 0.4 wt% of NiO loading indicates overall reduction in packing density of polymer network. The decreased o-Ps lifetime (τ3) at higher concentration of NiO indicates improved interfacial interaction between the surface of NiO nanoparticles and side chain of PSAN polymer matrix. The increased AC/DC conductivity at lower wt% of NiO loading demonstrates increased number of electric charge carriers/mobile ions and their mobility. The increased dielectric constant and dielectric loss up to 0.4 wt% of NiO loading suggests the increased dipoles polarization.

The effect of extended polymer chains on the properties of transparent multi-walled carbon nanotubes/poly(methyl methacrylate/acrylic acid) film

NASA Astrophysics Data System (ADS)

Huang, Yuan-Li; Tien, Hsi-Wen; Ma, Chen-Chi M.; Yu, Yi-Hsiuan; Yang, Shin-Yi; Wei, Ming-Hsiung; Wu, Sheng-Yen

2010-05-01

Optically transparent and electrically conductive thin films composed of multi-walled carbon nanotube (MWCNT) reinforced polymethyl methacrylate/acrylic acid (PMMA/AA) were fabricated using a wire coating technique. Poly(acrylic acid) controls the level of MWCNT dispersion in aqueous mixtures and retains the well-dispersed state in the polymer matrix after solidification resulting from extended polymer chains by adjusting the pH value. The exfoliating the MWCNT bundles by extended polymer chains results in the excellent dispersion of MWCNT. It causes a lower surface electrical resistance at the same MWCNT content. The hydrophilic functional groups (-COO - NA + ) also caused a decrease in the crystallization of PMMA and led to an increase in the transmittance.

The effect of extended polymer chains on the properties of transparent multi-walled carbon nanotubes/poly(methyl methacrylate/acrylic acid) film.

PubMed

Huang, Yuan-Li; Tien, Hsi-Wen; Ma, Chen-Chi M; Yu, Yi-Hsiuan; Yang, Shin-Yi; Wei, Ming-Hsiung; Wu, Sheng-Yen

2010-05-07

Optically transparent and electrically conductive thin films composed of multi-walled carbon nanotube (MWCNT) reinforced polymethyl methacrylate/acrylic acid (PMMA/AA) were fabricated using a wire coating technique. Poly(acrylic acid) controls the level of MWCNT dispersion in aqueous mixtures and retains the well-dispersed state in the polymer matrix after solidification resulting from extended polymer chains by adjusting the pH value. The exfoliating the MWCNT bundles by extended polymer chains results in the excellent dispersion of MWCNT. It causes a lower surface electrical resistance at the same MWCNT content. The hydrophilic functional groups (-COO( - )NA( + )) also caused a decrease in the crystallization of PMMA and led to an increase in the transmittance.

Graphene-Reinforced Metal and Polymer Matrix Composites

NASA Astrophysics Data System (ADS)

Kasar, Ashish K.; Xiong, Guoping; Menezes, Pradeep L.

2018-03-01

Composites have tremendous applicability due to their excellent capabilities. The performance of composites mainly depends on the reinforcing material applied. Graphene is successful as an efficient reinforcing material due to its versatile as well as superior properties. Even at very low content, graphene can dramatically improve the properties of polymer and metal matrix composites. This article reviews the fabrication followed by mechanical and tribological properties of metal and polymer matrix composites filled with different kinds of graphene, including single-layer, multilayer, and functionalized graphene. Results reported to date in literature indicate that functionalized graphene or graphene oxide-polymer composites are promising materials offering significantly improved strength and frictional properties. A similar trend of improved properties has been observed in case of graphene-metal matrix composites. However, achieving higher graphene loading with uniform dispersion in metal matrix composites remains a challenge. Although graphene-reinforced composites face some challenges, such as understanding the graphene-matrix interaction or fabrication techniques, graphene-reinforced polymer and metal matrix composites have great potential for application in various fields due to their outstanding properties.

Graphene-Reinforced Metal and Polymer Matrix Composites

NASA Astrophysics Data System (ADS)

Kasar, Ashish K.; Xiong, Guoping; Menezes, Pradeep L.

2018-06-01

Composites have tremendous applicability due to their excellent capabilities. The performance of composites mainly depends on the reinforcing material applied. Graphene is successful as an efficient reinforcing material due to its versatile as well as superior properties. Even at very low content, graphene can dramatically improve the properties of polymer and metal matrix composites. This article reviews the fabrication followed by mechanical and tribological properties of metal and polymer matrix composites filled with different kinds of graphene, including single-layer, multilayer, and functionalized graphene. Results reported to date in literature indicate that functionalized graphene or graphene oxide-polymer composites are promising materials offering significantly improved strength and frictional properties. A similar trend of improved properties has been observed in case of graphene-metal matrix composites. However, achieving higher graphene loading with uniform dispersion in metal matrix composites remains a challenge. Although graphene-reinforced composites face some challenges, such as understanding the graphene-matrix interaction or fabrication techniques, graphene-reinforced polymer and metal matrix composites have great potential for application in various fields due to their outstanding properties.

1,2-diketones promoted degradation of poly(epsilon-caprolactone)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Danko, Martin; Borska, Katarina; Ragab, Sherif Shaban

2012-07-11

Photochemical reactions of Benzil and Camphorquinone were used for modification of poly({epsilon}-caprolactone) polymer films. Photochemistry of dopants was followed by infrared spectroscopy, changes on polymer chains of matrix were followed by gel permeation chromatography. Benzoyl peroxide was efficiently photochemically generated from benzyl in solid polymer matrix in the presence of air. Following decomposition of benzoyl peroxide led to degradation of matrix. Photochemical transformation of benzil in vacuum led to hydrogen abstraction from the polymer chains in higher extent, which resulted to chains recombination and formation of gel. Photochemical transformation of camphorquinone to corresponding camphoric peroxide was not observed. Only decreasemore » of molecular weight of polymer matrix doped with camphorquinone was observed during the irradiation.« less

Experimental research on continuous basalt fiber and basalt-fibers-reinforced polymers

NASA Astrophysics Data System (ADS)

Zhang, Xueyi; Zou, Guangping; Shen, Zhiqiang

2008-11-01

The interest for continuous basalt fibers and reinforced polymers has recently grown because of its low price and rich natural resource. Basalt fiber was one type of high performance inorganic fibers which were made from natural basalt by the method of melt extraction. This paper discusses basic mechanical properties of basalt fiber. The other work in this paper was to conduct tensile testing of continuous basalt fiber-reinforced polymer rod. Tensile strength and stress-strain curve were obtained in this testing. The strength of rod was fairly equal to rod of E-glass fibers and weaker than rod of carbon fibers. Surface of crack of rod was studied. An investigation of fracture mechanism between matrix and fiber was analyzed by SEM (Scanning electron microscopy) method. A poor adhesion between the matrix and fibers was also shown for composites analyzing SEM photos. The promising tensile properties of the presented basalt fibers composites have shown their great potential as alternative classical composites.

Low percolation transitions in carbon nanotube networks dispersed in a polymer matrix: dielectric properties, simulations and experiments.

PubMed

Simoes, Ricardo; Silva, Jaime; Vaia, Richard; Sencadas, Vítor; Costa, Pedro; Gomes, João; Lanceros-Méndez, Senentxu

2009-01-21

The low concentration behaviour and the increase of the dielectric constant in carbon nanotubes/polymer nanocomposites near the percolation threshold are still not well understood. In this work, a numerical model has been developed which focuses on the effect of the inclusion of conductive fillers in a dielectric polymer matrix on the dielectric constant and the dielectric strength. Experiments have been carried out in carbon nanotubes/poly(vinylidene fluoride) nanocomposites in order to compare to the simulation results. This work shows how the critical concentration is related to the formation of capacitor networks and that these networks give rise to high variations in the electrical properties of the composites. Based on numerical studies, the dependence of the percolation transition on the preparation of the nanocomposite is discussed. Finally, based on numerical and experimental results, both ours and from other authors, the causes of anomalous percolation behaviour of the dielectric constant are identified.

Floating matrix tablets based on low density foam powder: effects of formulation and processing parameters on drug release.

PubMed

Streubel, A; Siepmann, J; Bodmeier, R

2003-01-01

The aim of this study was to develop and physicochemically characterize single unit, floating controlled drug delivery systems consisting of (i). polypropylene foam powder, (ii). matrix-forming polymer(s), (iii). drug, and (iv). filler (optional). The highly porous foam powder provided low density and, thus, excellent in vitro floating behavior of the tablets. All foam powder-containing tablets remained floating for at least 8 h in 0.1 N HCl at 37 degrees C. Different types of matrix-forming polymers were studied: hydroxypropyl methylcellulose (HPMC), polyacrylates, sodium alginate, corn starch, carrageenan, gum guar and gum arabic. The tablets eroded upon contact with the release medium, and the relative importance of drug diffusion, polymer swelling and tablet erosion for the resulting release patterns varied significantly with the type of matrix former. The release rate could effectively be modified by varying the "matrix-forming polymer/foam powder" ratio, the initial drug loading, the tablet geometry (radius and height), the type of matrix-forming polymer, the use of polymer blends and the addition of water-soluble or water-insoluble fillers (such as lactose or microcrystalline cellulose). The floating behavior of the low density drug delivery systems could successfully be combined with accurate control of the drug release patterns.

Effect of Nanofiller Shape on Effective Thermal Conductivity of Fluoropolymer Composites

DTIC Science & Technology

2015-08-24

SECURITY CLASSIFICATION OF: Filler particle size and shape influence interconnectivity within a polymer matrix and play a significant role in controlling...the effective thermal conductivity of a composite. This study examines the effect of nanofiller particle shape in a polytetrafluorethylene (PTFE...carbon fillers: nano-diamond spheres, carbon nanotubes (CNT) and graphene flakes. The experimental results are coupled with a particle connectivity model

Long-Term Durability of a Matrix for High-Temperature Composites Predicted

NASA Technical Reports Server (NTRS)

Bowles, Kenneth J.

2001-01-01

Polymer matrix composites (PMC's) are being increasingly used in applications where they are exposed for long durations to harsh environments such as elevated temperatures, moisture, oils and solvents, and thermal cycling. The exposure to these environments leads to the degradation of structures made from these materials. This also affects the useful lifetimes of these structures. Some of the more prominent aerospace applications of polymer matrix composites include engine supports and cowlings, reusable launch vehicle parts, radomes, thrust-vectoring flaps, and the thermal insulation of rocket motors. This demand has led to efforts to develop lightweight, high-strength, high-modulus materials that have upper-use temperatures over 316 C. A cooperative program involving two grants to the Massachusetts Institute of Technology and in-house work at the NASA Glenn Research Center was conducted to identify the mechanisms and the measurement of mechanical and physical properties that are necessary to formulate a mechanism-based model for predicting the lifetime of high-temperature polymer matrix composites. The polymer that was studied was PMR-15 polyimide, a leading matrix resin for use in high-temperature-resistant aerospace composite structures such as propulsion systems. The temperature range that was studied was from 125 to 316 C. The diffusion behavior of PMR-15 neat resin was characterized and modeled. Thermogravimetric analysis (TGA) was also conducted in nitrogen, oxygen, and air to provide quantitative information on thermal and oxidative degradation reactions. A new low-cost technique was developed to collect chemical degradation data for isothermal tests lasting up to 4000 hr in duration. In the temperature range studied, results indicate complex behavior that was not observed by previous TGA tests, including the presence of weight-gain reactions. These were found to be significant in the initial periods of aging from 125 to 225 C. Two types of weight loss reactions dominated at aging temperatures above 225 C. One was concentrated at the surface of the polymer and was very active at temperatures above 225 C. The second was observed to dominate in the latter stages of aging at temperatures below 260 C. This three-reaction model satisfactorily explains past findings that the degradation mechanism of PMR-15 appears to change around 316 C. It also indicates that the second weight gain mechanism is a significant factor at temperatures below 204 C. On the basis of these results, a predictive model was developed for the thermal degradation of PMR-15 at 316 C. A comparison of data generated by this model with actual experimental data is shown in the following figure.

Development of controlled drug release systems based on thiolated polymers.

PubMed

Bernkop-Schnürch, A; Scholler, S; Biebel, R G

2000-05-03

The purpose of the present study was to generate mucoadhesive matrix-tablets based on thiolated polymers. Mediated by a carbodiimide, L-cysteine was thereby covalently linked to polycarbophil (PCP) and sodium carboxymethylcellulose (CMC). The resulting thiolated polymers displayed 100+/-8 and 1280+/-84 micromol thiol groups per gram, respectively (means+/-S.D.; n=6-8). In aqueous solutions these modified polymers were capable of forming inter- and/or intramolecular disulfide bonds. The velocity of this process augmented with increase of the polymer- and decrease of the proton-concentration. The oxidation proceeded more rapidly within thiolated PCP than within thiolated CMC. Due to the formation of disulfide bonds within thiol-containing polymers, the stability of matrix-tablets based on such polymers could be strongly improved. Whereas tablets based on the corresponding unmodified polymer disintegrated within 2 h, the swollen carrier matrix of thiolated CMC and PCP remained stable for 6.2 h (mean, n=4) and more than 48 h, respectively. Release studies of the model drug rifampicin demonstrated that a controlled release can be provided by thiolated polymer tablets. The combination of high stability, controlled drug release and mucoadhesive properties renders matrix-tablets based on thiolated polymers useful as novel drug delivery systems.

Humidity influence on atomic force microscopy electrostatic nanolithography

NASA Astrophysics Data System (ADS)

Lyuksyutov, Sergei; Juhl, Shane; Vaia, Richard

2006-03-01

The formation and sustainability of water menisci and bridges between solid dielectric surface and nano-asperity under external electrostatic potential is a mystery, which must be adequately explained. The goal of our study is twofold: (i) To address the influence of an ambient humidity through the water meniscus formation on the nanostructure formation in soften polymeric surfaces; (ii) Estimate an electric charge generation and transport inside the water meniscus in vicinity of nanoscale asperity taking into consideration an induced water ionization in strong non-uniform electric field of magnitude up to 10^10 Vm-1. It is suspected that strong electric field inside a polymer matrix activates the hoping mechanism of conductivity. The electrons are supplied by tunneling of conductive tip, and also through water ionization. Electric current associated with these free carriers produces Jule heating of a small volume of polymer film heating it above the glass transition temperature. Nanostructures are created by mass transport of visco-elastic polymer melt enabling high structure densities on polymer film.

Prediction of Material Properties of Nanostructured Polymer Composites Using Atomistic Simulations

NASA Technical Reports Server (NTRS)

Hinkley, J.A.; Clancy, T.C.; Frankland, S.J.V.

2009-01-01

Atomistic models of epoxy polymers were built in order to assess the effect of structure at the nanometer scale on the resulting bulk properties such as elastic modulus and thermal conductivity. Atomistic models of both bulk polymer and carbon nanotube polymer composites were built. For the bulk models, the effect of moisture content and temperature on the resulting elastic constants was calculated. A relatively consistent decrease in modulus was seen with increasing temperature. The dependence of modulus on moisture content was less consistent. This behavior was seen for two different epoxy systems, one containing a difunctional epoxy molecule and the other a tetrafunctional epoxy molecule. Both epoxy structures were crosslinked with diamine curing agents. Multifunctional properties were calculated with the nanocomposite models. Molecular dynamics simulation was used to estimate the interfacial thermal (Kapitza) resistance between the carbon nanotube and the surrounding epoxy matrix. These estimated values were used in a multiscale model in order to predict the thermal conductivity of a nanocomposite as a function of the nanometer scaled molecular structure.

Studies on Relaxation Behavior of Corona Poled Aromatic Dipolar Molecules in a Polymer Matrix

DTIC Science & Technology

1990-08-03

concentration upto 30 weight percent. Orientation As expected optically responsive molecules are randomly oriented in the polymer matrix although a small amount...INSERT Figure 4 The retention of SH intensity of the small molecule such as MNA was found to be very poor in the PMMA matrix while the larger rodlike...Polym. Prepr. Am. Chem. Soc., Div. Polym. Chem. 24(2), 309 (1983). 16.- H. Ringsdorf and H. W. Schmidt. Makromol. Chem. 185, 1327 (1984). 17. S. Musikant

A Study of the Critical Factors Controlling the Synthesis of Ceramic Matrix Composites from Preceramic Polymers

DTIC Science & Technology

1990-12-15

THE SYNTHESIS OF CERAMIC MATRIX COMPOSITES PE - 61102F FROM PRECERAMIC POLYMERS PR -9999 6. AUTHOR(S) TA - 99 J. R. Strife(l), J. P. Wesson(1 ), and H...stability at temperatures up to 15000 C. 14. SUBJECT TERMS 15. NUMBER OF PAGES 49 C- SiC composites vinylmethylsilane 16. PRICE CODE polymer precursor...vapor infiltration of fibrous preforms. More recently, the conversion of preceramic polymers as a matrix synthesis process is being considered. This

Magnetic behaviour of composites containing polyaniline-coated manganese-zinc ferrite

NASA Astrophysics Data System (ADS)

Kazantseva, N. E.; Vilčáková, J.; Křesálek, V.; Sáha, P.; Sapurina, I.; Stejskal, J.

2004-02-01

Polycrystalline manganese-zinc ferrite has been coated with polyaniline (PANI) and embedded into a polyurethane matrix. The complex permeability of the composites was studied in the frequency range 1 MHz-3 GHz. The conductivity of PANI coating was adjusted by controlled protonation with picric acid. Large shifts in the resonance frequency were observed as a function of varying PANI conductivity. The changes in the magnetic properties of the PANI-coated composite material are due to the change of the boundary conditions of the microwave field at the interface between the ferrite particle and polymer matrix. This effect is observed especially when the magnetic anisotropy of ferrite is low.

Low Cost Polymer heat Exchangers for Condensing Boilers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Butcher, Thomas; Trojanowski, Rebecca; Wei, George

2015-09-30

Work in this project sought to develop a suitable design for a low cost, corrosion resistant heat exchanger as part of a high efficiency condensing boiler. Based upon the design parameters and cost analysis several geometries and material options were explored. The project also quantified and demonstrated the durability of the selected polymer/filler composite under expected operating conditions. The core material idea included a polymer matrix with fillers for thermal conductivity improvement. While the work focused on conventional heating oil, this concept could also be applicable to natural gas, low sulfur heating oil, and biodiesel- although these are considered tomore » be less challenging environments. An extruded polymer composite heat exchanger was designed, built, and tested during this project, demonstrating technical feasibility of this corrosion-resistant material approach. In such flue gas-to-air heat exchangers, the controlling resistance to heat transfer is in the gas-side convective layer and not in the tube material. For this reason, the lower thermal conductivity polymer composite heat exchanger can achieve overall heat transfer performance comparable to a metal heat exchanger. However, with the polymer composite, the surface temperature on the gas side will be higher, leading to a lower water vapor condensation rate.« less

Study of montmorillonite nanoparticles and electron beam irradiation interaction of ethylene vinyl acetate (EVA)/de-vulcanized waste rubber thermoplastic composites

NASA Astrophysics Data System (ADS)

Bee, Soo-Tueen; Sin, Lee Tin; Hoe, Tie Teck; Ratnam, C. T.; Bee, Soo Ling; Rahmat, A. R.

2018-05-01

The purpose of this work was to investigate the effects of montmorillonite (MMT) loading level and electron beam irradiation on the physical-mechanical properties and thermal stability of ethylene vinyl acetate (EVA)- devulcanised waste rubber blends. The addition of MMT particles has significantly increased the d-spacing and interchain separation of deflection peak (0 0 2) of MMT particles. This indicates that MMT particles have effectively intercalated in polymer matrix of EVA-devulcanised waste rubber blends. Besides, the application of electron beam irradiation dosages <150 kGy could also significantly induce the effective intercalation effect of MMT particles in polymer matrix by introducing crosslinking networks. The increasing of electron beam irradiation dosages up to 250 kGy has gradually increased the gel content of all EVA-devulcanized rubber blends by inducing the formation of crosslinking networks in polymer matrix. Also, the tensile strength of all EVA-devulcanized waste rubber blends was gradually increased when irradiated up to 150 kGy. This is due to the occurrence of crosslinking networks by irradiation could significantly provide reinforcement effect to polymer matrix by effectively transferring the stress applied on polymer matrix throughout the whole polymer matrix.

Associative Flow Rule Used to Include Hydrostatic Stress Effects in Analysis of Strain-Rate-Dependent Deformation of Polymer Matrix Composites

NASA Technical Reports Server (NTRS)

Goldberg, Robert K.; Roberts, Gary D.

2004-01-01

designing reliable composite engine cases that are lighter than the metal cases in current use. The types of polymer matrix composites that are likely to be used in such an application have a deformation response that is nonlinear and that varies with strain rate. The nonlinearity and the strain-rate dependence of the composite response are due primarily to the matrix constituent. Therefore, in developing material models to be used in the design of impact-resistant composite engine cases, the deformation of the polymer matrix must be correctly analyzed. However, unlike in metals, the nonlinear response of polymers depends on the hydrostatic stresses, which must be accounted for within an analytical model. By applying micromechanics techniques along with given fiber properties, one can also determine the effects of the hydrostatic stresses in the polymer on the overall composite deformation response. First efforts to account for the hydrostatic stress effects in the composite deformation applied purely empirical methods that relied on composite-level data. In later efforts, to allow polymer properties to be characterized solely on the basis of polymer data, researchers at the NASA Glenn Research Center developed equations to model the polymers that were based on a non-associative flow rule, and efforts to use these equations to simulate the deformation of representative polymer materials were reasonably successful. However, these equations were found to have difficulty in correctly analyzing the multiaxial stress states found in the polymer matrix constituent of a composite material. To correct these difficulties, and to allow for the accurate simulation of the nonlinear strain-rate-dependent deformation analysis of polymer matrix composites, in the efforts reported here Glenn researchers reformulated the polymer constitutive equations from basic principles using the concept of an associative flow rule. These revised equations were characterized and validated in an experimental program carried out through a university grant with the Ohio State University, wherein tensile and shear deformation data were obtained for a representative polymer for strain rates ranging from quasi-static to high rates of several hundred per second. Tensile deformation data also were obtained over a variety of strain rates and fiber orientation angles for a representative polymer matrix composite composed using the polymer.

Features of the supercritical CO2-assisted immobilization of fluorinated tetraphenylporphyrins into tetrafluoroethylene copolymers

NASA Astrophysics Data System (ADS)

Shershnev, I. V.; Cherkasova, A. V.; Kopylov, A. S.; Glagolev, N. N.; Bragina, N. A.; Solov'eva, A. B.

2017-07-01

The immobilization of fluorinated tetraphenylporphyrins (FTPPs) into tetrafluoroethylene copolymers (fluoroplast F-42 and MF-4SK, a perfluorinated sulfonic acid cation exchanger in H+-form) is conducted in supercritical CO2 (scCO2). The effects the conditions of immobilization (the temperature and pressure of scCO2, reaction time, and the addition of cosolvents) and the structure of the carrier polymer have on the content of porphyrin in these polymers is studied. The porphyrin-loaded polymer systems are shown to exhibit photosensitizing activity in anthracene and cholesterol oxidation in scCO2. Under conditions of photocatalysis, chemical and functional stability is a feature of only MF-4SK polymer systems; this is attributed to the formation of protonated forms of the porphyrins and their interaction with SO3 --groups of the polymer (an ion exchange process), which prevents leaching of the FTPP from the polymer matrix. The photocatalytic process actually occurs inside the matrix of the perfluorinated copolymer, with the protonated form of the porphyrin acting as a photosensitizer. The rate constant of anthracene photooxidation in the presence of FTPP-loaded MF-4SK films in scCO2 is found to pass through a maximum as a function of the porphyrin content and the polymer film thickness. The use of such catalytic systems for cholesterol photooxidation in scCO2 is shown to produce a virtual monoproduct (yield, 10%): 6-formyl-B-norcholestane-3,5-diol, a compound with high biological activity.

Evaluation of Matrix Tablets Based on Eudragit®E100/Carbopol®971P Combinations for Controlled Release and Improved Compaction Properties of Water Soluble Model Drug Paracetamol.

PubMed

Obeidat, Wasfy M; Nokhodchi, Ali; Alkhatib, Hatim

2015-10-01

The purpose of this work was to investigate the influence of Eudragit®E100 polymer in modifying the release rates and compaction properties of water soluble model drug paracetamol from Carbopol®971P NF polymer matrix tablets prepared by direct compression. The effects of the ratio of the two polymers, the total polymeric content, and the tablets mechanical strength on paracetamol release rates were investigated. Dissolution studies were conducted using USP XX Π rotating paddle apparatus at 50 rpm and 37°C at three different stages (pH 1.2, 4.8, and 6.8). Results showed that the polymers combination improved significantly the compaction properties of paracetamol tablets as evident by the higher crushing strengths (8.3 ± 0.4 Kp) compared to polymer-free tablets (3.4 ± 0.2 Kp) at intermediate compression pressure of 490 MPa. When combined with Carbopol®971P NF, Eudragit®E100 was found to be capable of extending paracetamol release for more than 12 h compared to 1 h for polymers-free tablets. The combined polymers were able to control paracetamol release in a pH independent pattern. The f2 (similarity factor) analysis showed that the ratio between the polymers and the total polymer concentration exhibited significant impact on drug release rates. In conclusion, Eudragit®E100 when combined with Carbopol®971P NF was capable of improving the compaction and sustained release properties of paracetamol. Korsmeyer-Peppas model was found to be the most suitable for fitting drug release data. The polymer combinations can potentially be used to control the release rates of highly water soluble drugs.

Copper-polydopamine composite derived from bioinspired polymer coating

DOE PAGES

Zhao, Yao; Wang, Hsin; Qian, Bosen; ...

2018-04-01

Metal matrix composites with nanocarbon phases, such carbon nanotube (CNT) and graphene, have shown potentials to achieve improved mechanical, thermal, and electrical properties. However, incorporation of these nanocarbons into the metal matrix usually involves complicated processes. Here, this study explored a new processing method to fabricate copper (Cu) matrix composite by coating Cu powder particles with nanometer-thick polydopamine (PDA) thin films and sintering of the powder compacts. For sintering temperatures between 300°C and 750°C, the Cu-PDA composite samples showed higher electrical conductivity and thermal conductivity than the uncoated Cu samples, which is likely related to the higher mass densities ofmore » the composite samples. After being sintered at 950°C, the thermal conductivity of the Cu-PDA sample was approximately 12% higher than the Cu sample, while the electrical conductivity did not show significant difference. On the other hand, Knoop micro-hardness values were comparable between the Cu-PDA and Cu samples sintered at the same temperatures.« less

Copper-polydopamine composite derived from bioinspired polymer coating

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhao, Yao; Wang, Hsin; Qian, Bosen

Metal matrix composites with nanocarbon phases, such carbon nanotube (CNT) and graphene, have shown potentials to achieve improved mechanical, thermal, and electrical properties. However, incorporation of these nanocarbons into the metal matrix usually involves complicated processes. Here, this study explored a new processing method to fabricate copper (Cu) matrix composite by coating Cu powder particles with nanometer-thick polydopamine (PDA) thin films and sintering of the powder compacts. For sintering temperatures between 300°C and 750°C, the Cu-PDA composite samples showed higher electrical conductivity and thermal conductivity than the uncoated Cu samples, which is likely related to the higher mass densities ofmore » the composite samples. After being sintered at 950°C, the thermal conductivity of the Cu-PDA sample was approximately 12% higher than the Cu sample, while the electrical conductivity did not show significant difference. On the other hand, Knoop micro-hardness values were comparable between the Cu-PDA and Cu samples sintered at the same temperatures.« less

High Temperature Polymer Matrix Composites

NASA Technical Reports Server (NTRS)

1985-01-01

These are the proceedings of the High Temperature Polymer Matrix Composites Conference held at the NASA Lewis Research Center on March 16 to 18, 1983. The purpose of the conference is to provide scientists and engineers working in the field of high temperature polymer matrix composites an opportunity to review, exchange, and assess the latest developments in this rapidly expanding area of materials technology. Technical papers are presented in the following areas: (1) matrix development; (2) adhesive development; (3) characterization; (4) environmental effects; and (5) applications.

Interfacial crowding of nanoplatelets in co-continuous polymer blends: assembly, elasticity and structure of the interfacial nanoparticle network.

PubMed

Altobelli, R; Salzano de Luna, M; Filippone, G

2017-09-27

The sequence of events which leads to the interfacial crowding of plate-like nanoparticles in co-continuous polymer blends is investigated through a combination of morphological and rheological analyses. Very low amounts (∼0.2 vol%) of organo-modified clay are sufficient to suppress phase coarsening in a co-continuous polystyrene/poly(methyl methacrylate) blend, while lower particle loading allows for a tuning of the characteristic size of the polymer phases at the μm-scale. In any case, an interfacial network of nanoparticles eventually forms, which is driven by the preferred polymer-polymer interface. The elastic features and stress-bearing ability of this peculiar nanoparticle assembly are studied in detail by means of a descriptive two-phase viscoelastic model, which allows isolation of the contribution of the filler network. The role of the co-continuous matrix in driving the space arrangement of the nanoparticles is emphasized by means of comparative analysis with systems based on the same polymers and nanoparticles, but in which the matrix is either a pure polymer or a blend with drop-in-matrix morphology. The relaxation dynamics of the interfacial network was found not to depend on the matrix microstructure, which instead substantially affects the assembly of the nanoplatelets. When the host medium is co-continuous, the particles align along the preferred polymer-polymer interface, percolating at a very low amount (∼0.17 vol%) and prevalently interacting edge-to-edge. The stress bearing ability of such a network is much higher than that in the case of matrix based on a homogeneous polymer or a drop-in-matrix blend, but its elasticity shows low sensitivity to the filler content.

Molecular Dynamics Simulations of Ion Transport and Mechanisms in Polymer Nanocomposites

NASA Astrophysics Data System (ADS)

Mogurampelly, Santosh; Ganesan, Venkat

2015-03-01

Using all atom molecular dynamics and trajectory-extending kinetic Monte Carlo simulations, we study the influence of Al2O3 nanoparticles on the transport properties of Li+ ions in polymer electrolytes consisting of polyethylene oxide (PEO) melt solvated with LiBF4 salt. We observe that the nanoparticles have a strong influence on polymer segmental dynamics which in turn correlates with the mobility of Li+ ions. Explicitly, polymer segmental relaxation times and Li+ ion residence times around polymer were found to increase with the addition of nanoparticles. We also observe that increasing short range repulsive interactions between nanoparticles and polymer membrane leads to increasing polymer dynamics and ion mobility. Overall, our simulation results suggest that nanoparticle induced changes in conformational and dynamic properties of the polymer influences the ion mobilities in polymer electrolytes and suggests possible directions for using such findings to improve the polymer matrix conductivity. The authors acknowledge the Texas Advanced Computing Center (TACC) at The University of Texas at Austin for providing computing resources that have contributed to the research.

Closeup of LDEF experiment trays documented during STS-32 photo survey

NASA Image and Video Library

1990-01-20

Closeup of Long Duration Exposure Facility (LDEF) experiment trays is documented during STS-32 retrieval activity and photo survey conducted by crewmembers onboard Columbia, Orbiter Vehicle (OV) 102. Partially visible is the Polymer Matrix Composite Materials Experiment. In the background is the surface of the Earth.

Electroactive semi-interpenetrating polymer networks architecture with tunable IR reflectivity

NASA Astrophysics Data System (ADS)

Chevrot, C.; Teyssié, D.; Verge, P.; Goujon, L.; Tran-Van, F.; Vidal, F.; Aubert, P. H.; Peralta, S.; Sauques, L.

2011-04-01

A promising alternative of multi-layered devices showing electrochromic properties results from the design of a self-supported semi-interpenetrating polymer network (semi-IPN) including an electronic conductive polymer (ECP) formed within. The formation of the ECP in the network has already been described by oxidative polymerization using iron trichloride as an oxidant and leading to conducting semi-IPN with mixed electronic and ionic conductivities as well as convenient mechanical properties. This presentation relates to the elaboration of such semi-IPN using polyethyleneoxide (PEO) network or a PEO/NBR (Nitrile Butadiene Rubber) IPN in which a linear poly (3,4-ethylenedioxythiophene) (PEDOT) is formed symmetrically and selectively as very thin layers very next to the two main faces of the film matrix. PEO/PEDOT semi-IPNs lead to interesting optical reflective properties in the IR between 0.8 and 25 μm. Reflectance contrasts up to 35 % is observed when, after swelling in an ionic liquid, a low voltage is applied between the two main faces of the film. However the low flexibility and brittleness of the film and a slow degradation in air at temperature up from 60°C prompted to replace the PEO matrix by a flexible PEO/NBR IPN one. Indeed, the combination of NBR and PEO in an IPN leads to materials possessing flexible properties, good ionic conductivity at 25°C as well as a better resistance to thermal ageing. Finally, NBR/PEO/PEDOT semi-IPNs allow observing comparable reflectance contrast in the IR range than those shown by PEO/PEDOT semi-IPNs.

Effects of Prior Aging at 288 deg C in Argon Environment on Creep Response of Carbon Fiber Reinforced PMR-15 Composite with + or - 45 deg Fiber Orientation at 288 deg C

DTIC Science & Technology

2009-06-01

typically consists of a thermoset or thermoplastic polymer matrix reinforced with fibers that are much stronger and stiffer than the matrix. The PMCs are...high thermal or electrical conductivity, stealth characteristics , the ability to self-heal, communication, and sensor capabilities. The multi...have factual evidence of limitations and characteristics so as to utilize the material in a manner consistent with its strengths and weaknesses

Various applications of immobilized glucose oxidase and polyphenol oxidase in a conducting polymer matrix.

PubMed

Cil, M; Böyükbayram, A E; Kiralp, S; Toppare, L; Yağci, Y

2007-06-01

In this study, glucose oxidase and polyphenol oxidase were immobilized in conducting polymer matrices; polypyrrole and poly(N-(4-(3-thienyl methylene)-oxycarbonyl phenyl) maleimide-co-pyrrole) via electrochemical method. Fourier transform infrared and scanning electron microscope were employed to characterize the copolymer of (N-(4-(3-thienyl methylene)-oxycarbonyl phenyl) maleimide) with pyrrole. Kinetic parameters, maximum reaction rate and Michealis-Menten constant, were determined. Effects of temperature and pH were examined for immobilized enzymes. Also, storage and operational stabilities of enzyme electrodes were investigated. Glucose and polyphenol oxidase enzyme electrodes were used for determination of the glucose amount in orange juices and human serum and phenolic amount in red wines, respectively.

Conductivity study of thermally stabilized RuO2/polythiophene nanocomposites

NASA Astrophysics Data System (ADS)

Hebbar, Vidyashree; Bhajantri, R. F.

2018-04-01

The polymer nanocomposites of Ruthenium oxide (RuO2) filled polythiophene (PT) were synthesized by polymerization using chemical method. The purity of the synthesized polymer composite is verified using X-Ray diffraction (XRD). The structural discrepancies of the RuO2 filled PT composites are studied by Fourier transform infrared (FT-IR) spectroscopy. The phase transition and thermal stability of the prepared composite is revised by thermal characterization such as differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). The DC conductivity of RuO2 filled PT composite in the form of pellets is calculated using current-voltage (I-V) characterization by two-probe method. The enhancement in conductivity with increased RuO2 content in PT matrix is examined, which is the required property for electrical and electronic applications in supercapacitors.

Multiscale Modeling of Thermal Conductivity of Polymer/Carbon Nanocomposites

NASA Technical Reports Server (NTRS)

Clancy, Thomas C.; Frankland, Sarah-Jane V.; Hinkley, Jeffrey A.; Gates, Thomas S.

2010-01-01

Molecular dynamics simulation was used to estimate the interfacial thermal (Kapitza) resistance between nanoparticles and amorphous and crystalline polymer matrices. Bulk thermal conductivities of the nanocomposites were then estimated using an established effective medium approach. To study functionalization, oligomeric ethylene-vinyl alcohol copolymers were chemically bonded to a single wall carbon nanotube. The results, in a poly(ethylene-vinyl acetate) matrix, are similar to those obtained previously for grafted linear hydrocarbon chains. To study the effect of noncovalent functionalization, two types of polyethylene matrices. -- aligned (extended-chain crystalline) vs. amorphous (random coils) were modeled. Both matrices produced the same interfacial thermal resistance values. Finally, functionalization of edges and faces of plate-like graphite nanoparticles was found to be only modestly effective in reducing the interfacial thermal resistance and improving the composite thermal conductivity

Synthesis of Conductive Polymeric Nanocomposites for Applications in Responsive Materials

NASA Astrophysics Data System (ADS)

Chavez, Jessica

The development of next generation "smart" textiles has emerged with significant interest due to the immense demand for high-performance wearable technology. The economic market for wearable technologies is predicted to increase significantly in both volume and value. In the next four years, the wearable technology market will be valued at $34 billion. This large demand has opened up a new research area involving smart wearable devices and conductive fabrics. Many research groups have taken various paths to study and ultimately fabricate wearable devices. Due to the limiting capabilities of conventional conductors, researchers have centered their research on the integration of conductive polymers into textile materials for applications involving responsive material. Conducive polymers are very unique organic molecules that have the ability to transfer electrons across their molecular structure due to the excess presence of pi-electrons. Conductive polymers are favored over conventional conductors because they can be easily manipulated and integrated into flexible material. Two very common conductive polymers are polyaniline (PANI) and polypyrrole (PPY) because of their large favorability in literature, high conductance values, and environmental stability. Common commercial fibers were coated via the chemical polymerization of PANI or PPY. A series of reactions were done to study the polymerization process of each polymer. The conductive efficiency of each conducting polymer is highly dependent on the type of reactants used, the acidic nature of the reaction, and the temperature of the reaction. The coated commercial fiber nanocomposites produced higher conductivity values when the polymerization reaction was run using ammonium peroxydisulfate (APS) as the oxidizing agent, run in an acidic environment, and run at very low temperatures. Other factors that improved the overall efficiency of the coated commercial fiber nanocomposites was the increase in polymer concentration as well as the extension of the reaction time. The overall interaction between the conductive polymer and the commercial fibers showed that the conductive polymer was physically adsorbed to the commercial fiber. This physical adsorption caused a decrease in conductive efficiency as a function of repeated washes because the weak intermolecular forces between the conductive polymer and the commercial fiber. This led to the synthesis of conductive films and nanofibers by integrating the conductive polymers directly into a cellulose acetate matrix. The voltage efficiency of the conductive films was lower compared to the coated commercial fiber nanocomposites. However, the conductive material generated greater lux values compared to the coated commercial fiber nanocomposites. Theses conductive materials can be applied to applications in both the medical field and water filtration. The conductive films can be used to create a sensor based system that can trigger a sensor to signify when bandages used for wound management need to be changed. The conductive nanofibers can be used in water filtration as a means of electroplating metals ions from contaminated water. Overall, the synthesis of these conductive materials can be applicable for responsive materials.

Creep-rupture of polymer-matrix composites. [graphite-epoxy laminates

NASA Technical Reports Server (NTRS)

Brinson, H. F.; Griffith, W. I.; Morris, D. H.

1980-01-01

An accelerated characterization method for resin matrix composites is reviewed. Methods for determining modulus and strength master curves are given. Creep rupture analytical models are discussed as applied to polymers and polymer matrix composites. Comparisons between creep rupture experiments and analytical models are presented. The time dependent creep rupture process in graphite epoxy laminates is examined as a function of temperature and stress level.

Hierarchical nanostructured conducting polymer hydrogel with high electrochemical activity

PubMed Central

Pan, Lijia; Yu, Guihua; Zhai, Dongyuan; Lee, Hye Ryoung; Zhao, Wenting; Liu, Nian; Wang, Huiliang; Tee, Benjamin C.-K.; Shi, Yi; Cui, Yi; Bao, Zhenan

2012-01-01

Conducting polymer hydrogels represent a unique class of materials that synergizes the advantageous features of hydrogels and organic conductors and have been used in many applications such as bioelectronics and energy storage devices. They are often synthesized by polymerizing conductive polymer monomer within a nonconducting hydrogel matrix, resulting in deterioration of their electrical properties. Here, we report a scalable and versatile synthesis of multifunctional polyaniline (PAni) hydrogel with excellent electronic conductivity and electrochemical properties. With high surface area and three-dimensional porous nanostructures, the PAni hydrogels demonstrated potential as high-performance supercapacitor electrodes with high specific capacitance (∼480 F·g-1), unprecedented rate capability, and cycling stability (∼83% capacitance retention after 10,000 cycles). The PAni hydrogels can also function as the active component of glucose oxidase sensors with fast response time (∼0.3 s) and superior sensitivity (∼16.7 μA·mM-1). The scalable synthesis and excellent electrode performance of the PAni hydrogel make it an attractive candidate for bioelectronics and future-generation energy storage electrodes. PMID:22645374

Carbon Nanotube/Conductive Additive/Space Durable Polymer Nanocomposite Films for Electrostatic Charge Dissipation

NASA Technical Reports Server (NTRS)

Smith, Joseph G., Jr.; Watson, Kent A.; Delozier, Donavon M.; Connell, John W.

2003-01-01

Thin film membranes of space environmentally stable polymeric materials possessing low color/solar absorptivity (alpha) are of interest for potential applications on Gossamer spacecraft. In addition to these properties, sufficient electrical conductivity is required in order to dissipate electrostatic charge (ESC) build-up brought about by the charged orbital environment. One approach to achieve sufficient electrical conductivity for ESC mitigation is the incorporation of single wall carbon nanotubes (SWNTs). However, when the SWNTs are dispersed throughout the polymer matrix, the nanocomposite films tend to be significantly darker than the pristine material resulting in a higher alpha. The incorporation of conductive additives in combination with a decreased loading level of SWNTs is one approach for improving alpha while retaining conductivity. Taken individually, the low loading level of conductive additives and SWNTs is insufficient in achieving the percolation level necessary for electrical conductivity. When added simultaneously to the film, conductivity is achieved through a synergistic effect. The chemistry, physical, and mechanical properties of the nanocomposite films will be presented.

Polymer-phyllosilicate nanocomposites and their preparation

DOEpatents

Chaiko, David J.

2007-01-09

Polymer-phyllosilicate nanocomposites that exhibit superior properties compared to the polymer alone, and methods-for producing these polymer-phyllosilicate nanocomposites, are provided. Polymeric surfactant compatabilizers are adsorbed onto the surface of hydrophilic or natural phyllosilicates to facilitate the dispersal and exfoliation of the phyllosilicate in a polymer matrix. Utilizing polymeric glycol based surfactants, polymeric dicarboxylic acids, polymeric diammonium surfactants, and polymeric diamine surfactants as compatabilizers facilitates natural phyllosilicate and hydrophilic organoclay dispersal in a polymer matrix to produce nanocomposites.

Modeling the Effects of Interfacial Characteristics on Gas Permeation Behavior of Nanotube-Mixed Matrix Membranes.

PubMed

Chehrazi, Ehsan; Sharif, Alireza; Omidkhah, Mohammadreza; Karimi, Mohammad

2017-10-25

Theoretical approaches that accurately predict the gas permeation behavior of nanotube-containing mixed matrix membranes (nanotube-MMMs) are scarce. This is mainly due to ignoring the effects of nanotube/matrix interfacial characteristics in the existing theories. In this paper, based on the analogy of thermal conduction in polymer composites containing nanotubes, we develop a model to describe gas permeation through nanotube-MMMs. Two new parameters, "interfacial thickness" (a int ) and "interfacial permeation resistance" (R int ), are introduced to account for the role of nanotube/matrix interfacial interactions in the proposed model. The obtained values of a int , independent of the nature of the permeate gas, increased by increasing both the nanotubes aspect ratio and polymer-nanotube interfacial strength. An excellent correlation between the values of a int and polymer-nanotube interaction parameters, χ, helped to accurately reproduce the existing experimental data from the literature without the need to resort to any adjustable parameter. The data includes 10 sets of CO 2 /CH 4 permeation, 12 sets of CO 2 /N 2 permeation, 3 sets of CO 2 /O 2 permeation, and 2 sets of CO 2 /H 2 permeation through different nanotube-MMMs. Moreover, the average absolute relative errors between the experimental data and the predicted values of the proposed model are very small (less than 5%) in comparison with those of the existing models in the literature. To the best of our knowledge, this is the first study where such a systematic comparison between model predictions and such extensive experimental data is presented. Finally, the new way of assessing gas permeation data presented in the current work would be a simple alternative to complex approaches that are usually utilized to estimate interfacial thickness in polymer composites.

Ferrocene-functionalized 4-(2,5-Di(thiophen-2-yl)-1H-pyrrol-1-yl)aniline: a novel design in conducting polymer-based electrochemical biosensors.

PubMed

Ayranci, Rukiye; Demirkol, Dilek Odaci; Ak, Metin; Timur, Suna

2015-01-13

Herein, we report a novel ferrocenyldithiophosphonate functional conducting polymer and its use as an immobilization matrix in amperometric biosensor applications. Initially, 4-(2,5-di(thiophen-2-yl)-1H-pyrrol-1-yl)amidoferrocenyldithiophosphonate was synthesized and copolymerized with 4-(2,5-di(thiophen-2-yl)-1H-pyrrol-1-yl)benzenamine at graphite electrodes. The amino groups on the polymer were utilized for covalent attachment of the enzyme glucose oxidase. Besides, ferrocene on the backbone was used as a redox mediator during the electrochemical measurements. Prior to the analytical characterization, optimization studies were carried out. The changes in current signals at +0.45 V were proportional to glucose concentration from 0.5 to 5.0 mM. Finally, the resulting biosensor was applied for glucose analysis in real samples and the data were compared with the spectrophotometric Trinder method.

A Solution-Doped Polymer Semiconductor:Insulator Blend for Thermoelectrics.

PubMed

Kiefer, David; Yu, Liyang; Fransson, Erik; Gómez, Andrés; Primetzhofer, Daniel; Amassian, Aram; Campoy-Quiles, Mariano; Müller, Christian

2017-01-01

Poly(ethylene oxide) is demonstrated to be a suitable matrix polymer for the solution-doped conjugated polymer poly(3-hexylthiophene). The polarity of the insulator combined with carefully chosen processing conditions permits the fabrication of tens of micrometer-thick films that feature a fine distribution of the F4TCNQ dopant:semiconductor complex. Changes in electrical conductivity from 0.1 to 0.3 S cm -1 and Seebeck coefficient from 100 to 60 μV K -1 upon addition of the insulator correlate with an increase in doping efficiency from 20% to 40% for heavily doped ternary blends. An invariant bulk thermal conductivity of about 0.3 W m -1 K -1 gives rise to a thermoelectric Figure of merit ZT ∼ 10 -4 that remains unaltered for an insulator content of more than 60 wt%. Free-standing, mechanically robust tapes illustrate the versatility of the developed dopant:semiconductor:insulator ternary blends.

Dense Vertically Aligned Copper Nanowire Composites as High Performance Thermal Interface Materials.

PubMed

Barako, Michael T; Isaacson, Scott G; Lian, Feifei; Pop, Eric; Dauskardt, Reinhold H; Goodson, Kenneth E; Tice, Jesse

2017-12-06

Thermal interface materials (TIMs) are essential for managing heat in modern electronics, and nanocomposite TIMs can offer critical improvements. Here, we demonstrate thermally conductive, mechanically compliant TIMs based on dense, vertically aligned copper nanowires (CuNWs) embedded into polymer matrices. We evaluate the thermal and mechanical characteristics of 20-25% dense CuNW arrays with and without polydimethylsiloxane infiltration. The thermal resistance achieved is below 5 mm 2 K W -1 , over an order of magnitude lower than commercial heat sink compounds. Nanoindentation reveals that the nonlinear deformation mechanics of this TIM are influenced by both the CuNW morphology and the polymer matrix. We also implement a flip-chip bonding protocol to directly attach CuNW composites to copper surfaces, as required in many thermal architectures. Thus, we demonstrate a rational design strategy for nanocomposite TIMs that simultaneously retain the high thermal conductivity of aligned CuNWs and the mechanical compliance of a polymer.

Self-constructed tree-shape high thermal conductivity nanosilver networks in epoxy.

PubMed

Pashayi, Kamyar; Fard, Hafez Raeisi; Lai, Fengyuan; Iruvanti, Sushumna; Plawsky, Joel; Borca-Tasciuc, Theodorian

2014-04-21

We report the formation of high aspect ratio nanoscale tree-shape silver networks in epoxy, at low temperatures (<150 °C) and atmospheric pressures, that are correlated to a ∼200 fold enhancement of thermal conductivity (κ) of the nanocomposite compared to the polymer matrix. The networks form through a three-step process comprising of self-assembly by diffusion limited aggregation of polyvinylpyrrolidone (PVP) coated nanoparticles, removal of PVP coating from the surface, and sintering of silver nanoparticles in high aspect ratio networked structures. Controlling self-assembly and sintering by carefully designed multistep temperature and time processing leads to κ of our silver nanocomposites that are up to 300% of the present state of the art polymer nanocomposites at similar volume fractions. Our investigation of the κ enhancements enabled by tree-shaped network nanocomposites provides a basis for the development of new polymer nanocomposites for thermal transport and storage applications.

Fluorine-free electrolytes for all-solid sodium-ion batteries based on percyano-substituted organic salts

PubMed Central

Bitner-Michalska, Anna; Nolis, Gene M.; Żukowska, Grażyna; Zalewska, Aldona; Poterała, Marcin; Trzeciak, Tomasz; Dranka, Maciej; Kalita, Michał; Jankowski, Piotr; Niedzicki, Leszek; Zachara, Janusz; Marcinek, Marek; Wieczorek, Władysław

2017-01-01

A new family of fluorine-free solid-polymer electrolytes, for use in sodium-ion battery applications, is presented. Three novel sodium salts withdiffuse negative charges: sodium pentacyanopropenide (NaPCPI), sodium 2,3,4,5-tetracyanopirolate (NaTCP) and sodium 2,4,5-tricyanoimidazolate (NaTIM) were designed andtested in a poly(ethylene oxide) (PEO) matrix as polymer electrolytes for anall-solid sodium-ion battery. Due to unique, non-covalent structural configurations of anions, improved ionic conductivities were observed. As an example, “liquid-like” high conductivities (>1 mS cm−1) were obtained above 70 °C for solid-polymer electrolyte with a PEO to NaTCP molar ratio of 16:1. All presented salts showed high thermal stability and suitable windows of electrochemical stability between 3 and 5 V. These new anions open a new class of compounds with non-covalent structure for electrolytes system applications. PMID:28067301

Fluorine-free electrolytes for all-solid sodium-ion batteries based on percyano-substituted organic salts

NASA Astrophysics Data System (ADS)

Bitner-Michalska, Anna; Nolis, Gene M.; Żukowska, Grażyna; Zalewska, Aldona; Poterała, Marcin; Trzeciak, Tomasz; Dranka, Maciej; Kalita, Michał; Jankowski, Piotr; Niedzicki, Leszek; Zachara, Janusz; Marcinek, Marek; Wieczorek, Władysław

2017-01-01

A new family of fluorine-free solid-polymer electrolytes, for use in sodium-ion battery applications, is presented. Three novel sodium salts withdiffuse negative charges: sodium pentacyanopropenide (NaPCPI), sodium 2,3,4,5-tetracyanopirolate (NaTCP) and sodium 2,4,5-tricyanoimidazolate (NaTIM) were designed andtested in a poly(ethylene oxide) (PEO) matrix as polymer electrolytes for anall-solid sodium-ion battery. Due to unique, non-covalent structural configurations of anions, improved ionic conductivities were observed. As an example, “liquid-like” high conductivities (>1 mS cm-1) were obtained above 70 °C for solid-polymer electrolyte with a PEO to NaTCP molar ratio of 16:1. All presented salts showed high thermal stability and suitable windows of electrochemical stability between 3 and 5 V. These new anions open a new class of compounds with non-covalent structure for electrolytes system applications.

Synthesis and characterization of structural and magnetic properties of polyaniline-cobalt ferrite (PA-CoFe) nanocomposites

NASA Astrophysics Data System (ADS)

Thakur, Sonika; Kaur, Parminder; Singh, Lakhwant

2018-05-01

The growing interest in the investigation of the properties of modified conducting polymers stems from their potential applications in various fields such as in sensing and catalytic devices. The present work reports the modification of conducting polymer polyaniline with cobalt ferrite (CoFe) nanoparticles, where CoFe nanoparticles are added in different successive weight percents. The composite samples were synthesized by in-situ chemical oxidative polymerization technique. The density of the samples has been found to increase with an increase in the CoFe content. Structural analysis of the synthesized sample has been done using X-ray diffraction studies. Perusal of the hysteresis curves of the prepared samples depicts that the introduction of CoFe into the polymer matrix leads to enhancement in the ferromagnetic behavior of the synthesized samples, suggesting that these nanocomposites have excellent microwave absorbing capacity.

A Solution‐Doped Polymer Semiconductor:Insulator Blend for Thermoelectrics

PubMed Central

Kiefer, David; Yu, Liyang; Fransson, Erik; Gómez, Andrés; Primetzhofer, Daniel; Amassian, Aram; Campoy‐Quiles, Mariano

2016-01-01

Poly(ethylene oxide) is demonstrated to be a suitable matrix polymer for the solution‐doped conjugated polymer poly(3‐hexylthiophene). The polarity of the insulator combined with carefully chosen processing conditions permits the fabrication of tens of micrometer‐thick films that feature a fine distribution of the F4TCNQ dopant:semiconductor complex. Changes in electrical conductivity from 0.1 to 0.3 S cm−1 and Seebeck coefficient from 100 to 60 μV K−1 upon addition of the insulator correlate with an increase in doping efficiency from 20% to 40% for heavily doped ternary blends. An invariant bulk thermal conductivity of about 0.3 W m−1 K−1 gives rise to a thermoelectric Figure of merit ZT ∼ 10−4 that remains unaltered for an insulator content of more than 60 wt%. Free‐standing, mechanically robust tapes illustrate the versatility of the developed dopant:semiconductor:insulator ternary blends. PMID:28105396

Ferrocene-Functionalized 4-(2,5-Di(thiophen-2-yl)-1H-pyrrol-1-yl)aniline: A Novel Design in Conducting Polymer-Based Electrochemical Biosensors

PubMed Central

Ayranci, Rukiye; Demirkol, Dilek Odaci; Ak, Metin; Timur, Suna

2015-01-01

Herein, we report a novel ferrocenyldithiophosphonate functional conducting polymer and its use as an immobilization matrix in amperometric biosensor applications. Initially, 4-(2,5-di(thiophen-2-yl)-1H-pyrrol-1-yl)amidoferrocenyldithiophosphonate was synthesized and copolymerized with 4-(2,5-di(thiophen-2-yl)-1H-pyrrol-1-yl)benzenamine at graphite electrodes. The amino groups on the polymer were utilized for covalent attachment of the enzyme glucose oxidase. Besides, ferrocene on the backbone was used as a redox mediator during the electrochemical measurements. Prior to the analytical characterization, optimization studies were carried out. The changes in current signals at +0.45 V were proportional to glucose concentration from 0.5 to 5.0 mM. Finally, the resulting biosensor was applied for glucose analysis in real samples and the data were compared with the spectrophotometric Trinder method. PMID:25591169

Sensing/actuating materials made from carbon nanotube polymer composites and methods for making same

NASA Technical Reports Server (NTRS)

Ounaies, Zoubeida (Inventor); Park, Cheol (Inventor); Harrison, Joycelyn S. (Inventor); Holloway, Nancy M. (Inventor); Draughon, Gregory K. (Inventor)

2008-01-01

An electroactive sensing or actuating material comprises a composite made from a polymer with polarizable moieties and an effective amount of carbon nanotubes incorporated in the polymer for a predetermined electromechanical operation of the composite when such composite is affected by an external stimulus. In another embodiment, the composite comprises a third component of micro-sized to nano-sized particles of an electroactive ceramic that is also incorporated in the polymer matrix. The method for making the three-phase composite comprises either incorporating the carbon nanotubes in the polymer matrix before incorporation of the particles of ceramic or mixing the carbon nanotubes and particles of ceramic together in a solution before incorporation in the polymer matrix.

Method of Making an Electroactive Sensing/Actuating Material for Carbon Nanotube Polymer Composite

NASA Technical Reports Server (NTRS)

Ounaies, Zoubeida (Inventor); Park, Cheol (Inventor); Harrison, Joycelyn S. (Inventor); Holloway, Nancy M. (Inventor); Draughon, Gregory K. (Inventor)

2009-01-01

An electroactive sensing or actuating material comprises a composite made from a polymer with polarizable moieties and an effective amount of carbon nanotubes incorporated in the polymer for a predetermined electromechanical operation of the composite when such composite is affected by an external stimulus. In another embodiment, the composite comprises a, third component of micro -sized to nano-sized particles of an electroactive ceramic that is also incorporated in the polymer matrix. The method for making the three-phase composite comprises either incorporating the carbon nanotubes in the polymer matrix before incorporation of the particles of ceramic or mixing the carbon nanotubes and particles of ceramic together in a solution before incorporation in the polymer matrix.

Polymeric matrix materials for infrared metamaterials

DOEpatents

Dirk, Shawn M; Rasberry, Roger D; Rahimian, Kamyar

2014-04-22

A polymeric matrix material exhibits low loss at optical frequencies and facilitates the fabrication of all-dielectric metamaterials. The low-loss polymeric matrix material can be synthesized by providing an unsaturated polymer, comprising double or triple bonds; partially hydrogenating the unsaturated polymer; depositing a film of the partially hydrogenated polymer and a crosslinker on a substrate; and photopatterning the film by exposing the film to ultraviolet light through a patterning mask, thereby cross-linking at least some of the remaining unsaturated groups of the partially hydrogenated polymer in the exposed portions.

Effects of different surface modification and contents on municipal solid waste incineration fly ash/epoxy composites.

PubMed

Goh, C K; Valavan, S E; Low, T K; Tang, L H

2016-12-01

Incineration fly ash, a waste from municipal solid waste incineration plant can be used to replace conventional filler as reinforcing filler to enhance the mechanical strength of a composite. Surface modification was performed on the incineration fly ash before mixing into the soft polymer matrix so as to improve interfacial bond of the filler and epoxy resin. In this study, detailed characterisation of mechanical, morphological and leaching behaviours of municipal solid waste incineration (MSWI) fly ash infused composite has been carried out. Flexural and tensile test was conducted to determine the effect on mechanical properties of the composite by varying the concentration of incineration fly ash filler added into polymer matrix and surface modification of incineration fly ash filler using silane coupling agent and colloidal mesoporous silica (CMS). The results indicated that composite infused with incineration fly ash filler surface treated with CMS shown improvement on the tensile and flexural strengths. In addition, SEM images showed that surface modification of incineration fly ash with colloidal mesoporous silica enhanced the interfacial bonding with polymer resin which explained the improvement of mechanical strength. Leaching test showed result of toxic metals such as Pb, Zn, Fe, Cu, Cr, Cd and Rb immobilised in the polymer matrix of the composite. Hence, the use of MSWI fly ash as reinforcing filler in the composite appears green and sustainable because this approach is a promising opportunity to substitute valuable raw material with MSWI fly ash. Copyright © 2016 Elsevier Ltd. All rights reserved.

Recycling and processing of several typical crosslinked polymer scraps with enhanced mechanical properties based on solid-state mechanochemical milling

NASA Astrophysics Data System (ADS)

Lu, Canhui; Zhang, Xinxing; Zhang, Wei

2015-05-01

The partially devulcanization or de-crosslinking of ground tire rubber (GTR), post-vulcanized fluororubber scraps and crosslinked polyethylene from cable scraps through high-shear mechanochemical milling (HSMM) was conducted by a modified solid-state mechanochemical reactor. The results indicated that the HSMM treated crosslinked polymer scraps can be reprocessed as virgin rubbers or thermoplastics to produce materials with high performance. The foamed composites of low density polyethylene/GTR and the blend of post-vulcanized flurorubber (FKM) with polyacrylate rubber (ACM) with better processability and mechanical properties were obtained. The morphology observation showed that the dispersion and compatibility between de-crosslinked polymer scraps and matrix were enhanced. The results demonstrated that HSMM is a feasible alternative technology for recycling post-vulcanized or crosslinked polymer scraps.

Effects of fiber/matrix interactions on the interfacial deformation micromechanics of cellulose-fiber/polymer composites

NASA Astrophysics Data System (ADS)

Tze, William Tai-Yin

The overall objective of this dissertation was to gain an understanding of the relationship between interfacial chemistry and the micromechanics of the cellulose-fiber/polymer composites. Regenerated cellulose (lyocell) fibers were treated with amine-, phenylamine-, phenyl-, and octadecyl-silanes, and also styrene-maleic anhydride copolymer. Inverse gas chromatography was conducted to evaluate the modified surfaces and to examine the adsorption behavior of ethylbenzene, a model compound for polystyrene, onto the fibers. Micro-composites were formed by depositing micro-droplets of polystyrene onto single fibers. The fiber was subjected to a tensile strain, and Raman spectroscopy was employed to determine the point-to-point variation of the strain- and stress-sensitive 895 cm-1 band of cellulose along the embedded region. Inverse gas chromatography studies reveal that the Ia-b values, calculated by matching the Lewis acid parameter ( KA) and basic parameter (KB) between polystyrene and different fibers, were closely correlated to the acid-base adsorption enthalpies of ethylbenzene onto the corresponding fibers. Hence, Ia-b was subsequently used as a convenient indicator for fiber/matrix acid-base interaction. The Raman micro-spectroscopic studies demonstrate that the interfacial tensile strain and stress are highest at the edge of the droplet, and these values decline from the edge region to the middle region of the embedment. The maximum of these local strains corresponds to a strain-control fracture of the matrix polymer. The minimum of the local tensile stress corresponds to the extent of fiber-to-matrix load transfer. The slope of the tensile stress profile allows for an estimation of the maximum interfacial shear stress, which is indicative of fiber/polymer (practical) adhesion. As such, a novel micro-Raman tensile technique was established for evaluating the ductile-fiber/brittle-polymer system in this study. The micro-Raman tensile technique provided maximum interfacial shear stress values of 8.0 to 13.8 MPa, ranking functional groups according to their practical adhesion to polystyrene: alkyl < untreated < phenyl = phenylamine = styrene copolymer < amine. Overall, interfacial bonding can be increased by increasing the acid-base interactions (Ia-b) or reducing the chemical incompatibility (Deltadelta) between the fibers and matrix. Therefore, interfacial chemistry can be employed to enhance and predict cellulose-fiber/polymer adhesion to better engineer composite properties and ultimately better utilize bio-resources.

The sintered microsphere matrix for bone tissue engineering: in vitro osteoconductivity studies.

PubMed

Borden, Mark; Attawia, Mohamed; Laurencin, Cato T

2002-09-05

A tissue engineering approach has been used to design three-dimensional synthetic matrices for bone repair. The osteoconductivity and degradation profile of a novel polymeric bone-graft substitute was evaluated in an in vitro setting. Using the copolymer poly(lactide-co-glycolide) [PLAGA], a sintering technique based on microsphere technology was used to fabricate three-dimensional porous scaffolds for bone regeneration. Osteoblasts and fibroblasts were seeded onto a 50:50 PLAGA scaffold. Morphologic evaluation through scanning electron microscopy demonstrated that both cell types attached and spread over the scaffold. Cells migrated through the matrix using cytoplasmic extensions to bridge the structure. Cross-sectional images indicated that cellular proliferation had penetrated into the matrix approximately 700 microm from the surface. Examination of the surfaces of cell/matrix constructs demonstrated that cellular proliferation had encompassed the pores of the matrix by 14 days of cell culture. With the aim of optimizing polymer composition and polymer molecular weight, a degradation study was conducted utilizing the matrix. The results demonstrate that degradation of the sintered matrix is dependent on molecular weight, copolymer ratio, and pore volume. From this data, it was determined that 75:25 PLAGA with an initial molecular weight of 100,000 has an optimal degradation profile. These studies show that the sintered microsphere matrix has an osteoconductive structure capable of functioning as a cellular scaffold with a degradation profile suitable for bone regeneration. Copyright 2002 Wiley Periodicals, Inc.

Enhanced Proton Conductivity and Methanol Permeability Reduction via Sodium Alginate Electrolyte-Sulfonated Graphene Oxide Bio-membrane

NASA Astrophysics Data System (ADS)

Shaari, N.; Kamarudin, S. K.; Basri, S.; Shyuan, L. K.; Masdar, M. S.; Nordin, D.

2018-03-01

The high methanol crossover and high cost of Nafion® membrane are the major challenges for direct methanol fuel cell application. With the aim of solving these problems, a non-Nafion polymer electrolyte membrane with low methanol permeability and high proton conductivity based on the sodium alginate (SA) polymer as the matrix and sulfonated graphene oxide (SGO) as an inorganic filler (0.02-0.2 wt%) was prepared by a simple solution casting technique. The strong electrostatic attraction between -SO3H of SGO and the sodium alginate polymer increased the mechanical stability, optimized the water absorption and thus inhibited the methanol crossover in the membrane. The optimum properties and performances were presented by the SA/SGO membrane with a loading of 0.2 wt% SGO, which gave a proton conductivity of 13.2 × 10-3 Scm-1, and the methanol permeability was 1.535 × 10-7 cm2 s-1 at 25 °C, far below that of Nafion (25.1 × 10-7 cm2 s-1) at 25 °C. The mechanical properties of the sodium alginate polymer in terms of tensile strength and elongation at break were improved by the addition of SGO.

Hydraulic Testing of Polymer Matrix Composite 102mm Tube Section Technical Report

DTIC Science & Technology

2018-04-01

Technical Report ARWSB-TR-18025 Hydraulic Testing of Polymer Matrix Composite 102mm Tube Section Technical Report Lucas B...1. REPORT DATE (DD-MM-YYYY) April 2018 2. REPORT TYPE Technical 3. DATES COVERED (From - To) 4. TITLE AND SUBTITLE Hydraulic Testing of...Polymer Matrix Composite 102mm Tube Section Technical Report 5a. CONTRACT NUMBER 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER

Stretchable and flexible thermoelectric polymer composites

NASA Astrophysics Data System (ADS)

Slobodian, P.; Riha, P.; Matyas, J.; Olejnik, R.

2018-03-01

Polymer composites were manufactured from pristine and oxidized multi-walled carbon nanotubes and ethylene-octene copolymer. The composites had thermoelectric properties and exhibit thermoelectric effect, that is, the conversion of temperature differences into electricity. Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy of the multi-walled carbon nanotubes in ethylene-octene copolymer matrix showed that the oxidation with HNO3 or KMnO4 enhanced its p-type electrical conductivity and that the thermoelectric power increase was proportional to the formation of new oxygen-containing functional groups on the surface of carbon nanotubes.

Polymer and ceramic nanocomposites for aerospace applications

NASA Astrophysics Data System (ADS)

Rathod, Vivek T.; Kumar, Jayanth S.; Jain, Anjana

2017-11-01

This paper reviews the potential of polymer and ceramic matrix composites for aerospace/space vehicle applications. Special, unique and multifunctional properties arising due to the dispersion of nanoparticles in ceramic and metal matrix are briefly discussed followed by a classification of resulting aerospace applications. The paper presents polymer matrix composites comprising majority of aerospace applications in structures, coating, tribology, structural health monitoring, electromagnetic shielding and shape memory applications. The capabilities of the ceramic matrix nanocomposites to providing the electromagnetic shielding for aircrafts and better tribological properties to suit space environments are discussed. Structural health monitoring capability of ceramic matrix nanocomposite is also discussed. The properties of resulting nanocomposite material with its disadvantages like cost and processing difficulties are discussed. The paper concludes after the discussion of the possible future perspectives and challenges in implementation and further development of polymer and ceramic nanocomposite materials.

A plasticized polymer-electrolyte-based photoelectrochemical solar cell

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mao, D.; Ibrahim, M.A.; Frank, A.J.

1998-01-01

A photoelectrochemical solar cell based on an n-GaAs/polymer-redox-electrolyte junction is reported. Di(ethylene glycol) ethyl ether acrylate containing ferrocene as a redox species and benzoin methyl ether as a photoinitiator is polymerized in situ. Propylene carbonate is used as a plasticizer to improve the conductivity of the polymer redox electrolyte. For thin (1 {micro}m) polymer electrolytes, the series resistance of the cell is negligible. However, the short-circuit photocurrent density of the cell at light intensities above 10 mW/cm{sup 2} is limited by mass transport of redox species within the polymer matrix. At a light intensity of 70 mW/cm{sup 2}, a moderatemore » light-to-electrical energy conversion efficiency (3.1%) is obtained. The interfacial charge-transfer properties of the cell in the dark and under illumination are studied.« less

Mean-Field Models of Structure and Dispersion of Polymer-nanoparticle Mixtures

DTIC Science & Technology

2010-07-29

out of the seminal descriptions of the wetting and dewetting of polymer melts on polymer brushes advanced by Leibler and coworkers.118,119 Explicitly...using scaling ideas and strong segregation theory calculations they delineated the regions where the matrix polymer wets or dewets the brush. In the...Explicitly, when dewetting of the melt chains is expected ( dry brush). In other words, situations involving long matrix polymers and/or densely grafted

Improved dielectric properties, mechanical properties, and thermal conductivity properties of polymer composites via controlling interfacial compatibility with bio-inspired method

NASA Astrophysics Data System (ADS)

Ruan, Mengnan; Yang, Dan; Guo, Wenli; Zhang, Liqun; Li, Shuxin; Shang, Yuwei; Wu, Yibo; Zhang, Min; Wang, Hao

2018-05-01

Surface functionalization of Al2O3 nano-particles by mussel-inspired poly(dopamine) (PDA) was developed to improve the dielectric properties, mechanical properties, and thermal conductivity properties of nitrile rubber (NBR) matrix. As strong adhesion of PDA to Al2O3 nano-particles and hydrogen bonds formed by the catechol groups of PDA and the polar acrylonitrile groups of NBR, the dispersion of Al2O3-PDA/NBR composites was improved and the interfacial force between Al2O3-PDA and NBR matrix was enhanced. Thus, the Al2O3-PDA/NBR composites exhibited higher dielectric constant, better mechanical properties, and larger thermal conductivity comparing with Al2O3/NBR composites at the same filler content. The largest thermal conductivity of Al2O3-PDA/NBR composite filled with 30 phr Al2O3-PDA was 0.21 W/m K, which was 122% times of pure NBR. In addition, the Al2O3-PDA/NBR composite filled with 30 phr Al2O3-PDA displayed a high tensile strength about 2.61 MPa, which was about 255% of pure NBR. This procedure is eco-friendly and easy handling, which provides a promising route to polymer composites in application of thermal conductivity field.

Visualizing phase transition behavior of dilute stimuli responsive polymer solutions via Mueller matrix polarimetry.

PubMed

Narayanan, Amal; Chandel, Shubham; Ghosh, Nirmalya; De, Priyadarsi

2015-09-15

Probing volume phase transition behavior of superdiluted polymer solutions both micro- and macroscopically still persists as an outstanding challenge. In this regard, we have explored 4 × 4 spectral Mueller matrix measurement and its inverse analysis for excavating the microarchitectural facts about stimuli responsiveness of "smart" polymers. Phase separation behavior of thermoresponsive poly(N-isopropylacrylamide) (PNIPAM) and pH responsive poly(N,N-(dimethylamino)ethyl methacrylate) (PDMAEMA) and their copolymers were analyzed in terms of Mueller matrix derived polarization parameters, namely, depolarization (Δ), diattenuation (d), and linear retardance (δ). The Δ, d, and δ parameters provided useful information on both macro- and microstructural alterations during the phase separation. Additionally, the two step action ((i) breakage of polymer-water hydrogen bonding and (ii) polymer-polymer aggregation) at the molecular microenvironment during the cloud point generation was successfully probed via these parameters. It is demonstrated that, in comparison to the present techniques available for assessing the hydrophobic-hydrophilic switch over of simple stimuli-responsive polymers, Mueller matrix polarimetry offers an important advantage requiring a few hundred times dilute polymer solution (0.01 mg/mL, 1.1-1.4 μM) at a low-volume format.

Enhancing Thermal Conductive Performance of Vertically Aligned Carbon Nanotube Array Composite by Pre-Annealing Treatment.

PubMed

Wang, Miao; Chen, Hong-Yuan; Xing, Ya-Juan; Wei, Han-Xing; Li, Qiang; Chen, Ming-Hai; Li, Qing-Wen; Xuan, Yi-Min

2015-04-01

Vertically aligned carbon nanotube (VACNT) array/polymer composite has already been recognized as a promising candidate for advanced thermal pad in thermal management of high-power electronic devices. However, the thermal conductive performance of this composite was limited by the quality of CNTs arrays. In this study, pre-annealing treatment was used to purify CNT arrays and improve thermal conductive performance of VACNT arrays/silicone composite. The thermal conductivity of the composite was enhanced by 34.52% and the thermal interface resistance was also reduced by 65.94% at a pre-annealing temperature of 490 °C for 5 min. The annealing process could remove some amorphous carbon and open the tips of CNTs. As a result, the interfacial compatibility in composite between carbon nanotube and polymer matrix was improved. The cyclic compression and tension performance of VACNT/S160 composite was investigated for further application.

Synthesis and characterization of Au-MWCNT/PEDOT: PSS composite film for optoelectronic applications

NASA Astrophysics Data System (ADS)

Jasna, M.; Anjana, R.; Jayaraj, M. K.

2017-08-01

Recently, flexible organic optoelectronics have got great attention because of their light weight, mechanical flexibility and cost effective fabrication process. Conjugated polymers like PEDOT: PSS are widely used for the transparent electrode applications due to its chemical stability, high conductivity, flexibility and optical transparency in the visible region. Conductivity of the PEDOT: PSS polymer can be enhanced by adding organic solvents or conducting nano fillers like CNT, graphene, etc. Carbon nanotubes are good nano fillers to enhance the conductivity and mechanical strength of PEDOT: PSS composite film. Inthe present work, the effect of gold nano particles in PEDOT: PSS/CNT composite is studied. The conductivity enhancement in PEDOT: PSS/CNT thin films can be attributed to the formation of CNT network in the polymer matrix and conformational change of the PEDOT from benzoid to quinoid structure. Even though the conductivity was enhanced, the transparency of the composite thin films decreased with increase in CNT concentration. To overcome this problem, gold nano particles were attached to CNT walls via chemical route. AuMWCNT/PEDOT: PSS composite films were prepared by spin coating method. TEM images confirmed the decoration of gold nano particles on CNT walls. Electrical and optical properties of the composite films were studied. This simple solution processed conducting films are suitable for optoelectronic applications

High-Efficiency Heterojunction Photovoltaic Devices by Block Copolymer Nanotemplates

DTIC Science & Technology

2005-08-01

membranes and the anodized aluminum oxide ( AAO ...substrate. Such structures could not be achieved by the electropolymerization of a conducting polymer inside an anodized alminium oxide ( AAO ) membrane ... oxide ( AAO ) membrane , where the nanowires were found to fall onto the substrate after the AAO was removed. After removal of the PS matrix, the HOMO

Multifunctional and biologically active matrices from multicomponent polymeric solutions

NASA Technical Reports Server (NTRS)

Kiick, Kristi L. (Inventor); Yamaguchi, Nori (Inventor)

2010-01-01

The present invention relates to a biologically active functionalized electrospun matrix to permit immobilization and long-term delivery of biologically active agents. In particular the invention relates to a functionalized polymer matrix comprising a matrix polymer, a compatibilizing polymer and a biomolecule or other small functioning molecule. In certain aspects the electrospun polymer fibers comprise at least one biologically active molecule functionalized with low molecular weight heparin. Examples of active molecules that may be used with the multicomponent polymer of the invention include, for example, a drug, a biopolymer, for example a growth factor, a protein, a peptide, a nucleotide, a polysaccharide, a biological macromolecule or the like. The invention is further directed to the formation of functionalized crosslinked matrices, such as hydrogels, that include at least one functionalized compatibilizing polymer capable of assembly.

Inorganic nanotubes reinforced polyvinylidene fluoride composites as low-cost electromagnetic interference shielding materials

PubMed Central

2011-01-01

Novel polymer nanocomposites comprising of MnO2 nanotubes (MNTs), functionalized multiwalled carbon nanotubes (f-MWCNTs), and polyvinylidene fluoride (PVDF) were synthesized. Homogeneous distribution of f-MWCNTs and MNTs in PVDF matrix were confirmed by field emission scanning electron microscopy. Electrical conductivity measurements were performed on these polymer composites using four probe technique. The addition of 2 wt.% of MNTs (2 wt.%, f-MWCNTs) to PVDF matrix results in an increase in the electrical conductivity from 10-16S/m to 4.5 × 10-5S/m (3.2 × 10-1S/m). Electromagnetic interference shielding effectiveness (EMI SE) was measured with vector network analyzer using waveguide sample holder in X-band frequency range. EMI SE of approximately 20 dB has been obtained with the addition of 5 wt.% MNTs-1 wt.% f-MWCNTs to PVDF in comparison with EMI SE of approximately 18 dB for 7 wt.% of f-MWCNTs indicating the potential use of the present MNT/f-MWCNT/PVDF composite as low-cost EMI shielding materials in X-band region. PMID:21711633

Photogeneration of heptacene in a polymer matrix.

PubMed

Mondal, Rajib; Shah, Bipin K; Neckers, Douglas C

2006-08-02

Heptacene (1) was generated by the photodecarbonylation of 7,16-dihydro-7,16-ethanoheptacene-19,20-dione (2) in a polymer matrix using a UV-LED lamp (395 +/- 25 nm). Compound 1 showed a long wavelength absorption band extending from 600 to 825 nm (lambdamax approximately 760 nm) and was found to be stable up to 4 h in the polymer matrix. However, irradiation of a solution of 2 in toluene produced only oxygen adducts.

Nanocellular foam with solid flame retardant

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chen, Liang; Kelly-Rowley, Anne M.; Bunker, Shana P.

Prepare nanofoam by (a) providing an aqueous solution of a flame retardant dissolved in an aqueous solvent, wherein the flame retardant is a solid at 23.degree. C. and 101 kiloPascals pressure when in neat form; (b) providing a fluid polymer composition selected from a solution of polymer dissolved in a water-miscible solvent or a latex of polymer particles in a continuous aqueous phase; (c) mixing the aqueous solution of flame retardant with the fluid polymer composition to form a mixture; (d) removing water and, if present, solvent from the mixture to produce a polymeric composition having less than 74 weight-percentmore » flame retardant based on total polymeric composition weight; (e) compound the polymeric composition with a matrix polymer to form a matrix polymer composition; and (f) foam the matrix polymer composition into nanofoam having a porosity of at least 60 percent.« less

Metal- and Polymer-Matrix Composites: Functional Lightweight Materials for High-Performance Structures

NASA Astrophysics Data System (ADS)

Gupta, Nikhil; Paramsothy, Muralidharan

2014-06-01

The special topic "Metal- and Polymer-Matrix Composites" is intended to capture the state of the art in the research and practice of functional composites. The current set of articles related to metal-matrix composites includes reviews on functionalities such as self-healing, self-lubricating, and self-cleaning capabilities; research results on a variety of aluminum-matrix composites; and investigations on advanced composites manufacturing methods. In addition, the processing and properties of carbon nanotube-reinforced polymer-matrix composites and adhesive bonding of laminated composites are discussed. The literature on functional metal-matrix composites is relatively scarce compared to functional polymer-matrix composites. The demand for lightweight composites in the transportation sector is fueling the rapid development in this field, which is captured in the current set of articles. The possibility of simultaneously tailoring several desired properties is attractive but very challenging, and it requires significant advancements in the science and technology of composite materials. The progress captured in the current set of articles shows promise for developing materials that seem capable of moving this field from laboratory-scale prototypes to actual industrial applications.

RIR-MAPLE deposition of conjugated polymers and hybrid nanocomposites for application to optoelectronic devices

DOE Office of Scientific and Technical Information (OSTI.GOV)

Stiff-Roberts, Adrienne D.; Pate, Ryan; McCormick, Ryan

2012-07-30

Resonant infrared matrix-assisted pulsed laser evaporation (RIR-MAPLE) is a variation of pulsed laser deposition that is useful for organic-based thin films because it reduces material degradation by selective absorption of infrared radiation in the host matrix. A unique emulsion-based RIR-MAPLE approach has been developed that reduces substrate exposure to solvents and provides controlled and repeatable organic thin film deposition. In order to establish emulsion-based RIR-MAPLE as a preferred deposition technique for conjugated polymer or hybrid nanocomposite optoelectronic devices, studies have been conducted to demonstrate the value added by the approach in comparison to traditional solution-based deposition techniques, and this workmore » will be reviewed. The control of hybrid nanocomposite thin film deposition, and the photoconductivity in such materials deposited using emulsion-based RIR-MAPLE, will also be reviewed. The overall result of these studies is the demonstration of emulsion-based RIR-MAPLE as a viable option for the fabrication of conjugated polymer and hybrid nanocomposite optoelectronic devices that could yield improved device performance.« less

Properties of hot-melt extruded theophylline tablets containing poly(vinyl acetate).

PubMed

Zhang, F; McGinity, J W

2000-09-01

The objectives of this study were to investigate the properties of poly(vinyl acetate) (PVAc) as a retardant polymer and to study the drug release mechanism of theophylline from matrix tablets prepared by hot-melt extrusion. A physical mixture of drug, polymer, and drug release modifiers was fed into the equipment and heated inside the barrel of the extruder. The cylindrical extrudates were either cut into tablets or ground into granules and compressed with other excipients into tablets. Due to the low glass transition temperature of the PVAc, the melt extrusion process was conducted at approximately 70 degrees C. Theophylline was used as the model drug in this study. Theophylline was present in the extrudate in its crystalline form and was released from the tablets by diffusion. The Higuchi diffusion model and percolation theories were applied to the dissolution data to explain the drug release properties of the matrix systems. The release rate was shown to be dependent on the granule size, drug particle size, and drug loading in the tablets. Water-soluble polymers were demonstrated to be efficient release rate modifiers for this system.

Nanostructural self-organization and dynamic adaptation of metal-polymer tribosystems

NASA Astrophysics Data System (ADS)

Mashkov, Yu. K.

2017-02-01

The results of investigating the effect of nanosize modifiers of a polymer matrix on the nanostructural self-organization of polymer composites and dynamic adaptation of metal-polymer tribosystems, which considerably affect the wear resistance of polymer composite materials, have been analyzed. It has been shown that the physicochemical nanostructural self-organization processes are developed in metal-polymer tribosystems with the formation of thermotropic liquid-crystal structures of the polymer matrix, followed by the transition of the system to the stationary state with a negative feedback that ensures dynamic adaptation of the tribosystem to given operating conditions.

78 FR 49780 - Notice of Intent To Grant Exclusive License

Federal Register 2010, 2011, 2012, 2013, 2014

2013-08-15

... ``Aerogel/Polymer Composite Materials;'' U.S. Patent No. 7,309,738; NASA Case No. KSC-12697 entitled ``Approach for Achieving Flame Retardancy While Retaining Physical Properties in a Compatible Polymer Matrix... Retaining Physical Properties in a Compatible Polymer Matrix;'' to AeroPlastic LP, having its principal...

Synergetic Improvement in Thermal Conductivity and Flame Retardancy of Epoxy/Silver Nanowires Composites by Incorporating "Branch-Like" Flame-Retardant Functionalized Graphene.

PubMed

Feng, Yuezhan; Li, Xiongwei; Zhao, Xiaoyu; Ye, Yunsheng; Zhou, Xingping; Liu, Hu; Liu, Chuntai; Xie, Xiaolin

2018-06-27

The significant fire hazards on the polymer-based thermal interface materials (TIM) used in electronic devices are but often neglected. Also, high filler loading with the incident deterioration of mechanical, thermal, and processing properties limits the further application of the traditional polymer-based TIMs. In this work, a ternary TIMs with epoxy resin (EP) matrix, silver nanowires (AgNWs), and a small amount of flame-retardant functionalized graphene (GP-DOPO) were proposed to address the above questions. Briefly, a facile "branch-like" strategy with a polymer as the backbone and flame-retardant molecule as the branch was first used to functionalize reduced graphene oxide (RGO) toward increasing the flame-retardant grafting ratio and RGO's compatibility in matrix, and the resulted GP-DOPO was then in situ introduced into the EP/AgNW composites. As expected, the incorporation of GP-DOPO (2 wt %) can increase the thermal conductivity to 1.413 W/(m K) at a very low AgNW loading (4 vol %), which is 545 and 56% increments compared to pure EP and EP/AgNW, respectively. The prominent improvement in thermal conductivity was put down to the synergetic effect of AgNW and GP-DOPO, i.e., the improving dispersion and bridging effect for AgNWs by adding GP-DOPO. Moreover, the high flame-retardant grafting amount and the excellent compatibility of GP-DOPO resulted in a strong catalytic charring effect on EP matrix, which further formed a robust protective char layer by combining the AgNW and graphene network. Therefore, the flame retardancy of EP/AgNW was significantly improved by introducing GP-DOPO, i.e., the peak heat release rate, total heat release and total smoke production reduced by 27.0, 32.4, and 30.9% reduction compared to EP/AgNW, respectively.

Local Structure and Ion Transport in Glassy Poly(ethylene oxide styrene) Copolymers

NASA Astrophysics Data System (ADS)

Yang, Han-Chang; Mays, Jimmy; Sokolov, Alexei P.; Winey, Karen I.

2014-03-01

Polymer electrolytes have attracted attention for a wide variety of applications in energy production such as lithium-ion batteries and fuel cells. The concept of free volume provides important information about ion mobility and chain dynamics in the polymer matrix. Researchers have recently demonstrated that ion transport in glassy polymer can be improved by designing a system with high free volume. We have studied the effect of temperature and humidity on the intermolecular correlations of poly(ethylene oxide styrene-block-styrene) (PEOSt- b-St) block copolymer and poly(ethylene oxide styrene) (PEOSt) homopolymer using in situ multi-angle x-ray scattering across a wide range of scattering angles (q = 0.007-1.5 Å-1) . An increase in backbone-to-backbone distance is observed, indicating an increase in free volume between different polymer main chains. Structural characterization of the polymer segments will be discussed together with conductivity and dielectric results to better understand the ion transport mechanism in the local environment of the polymer system. Department of Chemistry, University of Tennessee.

Multifunctional Polymer Nanocomposites

NASA Astrophysics Data System (ADS)

Galaska, Alexandra Maria; Song, Haixiang; Guo, Zhanhu

With more awareness of energy conversion/storage and saving, different strategies have been developed to utilize the sustainable and renewable energy. Introducing nanoscale fillers can make inert polymer matrix possess unique properties to satisfy certain functions. For example, alumina nanoparticles have strengthened the weak thermosetting polymers. A combined mixture of carbon nanofibers and magnetite nanoparticles have made the inert epoxy sensitive for magnetic field for sensing applications. Introducing silica nanoparticles into conductive polymers such as polyaniline has enhanced the giant magnetoresistance behaviors. The introduced nanoparticles have made the transparent polymer have the electromagnetic interference (EMI) shielding function while reduce the density significantly. With the desired miniaturization, the materials combining different functionalities have become importantly interesting. In this talk, methodologies to prepare nanocomposites and their effects on the produced nanocomposites will be discussed. A variety of advanced polymer nanocomposites will be introduced. Unique properties including mechanical, electrical, magnetoresistance etc. and the applications for environmental remediation, energy storage/saving, fire retardancy, electromagnetic interference shielding, and electronic devices will be presented.

Characterization of Hybrid CNT Polymer Matrix Composites

NASA Technical Reports Server (NTRS)

Grimsley, Brian W.; Cano, Roberto J.; Kinney, Megan C.; Pressley, James; Sauti, Godfrey; Czabaj, Michael W.; Kim, Jae-Woo; Siochi, Emilie J.

2015-01-01

Carbon nanotubes (CNTs) have been studied extensively since their discovery and demonstrated at the nanoscale superior mechanical, electrical and thermal properties in comparison to micro and macro scale properties of conventional engineering materials. This combination of properties suggests their potential to enhance multi-functionality of composites in regions of primary structures on aerospace vehicles where lightweight materials with improved thermal and electrical conductivity are desirable. In this study, hybrid multifunctional polymer matrix composites were fabricated by interleaving layers of CNT sheets into Hexcel® IM7/8552 prepreg, a well-characterized toughened epoxy carbon fiber reinforced polymer (CFRP) composite. The resin content of these interleaved CNT sheets, as well as ply stacking location were varied to determine the effects on the electrical, thermal, and mechanical performance of the composites. The direct-current electrical conductivity of the hybrid CNT composites was characterized by in-line and Montgomery four-probe methods. For [0](sub 20) laminates containing a single layer of CNT sheet between each ply of IM7/8552, in-plane electrical conductivity of the hybrid laminate increased significantly, while in-plane thermal conductivity increased only slightly in comparison to the control IM7/8552 laminates. Photo-microscopy and short beam shear (SBS) strength tests were used to characterize the consolidation quality of the fabricated laminates. Hybrid panels fabricated without any pretreatment of the CNT sheets resulted in a SBS strength reduction of 70 percent. Aligning the tubes and pre-infusing the CNT sheets with resin significantly improved the SBS strength of the hybrid composite To determine the cause of this performance reduction, Mode I and Mode II fracture toughness of the CNT sheet to CFRP interface was characterized by double cantilever beam (DCB) and end notch flexure (ENF) testing, respectively. Results are compared to the control IM7/8552 laminate.

Imaging Carbon Nanotubes in High Performance Polymer Composites via Magnetic Force Microscope

NASA Technical Reports Server (NTRS)

Lillehei, Peter T.; Park, Cheol; Rouse, Jason H.; Siochi, Emilie J.; Bushnell, Dennis M. (Technical Monitor)

2002-01-01

Application of carbon nanotubes as reinforcement in structural composites is dependent on the efficient dispersion of the nanotubes in a high performance polymer matrix. The characterization of such dispersion is limited by the lack of available tools to visualize the quality of the matrix/carbon nanotube interaction. The work reported herein demonstrates the use of magnetic force microscopy (MFM) as a promising technique for characterizing the dispersion of nanotubes in a high performance polymer matrix.

Analytical Modeling of the High Strain Rate Deformation of Polymer Matrix Composites

NASA Technical Reports Server (NTRS)

Goldberg, Robert K.; Roberts, Gary D.; Gilat, Amos

2003-01-01

The results presented here are part of an ongoing research program to develop strain rate dependent deformation and failure models for the analysis of polymer matrix composites subject to high strain rate impact loads. State variable constitutive equations originally developed for metals have been modified in order to model the nonlinear, strain rate dependent deformation of polymeric matrix materials. To account for the effects of hydrostatic stresses, which are significant in polymers, the classical 5 plasticity theory definitions of effective stress and effective plastic strain are modified by applying variations of the Drucker-Prager yield criterion. To verify the revised formulation, the shear and tensile deformation of a representative toughened epoxy is analyzed across a wide range of strain rates (from quasi-static to high strain rates) and the results are compared to experimentally obtained values. For the analyzed polymers, both the tensile and shear stress-strain curves computed using the analytical model correlate well with values obtained through experimental tests. The polymer constitutive equations are implemented within a strength of materials based micromechanics method to predict the nonlinear, strain rate dependent deformation of polymer matrix composites. In the micromechanics, the unit cell is divided up into a number of independently analyzed slices, and laminate theory is then applied to obtain the effective deformation of the unit cell. The composite mechanics are verified by analyzing the deformation of a representative polymer matrix composite (composed using the representative polymer analyzed for the correlation of the polymer constitutive equations) for several fiber orientation angles across a variety of strain rates. The computed values compare favorably to experimentally obtained results.

Synthesis and characterizations of novel polymer electrolytes

NASA Astrophysics Data System (ADS)

Chanthad, Chalathorn

Polymer electrolytes are an important component of many electrochemical devices. The ability to control the structures, properties, and functions of polymer electrolytes remains a key subject for the development of next generation functional polymers. Taking advantage of synthetic strategies is a promising approach to achieve the desired chemical structures, morphologies, thermal, mechanical, and electrochemical properties. Therefore, the major goal of this thesis is to develop synthetic methods for of novel proton exchange membranes and ion conductive membranes. In Chapter 2, new classes of fluorinated polymer- polysilsesquioxane nanocomposites have been designed and synthesized. The synthetic method employed includes radical polymerization using the functional benzoyl peroxide initiator for the telechelic fluorinated polymers with perfluorosulfonic acids in the side chains and a subsequent in-situ sol-gel condensation of the prepared triethoxylsilane-terminated fluorinated polymers with alkoxide precursors. The properties of the composite membranes have been studied as a function of the content and structure of the fillers. The proton conductivity of the prepared membranes increases steadily with the addition of small amounts of the polysilsesquioxane fillers. In particular, the sulfopropylated polysilsesquioxane based nanocomposites display proton conductivities greater than Nafion. This is attributed to the presence of pendant sulfonic acids in the fillers, which increases ion-exchange capacity and offers continuous proton transport channels between the fillers and the polymer matrix. The methanol permeability of the prepared membranes has also been examined. Lower methanol permeability and higher electrochemical selectivity than those of Nafion have been demonstrated in the polysilsesquioxane based nanocomposites. In Chapter 3, the synthesis of a new class of ionic liquid-containing triblock copolymers with fluoropolymer mid-block and imidazolium methacrylate end-blocks is described for the first time. The synthetic strategy involves the preparation of the telechelic fluoropolymers using a functional benzoyl peroxide initiator as the macro-chain transfer agent for subsequent RAFT polymerization of the imidazolium methacrylate monomer. As revealed in DSC, SAXS and dielectric relaxation spectroscopy (DRS) measurements, there was no microphase separation in the triblock copolymers, likely due to solubility of ionic liquid moieties in the fluoropolymer matrix. The anionic counterion has direct impact on the thermal properties, ionic conductivity and segmental dynamics of the polymers. The temperature dependence of the ionic conductivity is well described by the Vogel-Tamman-Fulcher model, suggesting that ion motion is closely coupled to segmental motion. In Chapter 4 and 5, new solid electrolytes for lithium cations have been synthesized by catalyzed hydrosilylation reaction involving hydrogen atoms of polysiloxane and polyhedral oligomeric silsesquioxane (POSS) and double bonds of vinyl tris17-bromo-3,6,9,12,15- pentaoxaheptadecan-1-ol silane. The obtained structures are based on branched or dendritic with ionic liquid-ethylene oxide oligomer. High room temperature ionic conductivities have been obtained in the range of 10-4-10-5 can be regarded as solid electrolytes. This is attributed to the high concentration of ions from ionic liquid moieties in the tripodand molecule, high segmental mobility, and high ion dissociation from ethylene oxide spacers. The influence of anion structures and lithium salts and concentration has been investigated.

Composite-Based High Performance Electroactive Polymers For Remotely Controlled Mechanical Manipulations in NASA Applications

NASA Technical Reports Server (NTRS)

Zhang, Q. M.

2003-01-01

This program supported investigation of an all-polymer percolative composite which exhibits very high dielectric constant (less than 7,000). The experimental results show that the dielectric behavior of this new class of percolative composites follows the prediction of the percolation theory and the analysis of the conductive percolation phenomena. The very high dielectric constant of the all-polymer composites which are also very flexible and possess elastic modulus not very much different from that of the insulation polymer matrix makes it possible to induce a high electromechanical response under a much reduced electric field (a strain of 2.65% with an elastic energy density of 0.18 J/cu cm can be achieved under a field of 16 MV/m). Data analysis also suggests that in these composites, the non-uniform local field distribution as well as interface effects can significantly enhance the strain responses. Furthermore, the experimental data as well as the data analysis indicate that the conduction loss in these composites will not affect the strain hysteresis.

Electrospun conductive nanofibrous scaffolds for engineering cardiac tissue and 3D bioactuators.

PubMed

Wang, Ling; Wu, Yaobin; Hu, Tianli; Guo, Baolin; Ma, Peter X

2017-09-01

Mimicking the nanofibrous structure similar to extracellular matrix and conductivity for electrical propagation of native myocardium would be highly beneficial for cardiac tissue engineering and cardiomyocytes-based bioactuators. Herein, we developed conductive nanofibrous sheets with electrical conductivity and nanofibrous structure composed of poly(l-lactic acid) (PLA) blending with polyaniline (PANI) for cardiac tissue engineering and cardiomyocytes-based 3D bioactuators. Incorporating of varying contents of PANI from 0wt% to 3wt% into the PLA polymer, the electrospun nanofibrous sheets showed enhanced conductivity while maintaining the same fiber diameter. These PLA/PANI conductive nanofibrous sheets exhibited good cell viability and promoting effect on differentiation of H9c2 cardiomyoblasts in terms of maturation index and fusion index. Moreover, PLA/PANI nanofibrous sheets enhanced the cell-cell interaction, maturation and spontaneous beating of primary cardiomyocytes. Furthermore, the cardiomyocytes-laden PLA/PANI conductive nanofibrous sheets can form 3D bioactuators with tubular and folding shapes, and spontaneously beat with much higher frequency and displacement than that on cardiomyocytes-laden PLA nanofibrous sheets. Therefore, these PLA/PANI conductive nanofibrous sheets with conductivity and extracellular matrix like nanostructure demonstrated promising potential in cardiac tissue engineering and cardiomyocytes-based 3D bioactuators. Cardiomyocytes-based bioactuators have been paid more attention due to their spontaneous motion by integrating cardiomyocytes into polymer structures, but developing suitable scaffolds for bioactuators remains challenging. Electrospun nanofibrous scaffolds have been widely used in cardiac tissue engineering because they can mimic the extracellular matrix of myocardium. Developing conductive nanofibrous scaffolds by electrospinning would be beneficial for cardiomyocytes-based bioactuators, but such scaffolds have been rarely reported. This work presented a conductive nanofibrous sheet based on polylactide and polyaniline via electrospinning with tunable conductivity. These conductive nanofibrous sheets performed the ability to enhance cardiomyocytes maturation and spontaneous beating, and further formed cardiomyocytes-based 3D bioactuators with tubular and folding shapes, which indicated their great potential in cardiac tissue engineering and bioactuators applications. Copyright © 2017 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Decoupling Mechanical and Ion Transport Properties in Polymer Electrolyte Membranes

NASA Astrophysics Data System (ADS)

McIntosh, Lucas D.

Polymer electrolytes are mixtures of a polar polymer and salt, in which the polymer replaces small molecule solvents and provides a dielectric medium so that ions can dissociate and migrate under the influence of an external electric field. Beginning in the 1970s, research in polymer electrolytes has been primarily motivated by their promise to advance electrochemical energy storage and conversion devices, such as lithium ion batteries, flexible organic solar cells, and anhydrous fuel cells. In particular, polymer electrolyte membranes (PEMs) can improve both safety and energy density by eliminating small molecule, volatile solvents and enabling an all-solid-state design of electrochemical cells. The outstanding challenge in the field of polymer electrolytes is to maximize ionic conductivity while simultaneously addressing orthogonal mechanical properties, such as modulus, fracture toughness, or high temperature creep resistance. The crux of the challenge is that flexible, polar polymers best-suited for polymer electrolytes (e.g., poly(ethylene oxide)) offer little in the way of mechanical robustness. Similarly, polymers typically associated with superior mechanical performance (e.g., poly(methyl methacrylate)) slow ion transport due to their glassy polymer matrix. The design strategy is therefore to employ structured electrolytes that exhibit distinct conducting and mechanically robust phases on length scales of tens of nanometers. This thesis reports a remarkably simple, yet versatile synthetic strategy---termed polymerization-induced phase separation, or PIPS---to prepare PEMs exhibiting an unprecedented combination of both high conductivity and high modulus. This performance is enabled by co-continuous, isotropic networks of poly(ethylene oxide)/ionic liquid and highly crosslinked polystyrene. A suite of in situ, time-resolved experiments were performed to investigate the mechanism by which this network morphology forms, and it appears to be tied to the disordered structure observed in diblock polymer melts near the order-disorder transition. In the resulting solid PEMs, the conductivity and modulus are both high, exceeding the 1 mS/cm and approaching the 1 GPa metrics, respectively, often cited for lithium-metal batteries. In the final chapter, an alternative synthetic route to generate nanostructured PEMs is presented. This strategy relies on the formation of a thermodynamically stable network morphology exhibited by a triblock terpolymer prepared with crosslinking moieties along the backbone. Although the mechanical properties of the resulting PEM are excellent, the conductivity is found to be somewhat limited by network defects that result from the solvent-casting procedure.

Recycling and processing of several typical crosslinked polymer scraps with enhanced mechanical properties based on solid-state mechanochemical milling

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lu, Canhui; Zhang, Xinxing; Zhang, Wei

The partially devulcanization or de-crosslinking of ground tire rubber (GTR), post-vulcanized fluororubber scraps and crosslinked polyethylene from cable scraps through high-shear mechanochemical milling (HSMM) was conducted by a modified solid-state mechanochemical reactor. The results indicated that the HSMM treated crosslinked polymer scraps can be reprocessed as virgin rubbers or thermoplastics to produce materials with high performance. The foamed composites of low density polyethylene/GTR and the blend of post-vulcanized flurorubber (FKM) with polyacrylate rubber (ACM) with better processability and mechanical properties were obtained. The morphology observation showed that the dispersion and compatibility between de-crosslinked polymer scraps and matrix were enhanced. Themore » results demonstrated that HSMM is a feasible alternative technology for recycling post-vulcanized or crosslinked polymer scraps.« less

Matrices for Sensors from Inorganic, Organic, and Biological Nanocomposites

PubMed Central

Nicolini, Claudio; Sivozhelezov, Victor; Bavastrello, Valter; Bezzerra, Tercio; Scudieri, Dora; Spera, Rosanna; Pechkova, Eugenia

2011-01-01

Matrices and sensors resulting from inorganic, organic and biological nanocomposites are presented in this overview. The term nanocomposite designates a solid combination of a matrix and of nanodimensional phases differing in properties from the matrix due to dissimilarities in structure and chemistry. The nanoocomposites chosen for a wide variety of health and environment sensors consist of Anodic Porous Allumina and P450scc, Carbon nanotubes and Conductive Polymers, Langmuir Blodgett Films of Lipases, Laccases, Cytochromes and Rhodopsins, Three-dimensional Nanoporous Materials and Nucleic Acid Programmable Protein Arrays. PMID:28824154

Thermoelectric plastics: from design to synthesis, processing and structure–property relationships

PubMed Central

Kroon, Renee; Mengistie, Desalegn Alemu; Kiefer, David; Hynynen, Jonna; Ryan, Jason D.; Yu, Liyang

2016-01-01

Thermoelectric plastics are a class of polymer-based materials that combine the ability to directly convert heat to electricity, and vice versa, with ease of processing. Potential applications include waste heat recovery, spot cooling and miniature power sources for autonomous electronics. Recent progress has led to surging interest in organic thermoelectrics. This tutorial review discusses the current trends in the field with regard to the four main building blocks of thermoelectric plastics: (1) organic semiconductors and in particular conjugated polymers, (2) dopants and counterions, (3) insulating polymers, and (4) conductive fillers. The design and synthesis of conjugated polymers that promise to show good thermoelectric properties are explored, followed by an overview of relevant structure–property relationships. Doping of conjugated polymers is discussed and its interplay with processing as well as structure formation is elucidated. The use of insulating polymers as binders or matrices is proposed, which permit the adjustment of the rheological and mechanical properties of a thermoelectric plastic. Then, nanocomposites of conductive fillers such as carbon nanotubes, graphene and inorganic nanowires in a polymer matrix are introduced. A case study examines poly(3,4-ethylenedioxythiophene) (PEDOT) based materials, which up to now have shown the most promising thermoelectric performance. Finally, a discussion of the advantages provided by bulk architectures e.g. for wearable applications highlights the unique advantages that thermoelectric plastics promise to offer. PMID:27385496

LS-DYNA Implementation of Polymer Matrix Composite Model Under High Strain Rate Impact

NASA Technical Reports Server (NTRS)

Zheng, Xia-Hua; Goldberg, Robert K.; Binienda, Wieslaw K.; Roberts, Gary D.

2003-01-01

A recently developed constitutive model is implemented into LS-DYNA as a user defined material model (UMAT) to characterize the nonlinear strain rate dependent behavior of polymers. By utilizing this model within a micromechanics technique based on a laminate analogy, an algorithm to analyze the strain rate dependent, nonlinear deformation of a fiber reinforced polymer matrix composite is then developed as a UMAT to simulate the response of these composites under high strain rate impact. The models are designed for shell elements in order to ensure computational efficiency. Experimental and numerical stress-strain curves are compared for two representative polymers and a representative polymer matrix composite, with the analytical model predicting the experimental response reasonably well.

Ceramic matrix and resin matrix composites: A comparison

NASA Technical Reports Server (NTRS)

Hurwitz, Frances I.

1987-01-01

The underlying theory of continuous fiber reinforcement of ceramic matrix and resin matrix composites, their fabrication, microstructure, physical and mechanical properties are contrasted. The growing use of organometallic polymers as precursors to ceramic matrices is discussed as a means of providing low temperature processing capability without the fiber degradation encountered with more conventional ceramic processing techniques. Examples of ceramic matrix composites derived from particulate-filled, high char yield polymers and silsesquioxane precursors are provided.

Ceramic matrix and resin matrix composites - A comparison

NASA Technical Reports Server (NTRS)

Hurwitz, Frances I.

1987-01-01

The underlying theory of continuous fiber reinforcement of ceramic matrix and resin matrix composites, their fabrication, microstructure, physical and mechanical properties are contrasted. The growing use of organometallic polymers as precursors to ceramic matrices is discussed as a means of providing low temperature processing capability without the fiber degradation encountered with more conventional ceramic processing techniques. Examples of ceramic matrix composites derived from particulate-filled, high char yield polymers and silsesquioxane precursors are provided.

Structural, microstructural and electrochemical properties of dispersed-type polymer nanocomposite films

NASA Astrophysics Data System (ADS)

Arya, Anil; Sharma, A. L.

2018-01-01

Free-standing solid polymer nanocomposite (PEO-PVC)  +  LiPF6-TiO2 films have been prepared through a standard solution-cast technique. The improvement in structural, microstructural and electrochemical properties has been observed on the dispersion of nanofiller in polymer salt complex. X-ray diffraction studies clearly reflect the formation of complex formation, as no corresponding salt peak appeared in the diffractograms. The Fourier transform infrared analysis suggested clear and convincing evidence of polymer-ion, ion-ion and polymer-ion-nanofiller interaction. The highest ionic conductivity of the prepared solid polymer electrolyte (SPE) films is ~5  ×  10-5 S cm-1 for 7 wt.% TiO2. The linear sweep voltammetry provides the electrochemical stability window of the prepared SPE films, about ~3.5 V. The ion transference number has been estimated, t ion  =  0.99 through the DC polarization technique. Dielectric spectroscopic studies were performed to understand the ion transport process in polymer electrolytes. All solid polymer electrolytes possess good thermal stability up to 300 °C. Differential scanning calorimetry analysis confirms the decrease of the melting temperature and signal of glass transition temperature with the addition of nanofiller, which indicates the decrease of crystallinity of the polymer matrix. An absolute correlation between diffusion coefficient (D), ion mobility (µ), number density (n), double-layer capacitance (C dl), glass transition temperature, melting temperature (T m), free ion area (%) and conductivity (σ) has been observed. A convincing model to study the role of nanofiller in a polymer salt complex has been proposed, which supports the experimental findings. The prepared polymer electrolyte system with significant ionic conductivity, high ionic transference number, and good thermal and voltage stability could be suggested as a potential candidate as electrolyte cum separator for the fabrication of a rechargeable lithium-ion battery system.

Thermal Analysis of Filler Reinforced Polymeric Composites

NASA Astrophysics Data System (ADS)

Ghadge, Mahesh Devidas

Improving heat dissipating property of composite materials is becoming increasingly important in domains ranging from the automotive industry, electronic devices to aeronautical industry. Effective heat dissipation is required especially in aircraft and racing tires to guarantee high performance and good service life [1]. The present study is focused on improving the thermal conductivity of Emulsion-styrene butadiene rubber (ESBR) which is a cheap alternative to other rubber composites. The disadvantages of ESBR are low thermal conductivity and high heat generation. Adding fillers with high thermal conductivity to ESBR is proposed as a technique for improving the thermal conductivity of ESBR. The purpose of the research is to predict the thermal conductivity of ESBR when filled with fillers of much higher thermal conductivity and also to find out to what extent the filler properties affect the heat transfer capabilities of the composite matrix. The influence of different filler shapes i.e. spherical, cylindrical and platelets on the overall thermal capability of composite matrix is studied, the finite element modelings are conducted using Abaqus. Three-dimensional and two-dimensional models are created in Abaqus to simulate the microstructure of the composite matrix filled with fillers. Results indicate that the overall thermal conductivity increases with increasing filler loading i.e. for a filler volume fraction of 0.27, the conductivity increased by around 50%. Filler shapes, orientation angle, and aspect ratio of the fillers significantly influences the thermal conductivity. Conductivity increases with increasing aspect ratio (length/diameter) of the cylindrical fillers since longer conductive chains are able to form at the same volume percentage as compared to spherical fillers. The composite matrix reaches maximum thermal conductivity when the cylindrical fillers are oriented in the direction of heat flow. The heat conductivity predicted by FEM for ESBR is compared with that predicted by mean field theories. At low volume fractions the FEM and mean field theory results are matching. However, at high volume fractions, the results obtained by the two methods are not in agreement. This is due to the fact that mean field theory do not consider the particle interactions happening at higher volume fractions. The present analysis can be used to tailor the thermal properties of ESBR for required thermal conductivity for a wide range of applications such as racing tires, electronic gadgets or aeronautical components. In addition, the proposed FEM models can be used to design and optimize the properties of new composite materials providing more insight into the thermal conductivity of composite polymers and aid in understanding heat transfer mechanism of reinforced polymers.

Polymer matrix and graphite fiber interface study

NASA Technical Reports Server (NTRS)

Adams, D. F.; Zimmerman, R. S.; Odom, E. M.

1985-01-01

Hercules AS4 graphite fiber, unsized, or with EPON 828, PVA, or polysulfone sizing, was combined with three different polymer matrices. These included Hercules 3501-6 epoxy, Hercules 4001 bismaleimide, and Hexcel F155 rubber toughened epoxy. Unidirectional composites in all twelve combinations were fabricated and tested in transverse tension and axial compression. Quasi-isotropic laminates were tested in axial tension and compression, flexure, interlaminar shear, and tensile impact. All tests were conducted at both room temperature, dry and elevated temperature, and wet conditions. Single fiber pullout testing was also performed. Extensive scanning electron microphotographs of fracture surfaces are included, along with photographs of single fiber pullout failures. Analytical/experimental correlations are presented, based on the results of a finite element micromechanics analysis. Correlations between matrix type, fiber sizing, hygrothermal environment, and loading mode are presented. Results indicate that the various composite properties were only moderately influenced by the fiber sizings utilized.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li Hong.

A new technique was developed and demonstrated for combining carbon fibers with aromatic thermoplastic matrices to form a high-quality towpreg. The developed technique utilizes an in-situ electrochemical process (Electrochemical polymerization - ECP) to create the entire polymer matrix surrounding the fiber array by direct polymerization of monomer. Poly-paraxylylene (PPX) and derivatives are successfully polymerized in-situ on carbon fiber surfaces through ECP. A PPX/carbon-fiber towpreg with 40 vol % of matrix is achieved in a fairly short reaction time with a high polymer-coating efficiency. Vapor deposition polymerization (VDP) was also studied. PPX and carbon-fiber towpreg were made successfully by this process.more » A comparison between ECP and VDP was conducted. A study on electrochemical oxidation (ECO) of carbon fibers was also performed. The ECO treatment may be suitable for carbon fibers incorporated in composites with high-temperature curing resins and thermoplastic matrices.« less

Composite electrolytes of polyethylene oxides/garnets interfacially wetted by ionic liquid for room-temperature solid-state lithium battery

NASA Astrophysics Data System (ADS)

Huo, Hanyu; Zhao, Ning; Sun, Jiyang; Du, Fuming; Li, Yiqiu; Guo, Xiangxin

2017-12-01

Paramount attention has been paid on solid polymer electrolytes due to their potential in enhancement of energy density as well as improvement of safety. Herein, the composite electrolytes consisting of Li-salt-free polyethylene oxides and 200 nm-sized Li6.4La3Zr1.4Ta0.6O12 particles interfacially wetted by [BMIM]TF2N of 1.8 μL cm-2 have been prepared. Such wetted ionic liquid remains the solid state of membrane electrolytes and decreases the interface impedance between the electrodes and the electrolytes. There is no release of the liquid phase from the PEO matrix when the pressure of 5.0 × 104 Pa being applied for 24 h. The interfacially wetted membrane electrolytes show the conductivity of 2.2 × 10-4 S cm-1 at 20 °C, which is one order of magnitude greater than that of the membranes without the wetted ionic liquids. The conduction mechanism is related to a large number of lithium ions releasing from Li6.4La3Zr1.4Ta0.6O12 particles and the improved conductive paths along the ion-liquid-wetted interfaces between the polymer matrix and ceramic grains. When the membranes being used in the solid-state LiFePO4/Li and LiFe0.15Mn0.85PO4/Li cells at 25 °C, the excellent rate capability and superior cycle stability has been shown. The results provide a new prospect for solid polymer electrolytes used for room-temperature solid-state lithium batteries.

Conductive Polymeric Binder for Lithium-Ion Battery Anode

NASA Astrophysics Data System (ADS)

Gao, Tianxiang

Tin (Sn) has a high-specific capacity (993 mAhg-1) as an anode material for Li-ion batteries. To overcome the poor cycling performance issue caused by its large volume expansion and pulverization during the charging and discharging process, many researchers put efforts into it. Most of the strategies are through nanostructured material design and introducing conductive polymer binders that serve as matrix of the active material in anode. This thesis aims for developing a novel method for preparing the anode to improve the capacity retention rate. This would require the anode to have high electrical conductivity, high ionic conductivity, and good mechanical properties, especially elasticity. Here the incorporation of a conducting polymer and a conductive hydrogel in Sn-based anodes using a one-step electrochemical deposition via a 3-electrode cell method is reported: the Sn particles and conductive component can be electrochemically synthesized and simultaneously deposited into a hybrid thin film onto the working electrode directly forming the anode. A well-defined three dimensional network structure consisting of Sn nanoparticles coated by conducting polymers is achieved. Such a conductive polymer-hydrogel network has multiple advantageous features: meshporous polymeric structure can offer the pathway for lithium ion transfer between the anode and electrolyte; the continuous electrically conductive polypyrrole network, with the electrostatic interaction with elastic, porous hydrogel, poly (2-acrylamido-2-methyl-1-propanesulfonic acid-co-acrylonitrile) (PAMPS) as both the crosslinker and doping anion for polypyrrole (PPy) can decrease the volume expansion by creating porous scaffold and softening the system itself. Furthermore, by increasing the amount of PAMPS and creating an interval can improve the cycling performance, resulting in improved capacity retention about 80% after 20 cycles, compared with only 54% of that of the control sample without PAMPS. The cycle is performed under current of 0.1 C.

Structure and performance of polymer-derived bulk ceramics determined by method of filler incorporation

NASA Astrophysics Data System (ADS)

Konegger, T.; Schneider, P.; Bauer, V.; Amsüss, A.; Liersch, A.

2013-12-01

The effect of four distinct methods of incorporating fillers into a preceramic polymer matrix was investigated with respect to the structural and mechanical properties of the resulting materials. Investigations were conducted with a polysiloxane/Al2O3/ZrO2 model system used as a precursor for mullite/ZrO2 composites. A quantitative evaluation of the uniformity of filler distribution was obtained by employing a novel image analysis. While solvent-free mixing led to a heterogeneous distribution of constituents resulting in limited mechanical property values, a strong improvement of material homogeneity and properties was obtained by using solvent-assisted methods. The results demonstrate the importance of the processing route on final characteristics of polymer-derived ceramics.

Graphene oxide based nanohybrid proton exchange membranes for fuel cell applications: An overview.

PubMed

Pandey, Ravi P; Shukla, Geetanjali; Manohar, Murli; Shahi, Vinod K

2017-02-01

In the context of many applications, such as polymer composites, energy-related materials, sensors, 'paper'-like materials, field-effect transistors (FET), and biomedical applications, chemically modified graphene was broadly studied during the last decade, due to its excellent electrical, mechanical, and thermal properties. The presence of reactive oxygen functional groups in the grapheme oxide (GO) responsible for chemical functionalization makes it a good candidate for diversified applications. The main objectives for developing a GO based nanohybrid proton exchange membrane (PEM) include: improved self-humidification (water retention ability), reduced fuel crossover (electro-osmotic drag), improved stabilities (mechanical, thermal, and chemical), enhanced proton conductivity, and processability for the preparation of membrane-electrode assembly. Research carried on this topic may be divided into protocols for covalent grafting of functional groups on GO matrix, preparation of free-standing PEM or choice of suitable polymer matrix, covalent or hydrogen bonding between GO and polymer matrix etc. Herein, we present a brief literature survey on GO based nano-hybrid PEM for fuel cell applications. Different protocols were adopted to produce functionalized GO based materials and prepare their free-standing film or disperse these materials in various polymer matrices with suitable interactions. This review article critically discussed the suitability of these PEMs for fuel cell applications in terms of the dependency of the intrinsic properties of nanohybrid PEMs. Potential applications of these nanohybrid PEMs, and current challenges are also provided along with future guidelines for developing GO based nanohybrid PEMs as promising materials for fuel cell applications. Copyright © 2016 Elsevier B.V. All rights reserved.

Approaches to polymer-derived CMC matrices

NASA Technical Reports Server (NTRS)

Hurwitz, Frances I.

1992-01-01

The use of polymeric precursors to ceramics permits the fabrication of large, complex-shaped ceramic matrix composites (CMC's) at temperatures which do not degrade the fiber. Processing equipment and techniques readily available in the resin matrix composite industry can be adapted for CMC fabrication using this approach. Criteria which influence the choice of candidate precursor polymers, the use of fillers, and the role of fiber architecture and ply layup are discussed. Three polymer systems, polycarbosilanes, polysilazanes, and polysilsesquioxanes, are compared as candidate ceramic matrix precursors.

Mechanical Properties of Nanostructured Materials Determined Through Molecular Modeling Techniques

NASA Technical Reports Server (NTRS)

Clancy, Thomas C.; Gates, Thomas S.

2005-01-01

The potential for gains in material properties over conventional materials has motivated an effort to develop novel nanostructured materials for aerospace applications. These novel materials typically consist of a polymer matrix reinforced with particles on the nanometer length scale. In this study, molecular modeling is used to construct fully atomistic models of a carbon nanotube embedded in an epoxy polymer matrix. Functionalization of the nanotube which consists of the introduction of direct chemical bonding between the polymer matrix and the nanotube, hence providing a load transfer mechanism, is systematically varied. The relative effectiveness of functionalization in a nanostructured material may depend on a variety of factors related to the details of the chemical bonding and the polymer structure at the nanotube-polymer interface. The objective of this modeling is to determine what influence the details of functionalization of the carbon nanotube with the polymer matrix has on the resulting mechanical properties. By considering a range of degree of functionalization, the structure-property relationships of these materials is examined and mechanical properties of these models are calculated using standard techniques.

Swelling kinetics and electrical charge transport in PEDOT:PSS thin films exposed to water vapor.

PubMed

Sarkar, Biporjoy; Jaiswal, Manu; Satapathy, Dillip K

2018-06-06

We report the swelling kinetics and evolution of the electrical charge transport in poly(3,4-ethylene dioxythiophene) polystyrene sulfonate (PEDOT:PSS) thin films subjected to water vapor. Polymer films swell by the diffusion of water vapor and are found to undergo structural relaxations. Upon exposure to water vapor, primarily the hygroscopic PSS shell, which surrounds the conducting PEDOT-rich cores, takes up water vapor and subsequently swells. We found that the degree of swelling largely depends on the PEDOT to PSS ratio. Swelling driven microscopic rearrangement of the conducting PEDOT-rich cores in the PSS matrix strongly influences the electrical charge transport of the polymer film. Swelling induced increase as well as decrease of electrical resistance are observed in polymer films having different PEDOT to PSS ratio. This anomalous charge transport behavior in PEDOT:PSS films is reconciled by taking into account the contrasting swelling behavior of the PSS and the conducting PEDOT-rich cores leading to spatial segregation of PSS in films with PSS as a minority phase and by a net increase in mean separation between conducting PEDOT-rich cores for films having abundance of PSS.

Swelling kinetics and electrical charge transport in PEDOT:PSS thin films exposed to water vapor

NASA Astrophysics Data System (ADS)

Sarkar, Biporjoy; Jaiswal, Manu; Satapathy, Dillip K.

2018-06-01

We report the swelling kinetics and evolution of the electrical charge transport in poly(3,4-ethylene dioxythiophene) polystyrene sulfonate (PEDOT:PSS) thin films subjected to water vapor. Polymer films swell by the diffusion of water vapor and are found to undergo structural relaxations. Upon exposure to water vapor, primarily the hygroscopic PSS shell, which surrounds the conducting PEDOT-rich cores, takes up water vapor and subsequently swells. We found that the degree of swelling largely depends on the PEDOT to PSS ratio. Swelling driven microscopic rearrangement of the conducting PEDOT-rich cores in the PSS matrix strongly influences the electrical charge transport of the polymer film. Swelling induced increase as well as decrease of electrical resistance are observed in polymer films having different PEDOT to PSS ratio. This anomalous charge transport behavior in PEDOT:PSS films is reconciled by taking into account the contrasting swelling behavior of the PSS and the conducting PEDOT-rich cores leading to spatial segregation of PSS in films with PSS as a minority phase and by a net increase in mean separation between conducting PEDOT-rich cores for films having abundance of PSS.

Multi-Ferroic Polymer Nanoparticle Composites for Next Generation Metamaterials

DTIC Science & Technology

2016-05-23

another application, electromagnetic wave shielding . Electromagnetic wave induces current which results in loss of energy. Thus magnetic nanoparticles...applicable for electromagnetic wave shielding . For better electromagnetic wave shielding capability, i) high dielectric constant, ii) high magnetic ...electromagnetic wave shielding properties7,8. In such point of view, designing a structure, magnetic nanoparticles in two dimensional electric conductive matrix

Effect of Al2O3 in poly(methyl methacrylate) composite polymer electrolytes

NASA Astrophysics Data System (ADS)

Sun, C. C.; You, A. H.; Teo, L. L.; Thong, L. W.

2018-05-01

In this work, the effect of inert fillers on poly(methyl methacrylate) (PMMA) composite polymer electrolytes (CPEs) are investigated. The PMMA-LiCF3SO3-EC-Al2O3 composite polymer electrolytes were prepared using solution casting method at room temperature. Lithium trifluoromethanesulfonate (LiCF3SO3) is used as the electrolyte salt which plays an important role in Li ion transfer. In order to soften the polymer matrix, ethylene carbonate (EC) is introduced into the CPEs to help in the disassociation of lithium salt ion pairs. Nano sized aluminium oxide (Al2O3) is then incorporated to enhance mechanical strength and ionic conductivity of the polymer electrolyte. The optimum of 2 wt.% 50 nm Al2O3 was added into the PMMA polymer electrolyte sample. Through Electrochemical Impedance Spectroscopy (EIS) measurements, the highest ionic conductivity at room temperature is determined as 1.52×10-4 S/cm. FTIR spectra analysis showed CH2 twisting mode at 1383.43 cm-1, C=O stretching mode at 1721.56 cm-1 which proven the interaction between host polymer and lithium salt and CH3 stretching mode at 2981.34 cm-1. XRD analysis had also been performed to study the structural behaviour of the PMMA polymer electrolyte. The intense peak at position 2θ angle of 15.04°, 30.92° and 45.58° occur upon interaction with Al2O3. Lastly, the surface morphology is studied through SEM+EDX analysis.

Review of Recent Developments on Using an Off-Lattice Monte Carlo Approach to Predict the Effective Thermal Conductivity of Composite Systems with Complex Structures

PubMed Central

Gong, Feng; Duong, Hai M.; Papavassiliou, Dimitrios V.

2016-01-01

Here, we present a review of recent developments for an off-lattice Monte Carlo approach used to investigate the thermal transport properties of multiphase composites with complex structure. The thermal energy was quantified by a large number of randomly moving thermal walkers. Different modes of heat conduction were modeled in appropriate ways. The diffusive heat conduction in the polymer matrix was modeled with random Brownian motion of thermal walkers within the polymer, and the ballistic heat transfer within the carbon nanotubes (CNTs) was modeled by assigning infinite speed of thermal walkers in the CNTs. Three case studies were conducted to validate the developed approach, including three-phase single-walled CNTs/tungsten disulfide (WS2)/(poly(ether ether ketone) (PEEK) composites, single-walled CNT/WS2/PEEK composites with the CNTs clustered in bundles, and complex graphene/poly(methyl methacrylate) (PMMA) composites. In all cases, resistance to heat transfer due to nanoscale phenomena was also modeled. By quantitatively studying the influencing factors on the thermal transport properties of the multiphase composites, it was found that the orientation, aggregation and morphology of fillers, as well as the interfacial thermal resistance at filler-matrix interfaces would limit the transfer of heat in the composites. These quantitative findings may be applied in the design and synthesis of multiphase composites with specific thermal transport properties. PMID:28335270

High Thermal Conductivity Polymer Matrix Composites (PMC) for Advanced Space Radiators

NASA Technical Reports Server (NTRS)

Shin, E. Eugene; Bowman, Cheryl; Beach, Duane

2007-01-01

High temperature polymer matrix composites (PMC) reinforced with high thermal conductivity (approx. 1000 W/mK) pitch-based carbon fibers are evaluated for a facesheet/fin structure of large space radiator systems. Significant weight reductions along with improved thermal performance, structural integrity and space durability toward its metallic counterparts were envisioned. Candidate commercial resin systems including Cyanate Esters, BMIs, and polyimide were selected based on thermal capabilities and processability. PMC laminates were designed to match the thermal expansion coefficient of various metal heat pipes or tubes. Large, but thin composite panels were successfully fabricated after optimizing cure conditions. Space durability of PMC with potential degradation mechanisms was assessed by simulated thermal aging tests in high vacuum, 1-3 x 10(exp -6) torr, at three temperatures, 227 C, 277 C, and 316 C for up to one year. Nanocomposites with vapor-grown carbon nano-fibers and exfoliated graphite flakes were attempted to improve thermal conductivity (TC) and microcracking resistance. Good quality nanocomposites were fabricated and evaluated for TC and durability including radiation resistance. TC was measured in both in-plan and thru-the-thickness directions, and the effects of microcracks on TC are also being evaluated. This paper will discuss the systematic experimental approaches, various performance-durability evaluations, and current subcomponent design and fabrication/manufacturing efforts.

New strategy and easy fabrication of solid-state supercapacitor based on polypyrrole and nitrile rubber.

PubMed

Lee, Sangyool; Lee, Youngkwan; Cho, Mi-Suk; Nam, Jae-Do

2008-09-01

Solid state redox supercapacitors were fabricated using a solid polymer electrolyte, nitrile butadiene rubber (NBR)-KCI and chemically deposited polypyrrole (PPy) as the conducting polymer electrodes on both surfaces of a NBR film. The optimal conditions for the preparation of the PPy/NBR electrode were confirmed as functions of the uptake of pyrrole monomer into the NBR matrix as well as the immersion time in an oxidant solution. The morphology of the PPy-NBR-KCI capacitor was observed using scanning electron microscopy. The performance of the capacitors was characterized using a galvanostatic charge-discharge technique.

Novel approach to synthesis and characterization of POT/ZnO nanocomposites

NASA Astrophysics Data System (ADS)

Islam, Shama; Khan, Hana; Khan, Zubair MSH; Kumar, Shabir Ahmad; Rahman, Raja Saifu; Zulfequar, M.

2018-05-01

The novel insitu polymerization method has been used to synthesis poly o-toluidine/Zinc Oxide (POT/ZnO) nanocomposites with varying weight percentages (5, 10, 15, 20) of ZnO in polymer matrix. The structural properties of synthesized polymer has been discussed with XRD and SEM techniques and found that the crystallinity of the material increases with ZnO doping. Electrical conductivity of the compressed pellets of nanocomposites is depends on the concentration of ZnO in POT and found to increase upto five orders. The indirect bandgap of nanocomposites decreases with increasing ZnO.

A study of optical, mechanical and electrical properties of poly(methacrylic acid)/TiO2 nanocomposite

NASA Astrophysics Data System (ADS)

AL-Baradi, Ateyyah M.; Al-Shehri, Samar F.; Badawi, Ali; Merazga, Amar; Atta, A. A.

2018-06-01

This work is concerned with the study of the effect of titanium dioxide (TiO2) nanofillers on the optical, mechanical and electrical properties of poly(methacrylic acid) (PMAA) networks as a function of TiO2 concentration and crosslink density. The structure of the prepared samples was investigated by X-ray diffractometry (XRD) and Transmittance Electron Microscope (TEM). XRD results showed a single phase for the nanocomposites indicating that no large TiO2 aggregates in the polymer matrix. The optical properties of the prepared samples including the absorption, transmittance, energy band gap and refractive index were explored using Spectrophotometer. These measurements showed that there is a red-shift in the absorption caused by the increase of TiO2 concentration. However, the crosslink density in the polymer plays no role in changing the absorption. The energy band gap (Eg) decreases with increasing the concentration of TiO2 in the polymer matrix; whereas Eg increases with increasing the crosslink density. Moreover, the mechanical properties of PMAA/TiO2 nanocomposites by Dynamic Mechanical Analysis (DMA) showed that the viscoelasticity of PMAA decreases with adding TiO2 nanoparticles and the glass transition temperature (Tg) was also found to drop from 130 °C to 114 °C. Finally, the DC conductivity of the obtained systems was found to increase with increasing TiO2 nanoparticles in the matrix.

Microscopic Chain Motion in Polymer Nanocomposites with Dynamically Asymmetric Interphases

PubMed Central

Senses, Erkan; Faraone, Antonio; Akcora, Pinar

2016-01-01

Dynamics of the interphase region between matrix and bound polymers on nanoparticles is important to understand the macroscopic rheological properties of nanocomposites. Here, we present neutron scattering investigations on nanocomposites with dynamically asymmetric interphases formed by a high-glass transition temperature polymer, poly(methyl methacrylate), adsorbed on nanoparticles and a low-glass transition temperature miscible matrix, poly(ethylene oxide). By taking advantage of selective isotope labeling of the chains, we studied the role of interfacial polymer on segmental and collective dynamics of the matrix chains from subnanoseconds to 100 nanoseconds. Our results show that the Rouse relaxation remains unchanged in a weakly attractive composite system while the dynamics significantly slows down in a strongly attractive composite. More importantly, the chains disentangle with a remarkable increase of the reptation tube size when the bound polymer is vitreous. The glassy and rubbery states of the bound polymer as temperature changes underpin the macroscopic stiffening of nanocomposites. PMID:27457056

Mechanistic modelling of drug release from polymer-coated and swelling and dissolving polymer matrix systems.

PubMed

Kaunisto, Erik; Marucci, Mariagrazia; Borgquist, Per; Axelsson, Anders

2011-10-10

The time required for the design of a new delivery device can be sensibly reduced if the release mechanism is understood and an appropriate mathematical model is used to characterize the system. Once all the model parameters are obtained, in silico experiments can be performed, to provide estimates of the release from devices with different geometries and compositions. In this review coated and matrix systems are considered. For coated formulations, models describing the diffusional drug release, the osmotic pumping drug release, and the lag phase of pellets undergoing cracking in the coating due to the build-up of a hydrostatic pressure are reviewed. For matrix systems, models describing pure polymer dissolution, diffusion in the polymer and drug release from swelling and eroding polymer matrix formulations are reviewed. Importantly, the experiments used to characterize the processes occurring during the release and to validate the models are presented and discussed. Copyright © 2011 Elsevier B.V. All rights reserved.

Transparent and conductive polyethylene oxide film by the introduction of individualized single-walled carbon nanotubes.

PubMed

Jung, Yong Chae; Muramatsu, Hiroyuki; Park, Ki Chul; Shimamoto, Daisuke; Kim, Jin Hee; Hayashi, Takuya; Song, Sung Moo; Kim, Yoong Ahm; Endo, Morinobu; Dresselhaus, Mildred S

2009-12-16

It is demonstrated that an optically transparent and electrically conductive polyethylene oxide (PEO) film is fabricated by the introduction of individualized single-walled carbon nanotubes (SWNTs). The incorporated SWNTs in the PEO film sustain their intrinsic electronic and optical properties and, in addition, the intrinsic properties of the polymer matrix are retained. The individualized SWNTs with smaller diameter provide high transmittance as well as good electrical conductivity in PEO films. Copyright © 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

3D Printing: 3D Printing of Conductive Complex Structures with In Situ Generation of Silver Nanoparticles (Adv. Mater. 19/2016).

PubMed

Fantino, Erika; Chiappone, Annalisa; Roppolo, Ignazio; Manfredi, Diego; Bongiovanni, Roberta; Pirri, Candido Fabrizio; Calignano, Flaviana

2016-05-01

On page 3712, E. Fantino, A. Chiappone, and co-workers fabricate conductive 3D hybrid structures by coupling the photo-reduction of metal precursors with 3D printing technology. The generated structures consist of metal nanoparticles embedded in a polymer matrix shaped into complex multilayered architectures. 3D conductive structures are fabricated with a digital light-processing printer incorporating silver salt into photocurable formulations. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Polymer sol-gel composite inverse opal structures.

PubMed

Zhang, Xiaoran; Blanchard, G J

2015-03-25

We report on the formation of composite inverse opal structures where the matrix used to form the inverse opal contains both silica, formed using sol-gel chemistry, and poly(ethylene glycol), PEG. We find that the morphology of the inverse opal structure depends on both the amount of PEG incorporated into the matrix and its molecular weight. The extent of organization in the inverse opal structure, which is characterized by scanning electron microscopy and optical reflectance data, is mediated by the chemical bonding interactions between the silica and PEG constituents in the hybrid matrix. Both polymer chain terminus Si-O-C bonding and hydrogen bonding between the polymer backbone oxygens and silanol functionalities can contribute, with the polymer mediating the extent to which Si-O-Si bonds can form within the silica regions of the matrix due to hydrogen-bonding interactions.

Composite Materials With Uncured Epoxy Matrix Exposed in Stratosphere During NASA Stratospheric Balloon Flight

NASA Technical Reports Server (NTRS)

Kondyurin, Alexey; Kondyurina, Irina; Bilek, Marcela; de Groh, Kim K.

2013-01-01

A cassette of uncured composite materials with epoxy resin matrixes was exposed in the stratosphere (40 km altitude) over three days. Temperature variations of -76 to 32.5C and pressure up to 2.1 torr were recorded during flight. An analysis of the chemical structure of the composites showed, that the polymer matrix exposed in the stratosphere becomes crosslinked, while the ground control materials react by way of polymerization reaction of epoxy groups. The space irradiations are considered to be responsible for crosslinking of the uncured polymers exposed in the stratosphere. The composites were cured on Earth after landing. Analysis of the cured composites showed that the polymer matrix remains active under stratospheric conditions. The results can be used for predicting curing processes of polymer composites in a free space environment during an orbital space flight.

Dispersions of Carbon nanotubes in Polymer Matrices

NASA Technical Reports Server (NTRS)

Wise, Kristopher Eric (Inventor); Park, Cheol (Inventor); Siochi, Emilie J. (Inventor); Harrison, Joycelyn S. (Inventor); Lillehei, Peter T. (Inventor); Lowther, Sharon E. (Inventor)

2010-01-01

Dispersions of carbon nanotubes exhibiting long term stability are based on a polymer matrix having moieties therein which are capable of a donor-acceptor complexation with carbon nanotubes. The carbon nanotubes are introduced into the polymer matrix and separated therein by standard means. Nanocomposites produced from these dispersions are useful in the fabrication of structures, e.g., lightweight aerospace structures.

Characterization of Nanostructured Polymer Films

DTIC Science & Technology

2014-12-23

discovered that polymer films with exceptional thermal and kinetic stability could be formed by Matrix Assisted Pulsed Laser Evaporation ( MAPLE ) onto...thermal properties of amorphous polymer nanoglobules fabricated via Matrix-Assisted Pulsed Laser Deposition ( MAPLE ). We discovered that stability in... MAPLE , Glass Transition Temperature 16. SECURITY CLASSIFICATION OF: 17. LIMITATION OF ABSTRACT 18. NUMBER OF PAGES 19a. NAME OF RESPONSIBLE PERSON

Styrene-butadiene-styrene copolymer compatibilized carbon black/polypropylene/polystyrene composites with tunable morphology, electrical conduction and rheological stabilities.

PubMed

Song, Yihu; Xu, Chunfeng; Zheng, Qiang

2014-04-21

We report a facile kinetic strategy in combination with styrene-butadiene-styrene (SBS) copolymer compatibilizers for preparing carbon black (CB) filled immiscible polypropylene (PP)/polystyrene (PS) (1/1) blends with finely tuned morphologies and show the important role of location and migration of CB nanoparticles in determining the electrical conductivity and rheological behaviour of the composites. A novel method of mixing a SBS/CB (5/3) masterbatch with the polymers allowed producing composites with CB aggregates dispersed partially in the unfavorable PP phase and partially in the PP side of the interface to exhibit diverse phase connectivity and electrical conductivity depending on the compounding sequences. A cocontinuous morphology with CB enrichment along the interface was formed in the composite prepared by mixing the SBS/CB masterbatch with the premixed PP/PS blend, giving rise to a highest electrical conductivity and dynamic moduli at low frequencies. On the other hand, mixing the masterbatch with one and then with another polymer yielded droplet (PS)-in-matrix (filled PP) composites. The composites underwent phase coalescence and CB redistribution accompanied by marked dynamic electrical conduction and modulus percolations as a function of time during thermal annealing at 180 °C. The composites with the initial droplet-in-matrix morphology progressed anomalously into the cocontinuous morphology, reflecting a common mechanism being fairly nonspecific for understanding the processing of filled multicomponent composites with tailored performances of general concern.

Nano-Particle Enhanced Polymer Materials for Space Flight Applications

NASA Technical Reports Server (NTRS)

Criss, Jim M., Jr.; Powell, William D.; Connell, John W.; Stallworth-Bordain, Yemaya; Brown, Tracy R.; Mintz, Eric A.; Schlea, Michelle R.; Shofne, Meisha L.

2009-01-01

Recent advances in materials technology both in polymer chemistry and nano-materials warrant development of enhanced structures for space flight applications. This work aims to develop spacecraft structures based on polymer matrix composites (PMCs) that utilize these advancements.. Multi-wall carbon nano-tubes (MWCNTs) are expected ·to increase mechanical performance, lower coefficient of thermal expansion (CTE), increase electrical conductivity (mitigate electrostatic charge), increase thermal conductivity, and reduce moisture absorption of the resultant space structures. In this work, blends of MWCNTs with PETI-330 were prepared and characterized. The nano-reinforced resins were then resin transfer molded (RTM) into composite panels using M55J carbon fabric and compared to baseline panels fabricated from a cyanate ester (RS-3) or a polyimide (PETI-330) resin containing no MWCNTs. In addition, methods of pre-loading the fabric with the MWCNTs were also investigated. The effects of the MWCNTs on the resin processing properties and on the composite end-use properties were also determined.

Development and evaluation of natural gum-based extended release matrix tablets of two model drugs of different water solubilities by direct compression.

PubMed

Ofori-Kwakye, Kwabena; Mfoafo, Kwadwo Amanor; Kipo, Samuel Lugrie; Kuntworbe, Noble; Boakye-Gyasi, Mariam El

2016-01-01

The study was aimed at developing extended release matrix tablets of poorly water-soluble diclofenac sodium and highly water-soluble metformin hydrochloride by direct compression using cashew gum, xanthan gum and hydroxypropylmethylcellulose (HPMC) as release retardants. The suitability of light grade cashew gum as a direct compression excipient was studied using the SeDeM Diagram Expert System. Thirteen tablet formulations of diclofenac sodium (∼100 mg) and metformin hydrochloride (∼200 mg) were prepared with varying amounts of cashew gum, xanthan gum and HPMC by direct compression. The flow properties of blended powders and the uniformity of weight, crushing strength, friability, swelling index and drug content of compressed tablets were determined. In vitro drug release studies of the matrix tablets were conducted in phosphate buffer (diclofenac: pH 7.4; metformin: pH 6.8) and the kinetics of drug release was determined by fitting the release data to five kinetic models. Cashew gum was found to be suitable for direct compression, having a good compressibility index (ICG) value of 5.173. The diclofenac and metformin matrix tablets produced generally possessed fairly good physical properties. Tablet swelling and drug release in aqueous medium were dependent on the type and amount of release retarding polymer and the solubility of drug used. Extended release of diclofenac (∼24 h) and metformin (∼8-12 h) from the matrix tablets in aqueous medium was achieved using various blends of the polymers. Drug release from diclofenac tablets fitted zero order, first order or Higuchi model while release from metformin tablets followed Higuchi or Hixson-Crowell model. The mechanism of release of the two drugs was mostly through Fickian diffusion and anomalous non-Fickian diffusion. The study has demonstrated the potential of blended hydrophilic polymers in the design and optimization of extended release matrix tablets for soluble and poorly soluble drugs by direct compression.

Studies on the thermal behavior of CS:LiTFSI:[Amim] Cl polymer electrolytes exerted by different [Amim] Cl content

NASA Astrophysics Data System (ADS)

Ramesh, S.; Shanti, R.; Morris, Ezra

2012-01-01

The principle motivation of this research work is to develop environmental-friendly polymer electrolytes utilizing corn starch (CS), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) and 1-allyl-3-methylimidazolium chloride ([Amim] Cl) by solution casting technique. The highest ionic conductivity value was achieved for the composition CS:LiTFSI:[Amim] Cl (14 wt. %:6 wt. %:80 wt. %) which exhibits the ionic conductivity value of 5.68 × 10 -2 S cm -1 at 40 °C with the activation energy of 4.86 kJ mol -1. This sample possess high concentration of amorphous phase coupled with greater presence of conducting cations (lithium, Li + and imidazolium, [Amim] +) as depicted by the dielectric loss tangent plot. The conductivity-temperature plots were found to obey Arrhenius rule in which the conductivity mechanism is thermally assisted. The melting temperature of polymer electrolyte decreases with increase in [Amim] Cl content. This is attributed to the good miscibility of [Amim] Cl in CS:LiTFSI matrix inducing structural disorderliness. Reference to the TGA results it is found that the addition of [Amim] Cl diminishes the heat-resistivity whereas enhancement in the thermal stability occurred at the initial addition and declines with further doping of [Amim] Cl.

The use of polyimide-modified aluminum nitride fillers in AlN@PI/Epoxy composites with enhanced thermal conductivity for electronic encapsulation

PubMed Central

Zhou, Yongcun; Yao, Yagang; Chen, Chia-Yun; Moon, Kyoungsik; Wang, Hong; Wong, Ching-ping

2014-01-01

Polymer modified fillers in composites has attracted the attention of numerous researchers. These fillers are composed of core-shell structures that exhibit enhanced physical and chemical properties that are associated with shell surface control and encapsulated core materials. In this study, we have described an apt method to prepare polyimide (PI)-modified aluminum nitride (AlN) fillers, AlN@PI. These fillers are used for electronic encapsulation in high performance polymer composites. Compared with that of untreated AlN composite, these AlN@PI/epoxy composites exhibit better thermal and dielectric properties. At 40 wt% of filler loading, the highest thermal conductivity of AlN@PI/epoxy composite reached 2.03 W/mK. In this way, the thermal conductivity is approximately enhanced by 10.6 times than that of the used epoxy matrix. The experimental results exhibiting the thermal conductivity of AlN@PI/epoxy composites were in good agreement with the values calculated from the parallel conduction model. This research work describes an effective pathway that modifies the surface of fillers with polymer coating. Furthermore, this novel technique improves the thermal and dielectric properties of fillers and these can be used extensively for electronic packaging applications. PMID:24759082

Vertically Aligned and Interconnected SiC Nanowire Networks Leading to Significantly Enhanced Thermal Conductivity of Polymer Composites.

PubMed

Yao, Yimin; Zhu, Xiaodong; Zeng, Xiaoliang; Sun, Rong; Xu, Jian-Bin; Wong, Ching-Ping

2018-03-21

Efficient heat removal via thermal management materials has become one of the most critical challenges in the development of modern microelectronic devices. However, previously reported polymer composites exhibit limited enhancement of thermal conductivity, even when highly loaded with thermally conductive fillers, because of the lack of efficient heat transfer pathways. Herein, we report vertically aligned and interconnected SiC nanowire (SiCNW) networks as efficient fillers for polymer composites, achieving significantly enhanced thermal conductivity. The SiCNW networks are produced by freeze-casting nanowire aqueous suspensions followed by thermal sintering to consolidate the nanowire junctions, exhibiting a hierarchical architecture in which honeycomb-like SiCNW layers are aligned. The composite obtained by infiltrating SiCNW networks with epoxy resin, at a relatively low SiCNW loading of 2.17 vol %, represents a high through-plane thermal conductivity (1.67 W m -1 K -1 ) compared to the pure matrix, which is equivalent to a significant enhancement of 406.6% per 1 vol % loading. The orderly SiCNW network which can act as a macroscopic expressway for phonon transport is believed to be the main contributor for the excellent thermal performance. This strategy provides insights for the design of high-performance composites with potential to be used in advanced thermal management materials.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tahir, Dahlang, E-mail: dtahir@fmipa.unhas.ac.id; Bakri, Fahrul; Liong, Syarifuddin

We have studied the molecular properties, structural properties, and chemical composition of composites by Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD) spectroscopy, and X-ray fluorescence (XRF) spectroscopy, respectively. FTIR spectra shows absorption band of hydroxyl group (-OH), methyl group (-CH{sub 3}) and aromatic group (C-C). The absorption band for aromatic group (C-C) shows the formation of carbonaceous in composites. XRF shows chemical composition of composites, which the main chemicals are SO{sub 3}, Cl, and ZnO. The loss on ignition value (LOI) of activated charcoal indicates high carbonaceous matter. The crystallite size for diffraction pattern from hydrogel polymer is aboutmore » 17 nm and for activated charcoal are about 19 nm. The crystallite size of the polymer is lower than that of activated charcoal, which make possible of the particle from filler in contact with each other to form continuous conducting polymer through polymer matrix.« less

The characterization of high-density polyethylene/organoclay nanocomposites

NASA Astrophysics Data System (ADS)

Rodrigues, Tathiane Cordeiro; Tavares, Maria Inês Bruno; Soares, Igor Lopes; Moreira, Ana M.

2009-01-01

Polymeric nanocomposites, which are hybrids of polymers and modified inorganic clay with organic surfactants, are extremely attractive in both science and industry. These materials present improvements in such polymer properties as modulus, heat capacity, thermal stability, flame resistance, and so on. Research has been conducted in recent decades to obtain high-quality materials that can be used in applications like food packing, car components, and combustible cells. Polymeric nanocomposites present many advantages in relation to composites due to the quantity of filler added to the polymer and also to the improved properties. In a composite, the quantity of filler must be as high as possible (i.e., over 30%). In the polymeric nanocomposite the quantity of filler varies from 1% to 5% because of the nanosize of the particles. These nanoparticles often have a large surface area that results in improved polymer-matrix properties.

Holographic Recording Materials Development

NASA Technical Reports Server (NTRS)

Verber, C. M.; Schwerzel, R. E.; Perry, P. J.; Craig, R. A.

1976-01-01

Organic photorefractive materials were evaluated for application in a reversible holographic memory system. Representative indigo and thioindigo derivatives and several stilbene derivatives were studied as well as 15, 16-dialkyldihydropyrene derivatives the following goals were achieved: (1) the successful writing of phase holograms in a thioindigo/polymer gel system, (2) the successful writing and erasing of phase holograms in a variety of indigo/polymer gel and indigo/solid polymer systems, and (3) the identification of indigoid dyes and 15, 16-dialkyldihydropyrene derivatives as materials potentially suitable for utilization in an operational system. Photochemical studies of the stilbene, indigo, thioindigo, and dialkyldihydropyrene derivatives in solution and in a variety of polymer matrix materials were conducted with the goal of optimizing the photorefractive behavior of the chemical system as a whole. The spectroscopic properties required of optimal photorefractive materials were identified, and it was shown that both the indigoid dyes and the dialkyldihydropyrenes closely match the required properties.

Interplay of Transport and Morphology in Nanostructured Ion-Containing Polymers

NASA Astrophysics Data System (ADS)

Park, Moon Jeong

The global energy crisis and an increase in environmental pollution in the recent years have drawn the attention of the scientific community to develop innovative ways to improve energy storage and find more efficient methods of transporting the energy. Polymers containing charged species that show high ionic conductivity and good mechanical integrity are the essential components of these energy storage and transport systems. In this talk, first, I will present a fundamental understanding of the thermodynamics and transport in ion-containing block copolymers with a focus on the structure-property relationships. Tailoring the intermolecular interactions between the polymer matrix and the embedded charges appeared to be vital for controlling the transport properties. Particularly, the achievement of well-defined self-assembled morphologies with three-dimensional symmetries has proven to facilitate fast ion transport by constructing less tortuous ion-conducting pathways. Examples of attained morphologies include disorder, lamellae, gyroid, Fddd, hexagonal cylinder, body-centered cubic, face-centered cubic, and A15 phases. Second, various strategies for accessing high cation transference number as well as improved ionic conductivity from ionic-containing polymers are enclosed; (1) the inclusion of terminal ionic units as a new means to control the nanoscale morphologies and the transport efficiency of block copolymer electrolytes and (2) the addition of zwitterions that offered a polar medium close to water, and accordingly increased the charge density and ionic conductivity. The obtained knowledge on polymer electrolytes could be used in a wide range of emerging nanotechnologies such as fuel cells, lithium batteries, and electro-active actuators.

Implementation of an Associative Flow Rule Including Hydrostatic Stress Effects Into the High Strain Rate Deformation Analysis of Polymer Matrix Composites

NASA Technical Reports Server (NTRS)

Goldberg, Robert K.; Roberts, Gary D.; Gilat, Amos

2003-01-01

A previously developed analytical formulation has been modified in order to more accurately account for the effects of hydrostatic stresses on the nonlinear, strain rate dependent deformation of polymer matrix composites. State variable constitutive equations originally developed for metals have been modified in order to model the nonlinear, strain rate dependent deformation of polymeric materials. To account for the effects of hydrostatic stresses, which are significant in polymers, the classical J2 plasticity theory definitions of effective stress and effective inelastic strain, along with the equations used to compute the components of the inelastic strain rate tensor, are appropriately modified. To verify the revised formulation, the shear and tensile deformation of two representative polymers are computed across a wide range of strain rates. Results computed using the developed constitutive equations correlate well with experimental data. The polymer constitutive equations are implemented within a strength of materials based micromechanics method to predict the nonlinear, strain rate dependent deformation of polymer matrix composites. The composite mechanics are verified by analyzing the deformation of a representative polymer matrix composite for several fiber orientation angles across a variety of strain rates. The computed values compare well to experimentally obtained results.

pH-Sensitive Microparticles with Matrix-Dispersed Active Agent

NASA Technical Reports Server (NTRS)

Calle, Luz M. (Inventor); Jolley, Scott T. (Inventor); Buhrow, Jerry W. (Inventor); Li, Wenyan (Inventor)

2014-01-01

Methods to produce pH-sensitive microparticles that have an active agent dispersed in a polymer matrix have certain advantages over microcapsules with an active agent encapsulated in an interior compartment/core inside of a polymer wall. The current invention relates to pH-sensitive microparticles that have a corrosion-detecting or corrosion-inhibiting active agent or active agents dispersed within a polymer matrix of the microparticles. The pH-sensitive microparticles can be used in various coating compositions on metal objects for corrosion detecting and/or inhibiting.

Influence of confinement on polymer-electrolyte relaxational dynamics.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zanotti, J.-M.; Smith, L. J.; Price, D. L.

2004-01-01

Conception and industrial production of viable high specific energy/power batteries is a central issue for the development of non-polluting vehicles. In terms of stored energy and safety, solid-state devices using polymer electrolytes are highly desirable. One of the most studied systems is PEO (polyethylene oxide) complexed by Li salts. Polymer segmental motions and ionic conductivity are closely related. Bulk PEO is actually a biphasic system where an amorphous and a crystalline state (Tm 335 K) coexist. To improve ionic conduction in those systems requires a significant increase of the amorphous phase fraction where lithium conduction is known to mainly takemore » place. Confinement strongly affects properties of condensed matter and in particular the collective phenomena inducing crystallization. Confinement of the polymer matrix is therefore a possible alternative route to the unpractical use of high temperature. Results of a quasi-elastic incoherent neutron scattering study of the influence of confinement on polyethylene oxide (PEO) and (PEO)8Li+[(CF3SO2)2N]- (or (POE)8LiTFSI) dynamics are presented. The nano-confining media is Vycor, a silica based hydrophilic porous glass (characteristic size of the 3D pore network 50 {angstrom}). As expected, the presence of Li salt slows down the bulk polymer dynamics. The confinement also affects dramatically the apparent mean-square displacement of the polymer. Local relaxational PEO dynamics is described KWW model. We also present an alternate model and show how the detailed polymer dynamics (correlation times and local geometry of the motions) can be described without the use of such stretched exponentials so as to access a rheology-related meaningful physical quantity: the monomeric friction coefficient.« less

Dual phase polymer gel electrolyte based on non-woven poly(vinylidenefluoride-co-hexafluoropropylene)–layered clay nanocomposite fibrous membranes for lithium ion batteries

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shubha, Nageswaran; Prasanth, Raghavan; Energy Research Institute - NTU

2013-02-15

Graphical abstract: Display Omitted Highlights: ► P(VdF-co-HFP)–clay nanocomposite based electrospun membranes are prepared. ► The membranes are used as polymer gel electrolyte (PGE) in lithium ion batteries. ► The composite PGE shows ionic conductivity of 5.5 mS cm{sup −1} at room temperature. ► Li/PGE/LiFePO{sub 4} cell delivers initial discharge capacity of 160 mAh g{sup −1}. ► The use of prepared electrolyte significantly improved the cell performance. -- Abstract: A new approach for fabricating polymer gel electrolytes (PGEs) based on electrospun poly(vinylidenefluoride-co-hexafluoropropylene) (P(VdF-co-HFP)) incorporated with layered nanoclay has been employed to enhance the ionic conductivity and electrochemical properties of P(VdF-co-HFP) withoutmore » compromising its mechanical strength. The effect of layered nanoclay on properties of membranes has been evaluated by X-ray diffraction (XRD), differential scanning calorimetry (DSC) and thermal gravimetric analysis (TGA). Surface morphology of the membranes has been studied using field-emission scanning electron microscopy (FE-SEM). Polymer gel electrolytes are prepared by soaking the fibrous membrane into 1 M LiPF{sub 6} in EC/DEC. The electrochemical studies show that incorporation of layered nanoclay into the polymer matrix greatly enhanced the ionic conductivity and compatibility with lithium electrodes. The charge–discharge properties and cycling performance of Li/LiFePO{sub 4} cells comprising nanocomposite polymer gel electrolytes have been evaluated at room temperature.« less

Ultrasonic Assessment of Impact-Induced Damage and Microcracking in Polymer Matrix Composites

NASA Technical Reports Server (NTRS)

Liaw, Benjamin; Villars, Esther; Delmont, Frantz; Bowles, Kenneth J. (Technical Monitor)

2001-01-01

The main objective of this NASA FAR project is to conduct ultrasonic assessment of impact-induced damage and microcracking in polymer matrix composites at various temperatures. It is believed that the proposed study of impact damage assessment on polymer matrix composites will benefit several NASA missions and current interests, such as ballistic impact testing of composite fan containment and high strain rate deformation modeling of polymer matrix composites. Impact-induced damage mechanisms in GLARE and ARALL fiber-metal laminates subject to instrumented drop-weight impacts at various temperatures were studied. GLARE and ARALL are hybrid composites made of alternating layers of aluminum and glass (for GLARE) and aramid- (for ARALL) fiber-reinforced epoxy. Damage in pure aluminum panels impacted by foreign objects was mainly characterized by large plastic deformation surrounding a deep penetration dent. On the other hand, plastic deformation in fiber-metal laminates was often not as severe although the penetration dent was still produced. The more stiff fiber-reinforced epoxy layers provided better bending rigidity; thus, enhancing impact damage tolerance. Severe cracking, however, occurred due to the use of these more brittle fiber-reinforced epoxy layers. Fracture patterns, e.g., crack length and delamination size, were greatly affected by the lay-up configuration rather than by the number of layers, which implies that thickness effect was not significant for the panels tested in this study. Immersion ultrasound techniques were then used to assess damages generated by instrumented drop-weight impacts onto these fiber-metal laminate panels as well as 6061-T6 aluminum/cast acrylic sandwich plates adhered by epoxy. Depending on several parameters, such as impact velocity, mass, temperature, laminate configuration, sandwich construction, etc., various types of impact damage were observed, including plastic deformation, radiating cracks emanating from the impact site, ring cracks surrounding the impact site, partial and full delamination, and combinations of these damages.

Electrical conductivity, dielectric response and space charge dynamics of an electroactive polymer with and without nanofiller reinforcement

NASA Astrophysics Data System (ADS)

Kochetov, R.; Tsekmes, I. A.; Morshuis, P. H. F.

2015-07-01

Electroactive polymers have gained considerable attention over the last 20 years for exhibiting a large displacement in response to electrical stimulation. The promising fields of application include wave energy converters, muscle-like actuators, sensors, robotics, and biomimetics. For an electrical engineer, electroactive polymers can be seen as a dielectric elastomer film or a compliant capacitor with a highly deformable elastomeric medium. If the elastomer is pre-stretched and pre-charged, a reduction of the tensile force lets the elastomer revert to its original form and increases the electrical potential. The light weight of electroactive polymers, low cost, high intrinsic breakdown strength, cyclical way of operation, reliable performance, and high efficiency can be exploited to utilize the elastomeric material as a transducer. The energy storage for a linear dielectric polymer is determined by its relative permittivity and the applied electric field. The latter is limited by the dielectric breakdown strength of the material. Therefore, to generate a high energy density of a flexible capacitor, the film must be used at the voltage level close to the material’s breakdown or inorganic particles with high dielectric permittivity which can be introduced into the polymer matrix. In the present study, silicone-titania elastomer nanocomposites were produced and the influence of nanoparticles on the macroscopic dielectric properties of the neat elastomer including space charge dynamics, complex permittivity, and electrical conductivity, were investigated.

Calculating permittivity of semi-conductor fillers in composites based on simplified effective medium approximation models

NASA Astrophysics Data System (ADS)

Feng, Yefeng; Wu, Qin; Hu, Jianbing; Xu, Zhichao; Peng, Cheng; Xia, Zexu

2018-03-01

Interface induced polarization has a significant impact on permittivity of 0–3 type polymer composites with Si based semi-conducting fillers. Polarity of Si based filler, polarity of polymer matrix and grain size of filler are closely connected with induced polarization and permittivity of composites. However, unlike 2–2 type composites, the real permittivity of Si based fillers in 0–3 type composites could be not directly measured. Therefore, achieving the theoretical permittivity of fillers in 0–3 composites through effective medium approximation (EMA) models should be very necessary. In this work, the real permittivity results of Si based semi-conducting fillers in ten different 0–3 polymer composite systems were calculated by linear fitting of simplified EMA models, based on particularity of reported parameters in those composites. The results further confirmed the proposed interface induced polarization. The results further verified significant influences of filler polarity, polymer polarity and filler size on induced polarization and permittivity of composites as well. High self-consistency was gained between present modelling and prior measuring. This work might offer a facile and effective route to achieve the difficultly measured dielectric performances of discrete filler phase in some special polymer based composite systems.

Dispersion of Single Wall Carbon Nanotubes by in situ Polymerization Under Sonication

NASA Technical Reports Server (NTRS)

Park, Cheol; Ounaies, Zoubeida; Watson, Kent A.; Crooks, Roy E.; Smith, Joseph, Jr.; Lowther, Sharon E.; Connell, John W.; Siochi, Emilie J.; Harrison, Joycelyn S.; St.Clair, Terry L.

2002-01-01

Single wall nanotube reinforced polyimide nanocomposites were synthesized by in situ polymerization of monomers of interest in the presence of sonication. This process enabled uniform dispersion of single wall carbon nanotube (SWNT) bundles in the polymer matrix. The resultant SWNT-polyimide nanocomposite films were electrically conductive (antistatic) and optically transparent with significant conductivity enhancement (10 orders of magnitude) at a very low loading (0.1 vol%). Mechanical properties as well as thermal stability were also improved with the incorporation of the SWNT.

Incorporation of Mean Stress Effects into the Micromechanical Analysis of the High Strain Rate Response of Polymer Matrix Composites

NASA Technical Reports Server (NTRS)

Goldberg, Robert K.; Roberts, Gary D.; Gilat, Amos

2002-01-01

The results presented here are part of an ongoing research program, to develop strain rate dependent deformation and failure models for the analysis of polymer matrix composites subject to high strain rate impact loads. A micromechanics approach is employed in this work, in which state variable constitutive equations originally developed for metals have been modified to model the deformation of the polymer matrix, and a strength of materials based micromechanics method is used to predict the effective response of the composite. In the analysis of the inelastic deformation of the polymer matrix, the definitions of the effective stress and effective inelastic strain have been modified in order to account for the effect of hydrostatic stresses, which are significant in polymers. Two representative polymers, a toughened epoxy and a brittle epoxy, are characterized through the use of data from tensile and shear tests across a variety of strain rates. Results computed by using the developed constitutive equations correlate well with data generated via experiments. The procedure used to incorporate the constitutive equations within a micromechanics method is presented, and sample calculations of the deformation response of a composite for various fiber orientations and strain rates are discussed.

Gas response behaviour and photochemistry of borondiketonate in acrylic polymer matrices for sensing applications.

PubMed

Arias Espinoza, Juan Diego; Sazhnikov, Viacheslav; Smits, Edsger C P; Ionov, Dmirity; Kononevich, Yuriy; Yakimets, Iryna; Alfimov, Mikael; Schoo, Herman F M

2014-11-01

The fluorescent spectra in combination with gas response behavior of acrylic polymers doped with dibenzoyl(methanato)boron difluoride (DBMBF2) were studied by fluorescence spectroscopy and time-resolved fluorescence lifetime. The role of acrylic matrix polarity upon the fluorescence spectra and fluorescence lifetime was analyzed. Changes in emission of the dye doped polymers under exposure to toluene, n-hexane and ethanol were monitored. The fluorescence lifetimes were measured for the singlet excited state as well as the exciplex formed between DBMBF2 and toluene. A reduction of the transition energy to the first singlet-excited state in the four polymers was observed, compared to solution. Reversible exciplex formation, viz. a red shifted fluorescence emission was perceived when exposing the polymers to toluene, while for hexane and ethanol only reversible reduction of the fluorescence occurred. Longer singlet and shorter exciplex lifetimes were observed for non-polar matrixes. The latter mechanism is explained in function of the lower charge transfer character of the exciplex in non-polar matrixes. Additionally, the quantum yield of the dye in the polymer matrix increased almost seventh-fold compared to values for solution.

The correlation of low-velocity impact resistance of graphite-fiber-reinforced composites with matrix properties

NASA Technical Reports Server (NTRS)

Bowles, K. J.

1986-01-01

Summarized are basic studies that were conducted to correlate the impact resistance of graphite-fiber-reinforced composites with polymer matrix properties. Three crosslinked epoxy resins and a linear polysulfone were selected as composite matrices. As a group, these resins possess a significantly large range of mechanical properties. The mechanical properties of the resins and their respective composites were measured. Neat resin specimens and unidirectional and crossply composite specimens were impact tested with an instrumented dropweight tester. Impact resistances of the specimens were assessed on the basis of loading capability, energy absorption, and extent of damage.

High ionic conductivity P(VDF-TrFE)/PEO blended polymer electrolytes for solid electrochromic devices.

PubMed

Nguyen, Chien A; Xiong, Shanxin; Ma, Jan; Lu, Xuehong; Lee, Pooi See

2011-08-07

Solid polymer electrolytes with excellent ionic conductivity (above 10(-4) S cm(-1)), which result in high optical modulation for solid electrochromic (EC) devices are presented. The combination of a polar host matrix poly(vinylidene fluoride-trifluoroethylene) P(VDF-TrFE) and a solid plasticized of a low molecular weight poly(ethylene oxide) (PEO) (M(w)≤ 20,000) blended polymer electrolyte serves to enhance both the dissolution of lithium salt and the ionic transport. Calorimetric measurement shows a reduced crystallization due to a better intermixing of the polymers with small molecular weight PEO. Vibrational spectroscopy identifies the presence of free ions and ion pairs in the electrolytes with PEO of M(w)≤ 8000. The ionic dissolution is improved using PEO as a plasticizer when compared to liquid propylene carbonate, evidently shown in the transference number analysis. Ionic transport follows the Arrhenius equation with a low activation energy (0.16-0.2 eV), leading to high ionic conductivities. Solid electrochromic devices fabricated with the blended P(VDF-TrFE)/PEO electrolytes and polyaniline show good spectroelectrochemical performance in the visible (300-800 nm) and near-infrared (0.9-2.4 μm) regions with a modulation up to 60% and fast switching speed of below 20 seconds. The successful introduction of the solid polymer electrolytes with its best harnessed qualities helps to expedite the application of various electrochemical devices. This journal is © the Owner Societies 2011

E-beam-Cure Fabrication of Polymer Fiber/Matrix Composites for Multifunctional Radiation Shielding

NASA Technical Reports Server (NTRS)

Wilson, John W.; Jensen, Brian J.; Thibeault, Sheila A.; Hou, Tan-Hung; Saether, Erik; Glaessgen, Edward H.; Humes, Donald H.; Chang, Chie K.; Badavi, Francis F.; Kiefer, Rrichard L.;

Polymer-electrolyte-gated nanowire synaptic transistors for neuromorphic applications

NASA Astrophysics Data System (ADS)

Zou, Can; Sun, Jia; Gou, Guangyang; Kong, Ling-An; Qian, Chuan; Dai, Guozhang; Yang, Junliang; Guo, Guang-hua

2017-09-01

Polymer-electrolytes are formed by dissolving a salt in polymer instead of water, the conducting mechanism involves the segmental motion-assisted diffusion of ion in the polymer matrix. Here, we report on the fabrication of tin oxide (SnO2) nanowire synaptic transistors using polymer-electrolyte gating. A thin layer of poly(ethylene oxide) and lithium perchlorate (PEO/LiClO4) was deposited on top of the devices, which was used to boost device performances. A voltage spike applied on the in-plane gate attracts ions toward the polymer-electrolyte/SnO2 nanowire interface and the ions are gradually returned after the pulse is removed, which can induce a dynamic excitatory postsynaptic current in the nanowire channel. The SnO2 synaptic transistors exhibit the behavior of short-term plasticity like the paired-pulse facilitation and self-adaptation, which is related to the electric double-effect regulation. In addition, the synaptic logic functions and the logical function transformation are also discussed. Such single SnO2 nanowire-based synaptic transistors are of great importance for future neuromorphic devices.

A Fully Non-Metallic Gas Turbine Engine Enabled by Additive Manufacturing

NASA Technical Reports Server (NTRS)

Grady, Joseph E.

2015-01-01

The Non-Metallic Gas Turbine Engine project, funded by NASA Aeronautics Research Institute, represents the first comprehensive evaluation of emerging materials and manufacturing technologies that will enable fully nonmetallic gas turbine engines. This will be achieved by assessing the feasibility of using additive manufacturing technologies to fabricate polymer matrix composite and ceramic matrix composite turbine engine components. The benefits include: 50 weight reduction compared to metallic parts, reduced manufacturing costs, reduced part count and rapid design iterations. Two high payoff metallic components have been identified for replacement with PMCs and will be fabricated using fused deposition modeling (FDM) with high temperature polymer filaments. The CMC effort uses a binder jet process to fabricate silicon carbide test coupons and demonstration articles. Microstructural analysis and mechanical testing will be conducted on the PMC and CMC materials. System studies will assess the benefits of fully nonmetallic gas turbine engine in terms of fuel burn, emissions, reduction of part count, and cost. The research project includes a multidisciplinary, multiorganization NASA - industry team that includes experts in ceramic materials and CMCs, polymers and PMCs, structural engineering, additive manufacturing, engine design and analysis, and system analysis.

Near-Edge X-ray Absorption Fine Structure Studies of Electrospun Poly(dimethylsiloxane)/Poly (methyl methacrylate)/Multiwall Carbon Nanotube Composites

PubMed Central

Winter, A. Douglas; Larios, Eduardo; Alamgir, Faisal M.; Jaye, Cherno; Fischer, Daniel; Campo, Eva M.

2014-01-01

This work describes the near conduction band edge structure of electrospun mats of MWCNT-PDMS-PMMA by near edge X-Ray absorption fine structure (NEXAFS) spectroscopy. Effects of adding nanofillers of different sizes were addressed. Despite observed morphological variations and inhomogeneous carbon nanotube distribution, spun mats appeared homogeneous under NEXAFS analysis. Spectra revealed differences in emissions from glancing and normal spectra; which may evidence phase separation within the bulk of the micron-size fibers. Further, dichroic ratios show polymer chains did not align, even in the presence of nanofillers. Addition of nanofillers affected emissions in the C-H, C=O and C-C regimes, suggesting their involvement in interfacial matrix-carbon nanotube bonding. Spectral differences at glancing angles between pristine and composite mats suggest that geometric conformational configurations are taking place between polymeric chains and carbon nanotubes. These differences appear to be carbon nanotube-dimension dependent, and are promoted upon room temperature mixing and shear flow during electrospinning. CH-π bonding between polymer chains and graphitic walls, as well as H-bonds between impurities in the as-grown CNTs and polymer pendant groups are proposed bonding mechanisms promoting matrix conformation. PMID:24308286

Effect of Polymer Matrix on the Structure and Electric Properties of Piezoelectric Lead Zirconatetitanate/Polymer Composites

PubMed Central

Li, Rui; Zhou, Jun; Liu, Hujun; Pei, Jianzhong

2017-01-01

Piezoelectric lead zirconatetitanate (PZT)/polymer composites were prepared by two typical polymer matrixes using the hot-press method. The micromorphology, microstructure, dielectric properties, and piezoelectric properties of the PZT/polymer composites were characterized and investigated. The results showed that when the condition of frequency is 103 Hz, the dielectric and piezoelectric properties of PZT/poly(vinylidene fluoride) were both better than that of PZT/polyvinyl chloride (PVC). When the volume fraction of PZT was 50%, PZT/PVDF prepared by the hot-press method had better comprehensive electric property. PMID:28805730

Cross-Linked Nanohybrid Polymer Electrolytes With POSS Cross-Linker for Solid-State Lithium Ion Batteries.

PubMed

Zhang, Jinfang; Li, Xiaofeng; Li, Ying; Wang, Huiqi; Ma, Cheng; Wang, Yanzhong; Hu, Shengliang; Wei, Weifeng

2018-01-01

A new class of freestanding cross-linked hybrid polymer electrolytes (HPEs) with POSS as the cross-linker was prepared by a one-step free radical polymerization reaction. Octavinyl octasilsesquioxane (OV-POSS) with eight functional corner groups was used to provide cross-linking sites for the connection of polymer segments and the required mechanical strength to separate the cathode and anode. The unique cross-linked structure offers additional free volume for the motion of EO chains and provides fast and continuously interconnected ion-conducting channels along the nanoparticles/polymer matrix interface. The HPE exhibits the highest ionic conductivity of 1.39 × 10 -3 S cm -1 , as well as excellent interfacial compatibility with the Li electrode at 80°C. In particular, LiFePO 4 /Li cells based on the HPE deliver good rate capability and long-term cycling performance with an initial discharge capacity of 152.1 mAh g -1 and a capacity retention ratio of 88% after 150 cycles with a current density of 0.5 C at 80°C, demonstrating great potential application in high-performance LIBs at elevated temperatures.

Cross-linked Nanohybrid Polymer Electrolytes with POSS Cross-linker for Solid-state Lithium Ion Batteries

NASA Astrophysics Data System (ADS)

Zhang, Jinfang; Li, Xiaofeng; Li, Ying; Wang, Huiqi; Ma, Cheng; Wang, Yanzhong; Hu, Shengliang; Wei, Weifeng

2018-05-01

A new class of freestanding cross-linked hybrid polymer electrolytes (HPEs) with POSS as the cross-linker was prepared by a one-step free radical polymerization reaction. Octavinyl octasilsesquioxane (OV-POSS) with eight functional corner groups was used to provide cross-linking sites for the connection of polymer segments and the required mechanical strength to separate the cathode and anode. The unique cross-linked structure offers additional free volume for the motion of EO chains and provides fast and continuously interconnected ion-conducting channels along the nanoparticles/polymer matrix interface. The HPE exhibits the highest ionic conductivity of 1.39×10-3 S cm-1, as well as excellent interfacial compatibility with the Li electrode at 80 oC. In particular, LiFePO4/Li cells based on the HPE deliver good rate capability and long-term cycling performance with an initial discharge capacity of 152.1 mAh g-1 and a capacity retention ratio of 88% after 150 cycles with a current density of 0.5 C at 80 oC, demonstrating great potential application in high-performance LIBs at elevated temperatures.

Evaluation of tensile strength of hybrid fiber (jute/gongura) reinforced hybrid polymer matrix composites

NASA Astrophysics Data System (ADS)

Venkatachalam, G.; Gautham Shankar, A.; Vijay, Kumar V.; Chandan, Byral R.; Prabaharan, G. P.; Raghav, Dasarath

2015-07-01

The polymer matrix composites attract many industrial applications due to its light weight, less cost and easy for manufacturing. In this paper, an attempt is made to prepare and study of the tensile strength of hybrid (two natural) fibers reinforced hybrid (Natural + Synthetic) polymer matrix composites. The samples were prepared with hybrid reinforcement consists of two different fibers such as jute and Gongura and hybrid polymer consists of polyester and cashew nut shell resins. The hybrid composites tensile strength is evaluated to study the influence of various fiber parameters on mechanical strength. The parameters considered here are the duration of fiber treatment, the concentration of alkali in fiber treatment and nature of fiber content in the composites.

Effect of reduced graphene oxide-carbon nanotubes hybrid nanofillers in mechanical properties of polymer nanocomposites

NASA Astrophysics Data System (ADS)

Sa, Kadambinee; Mahakul, Prakash C.; Subramanyam, B. V. R. S.; Raiguru, Jagatpati; Das, Sonali; Alam, Injamul; Mahanandia, Pitamber

2018-03-01

Graphene and carbon nanotubes (CNTs) have tremendous interest as reinforcing fillers due to their excellent physical properties. However, their reinforcing effect in polymer matrix is limited due to agglomeration of graphene and CNTs within the polymer matrix. Mechanical properties by the admixture of reduced graphene oxide (rGO) and CNTs in Poly (methyl methacrylate) (PMMA) prepared by solution mixing method has been investigated. The prepared samples are characterized using X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM) and Raman spectroscopy. The hybrid composite shows improvement in the mechanical properties compared to rGO/PMMA and MWCNTs/PMMA composites due to better interaction between rGO-MWCNTs and polymer matrix.

Biointerface dynamics--Multi scale modeling considerations.

PubMed

Pajic-Lijakovic, Ivana; Levic, Steva; Nedovic, Viktor; Bugarski, Branko

2015-08-01

Irreversible nature of matrix structural changes around the immobilized cell aggregates caused by cell expansion is considered within the Ca-alginate microbeads. It is related to various effects: (1) cell-bulk surface effects (cell-polymer mechanical interactions) and cell surface-polymer surface effects (cell-polymer electrostatic interactions) at the bio-interface, (2) polymer-bulk volume effects (polymer-polymer mechanical and electrostatic interactions) within the perturbed boundary layers around the cell aggregates, (3) cumulative surface and volume effects within the parts of the microbead, and (4) macroscopic effects within the microbead as a whole based on multi scale modeling approaches. All modeling levels are discussed at two time scales i.e. long time scale (cell growth time) and short time scale (cell rearrangement time). Matrix structural changes results in the resistance stress generation which have the feedback impact on: (1) single and collective cell migrations, (2) cell deformation and orientation, (3) decrease of cell-to-cell separation distances, and (4) cell growth. Herein, an attempt is made to discuss and connect various multi scale modeling approaches on a range of time and space scales which have been proposed in the literature in order to shed further light to this complex course-consequence phenomenon which induces the anomalous nature of energy dissipation during the structural changes of cell aggregates and matrix quantified by the damping coefficients (the orders of the fractional derivatives). Deeper insight into the matrix partial disintegration within the boundary layers is useful for understanding and minimizing the polymer matrix resistance stress generation within the interface and on that base optimizing cell growth. Copyright © 2015 Elsevier B.V. All rights reserved.

Microstructure and Thermal Conductivity of Carbon Nanotube Reinforced Cu Composites.

PubMed

Chen, Pingan; Zhang, Jian; Shen, Qiang; Luo, Guoqiang; Dai, Yang; Wang, Chuanbing; Li, Meijuan; Zhang, Lianmeng

2017-04-01

Microstructure and thermal conductivity (TC) of carbon nanotubes reinforced Cu (CNT-Cu) composites have been studied. When CNTs were coated with nano Cu by electroless plating, the TC of CNT-Cu composites showed a noticeable improvement and increased with CNT contents. When 1.0 vol% CNTs was added, the TC of CNT-Cu composites increased to 420.4 W/(m · K), 30% higher than that of monolithic Cu (323.1 W/(m · K)). According to the measured TC of CNT-Cu composites, the interfacial thermal resistance of CNT-Cu composites was calculated as 3.0 × 10⁻⁹ m² K/W which was lower than the reported values of CNTs reinforced polymer matrix composites and ceramic matrix composites. Microstructures showed that CNTs modified with nano Cu were homogeneously dispersed and embedded in the Cu matrix, indicating that there was strong bonding between CNTs and Cu. The homogeneously dispersed CNTs and reduction of interfacial thermal resistance resulted in the improvement of thermal conductivity of CNT-Cu composites. Therefore, the prepared CNT-Cu composites are promising materials for thermal management applications.

Oriented nanofibers embedded in a polymer matrix

NASA Technical Reports Server (NTRS)

Barrera, Enrique V. (Inventor); Lozano, Karen (Inventor); Rodriguez-Macias, Fernando J. (Inventor); Chibante, Luis Paulo Felipe (Inventor); Stewart, David Harris (Inventor)

2011-01-01

A method of forming a composite of embedded nanofibers in a polymer matrix is disclosed. The method includes incorporating nanofibers in a plastic matrix forming agglomerates, and uniformly distributing the nanofibers by exposing the agglomerates to hydrodynamic stresses. The hydrodynamic said stresses force the agglomerates to break apart. In combination or additionally elongational flow is used to achieve small diameters and alignment. A nanofiber reinforced polymer composite system is disclosed. The system includes a plurality of nanofibers that are embedded in polymer matrices in micron size fibers. A method for producing nanotube continuous fibers is disclosed. Nanofibers are fibrils with diameters of 100 nm, multiwall nanotubes, single wall nanotubes and their various functionalized and derivatized forms. The method includes mixing a nanofiber in a polymer; and inducing an orientation of the nanofibers that enables the nanofibers to be used to enhance mechanical, thermal and electrical properties. Orientation is induced by high shear mixing and elongational flow, singly or in combination. The polymer may be removed from said nanofibers, leaving micron size fibers of aligned nanofibers.

Laboratory for the Processing and Evaluation of Inorganic Matrix Composites

DTIC Science & Technology

1989-06-01

preceramic polymers .’ Ceramic data (yield and elemental composition ) for the pyrolysis ... polymer matrix composites can feature apparent fracture energies as high as those of unreinforced metals (Ashby and Jones 1980). I I Fig. 1 SiC VLS...materials has pyrolysis of shaped bodies of such " preceramic " polymers . received much attention in recent years.’ This procedure The issues that are

Symposium Review: Metal and Polymer Matrix Composites at MS&T 2013

NASA Astrophysics Data System (ADS)

Gupta, Nikhil; Paramsothy, Muralidharan

2014-06-01

This article reflects on the presentations made during the Metal and Polymer Matrix Composites symposium at Materials Science and Technology 2013 (MS&T'13) held in Montreal (Quebec, Canada) from October 27 to 31. The symposium had three sessions on metal matrix composites and one session on polymer matrix composites containing a total of 23 presentations. While the abstracts and full-text papers are available through databases, the discussion that took place during the symposium is often not captured in writing and gets immediately lost. We have tried to recap some of the discussion in this article and hope that it will supplement the information present in the proceedings. The strong themes in the symposium were porous composites, aluminum matrix composites, and nanocomposites. The development of processing methods was also of interest to the speakers and attendees.

Mechanistic modelling of drug release from a polymer matrix using magnetic resonance microimaging.

PubMed

Kaunisto, Erik; Tajarobi, Farhad; Abrahmsen-Alami, Susanna; Larsson, Anette; Nilsson, Bernt; Axelsson, Anders

2013-03-12

In this paper a new model describing drug release from a polymer matrix tablet is presented. The utilization of the model is described as a two step process where, initially, polymer parameters are obtained from a previously published pure polymer dissolution model. The results are then combined with drug parameters obtained from literature data in the new model to predict solvent and drug concentration profiles and polymer and drug release profiles. The modelling approach was applied to the case of a HPMC matrix highly loaded with mannitol (model drug). The results showed that the drug release rate can be successfully predicted, using the suggested modelling approach. However, the model was not able to accurately predict the polymer release profile, possibly due to the sparse amount of usable pure polymer dissolution data. In addition to the case study, a sensitivity analysis of model parameters relevant to drug release was performed. The analysis revealed important information that can be useful in the drug formulation process. Copyright © 2013 Elsevier B.V. All rights reserved.

Concurrent release of admixed antimicrobials and salicylic acid from salicylate-based poly(anhydride-esters)

PubMed Central

Johnson, Michelle L.; Uhrich, Kathryn E.

2008-01-01

A polymer blend consisting of antimicrobials (chlorhexidine, clindamycin, and minocycline) physically admixed at 10% by weight into a salicylic acid-based poly (anhydride-ester) (SA-based PAE) was developed as an adjunct treatment for periodontal disease. The SA-based PAE/antimicrobial blends were characterized by multiple methods, including contact angle measurements and differential scanning calorimetry. Static contact angle measurements showed no significant differences in hydrophobicity between the polymer and antimicrobial matrix surfaces. Notable decreases in the polymer glass transition temperature (Tg) and the antimicrobials' melting points (Tm) were observed indicating that the antimicrobials act as plasticizers within the polymer matrix. In vitro drug release of salicylic acid from the polymer matrix and for each physically admixed antimicrobial was concurrently monitored by high pressure liquid chromatography during the course of polymer degradation and erosion. Although the polymer/antimicrobial blends were immiscible, the initial 24 h of drug release correlated to the erosion profiles. The SA-based PAE/antimicrobial blends are being investigated as an improvement on current localized drug therapies used to treat periodontal disease. PMID:19180627

Ionic Liquids as the MOFs/Polymer Interfacial Binder for Efficient Membrane Separation.

PubMed

Lin, Rijia; Ge, Lei; Diao, Hui; Rudolph, Victor; Zhu, Zhonghua

2016-11-23

Obtaining strong interfacial affinity between filler and polymer is critical to the preparation of mixed matrix membranes (MMMs) with high separation efficiency. However, it is still a challenge for micron-sized metal organic frameworks (MOFs) to achieve excellent compatibility and defect-free interface with polymer matrix. Thin layer of ionic liquid (IL) was immobilized on micron-sized HKUST-1 to eliminate the interfacial nonselective voids in MMMs with minimized free ionic liquid (IL) in polymer matrix, and then the obtained IL decorated HKUST-1 was incorporated into 4,4'-(hexafluoroisopropylidene)diphthalic anhydride-2,3,5,6-tetramethyl-1,3-phenyldiamine (6FDA-Durene) to fabricate MMMs. Acting as a filler/polymer interfacial binder, the favorable MOF/IL and IL/polymer interaction can facilitate the enhancement of MOF/polymer affinity. Compared to MMM with only HKUST-1 incorporation, MMM with IL decorated HKUST-1 succeeded in restricting the formation of nonselective interfacial voids, leading to an increment in CO 2 selectivity. The IL decoration method can be an effective approach to eliminate interfacial voids in MMMs, extending the filler selection to a wide range of large-sized fillers.

Improving Multi-Functional Properties in Polymer Based Nano Composites by Interfacial

NASA Astrophysics Data System (ADS)

Tajaddod, Navid

Polymer nanocomposites (PNCs) have become an area of increasing interest for study in the field of polymer science and technology since the rise of nanotechnology research. Despite the significant amount of progress being made towards producing high quality PNC materials, improvement in the mechanical, electrical, thermal and other functional properties still remain a challenge. To date, these properties are only a fraction of the expected theoretical values predicted for these materials. Development of interfacial regions between the filler and matrix within the composite has been found to be an important focus in terms of processing. Proper interfacial control and development may ensure excellent interaction and property transfer between the filler and polymer matrix in addition to improvement of multi-functional properties of PNCs. The property-structure importance for the existence of the interfacial and interphase region within PNCs is discussed in this thesis work. Two specific PNC systems are selected for study as part of this dissertation in order to understand the effect of interfacial region development on influencing multi-functional property trends. Polyethylene (PE)/boron nitride (BN) and polyacrylonitrile (PAN)/carbon nanotube (CNT) composites were selected to investigate their mechanical performance and thermal and electrical conductivity properties, respectively. For these systems it was found that the interfacial region structure is directly related to the enhancement of the subsequent multi-functional properties.

Crosslink Density and Molecular Weight Effects on the Viscoelastic Response of a Glassy High-Performance Polyimide

NASA Technical Reports Server (NTRS)

Nicholson, Lee M.; Whitley, Karen S.; Gates, Thomas S.

2001-01-01

Durability and long-term performance are among the primary concerns for the use of advanced polymer matrix composites (PMCs) in modern aerospace structural applications. For a PMC subJected to long-term exposure at elevated temperatures. the viscoelastic nature of the polymer matrix will contribute to macroscopic changes in composite stiffness, strength and fatigue life. Over time. changes in the polymer due to physical aging will have profound effects on tile viscoelastic compliance of the material, hence affecting its long-term durability. Thus, the ability to predict material performance using intrinsic properties, such as crosslink density and molecular weight, would greatly enhance the efficiency of design and development of PMCs. The objective of this paper is to discuss and present the results of an experimental study that considers the effects of crosslink density, molecular weight and temperature on the viscoelastic behavior including physical aging of an advanced polymer. Five distinct variations in crosslink density were used to evaluate the differences in mechanical performance of an advanced polyimide. The physical aging behavior was isolated by conducting sequenced, short-term isothermal creep compliance tests in tension. These tests were performed over a range of sub-glass transition temperatures. The material constants, material master curves and physical aging-related parameters were evaluated as a function of temperature crosslink density and molecular weight using time-temperature and time-aging time superposition techniques.

Compression and compaction properties of plasticised high molecular weight hydroxypropylmethylcellulose (HPMC) as a hydrophilic matrix carrier.

PubMed

Hardy, I J; Cook, W G; Melia, C D

2006-03-27

The compression and compaction properties of plasticised high molecular weight USP2208 HPMC were investigated with the aim of improving tablet formation in HPMC matrices. Experiments were conducted on binary polymer-plasticiser mixtures containing 17 wt.% plasticiser, and on a model hydrophilic matrix formulation. A selection of common plasticisers, propylene glycol (PG) glycerol (GLY), dibutyl sebacate (DBS) and triacetin (TRI), were chosen to provide a range of plasticisation efficiencies. T(g) values of binary mixtures determined by Dynamic Mechanical Thermal Analysis (DMTA) were in rank order PG>GLY>DBS>TRI>unplasticised HPMC. Mean yield pressure, strain rate sensitivity (SRS) and plastic compaction energy were measured during the compression process, and matrix properties were monitored by tensile strength and axial expansion post-compression. Compression of HPMC:PG binary mixtures resulted in a marked reduction in mean yield pressure and a significant increase in SRS, suggesting a classical plasticisation of HPMC analogous to that produced by water. The effect of PG was also reflected in matrix properties. At compression pressures below 70 MPa, compacts had greater tensile strength than those from native polymer, and over the range 35 and 70 MPa, lower plastic compaction values showed that less energy was required to produce the compacts. Axial expansion was also reduced. Above 70 MPa tensile strength was limited to 3 MPa. These results suggest a useful improvement of HPMC compaction and matrix properties by PG plasticisation, with lowering of T(g) resulting in improved deformation and internal bonding. These effects were also detectable in the model formulation containing a minimal polymer content for an HPMC matrix. Other plasticisers were largely ineffective, matrix strength was poor and axial expansion high. The hydrophobic plasticisers (DBS, TRI) reduced yield pressure substantially, but were poor plasticisers and showed compaction mechanisms that could be attributed to phase separation. The effect of different plasticisers suggests that the deformation characteristics of this HPMC in the solid state is dominated by hydroxyl mediated bonding, rather than by hydrophobic interactions between methoxyl-rich regions.

E-Beam Processing of Polymer Matrix Composites for Multifunctional Radiation Shielding

NASA Technical Reports Server (NTRS)

Hou, Tan-Hung; Wilson, John W.; Jensen, Brian J.; Thibeault, Sheila A.; Chang, Chie K.; Kiefer, Richard L.

2005-01-01

Aliphatic polymers were identified as optimum radiation shielding polymeric materials for building multifunctional structural elements for in-space habitats. Conceptual damage tolerant configurations of polyolefins have been proposed, but many manufacturing issues relied on methods and materials which have sub-optimal radiation shielding characteristics (for example, epoxy matrix and adhesives). In the present approach, we shall investigate e-beam processing technologies for inclusion of high-strength aliphatic polymer reinforcement structures into a highly cross-linked polyolefin matrix. This paper reports the baseline thermo-mechanical properties of low density polyethylene and highly crystallized polyethylene.

New Textile Sensors for In Situ Structural Health Monitoring of Textile Reinforced Thermoplastic Composites Based on the Conductive Poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) Polymer Complex

PubMed Central

Jerkovic, Ivona; Koncar, Vladan; Grancaric, Ana Marija

2017-01-01

Many metallic structural and non-structural parts used in the transportation industry can be replaced by textile-reinforced composites. Composites made from a polymeric matrix and fibrous reinforcement have been increasingly studied during the last decade. On the other hand, the fast development of smart textile structures seems to be a very promising solution for in situ structural health monitoring of composite parts. In order to optimize composites’ quality and their lifetime all the production steps have to be monitored in real time. Textile sensors embedded in the composite reinforcement and having the same mechanical properties as the yarns used to make the reinforcement exhibit actuating and sensing capabilities. This paper presents a new generation of textile fibrous sensors based on the conductive polymer complex poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) developed by an original roll to roll coating method. Conductive coating for yarn treatment was defined according to the preliminary study of percolation threshold of this polymer complex. The percolation threshold determination was based on conductive dry films’ electrical properties analysis, in order to develop highly sensitive sensors. A novel laboratory equipment was designed and produced for yarn coating to ensure effective and equally distributed coating of electroconductive polymer without distortion of textile properties. The electromechanical properties of the textile fibrous sensors confirmed their suitability for in situ structural damages detection of textile reinforced thermoplastic composites in real time. PMID:28994733

New Textile Sensors for In Situ Structural Health Monitoring of Textile Reinforced Thermoplastic Composites Based on the Conductive Poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) Polymer Complex.

PubMed

Jerkovic, Ivona; Koncar, Vladan; Grancaric, Ana Marija

2017-10-10

Many metallic structural and non-structural parts used in the transportation industry can be replaced by textile-reinforced composites. Composites made from a polymeric matrix and fibrous reinforcement have been increasingly studied during the last decade. On the other hand, the fast development of smart textile structures seems to be a very promising solution for in situ structural health monitoring of composite parts. In order to optimize composites' quality and their lifetime all the production steps have to be monitored in real time. Textile sensors embedded in the composite reinforcement and having the same mechanical properties as the yarns used to make the reinforcement exhibit actuating and sensing capabilities. This paper presents a new generation of textile fibrous sensors based on the conductive polymer complex poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) developed by an original roll to roll coating method. Conductive coating for yarn treatment was defined according to the preliminary study of percolation threshold of this polymer complex. The percolation threshold determination was based on conductive dry films' electrical properties analysis, in order to develop highly sensitive sensors. A novel laboratory equipment was designed and produced for yarn coating to ensure effective and equally distributed coating of electroconductive polymer without distortion of textile properties. The electromechanical properties of the textile fibrous sensors confirmed their suitability for in situ structural damages detection of textile reinforced thermoplastic composites in real time.

Crazing of nanocomposites with polymer-tethered nanoparticles

DOE PAGES

Meng, Dong; Kumar, Sanat K.; Ge, Ting; ...

2016-09-07

The crazing behavior of polymer nanocomposites formed by blending polymer grafted nanoparticles with an entangled polymer melt is studied by molecular dynamics simulations. We focus on the three key differences in the crazing behavior of a composite relative to the pure homopolymer matrix, namely, a lower yield stress, a smaller extension ratio, and a grafted chain length dependent failure stress. The yield behavior is found to be mostly controlled by the local nanoparticle-grafted polymer interfacial energy, with the grafted polymer-polymer matrix interfacial structure being of little to no relevance. Increasing the attraction between nanoparticle core and the grafted polymer inhibitsmore » void nucleation and leads to a higher yield stress. In the craze growth regime, the presence of “grafted chain” sections of ≈100 monomers alters the mechanical response of composite samples, giving rise to smaller extension ratios and higher drawing stresses than for the homopolymer matrix. As a result, the dominant failure mechanism of composite samples depends strongly on the length of the grafted chains, with disentanglement being the dominant mechanism for short chains, while bond breaking is the failure mode for chain lengths >10N e, where N e is the entanglement length.« less

Predictions of the electro-mechanical response of conductive CNT-polymer composites

NASA Astrophysics Data System (ADS)

Matos, Miguel A. S.; Tagarielli, Vito L.; Baiz-Villafranca, Pedro M.; Pinho, Silvestre T.

2018-05-01

We present finite element simulations to predict the conductivity, elastic response and strain-sensing capability of conductive composites comprising a polymeric matrix and carbon nanotubes. Realistic representative volume elements (RVE) of the microstructure are generated and both constituents are modelled as linear elastic solids, with resistivity independent of strain; the electrical contact between nanotubes is represented by a new element which accounts for quantum tunnelling effects and captures the sensitivity of conductivity to separation. Monte Carlo simulations are conducted and the sensitivity of the predictions to RVE size is explored. Predictions of modulus and conductivity are found in good agreement with published results. The strain-sensing capability of the material is explored for multiaxial strain states.

Selenium containing conducting polymer based pyranose oxidase biosensor for glucose detection.

PubMed

Gokoglan, Tugba Ceren; Soylemez, Saniye; Kesik, Melis; Toksabay, Sinem; Toppare, Levent

2015-04-01

A novel amperometric pyranose oxidase (PyOx) biosensor based on a selenium containing conducting polymer has been developed for the glucose detection. For this purpose, a conducting polymer; poly(4,7-bis(thieno[3,2-b]thiophen-2-yl)benzo[c][1,2,5] selenadiazole) (poly(BSeTT)) was synthesized via electropolymerisation on gold electrode to examine its matrix property for glucose detection. For this purpose, PyOx was used as the model enzyme and immobilised via physical adsorption technique. Amperometric detection of consumed oxygen was monitored at -0.7 V vs Ag reference electrode in a phosphate buffer (50 mM, pH 7.0). K(M)(app), Imax, LOD and sensitivity were calculated as 0.229 mM, 42.37 nA, 3.3 × 10(-4)nM and 6.4 nA/mM cm(2), respectively. Scanning electron microscopy (SEM), Electrochemical Impedance Spectroscopy (EIS) and cyclic voltammetry (CV) techniques were used to monitor changes in surface morphologies and to run electrochemical characterisations. Finally, the constructed biosensor was applied for the determination of glucose in beverages successfully. Copyright © 2014 Elsevier Ltd. All rights reserved.

Modification of polylactide bioplastic using hyperbranched polymer based nanostructures

NASA Astrophysics Data System (ADS)

Bhardwaj, Rahul

Polylactide (PLA) is the most well known renewable resource based biodegradable polymer. The inherent brittleness and poor processability of PLA pose considerable technical challenges and limit its range of commercial applications. The broad objective of this research was to investigate novel pathways for polylactide modification to enhance its mechanical and rheological properties. The focus of this work was to tailor the architecture of a dendritic hyperbranched polymer (HBP) and study its influence on the mechanical and rheological properties of PLA bioplastic. The hyperbranched polymers under consideration are biodegradable aliphatic hydroxyl-functional hyperbranched polyesters having nanoscale dimensions, unique physical properties and high peripheral functionalities. This work relates to identifying a new and industrially relevant research methodology to develop PLA based nanoblends having outstanding stiffness-toughness balance. In this approach, a hydroxyl functional hyperbranched polymer was crosslinked in-situ with a polyanhydride (PA) in the PLA matrix during melt processing, leading to the generation of new nanoscale hyperbranched polymer based domains in the PLA matrix. Transmission electron microscopy and atomic force microscopy revealed the "sea-island" morphology of PLA-crosslinked HBP blends. The domain size of a large portion of the crosslinked HBP particles in PLA matrix was less than 100 nm. The presence of crosslinked hyperbranched polymers exhibited more than 500% and 800% improvement in the tensile toughness and elongation at break values of PLA, respectively, with a minimal sacrifice of tensile strength and modulus as compared to unmodified PLA. The toughening mechanism of PLA in the presence of crosslinked HBP particles was comprised of shear yielding and crazing. The volume fraction of crosslinked HBP particles and matrix ligament thickness (inter-particle distance) were found to be the critical parameters for the toughening of PLA. The maximum average matrix ligament thickness was 114 nm for a toughened polylactide nanoblend and correlated well with the theoretical prediction of the matrix ligament thickness. Fourier transform infrared spectroscopy and dynamic mechanical thermal analysis proved the crosslinking of the HBP phase in the PLA matrix. The crosslinked HBP was effective at hydroxyl (-OH) to anhydride molar ratios of: 2:1, 1:1 or 1:2. The glass transition temperature values of the crosslinked HBP phase at these molar ratios were observed to deviate from the predictions made by the Fox equation. The hydrophilic nature of the hyperbranched polymer was altered to hydrophobic by incorporation of polyanhydride crosslinker, as demonstrated by the increase in the contact angle with water. Rheological studies showed that there was a network formation in the PLA matrix after in-situ crosslinking of HBP. The HBP was found to reduce the melt viscosity of PLA dramatically and this effect was maintained even after its in-situ crosslinking in the PLA matrix. Finally, the current research unwraps the new opportunities provided by the unique physical and chemical properties of highly functional hyperbranched polymers in generating new nanostructured multiphase polymer systems with enhanced properties.

Electrical conductivity of nanocomposites based on carbon nanotubes: a 3D multiscale modeling approach

NASA Astrophysics Data System (ADS)

Grabowski, Krzysztof; Zbyrad, Paulina; Staszewski, Wieslaw J.; Uhl, Tadeusz; Wiatr, Kazimierz; Packo, Pawel

2016-04-01

Remarkable electrical properties of carbon nanotubes (CNT) have lead to increased interest in studying CNT- based devices. Many of current researches are devoted to using all kinds of carbon nanomaterials in the con- struction of sensory elements. One of the most common applications is the development of high performance, large scale sensors. Due to the remarkable conductivity of CNT's such devices represent very high sensitivity. However, there are no sufficient tools for studying and designing such sensors. The main objective of this paper is to develop and validate a multiscale numerical model for a carbon nanotubes based sensor. The device utilises the change of electrical conductivity of a nanocomposite material under applied deformation. The nanocomposite consists of a number of CNTs dispersed in polymer matrix. The paper is devoted to the analysis of the impact of spatial distribution of carbon nanotubes in polymer matrix on electrical conductivity of the sensor. One of key elements is also to examine the impact of strain on electric charge ow in such anisotropic composite structures. In the following work a multiscale electro-mechanical model for CNT - based nanocomposites is proposed. The model comprises of two length scales, namely the meso- and the macro-scale for mechanical and electrical domains. The approach allows for evaluation of macro-scale mechanical response of a strain sensor. Electrical properties of polymeric material with certain CNT fractions were derived considering electrical properties of CNTs, their contact and the tunnelling effect.

Strain Rate Dependent Deformation and Strength Modeling of a Polymer Matrix Composite Utilizing a Micromechanics Approach. Degree awarded by Cincinnati Univ.

NASA Technical Reports Server (NTRS)

Goldberg, Robert K.

1999-01-01

Potential gas turbine applications will expose polymer matrix composites to very high strain rate loading conditions, requiring an ability to understand and predict the material behavior under extreme conditions. Specifically, analytical methods designed for these applications must have the capability of properly capturing the strain rate sensitivities and nonlinearities that are present in the material response. The Ramaswamy-Stouffer constitutive equations, originally developed to analyze the viscoplastic deformation of metals, have been modified to simulate the nonlinear deformation response of ductile, crystalline polymers. The constitutive model is characterized and correlated for two representative ductile polymers. Fiberite 977-2 and PEEK, and the computed results correlate well with experimental values. The polymer constitutive equations are implemented in a mechanics of materials based composite micromechanics model to predict the nonlinear, rate dependent deformation response of a composite ply. Uniform stress and uniform strain assumptions are applied to compute the effective stresses of a composite unit cell from the applied strains. The micromechanics equations are successfully verified for two polymer matrix composites. IM7/977-2 and AS4/PEEK. The ultimate strength of a composite ply is predicted with the Hashin failure criteria that were implemented in the composite micromechanics model. The failure stresses of the two composite material systems are accurately predicted for a variety of fiber orientations and strain rates. The composite deformation model is implemented in LS-DYNA, a commercially available transient dynamic explicit finite element code. The matrix constitutive equations are converted into an incremental form, and the model is implemented into LS-DYNA through the use of a user defined material subroutine. The deformation response of a bulk polymer and a polymer matrix composite are predicted by finite element analyses. The results compare reasonably well to experimental values, with some discrepancies. The discrepancies are at least partially caused by the method used to integrate the rate equations in the polymer constitutive model.

In-situ poling and structurization of piezoelectric particulate composites.

PubMed

Khanbareh, H; van der Zwaag, S; Groen, W A

2017-11-01

Composites of lead zirconate titanate particles in an epoxy matrix are prepared in the form of 0-3 and quasi 1-3 with different ceramic volume contents from 10% to 50%. Two different processing routes are tested. Firstly a conventional dielectrophoretic structuring is used to induce a chain-like particle configuration, followed by curing the matrix and poling at a high temperature and under a high voltage. Secondly a simultaneous combination of dielectrophoresis and poling is applied at room temperature while the polymer is in the liquid state followed by subsequent curing. This new processing route is practiced in an uncured thermoset system while the polymer matrix still possess a relatively high electrical conductivity. Composites with different degrees of alignment are produced by altering the magnitude of the applied electric field. A significant improvement in piezoelectric properties of quasi 1-3 composites can be achieved by a combination of dielectrophoretic alignment of the ceramic particles and poling process. It has been observed that the degree of structuring as well as the functional properties of the in-situ structured and poled composites enhance significantly compared to those of the conventionally manufactured structured composites. Improving the alignment quality enhances the piezoelectric properties of the particulate composites.

Multiple Interfacial Fe3O4@BaTiO3/P(VDF-HFP) Core-Shell-Matrix Films with Internal Barrier Layer Capacitor (IBLC) Effects and High Energy Storage Density.

PubMed

Zhou, Ling; Fu, Qiuyun; Xue, Fei; Tang, Xiahui; Zhou, Dongxiang; Tian, Yahui; Wang, Geng; Wang, Chaohong; Gou, Haibo; Xu, Lei

2017-11-22

Flexible nanocomposites composed of high dielectric constant fillers and polymer matrix have shown great potential for electrostatic capacitors and energy storage applications. To obtain the composited material with high dielectric constant and high breakdown strength, multi-interfacial composited particles, which composed of conductive cores and insulating shells and possessed the internal barrier layer capacitor (IBLC) effect, were adopted as fillers. Thus, Fe 3 O 4 @BaTiO 3 core-shell particles were prepared and loaded into the poly(vinylidene fluoride-co-hexafluoropropylene) (P(VDF-HFP)) polymer matrix. As the mass fraction of core-shell fillers increased from 2.5 wt % to 30 wt %, the dielectric constant of the films increased, while the loss tangent remained at a low level (<0.05 at 1 kHz). Both high electric displacement and high electric breakdown strength were achieved in the films with 10 wt % core-shell fillers loaded. The maximum energy storage density of 7.018 J/cm 3 was measured at 2350 kV/cm, which shows significant enhancement than those of the pure P(VDF-HFP) films and analogous composited films with converse insulating-conductive core-shell fillers. A Maxwell-Wagner capacitor model was also adopted to interpret the efficiency of IBLC effects on the suppressed loss tangent and the superior breakdown strength. This work explored an effective approach to prepare dielectric nanocomposites for energy storage applications experimentally and theoretically.

Multifunctional Nanostructured Conductive Polymer Gels: Synthesis, Properties, and Applications

DOE PAGES

Zhao, Fei; Shi, Ye; Pan, Lijia; ...

2017-06-26

Conductive polymers have attracted significant interest over the past few decades because they synergize the advantageous features of conventional polymeric materials and organic conductors. With rationally designed nanostructures, conductive polymers can further exhibit exceptional mechanical, electrical, and optical properties because of their confined dimensions at the nanoscale level. Among various nanostructured conductive polymers, conductive polymer gels (CPGs) with synthetically tunable hierarchical 3D network structures show great potential for a wide range of applications, such as bioelectronics, and energy storage/conversion devices owing to their structural features. CPGs retain the properties of nanosized conductive polymers during the assembly of the nanobuilding blocksmore » into a monolithic macroscopic structure while generating structure-derived features from the highly cross-linked network. In this Account, we review our recent progress on the synthesis, properties, and novel applications of dopant cross-linked CPGs. We first describe the synthetic strategies, in which molecules with multiple functional groups are adopted as cross-linkers to cross-link conductive polymer chains into a 3D molecular network. These cross-linking molecules also act as dopants to improve the electrical conductivity of the gel network. The microstructure and physical/chemical properties of CPGs can be tuned by controlling the synthetic conditions such as species of monomers and cross-linkers, reaction temperature, and solvents. By incorporating other functional polymers or particles into the CPG matrix, hybrid gels have been synthesized with tailored structures. These hybrid gel materials retain the functionalities from each component, as well as enable synergic effects to improve mechanical and electrical properties of CPGs. We then introduce the unique structure-derived properties of the CPGs. The network facilitates both electronic and ionic transport owing to the continuous pathways for electrons and hierarchical pores for ion diffusion. CPGs also provide high surface area and solvent compatibility, similar to natural gels. With these improved properties, CPGs have been explored to enable novel conceptual devices in diverse applications from smart electronics and ultrasensitive biosensors, to energy storage and conversion devices. CPGs have also been adopted for developing hybrid materials with multifunctionalities, such as stimuli responsiveness, self-healing properties, and super-repellency to liquid. With synthetically tunable physical/chemical properties, CPGs emerge as a unique material platform to develop novel multifunctional materials that have the potential to impact electronics, energy, and environmental technologies. Our hope is that this Account promotes further efforts toward synthetic control, fundamental investigation, and application exploration of CPGs.« less

Multifunctional Nanostructured Conductive Polymer Gels: Synthesis, Properties, and Applications

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhao, Fei; Shi, Ye; Pan, Lijia

Conductive polymers have attracted significant interest over the past few decades because they synergize the advantageous features of conventional polymeric materials and organic conductors. With rationally designed nanostructures, conductive polymers can further exhibit exceptional mechanical, electrical, and optical properties because of their confined dimensions at the nanoscale level. Among various nanostructured conductive polymers, conductive polymer gels (CPGs) with synthetically tunable hierarchical 3D network structures show great potential for a wide range of applications, such as bioelectronics, and energy storage/conversion devices owing to their structural features. CPGs retain the properties of nanosized conductive polymers during the assembly of the nanobuilding blocksmore » into a monolithic macroscopic structure while generating structure-derived features from the highly cross-linked network. In this Account, we review our recent progress on the synthesis, properties, and novel applications of dopant cross-linked CPGs. We first describe the synthetic strategies, in which molecules with multiple functional groups are adopted as cross-linkers to cross-link conductive polymer chains into a 3D molecular network. These cross-linking molecules also act as dopants to improve the electrical conductivity of the gel network. The microstructure and physical/chemical properties of CPGs can be tuned by controlling the synthetic conditions such as species of monomers and cross-linkers, reaction temperature, and solvents. By incorporating other functional polymers or particles into the CPG matrix, hybrid gels have been synthesized with tailored structures. These hybrid gel materials retain the functionalities from each component, as well as enable synergic effects to improve mechanical and electrical properties of CPGs. We then introduce the unique structure-derived properties of the CPGs. The network facilitates both electronic and ionic transport owing to the continuous pathways for electrons and hierarchical pores for ion diffusion. CPGs also provide high surface area and solvent compatibility, similar to natural gels. With these improved properties, CPGs have been explored to enable novel conceptual devices in diverse applications from smart electronics and ultrasensitive biosensors, to energy storage and conversion devices. CPGs have also been adopted for developing hybrid materials with multifunctionalities, such as stimuli responsiveness, self-healing properties, and super-repellency to liquid. With synthetically tunable physical/chemical properties, CPGs emerge as a unique material platform to develop novel multifunctional materials that have the potential to impact electronics, energy, and environmental technologies. Our hope is that this Account promotes further efforts toward synthetic control, fundamental investigation, and application exploration of CPGs.« less

Multifunctional Nanostructured Conductive Polymer Gels: Synthesis, Properties, and Applications.

PubMed

Zhao, Fei; Shi, Ye; Pan, Lijia; Yu, Guihua

2017-07-18

Conductive polymers have attracted significant interest over the past few decades because they synergize the advantageous features of conventional polymeric materials and organic conductors. With rationally designed nanostructures, conductive polymers can further exhibit exceptional mechanical, electrical, and optical properties because of their confined dimensions at the nanoscale level. Among various nanostructured conductive polymers, conductive polymer gels (CPGs) with synthetically tunable hierarchical 3D network structures show great potential for a wide range of applications, such as bioelectronics, and energy storage/conversion devices owing to their structural features. CPGs retain the properties of nanosized conductive polymers during the assembly of the nanobuilding blocks into a monolithic macroscopic structure while generating structure-derived features from the highly cross-linked network. In this Account, we review our recent progress on the synthesis, properties, and novel applications of dopant cross-linked CPGs. We first describe the synthetic strategies, in which molecules with multiple functional groups are adopted as cross-linkers to cross-link conductive polymer chains into a 3D molecular network. These cross-linking molecules also act as dopants to improve the electrical conductivity of the gel network. The microstructure and physical/chemical properties of CPGs can be tuned by controlling the synthetic conditions such as species of monomers and cross-linkers, reaction temperature, and solvents. By incorporating other functional polymers or particles into the CPG matrix, hybrid gels have been synthesized with tailored structures. These hybrid gel materials retain the functionalities from each component, as well as enable synergic effects to improve mechanical and electrical properties of CPGs. We then introduce the unique structure-derived properties of the CPGs. The network facilitates both electronic and ionic transport owing to the continuous pathways for electrons and hierarchical pores for ion diffusion. CPGs also provide high surface area and solvent compatibility, similar to natural gels. With these improved properties, CPGs have been explored to enable novel conceptual devices in diverse applications from smart electronics and ultrasensitive biosensors, to energy storage and conversion devices. CPGs have also been adopted for developing hybrid materials with multifunctionalities, such as stimuli responsiveness, self-healing properties, and super-repellency to liquid. With synthetically tunable physical/chemical properties, CPGs emerge as a unique material platform to develop novel multifunctional materials that have the potential to impact electronics, energy, and environmental technologies. We hope that this Account promotes further efforts toward synthetic control, fundamental investigation, and application exploration of CPGs.

Improved conductivity of carbon-nano-fiber (CNF)/polytetrafluoroethylene (PTFE) composite

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chandra, Sarita; Kalra, G. S.; Pushkar, Vinay K.

2016-05-23

A series of CNF/PTFE composite loaded with different weight % of CNFs as 0.01, 0.02, 0.03, 0.05, 1, 2, 3, 4, 5 into PTFE is fabricated. In this work, the 5wt% heat-treated CNFs were used as filler in PTFE. Current-voltage (I-V) study of the samples confirmed the samples as conducting composite. In scanning electron microscope (SEM) study, the conducting CNFs channels were observed from upper surface to inside throughout the polymer matrix. A sintered composite of 5 wt% loading of CNFs showed an improved conductivity and SEM image exhibited a good binding of CNFs into PTFE.

Thermo-Mechanical Fatigue of Polymer Matrix Composites

DTIC Science & Technology

1994-10-01

MATRIX COMPOSITES by L. H. Strait . - , 4- . [ : ’ . .. N ..::ii Technical Report No. TR 94-12 October 1994 94 11 3 002 Supported by: L.R. Hettche...mnechanical loading is an increasingly common service condition for polymer mnmx composite materials. Unfortunately, little or no information is available...regarding the behavior of polymer composites subject to this loading condition. The present thesis research program was undertaken to evaluate the effects

Effects of added surfactant on swelling and molecular transport in drug-loaded tablets based on hydrophobically modified poly(acrylic acid).

PubMed

Knöös, Patrik; Wahlgren, Marie; Topgaard, Daniel; Ulvenlund, Stefan; Piculell, Lennart

2014-08-14

A combination of NMR chemical shift imaging and self-diffusion experiments is shown to give a detailed molecular picture of the events that occur when tablets of hydrophobically modified poly(acrylic acid) loaded with a drug (griseofulvin) swell in water in the presence or absence of surfactant (sodium octylbenzenesulfonate). The hydrophobic substituents on the polymer bind and trap the surfactant molecules in mixed micelles, leading to a slow effective surfactant transport that occurs via a small fraction of individually dissolved surfactant molecules in the water domain. Because of the efficient binding of surfactant, the penetrating water is found to diffuse past the penetrating surfactant into the polymer matrix, pushing the surfactant front outward as the matrix swells. The added surfactant has little effect on the transport of drug because both undissolved solid drug and surfactant-solubilized drug function as reservoirs that essentially follow the polymer as it swells. However, the added surfactant nevertheless has a strong indirect effect on the release of griseofulvin, through the effect of the surfactant on the solubility and erosion of the polymer matrix. The surfactant effectively solubilizes the hydrophobically modified polymer, making it fully miscible with water, leading to a more pronounced swelling and a slower erosion of the polymer matrix.

Anisotropic thermal property of magnetically oriented carbon nanotube polymer composites

NASA Astrophysics Data System (ADS)

Li, Bin; Dong, Shuai; Wang, Caiping; Wang, Xiaojie; Fang, Jun

2016-04-01

This paper proposes a method for preparing multi-walled carbon nanotubea/polydimethylsiloxane (MWCNTs/PDMS) composites with enhanced thermal properties by using a high magnetic field (up to 10T). The MWCNT are oriented magnetically inside a silicone by in-situ polymerization method. The anisotropic structure would be expected to produce directional thermal conductivity. This study will provide a new approach to the development of anisotropic thermal-conductive polymer composites. Systematic studies with the preparation of silicone/graphene composites corresponding to their thermal and mechanical properties are carried out under various conditions: intensity of magnetic field, time, temperature, fillings. The effect of MWCNT/graphene content and preparation procedures on thermal conductivity of composites is investigated. Dynamic mechanical analysis (DMA) is used to reveal the mechanical properties of the composites in terms of the filling contents and magnetic field strength. The scanning electron microscope (SEM) is used to observe the micro-structure of the MWCNT composites. The alignment of MWCNTs in PDMS matrix is also studied by Raman spectroscopy. The thermal conductivity measurements show that the magnetically aligned CNT-composites feature high anisotropy in thermal conductivity.

Novel Biocatalytic Platform for Ethanol Production from Lignocellulosic Feedstock

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chen, Chyi-Shin; Tachea, Firehiwot; Brown, Sarah

2017-01-23

The goals of the CRADA were achieved by illustrating the scalability of immobilized yeast technology, demonstrating lignocellulosic feedstock consumption by the immobilized cells, and confirming Microvi’s proprietary polymer matrix ethanol toxicity tolerance. We conducted fermentations at 2L and 300L scales. For carbon source, we performed pretreatment and saccharification at 100L scale to produce lignocellulosic sugars with glucose and xylose.

Quantifying Non-Equilibrium in Hypersonic Flows Using Entropy Generation

DTIC Science & Technology

2007-03-01

mirror fabrication, 2) mirror actuation, and 3) control algorithms with a focus on potential for future space based applications. For a...electrodes transported via a conducting electrolyte [19]. When placed under a voltage potential , cations in a polymer matrix immediately swell...has the potential to create an over- damped surface preventing Wavescope from detecting any strains. The final step in the mirror fabrication is to

Effects of Adiabatic Heating on the High Strain Rate Deformation of Polymer Matrix Composites

NASA Technical Reports Server (NTRS)

Sorini, Chris; Chattopadhyay, Aditi; Goldberg, Robert K.

2017-01-01

Polymer matrix composites (PMCs) are increasingly being used in aerospace structures that are expected to experience complex dynamic loading conditions throughout their lifetime. As such, a detailed understanding of the high strain rate behavior of the constituents, particularly the strain rate, temperature, and pressure dependent polymer matrix, is paramount. In this paper, preliminary efforts in modeling experimentally observed temperature rises due to plastic deformation in PMCs subjected to dynamic loading are presented. To this end, an existing isothermal viscoplastic polymer constitutive formulation is extended to model adiabatic conditions by incorporating temperature dependent elastic properties and modifying the components of the inelastic strain rate tensor to explicitly depend on temperature. It is demonstrated that the modified polymer constitutive model is capable of capturing strain rate and temperature dependent yield as well as thermal softening associated with the conversion of plastic work to heat at high rates of strain. The modified constitutive model is then embedded within a strength of materials based micromechanics framework to investigate the manifestation of matrix thermal softening, due to the conversion of plastic work to heat, on the high strain rate response of a T700Epon 862 (T700E862) unidirectional composite. Adiabatic model predictions for high strain rate composite longitudinal tensile, transverse tensile, and in-plane shear loading are presented. Results show a substantial deviation from isothermal conditions; significant thermal softening is observed for matrix dominated deformation modes (transverse tension and in-plane shear), highlighting the importance of accounting for the conversion of plastic work to heat in the polymer matrix in the high strain rate analysis of PMC structures.

Synthesis and morphology of hydroxyapatite/polyethylene oxide nanocomposites with block copolymer compatibilized interfaces

NASA Astrophysics Data System (ADS)

Lee, Ji Hoon; Shofner, Meisha

2012-02-01

In order to exploit the promise of polymer nanocomposites, special consideration should be given to component interfaces during synthesis and processing. Previous results from this group have shown that nanoparticles clustered into larger structures consistent with their native shape when the polymer matrix crystallinity was high. Therefore in this research, the nanoparticles are disguised from a highly-crystalline polymer matrix by cloaking them with a matrix-compatible block copolymer. Specifically, spherical and needle-shaped hydroxyapatite nanoparticles were synthesized using a block copolymer templating method. The block copolymer used, polyethylene oxide-b-polymethacrylic acid, remained on the nanoparticle surface following synthesis with the polyethylene oxide block exposed. These nanoparticles were subsequently added to a polyethylene oxide matrix using solution processing. Characterization of the nanocomposites indicated that the copolymer coating prevented the nanoparticles from assembling into ordered clusters and that the matrix crystallinity was decreased at a nanoparticle spacing of approximately 100 nm.

Influence of Thin-Film Adhesives in Pullout Tests Between Nickel-Titanium Shape Memory Alloy and Carbon Fiber-Reinforced Polymer Matrix Composites

NASA Technical Reports Server (NTRS)

Quade, Derek J.; Jana, Sadhan; McCorkle, Linda S.

2018-01-01

Strips of nickel-titanium (NiTi) shape memory alloy (SMA) and carbon fiber-reinforced polymer matrix composite (PMC) were bonded together using multiple thin film adhesives and their mechanical strengths were evaluated under pullout test configuration. Tensile and lap shear tests were conducted to confirm the deformation of SMAs at room temperature and to evaluate the adhesive strength between the NiTi strips and the PMC. Optical and scanning electron microscopy techniques were used to examine the interfacial bonding after failure. Simple equations on composite tensile elongation were used to fit the experimental data on tensile properties. ABAQUS models were generated to show the effects of enhanced bond strength and the distribution of stress in SMA and PMC. The results revealed that the addition of thin film adhesives increased the average adhesive strength between SMA and PMC while halting the room temperature shape memory effect within the pullout specimen.

A Limited Comparison of the Thermal Durability of Polyimide Candidate Matrix Polymers with PMR-15

NASA Technical Reports Server (NTRS)

Bowles, Kenneth J.; Papadopoulos, Demetrios S.; Scheiman, Daniel A.; Inghram, Linda L.; McCorkle, Linda S.; Klans, Ojars V.

2003-01-01

Studies were conducted with six different candidate high-temperature neat matrix resin specimens of varied geometric shapes to investigate the mechanisms involved in the thermal degradation of polyimides like PMR-15. The metrics for assessing the quality of these candidates were chosen to be glass transition temperature (T(sub g)), thermo-oxidative stability, dynamic mechanical properties, microstructural changes, and dimensional stability. The processing and mechanical properties were not investigated in the study reported herein. The dimensional changes and surface layer growth were measured and recorded. The data were in agreement with earlier published data. An initial weight increase reaction was observed to be dominating at the lower temperatures. However, at the more elevated temperatures, the weight loss reactions were prevalent and probably masked the weight gain reaction. These data confirmed the findings of the existence of an initial weight gain reaction previously reported. Surface- and core-dependent weight losses were shown to control the polymer degradation at the higher temperatures.

Electrochemically triggered release of acetylcholine from scCO2 impregnated conductive polymer films evokes intracellular Ca2+ signaling in neurotypic SH-SY5Y cells.

PubMed

Löffler, Susanne; Seyock, Silke; Nybom, Rolf; Jacobson, Gunilla B; Richter-Dahlfors, Agneta

2016-12-10

Implantable devices for electronically triggered drug release are attractive to achieve spatial and temporal control over drug concentrations in patients. Realization of such devices is, however, associated with technical and biological challenges. Among these are containment of drug reservoirs, lack of precise control cues, as well as the charge and size of the drug. Here, we present a method for electronically triggered release of the quaternary ammonium cation acetylcholine (ACh) from an impregnated conductive polymer film. Using supercritical carbon dioxide (scCO 2 ), a film of PEDOT/PSS (poly(3,4)-ethylenedioxythiophene doped with poly(styrenesulfonate)) is impregnated with the neurotransmitter acetylcholine. The gentle scCO 2 process generated a dry, drug-impregnated surface, well suited for interaction with biological material, while maintaining normal electrochemical properties of the polymer. Electrochemical switching of impregnated PEDOT/PSS films stimulated release of ACh from the polymer matrix, likely due to swelling mediated by the influx and efflux of charged and solvated ions. Triggered release of ACh did not affect the biological activity of the drug. This was shown by real-time monitoring of intracellular Ca 2+ signaling in neurotypic cells growing on the impregnated polymer surface. Collectively, scCO 2 impregnation of conducting polymers offers the first one-step, dopant-independent drug impregnation process, potentially facilitating loading of both anionic and cationic drugs that can be dissolved in scCO2 on its own or by using a co-solvent. We foresee that scCO 2 -loaded devices for electronically triggered drug release will create novel opportunities when generating active bio-coatings, tunable for specific needs, in a variety of medical settings. Copyright © 2016 Elsevier B.V. All rights reserved.

Studies of fiber-matrix adhesion on compression strength

NASA Technical Reports Server (NTRS)

Bascom, Willard D.; Nairn, John A.; Boll, D. J.

1991-01-01

A study was initiated on the effect of the matrix polymer and the fiber matrix bond strength of carbon fiber polymer matrix composites. The work includes tests with micro-composites, single ply composites, laminates, and multi-axial loaded cylinders. The results obtained thus far indicate that weak fiber-matrix adhesion dramatically reduces 0 degree compression strength. Evidence is also presented that the flaws in the carbon fiber that govern compression strength differ from those that determine fiber tensile strength. Examination of post-failure damage in the single ply tests indicates kink banding at the crack tip.

Influence of matching solubility parameter of polymer matrix and CNT on electrical conductivity of CNT/rubber composite

PubMed Central

Ata, Seisuke; Mizuno, Takaaki; Nishizawa, Ayumi; Subramaniam, Chandramouli; Futaba, Don N.; Hata, Kenji

2014-01-01

We report a general approach to fabricate elastomeric composites possessing high electrical conductivity for applications ranging from wireless charging interfaces to stretchable electronics. By using arbitrary nine kinds of rubbers as matrices, we experimentally demonstrate that the matching the solubility parameter of CNTs and the rubber matrix is important to achieve higher electrical conductivity in CNT/rubber composite, resulting in continuous conductive pathways leading to electrical conductivities as high as 15 S/cm with 10 vol% CNT in fluorinated rubber. Further, using thermodynamic considerations, we demonstrate an approach to mix CNTs to arbitrary rubber matrices regardless of solubility parameter of matrices by adding small amounts of fluorinated rubber as a polymeric-compatibilizer of CNTs. We thereby achieved electrical conductivities ranging from 1.2 to 13.8 S/cm (10 vol% CNTs) using nine varieties of rubber matrices differing in chemical structures and physical properties. Finally, we investigated the components of solubility parameter of CNT by using Hansen solubility parameters, these findings may useful for controlling solubility parameter of CNTs. PMID:25434701

Ionic cross-linked polyether and silica gel mixed matrix membranes for CO 2 separation from flue gas

DOE PAGES

Sekizkardes, Ali K.; Zhou, Xu; Nulwala, Hunaid B.; ...

2017-09-22

Mixed matrix membranes (MMMs) were prepared by incorporating 10 wt%, 20 wt% and 30 wt% silica gel filler particles into novel ionic cross-linked polyether (IXPE) polymers. Porous silica gel has the advantage of high surface area that can increase the free volume and permeability in a polymer film while also being commercially available and low cost. The MMMs featured high chemical and thermal stability as well as a modest improvement in storage modulus. These features are due to the excellent interfacial interaction between silica gel filler particles and the polymer matrix. Increasing the loading of silica gel particles in MMMsmore » resulted in higher permeability up to 120 Barrer for CO 2, which is about 40% higher than the neat polymer matrix. Finally, most importantly, the MMMs maintained a very high CO 2/N 2 selectivity performance of around 41 for all particle loadings that were tested.« less

In Situ Gold Nanoparticle Gradient Formation in a 3D Meso- and Macroporous Polymer Matrix.

PubMed

Penders, Jelle; Rajasekharan, Anand K; Hulander, Mats; Andersson, Martin

2017-08-01

Herein, the development and characterization of a 3D gradient structure of gold nanoparticles is described. The gradient of gold nanoparticles is made in situ in a macroporous nonionic block copolymer hydrogel matrix, through gold ion diffusion control. The polymer provides a matrix for diffusion of gold ions, acts as a template for controlling nanoparticle growth, and facilitates the in situ reduction of gold ions to gold nanoparticles. A clear gradient in gold nanoparticles is observed across the 3D space of the polymer matrix using scanning electron microscopy, fluorescence microscopy, atomic force microscopy, and thermogravimetric analysis. The particle gradient is further functionalized with both hydrophobic and hydrophilic groups via thiol-gold linkage to demonstrate the ability to form gradients with different chemical functionalities. Using additive manufacturing, the polymer can also be printed as a porous network with possible applications for 3D cell culturing in, e.g., biomaterials research. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Approach for achieving flame retardancy while retaining physical properties in a compatible polymer matrix

NASA Technical Reports Server (NTRS)

Williams, Martha K. (Inventor); Smith, Trent M. (Inventor)

2007-01-01

The invention provides polymer blends containing polyhydroxyamide and one or more flammable polymers. The polymer blends are flame retardant and have improved durability and heat stability compared to the flammable polymer portion of the blends. Articles containing the polymer blends are also provided.

Approach for achieving flame retardancy while retaining physical properties in a compatible polymer matrix

NASA Technical Reports Server (NTRS)

Smith, Trent M. (Inventor); Williams, Martha K. (Inventor)

2011-01-01

The invention provides polymer blends containing polyhydroxyamide and one or more flammable polymers. The polymer blends are flame retardant and have improved durability and heat stability compared to the flammable polymer portion of the blends. Articles containing the polymer blends are also provided.

Stereoselectivity in ene reactions with 1O2: matrix effects in polymer supports, photo-oxygenation of organic salts and asymmetric synthesis.

PubMed

Griesbeck, Axel G; Bartoschek, Anna; Neudörfl, Jörg; Miara, Claus

2006-01-01

The ene reaction of chiral allylic alcohols is applied as a tool for the investigation of intrapolymer effects by means of the stereoselectivity of the singlet-oxygen addition. The diastereo selectivity strongly depends on the structure of the polymer, the substrate loading degree and also on the degree of conversion demonstrating additional supramolecular effects evolving during the reaction. The efficiency and the stability of polymer-bound sensitizers were evaluated by the ene reaction of singlet oxygen with citronellol. The ene reaction with chiral ammonium salts of tiglic acid was conducted under solution phase conditions or in polystyrene beads under chiral contact ion-pair conditions. The products thus obtained precipitate during the photoreaction as ammonium salts. Moderate asymmetric induction was observed for this procedure for the first time.

Radiation-grafted fluoropolymers soaked with imidazolium-based ionic liquids for high-performance ionic polymer-metal composite actuators.

PubMed

Lee, Jang Yeol; Wang, Hyuck Sik; Yoon, Bye Ri; Han, Man Jae; Jho, Jae Young

2010-11-01

On purpose to develop a polymer actuator with high stability in air-operation as well as large bending displacement, a series of ionic polymer-metal composites (IPMC) was constructed with poly(styrene sulfonate)-grafted fluoropolymers as ionomeric matrix and immidazolium-based ionic liquids (IL) as inner solvent. The prepared IPMC actuators exhibited greatly enhanced bending displacement compared to Nafion-based actuators. The actuators were stable in air-operation, maintaining initial displacement for up to 10(4) cycles or 24 h. Investigating the material parameters and morphology of the IPMCs, high ion exchange capacity of the ionomers resulted in high ion conductivity and robust electrode of IPMC, which synergistically contributed to the high bending performance. Copyright © 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Mechanical property characterization of polymeric composites reinforced by continuous microfibers

NASA Astrophysics Data System (ADS)

Zubayar, Ali

Innumerable experimental works have been conducted to study the effect of polymerization on the potential properties of the composites. Experimental techniques are employed to understand the effects of various fibers, their volume fractions and matrix properties in polymer composites. However, these experiments require fabrication of various composites which are time consuming and cost prohibitive. Advances in computational micromechanics allow us to study the various polymer based composites by using finite element simulations. The mechanical properties of continuous fiber composite strands are directional. In traditional continuous fiber laminated composites, all fibers lie in the same plane. This provides very desirable increases in the in-plane mechanical properties, but little in the transverse mechanical properties. The effect of different fiber/matrix combinations with various orientations is also available. Overall mechanical properties of different micro continuous fiber reinforced composites with orthogonal geometry are still unavailable in the contemporary research field. In this research, the mechanical properties of advanced polymeric composite reinforced by continuous micro fiber will be characterized based on analytical investigation and FE computational modeling. Initially, we have chosen IM7/PEEK, Carbon Fiber/Nylon 6, and Carbon Fiber/Epoxy as three different case study materials for analysis. To obtain the equivalent properties of the micro-hetero structures, a concept of micro-scale representative volume elements (RVEs) is introduced. Five types of micro scale RVEs (3 square and 2 hexagonal) containing a continuous micro fiber in the polymer matrix were designed. Uniaxial tensile, lateral expansion and transverse shear tests on each RVE were designed and conducted by the finite element computer modeling software ANSYS. The formulae based on elasticity theory were derived for extracting the equivalent mechanical properties (Young's moduli, shear moduli, and Poisson's ratios) from the numerical solutions of the RVEs undergone these three load tests. Validation of the obtained micro-scale mechanical properties will be performed using rule of mixture (ROM), 1st, and 2nd order of the mathematical model and experimental data.

Dry Process for Manufacturing Hybridized Boron Fiber/Carbon Fiber Thermoplastic Composite Materials from a Solution Coated Precursor

NASA Technical Reports Server (NTRS)

Belvin, Harry L. (Inventor); Cano, Roberto J. (Inventor)

2003-01-01

An apparatus for producing a hybrid boron reinforced polymer matrix composite from precursor tape and a linear array of boron fibers. The boron fibers are applied onto the precursor tapes and the precursor tape processed within a processing component having an impregnation bar assembly. After passing through variable-dimension forming nip-rollers, the precursor tape with the boron fibers becomes a hybrid boron reinforced polymer matrix composite. A driving mechanism is used to pulled the precursor tape through the method and a take-up spool is used to collect the formed hybrid boron reinforced polymer matrix composite.

Biocompatibility of Synthetic Poly(ester urethane)/Polyhedral Oligomeric Silsesquioxane Matrices with Embryonic Stem Cell Proliferation and Differentiation

PubMed Central

Guo, Yan-Lin; Wang, Wenshou; Otaigbe, Joshua U.

2010-01-01

Incorporation of polyhedral oligomeric silsesquioxanes (POSS) into poly (ester urethane)s (PEU) as a building block results in a PEU/POSS hybrid polymer with increased mechanical strength and thermostability. An attractive feature of the new polymer is that it forms a porous matrix when cast in the form of a thin film, making it potentially useful in tissue engineering. In this study, we present detailed microscopic analysis of the PEU/POSS matrix and demonstrate its biocompatibility with cell culture. The PEU/POSS polymer forms a continuous porous matrix with open pores and interconnected grooves. From SEM image analysis, it is calculated that there are about 950 pores per mm2 of the matrix area with pore size ranging from 1 to 15 μm in diameter. The area occupied by the pores represents approximately 7.6 % of matrix area. Using mouse embryonic stem cells (ESCs), we demonstrate that the PEU/POSS matrix provides excellent support for cell proliferation and differentiation. Under the cell culture condition optimized to maintain self-renewal, ESCs grown on a PEU/POSS matrix exhibit undifferentiated morphology, express pluripotency markers, and have similar growth rate to cells grown on gelatin. When induced for differentiation, ESCs underwent dramatic morphological change, characterized by the loss of clonogenecity and increased cell size with well-expanded cytoskeleton networks. Differentiated cells are able to form a continuous monolayer that is closely embedded on the matrix. The excellent compatibility between the PEU/POSS matrix and ESC proliferation/differentiation demonstrates the potential of using PEU/POSS polymers in future ESC-based tissue engineering. PMID:20213627

Laminated Object Manufacturing-Based Design Ceramic Matrix Composites

DTIC Science & Technology

2001-04-01

components for DoD applications. Program goals included the development of (1) a new LOM based design methodology for CMC, (2) optimized preceramic polymer ...3.1.1-20 3.1.1-12 Detail of LOM Composites Forming System w/ glass fiber/ polymer laminate................ 3.1.1-21 3.1.1-13...such as polymer matrix composites have faced similar barriers to implementation. These barriers have been overcome through the development of suitable

Use of Li.sub.2[B.sub.12H.sub.12] salt to absorb water into polymers

DOEpatents

Eastwood, Eric A.; Bowen, III, Daniel E.

2016-08-30

Methods of adjusting the properties of a composition are provided. The compositions comprise a polymer-containing matrix and a filler comprising a hygroscopic salt. Preferred such salts comprise a cage compound selected from the group consisting of borane cage compounds, carborane cage compounds, metal complexes thereof, residues thereof, mixtures thereof, and/or agglomerations thereof, where the cage compound is not covalently bound to the matrix polymer.

Properties of coatings on RFID p-Chips that support plasmonic fluorescence enhancement in bioassays

PubMed Central

Rich, Ryan; Li, Ji; Fudala, Rafal; Gryczynski, Zygmunt; Gryczynski, Ignacy; Mandecki, Wlodek

2012-01-01

Microtransponders (RFID p-Chips) derivatized with silver island film (SIF) have previously seen success as a platform for the quantification of low-abundance biomolecules in nucleic acid-based assays and immunoassays. In this study, we further characterized the morphology of the SIF as well as the polymer matrix enveloping it by scanning electron microscopy (SEM). The polymer was a two-layer silane-based matrix engulfing the p-Chip and SIF. Through a series of SEM and confocal fluorescence microscopy experiments we found the depth of the polymer matrix to be 1–2 µm. The radiative effects of the SIF/polymer layer were assessed by fluorescence lifetime imaging (FLIM) of p-Chips coated with the polymer to which a fluorophore (Alexa Fluor 555) was conjugated. FLIM images showed an 8.7-fold increase in fluorescence intensity and an increased rate of radiative decay, the latter of which is associated with improved photostability and both of which are linked to plasmonic enhancement by the SIF. Plasmonic enhancement was found to extend uniformly across the p-Chip and, interestingly, to a depth of about 1.2 µm. The substantial depth of enhancement suggests that the SIF/polymer layer constitutes a three-dimensional matrix that is accessible to solvent and small molecules such as fluorescent dyes. Finally, we confirmed that no surface-enhanced Raman scattering (SERS) is seen from the SIF/polymer combination. The analysis provides a possible mechanism by which the SIF/polymer-coated p-Chips allow a highly sensitive immunoassay and, as a result, leads to an improved bioassay platform. PMID:22960796

One pot electrochemical synthesis of polymer/CNT/metal nanoparticles for fuel cell applications

NASA Astrophysics Data System (ADS)

Ventrapragada, Lakshman; Zhu, Jingyi; Karakaya, Mehmet; Podila, Ramakrishna; Rao, Apparao; Clemson Nanomaterials center Team

Carbon nanotubes (CNTs) have become a key player in the design of materials for energy applications. They gained their popularity in industrial and scientific research due to their unique properties like excellent conductivity, high surface area, etc. Here we used chemical vapor deposition (CVD) to synthesize two types of CNTs namely, helically coiled CNTs and vertically aligned CNTs. These CNTs were subsequently used to make composites with conducting polymers and metal nanoparticles. One pot electrochemical synthesis was designed to electropolymerize aniline, pyrrole etc. on the surface of the electrode with simultaneous deposition of platinum and gold metal nanoparticles, and CNTs in the polymer matrix. The as synthesized composite materials were characterized with scanning electron microscope for surface morphology and spectroscopic techniques like Raman, UV-Vis for functionality. These were used to study electrocatalytic oxidation of methanol and ethanol for alkaline fuel cell applications. Electrodes fabricated from these composites not only showed good kinetics but also exhibited excellent stability. Uniqueness of this composite lies in its simple two step synthesis and it doesn't involve any surfactants unlike conventional chemical synthesis routes.

Material properties of biofilms – key methods for understanding permeability and mechanics

PubMed Central

Billings, Nicole; Birjiniuk, Alona; Samad, Tahoura S.; Doyle, Patrick S.; Ribbeck, Katharina

2015-01-01

Microorganisms can form biofilms, which are multicellular communities surrounded by a hydrated extracellular matrix of polymers. Central properties of the biofilm are governed by this extracellular matrix, which provides mechanical stability to the three-dimensional biofilm structure, regulates the ability of the biofilm to adhere to surfaces, and determines the ability of the biofilm to adsorb gasses, solutes, and foreign cells. Despite their critical relevance for understanding and eliminating of biofilms, the materials properties of the extracellular matrix are understudied. Here, we offer the reader a guide to current technologies that can be utilized to specifically assess the permeability and mechanical properties of the biofilm matrix and its interacting components. In particular, we highlight technological advances in instrumentation and interactions between multiple disciplines that have broadened the spectrum of methods available to conduct these studies. We review pioneering work that furthers our understanding of the material properties of biofilms. PMID:25719969

Material properties of biofilms—a review of methods for understanding permeability and mechanics

NASA Astrophysics Data System (ADS)

Billings, Nicole; Birjiniuk, Alona; Samad, Tahoura S.; Doyle, Patrick S.; Ribbeck, Katharina

2015-02-01

Microorganisms can form biofilms, which are multicellular communities surrounded by a hydrated extracellular matrix of polymers. Central properties of the biofilm are governed by this extracellular matrix, which provides mechanical stability to the 3D biofilm structure, regulates the ability of the biofilm to adhere to surfaces, and determines the ability of the biofilm to adsorb gases, solutes, and foreign cells. Despite their critical relevance for understanding and eliminating of biofilms, the materials properties of the extracellular matrix are understudied. Here, we offer the reader a guide to current technologies that can be utilized to specifically assess the permeability and mechanical properties of the biofilm matrix and its interacting components. In particular, we highlight technological advances in instrumentation and interactions between multiple disciplines that have broadened the spectrum of methods available to conduct these studies. We review pioneering work that furthers our understanding of the material properties of biofilms.

Effects of processing on the release profiles of matrix systems containing 5-aminosalicylic acid.

PubMed

Korbely, Anita; Kelemen, András; Kása, Péter; Pintye-Hódi, Klára

2012-12-01

The aim of this study was to investigate the influence of different processing methods on the profiles of 5-aminosalicylic acid dissolution from controlled-release matrix systems based on Eudragit® RL and Eudragit® RS water-insoluble polymers. The pure polymers and their mixtures were studied as matrix formers using different processing methods, i.e., direct compression, wet granulation of the active ingredient with the addition of polymer(s) to the external phase, wet granulation with water, and wet granulation with aqueous dispersions. In comparison with the directly compressed tablets, tablets made by wet granulation with water demonstrated a 6-19% increase in final drug dissolution, whereas when polymers were applied in the external phase during compression, a 0-13% decrease was observed in the amount of drug released. Wet granulation with aqueous polymer dispersions delayed the release of the drug; this was especially marked (a 54-56% decrease in drug release) in compositions, which contained a high amount of Eudragit RL 30D. The release profiles were mostly described by the Korsmeyer-Peppas model or the Hopfenberg model.

Monitoring Damage Propagation in Glass Fiber Composites Using Carbon Nanofibers.

PubMed

Al-Sabagh, Ahmed; Taha, Eman; Kandil, Usama; Nasr, Gamal-Abdelnaser; Reda Taha, Mahmoud

2016-09-10

In this work, we report the potential use of novel carbon nanofibers (CNFs), dispersed during fabrication of glass fiber composites to monitor damage propagation under static loading. The use of CNFs enables a transformation of the typically non-conductive glass fiber composites into new fiber composites with appreciable electrical conductivity. The percolation limit of CNFs/epoxy nanocomposites was first quantified. The electromechanical responses of glass fiber composites fabricated using CNFs/epoxy nanocomposite were examined under static tension loads. The experimental observations showed a nonlinear change of electrical conductivity of glass fiber composites incorporating CNFs versus the stress level under static load. Microstructural investigations proved the ability of CNFs to alter the polymer matrix and to produce a new polymer nanocomposite with a connected nanofiber network with improved electrical properties and different mechanical properties compared with the neat epoxy. It is concluded that incorporating CNFs during fabrication of glass fiber composites can provide an innovative means of self-sensing that will allow damage propagation to be monitored in glass fiber composites.

Facile and Reliable in Situ Polymerization of Poly(Ethyl Cyanoacrylate)-Based Polymer Electrolytes toward Flexible Lithium Batteries.

PubMed

Cui, Yanyan; Chai, Jingchao; Du, Huiping; Duan, Yulong; Xie, Guangwen; Liu, Zhihong; Cui, Guanglei

2017-03-15

Polycyanoacrylate is a very promising matrix for polymer electrolyte, which possesses advantages of strong binding and high electrochemical stability owing to the functional nitrile groups. Herein, a facile and reliable in situ polymerization strategy of poly(ethyl cyanoacrylate) (PECA) based gel polymer electrolytes (GPE) via a high efficient anionic polymerization was introduced consisting of PECA and 4 M LiClO 4 in carbonate solvents. The in situ polymerized PECA gel polymer electrolyte achieved an excellent ionic conductivity (2.7 × 10 -3 S cm -1 ) at room temperature, and exhibited a considerable electrochemical stability window up to 4.8 V vs Li/Li + . The LiFePO 4 /PECA-GPE/Li and LiNi 1.5 Mn 0.5 O 4 /PECA-GPE/Li batteries using this in-situ-polymerized GPE delivered stable charge/discharge profiles, considerable rate capability, and excellent cycling performance. These results demonstrated this reliable in situ polymerization process is a very promising strategy to prepare high performance polymer electrolytes for flexible thin-film batteries, micropower lithium batteries, and deformable lithium batteries for special purpose.

Surface characterization of LDEF carbon fiber/polymer matrix composites

NASA Technical Reports Server (NTRS)

Grammer, Holly L.; Wightman, James P.; Young, Philip R.; Slemp, Wayne S.

1995-01-01

XPS (x-ray photoelectron spectroscopy) and SEM (scanning electron microscopy) analysis of both carbon fiber/epoxy matrix and carbon fiber/polysulfone matrix composites revealed significant changes in the surface composition as a result of exposure to low-earth orbit. The carbon 1s curve fit XPS analysis in conjunction with the SEM photomicrographs revealed significant erosion of the polymer matrix resins by atomic oxygen to expose the carbon fibers of the composite samples. This erosion effect on the composites was seen after 10 months in orbit and was even more obvious after 69 months.

Improved Dielectric Properties and Energy Storage Density of Poly(vinylidene fluoride-co-hexafluoropropylene) Nanocomposite with Hydantoin Epoxy Resin Coated BaTiO3.

PubMed

Luo, Hang; Zhang, Dou; Jiang, Chao; Yuan, Xi; Chen, Chao; Zhou, Kechao

2015-04-22

Energy storage materials are urgently demanded in modern electric power supply and renewable energy systems. The introduction of inorganic fillers to polymer matrix represents a promising avenue for the development of high energy density storage materials, which combines the high dielectric constant of inorganic fillers with supernal dielectric strength of polymer matrix. However, agglomeration and phase separation of inorganic fillers in the polymer matrix remain the key barriers to promoting the practical applications of the composites for energy storage. Here, we developed a low-cost and environmentally friendly route to modifying BaTiO3 (BT) nanoparticles by a kind of water-soluble hydantoin epoxy resin. The modified BT nanoparticles exhibited homogeneous dispersion in the ferroelectric polymer poly(vinylidene fluoride-co-hexafluoropropylene) (P(VDF-HFP)) matrix and strong interfacial adhesion with the polymer matrix. The dielectric constants of the nanocomposites increased significantly with the increase of the coated BT loading, while the dielectric loss of the nanocomposites was still as low as that of the pure P(VDF-HFP). The energy storage density of the nanocomposites was largely enhanced with the coated BT loading at the same electric field. The nanocomposite with 20 vol % BT exhibited an estimated maximum energy density of 8.13 J cm(-3), which was much higher than that of pure P(VDF-HFP) and other dielectric polymers. The findings of this research could provide a feasible approach to produce high energy density materials for practical application in energy storage.

Effect of surface preparation on the failure load of a highly filled composite bonded to the polymer-monomer matrix of a fiber-reinforced composite.

PubMed

Shimizu, Hiroshi; Tsue, Fumitake; Chen, Zhao-Xun; Takahashi, Yutaka

2009-04-01

The purpose of the present study was to evaluate the effect of surface preparation on the maximum fracture load value of a highly filled composite bonded to the polymer-monomer matrix of a fiber-reinforced composite. A polymer-monomer matrix was made by mixing urethane dimethacrylate and triethyleneglycol dimethacrylate at a ratio of 1:1 with camphorquinone and 2-dimethylaminoethyl methacrylate as a light initiator. The matrix was then polymerized in a disk-shaped silicone mold with a light-polymerizing unit. The flat surfaces of the polymer-monomer matrix disk were prepared in one of the following ways: (1) without preparation; (2) application of silane coupling agent; or (3) application of matrix liquid and prepolymerization. A highly filled composite material was applied and polymerized with a light-polymerizing unit. Additional test specimens made entirely of the polymer-monomer matrix were fabricated as references; the disk and cylinder were fabricated in one piece using a mold specially made for the present study (group 4). Half the specimens were thermocycled up to 10,000 times in water with a 1-minute dwell time at each temperature (5 degrees C and 55 degrees C). The maximum fracture load values were determined using a universal testing machine (n = 10). The maximum fracture loads for group 3 were significantly enhanced both before and after thermocycling, whereas the maximum fracture loads of group 2 were significantly enhanced before thermocycling (p < 0.05); however, the failure loads decreased for all groups after thermocycling (p < 0.05). All the specimens in groups 1 and 2 debonded during thermocycling. The failure load of group 3 was significantly lower than that of group 4 both before and after thermocycling (p < 0.05). Within the limitations of the current in vitro study, the application and prepolymerization of a mixed dimethacrylate resin liquid prior to the application of a highly filled composite was an effective surface preparation for the polymer-monomer matrix of a fiber-reinforced composite; however, the bond durability may be insufficient.

Molecular imprinted polymer functionalized carbon nanotube sensors for detection of saccharides

NASA Astrophysics Data System (ADS)

Badhulika, Sushmee; Mulchandani, Ashok

2015-08-01

In this work, we report the synthesis and fabrication of an enzyme-free sugar sensor based on molecularly imprinted polymer (MIP) on the surface of single walled carbon nanotubes (SWNTs). Electropolymerization of 3-aminophenylboronic acid (3-APBA) in the presence of 10 M d-fructose and fluoride at neutral pH conditions resulted in the formation of a self-doped, molecularly imprinted conducting polymer (MICP) via the formation of a stable anionic boronic ester complex between poly(aniline boronic acid) and d-fructose. Template removal generated binding sites on the polymer matrix that were complementary to d-fructose both in structure, i.e., shape, size, and positioning of functional groups, thus enabling sensing of d-fructose with enhanced affinity and specificity over non-MIP based sensors. Using carbon nanotubes along with MICPs helped to develop an efficient electrochemical sensor by enhancing analyte recognition and signal generation. These sensors could be regenerated and used multiple times unlike conventional affinity based biosensors which suffer from physical and chemical stability.

Nanocomposites Based on Thermoplastic Polymers and Functional Nanofiller for Sensor Applications

PubMed Central

Coiai, Serena; Passaglia, Elisa; Pucci, Andrea; Ruggeri, Giacomo

2015-01-01

Thermoplastic polymers like polyolefins, polyesters, polyamide, and styrene polymers are the most representative commodity plastics thanks to their cost-efficient manufacturing processes, excellent thermomechanical properties and their good environmental compatibility, including easy recycling. In the last few decades much effort has been devoted worldwide to extend the applications of such materials by conferring on them new properties through mixing and blending with different additives. In this latter context, nanocomposites have recently offered new exciting possibilities. This review discusses the successful use of nanostructured dispersed substrates in designing new stimuli-responsive nanocomposites; in particular, it provides an updated description of the synthetic routes to prepare nanostructured systems having the typical properties of thermoplastic polymers (continuous matrix), but showing enhanced optical, conductive, and thermal features dependent on the dispersion topology. The controlled nanodispersion of functional labeled clays, noble metal nanoparticles and carbon nanotubes is here evidenced to play a key role in producing hybrid thermoplastic materials that have been used in the design of devices, such as NLO devices, chemiresistors, temperature and deformation sensors.

Localized in situ polymerization on graphene surfaces for stabilized graphene dispersions.

PubMed

Das, Sriya; Wajid, Ahmed S; Shelburne, John L; Liao, Yen-Chih; Green, Micah J

2011-06-01

We demonstrate a novel in situ polymerization technique to develop localized polymer coatings on the surface of dispersed pristine graphene sheets. Graphene sheets show great promise as strong, conductive fillers in polymer nanocomposites; however, difficulties in dispersion quality and interfacial strength between filler and matrix have been a persistent problem for graphene-based nanocomposites, particularly for pristine graphene. With this in mind, a physisorbed polymer layer is used to stabilize graphene sheets in solution. To create this protective layer, we formed an organic microenvironment around dispersed graphene sheets in surfactant solutions, and created a nylon 6, 10 or nylon 6, 6 coating via interfacial polymerization. Technique lies at the intersection of emulsion and admicellar polymerization; a similar technique was originally developed to protect luminescent properties of carbon nanotubes in solution. These coated graphene dispersions are aggregation-resistant and may be reversibly redispersed in water even after freeze-drying. The coated graphene holds promise for a number of applications, including multifunctional graphene-polymer nanocomposites. © 2011 American Chemical Society

High Strain Rate Deformation Modeling of a Polymer Matrix Composite. Part 2; Composite Micromechanical Model

NASA Technical Reports Server (NTRS)

Goldberg, Robert K.; Stouffer, Donald C.

1998-01-01

Recently applications have exposed polymer matrix composite materials to very high strain rate loading conditions, requiring an ability to understand and predict the material behavior under these extreme conditions. In this second paper of a two part report, a three-dimensional composite micromechanical model is described which allows for the analysis of the rate dependent, nonlinear deformation response of a polymer matrix composite. Strain rate dependent inelastic constitutive equations utilized to model the deformation response of a polymer are implemented within the micromechanics method. The deformation response of two representative laminated carbon fiber reinforced composite materials with varying fiber orientation has been predicted using the described technique. The predicted results compare favorably to both experimental values and the response predicted by the Generalized Method of Cells, a well-established micromechanics analysis method.

Reflective article having a sacrificial cathodic layer

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kabagambe, Benjamin; Buchanan, Michael J.; Scott, Matthew S.

The present invention relates to reflective articles, such as solar mirrors, that include a sacrificial cathodic layer. The reflective article, more particularly includes a substrate, such as glass, having a multi-layered coating thereon that includes a lead-free sacrificial cathodic layer. The sacrificial cathodic layer includes at least one transition metal, such as a particulate transition metal, which can be in the form of flakes (e.g., zinc flakes). The sacrificial cathodic layer can include an inorganic matrix formed from one or more organo-titanates. Alternatively, the sacrificial cathodic layer can include an organic polymer matrix (e.g., a crosslinked organic polymer matrix formedmore » from an organic polymer and an aminoplast crosslinking agent). The reflective article also includes an outer organic polymer coating, that can be electrodeposited over the sacrificial cathodic layer.« less

Solid-state radioluminescent compositions

DOEpatents

Clough, Roger L.; Gill, John T.; Hawkins, Daniel B.; Renschler, Clifford L.; Shepodd, Timothy J.; Smith, Henry M.

1991-01-01

A solid state radioluminescent composition for light source comprises an optically clear polymer organic matrix containing tritiated organic materials and dyes capable of "red" shifting primary scintillation emissions from the polymer matrix. The tritiated organic materials are made by reducing, with tritium, an unsaturated organic compound that prior to reduction contains olefinic or alkynylic bonds.

Amino acid-functionalized multi-walled carbon nanotubes for improving compatibility with chiral poly(amide-ester-imide) containing L-phenylalanine and L-tyrosine linkages

NASA Astrophysics Data System (ADS)

Abdolmaleki, Amir; Mallakpour, Shadpour; Borandeh, Sedigheh

2013-12-01

Amino acid functionalized multi-walled carbon nanotubes (f-MWCNTs)/poly(amide-ester-imide) (PAEI) composites were fabricated by solution mixing method. Proper functionalization and mixing strategy of MWCNTs provides the best opportunity for better distribution and bonding of nanoparticles to the polymer matrix. MWCNTs have been chemically modified with L-phenylalanine to improve their compatibility with L-phenylalanine based PAEI. Field emission scanning electron microscopy micrographs of composite revealed that f-MWCNTs made a good interaction with polymer chains by wrapping the polymer around them, and transmission electron microscopy results confirmed well dispersion with nano size of f-MWCNTs in the polymer matrix. In addition, thermal analysis showed good enhancement in thermal properties of composites compared to pure polymer. Thermal stability of the composites containing f-MWCNTs was enhanced due to their good dispersion and improved interfacial interaction between the amino acid based PAEI matrix and f-MWCNTs.

Polymer gel dosimeter with AQUAJOINT® as hydrogel matrix

NASA Astrophysics Data System (ADS)

Maeyama, Takuya; Ishida, Yasuhiro; Kudo, Yoshihiro; Fukasaku, Kazuaki; Ishikawa, Kenichi L.; Fukunishi, Nobuhisa

2018-05-01

We report a polymer gel dosimeter based on a new gel matrix (AQUAJOINT®) that is a thermo-irreversible hydrogel formed by mixing two types of water-based liquids at room temperature. Normoxic N-vinylpyrrolidone-based polymer gels were prepared with AQUAJOINT® instead of gelatin. This AQUAJOINT®-based gel dosimeter exhibits a 2.5-fold increase in sensitivity over a gelatin-based gel dosimeter and a linear dose-response in the dose range of 0-8 Gy. This gel has heat resistance in a jar and controlled gel properties such as viscoelastic and mechanical characters, which may be useful for deformable polymer gel dosimetry.

A noncovalent compatibilization approach to improve the filler dispersion and properties of polyethylene/graphene composites.

PubMed

Vasileiou, Alexandros A; Kontopoulou, Marianna; Docoslis, Aristides

2014-02-12

Graphene was prepared by low temperature vacuum-assisted thermal exfoliation of graphite oxide. The resulting thermally reduced graphene oxide (TRGO) had a specific surface area of 586 m(2)/g and consisted of a mixture of single-layered and multilayered graphene. The TRGO was added to maleated linear low-density polyethylene LLDPE and to its derivatives with pyridine aromatic groups by melt compounding. The LLDPE/TRGO composites exhibited very low electrical percolation thresholds, between 0.5 and 0.9 vol %, depending on the matrix viscosity and the type of functional groups. The dispersion of the TRGO in the compatibilized composites was improved significantly, due to enhanced noncovalent interactions between the aromatic moieties grafted onto the polymer matrix and the filler. Better dispersion resulted in a slight increase in the rheological and electrical percolation thresholds, and to significant improvements in mechanical properties and thermal conductivity, compared to the noncompatibilized composites. The presence of high surface area nanoplatelets within the polymer also resulted in a substantially improved thermal stability. Compared to their counterparts containing multiwalled carbon nanotubes, LLDPE/TRGO composites had lower percolation thresholds. Therefore, lower amounts of TRGO were sufficient to impart electrical conductivity and modulus improvements, without compromising the ductility of the composites.

The surface properties of carbon fibers and their adhesion to organic polymers

NASA Technical Reports Server (NTRS)

Bascom, W. D.; Drzal, L. T.

1987-01-01

The state of knowledge of the surface properties of carbon fibers is reviewed, with emphasis on fiber/matrix adhesion in carbon fiber reinforced plastics. Subjects treated include carbon fiber structure and chemistry, techniques for the study of the fiber surface, polymer/fiber bond strength and its measurement, variations in polymer properties in the interphase, and the influence of fiber matrix adhesion on composite mechanical properties. Critical issues are summarized and search recommendations are made.

Comparative analysis of poly-glycolic acid-based hybrid polymer starter matrices for in vitro tissue engineering.

PubMed

Generali, Melanie; Kehl, Debora; Capulli, Andrew K; Parker, Kevin K; Hoerstrup, Simon P; Weber, Benedikt

2017-10-01

Biodegradable scaffold matrixes form the basis of any in vitro tissue engineering approach by acting as a temporary matrix for cell proliferation and extracellular matrix deposition until the scaffold is replaced by neo-tissue. In this context several synthetic polymers have been investigated, however a concise systematic comparative analyses is missing. Therefore, the present study systematically compares three frequently used polymers for the in vitro engineering of extracellular matrix based on poly-glycolic acid (PGA) under static as well as dynamic conditions. Ultra-structural analysis was used to examine the polymers structure. For tissue engineering (TE) three human fibroblast cell lines were seeded on either PGA-poly-4-hydroxybutyrate (P4HB), PGA-poly-lactic acid (PLA) or PGA-poly-caprolactone (PCL) patches. These patches were analyzed after 21days of culture qualitative by histology and quantitative by determining the amount of DNA, glycosaminoglycan and hydroxyproline. We found that PGA-P4HB and PGA-PLA scaffolds enhance tissue formation significantly higher than PGA-PCL scaffolds (p<0.05). Polymer remnants were visualized by polarization microscopy. In addition, biomechanical properties of the tissue engineered patches were determined in comparison to native tissue. This study may allow future studies to specifically select certain polymer starter matrices aiming at specific tissue properties of the bioengineered constructs in vitro. Copyright © 2017 Elsevier B.V. All rights reserved.

Industrially Feasible Approach to Transparent, Flexible, and Conductive Carbon Nanotube Films: Cellulose-Assisted Film Deposition Followed by Solution and Photonic Processing

NASA Astrophysics Data System (ADS)

Kim, Yeji; Chikamatsu, Masayuki; Azumi, Reiko; Saito, Takeshi; Minami, Nobutsugu

2013-02-01

We report that single-walled nanotube (SWNT) films with precisely controlled thicknesses and transmittances can be produced through the doctor-blade method using SWNT-polymer inks. The matrix polymer around SWNTs were successfully removed by either solution curing or photonic curing at room temperature, which are advantageous processes enabling direct film formation on plastic substrates. Sheet resistances as low as 68-240 Ω/sq at T=89-98% were obtained. Furthermore, the SWNT film on poly(ethylene naphthalate) exhibited superior flexibility and stability in a flexure endurance test. The method may open a wide range of opportunities for flexible electrical devices.

Evaluation of Degradation Properties of Polyglycolide and Its Potential as Delivery Vehicle for Anticancer Agents

NASA Astrophysics Data System (ADS)

Noorsal, K.; Ghani, S. M.; Yunos, D. M.; Mohamed, M. S. W.; Yahya, A. F.

2010-03-01

Biodegradable polymers offer a unique combination of properties that can be tailored to suit nearly any controlled drug delivery application. The most common biodegradable polymers used for biomedical applications are semicrystalline polyesters and polyethers which possess good mechanical properties and have been used in many controlled release applications. Drug release from these polymers may be controlled by several mechanisms and these include diffusion of drug through a matrix, dissolution of polymer matrix and degradation of the polymer. This study aims to investigate the degradation and drug release properties of polyglycolide (1.03 dL/g), in which, cis platin, an anticancer agent was used as the model drug. The degradation behaviour of the chosen polymer is thought to largely govern the release of the anticancer agent in vitro.

Temperature characterization of dielectric permittivity and AC conductivity of nano copper oxide-doped polyaniline composite

NASA Astrophysics Data System (ADS)

Shubha, L. N.; Madhusudana Rao, P.

2016-06-01

The polyaniline/copper oxide (PANI/CuO) nanocomposite was prepared by mixing solutions of polyaniline and copper oxide nanoparticles in dimethyl sulfoxide (DMSO). The synthesized polymer nanocomposites were characterized by X-ray powder diffraction (XRD), scanning electron microscope (SEM) and UV-visible spectroscopy. The characteristic peaks in XRD and UV-visible spectra confirmed the presence of CuO in the polymer structure. SEM images indicated morphological changes in the composite matrix as compared to the pristine PANI. The DC conductivity measurements were performed using two-probe method for various temperatures. AC conductivity and dielectric response of the composites were investigated in the frequency range of 102-106Hz using LCR meter. Dielectric permittivity ɛ‧(w) and dielectric loss factor ɛ‧‧(w) were investigated. It was observed that ɛ‧(w) and ɛ‧‧(w) decrease with increase in frequency at all temperatures. At a particular frequency it is observed that both ɛ‧(w) and ɛ‧‧(w) increase with increase in temperature. It was also observed that AC conductivity increased with increase in frequency and temperature.

Corrigendum to “High-fidelity micro-scale modeling of the thermo-visco-plastic behavior of carbon fiber polymer matrix composites” [Compos Struct 134 (2015) 132–141

DOE PAGES

Bai, Xiaoming; Bessa, Miguel A.; Melro, Antonio R.; ...

2016-10-01

The authors would like to inform that one of the modifications proposed in the article “High-fidelity micro-scale modeling of the thermo-visco-plastic behavior of carbon fiber polymer matrix composites” [1] was found to be unnecessary: the paraboloid yield criterion is sufficient to describe the shear behavior of the epoxy matrix considered (Epoxy 3501-6). The authors recently noted that the experimental work [2] used to validate the pure matrix response considered engineering shear strain instead of its tensorial counter-part, which caused the apparent inconsistency with the paraboloid yield criterion. A recently proposed temperature dependency law for glassy polymers is evaluated herein, thusmore » better agreement with the experimental results for this epoxy is observed.« less

Improved high temperature resistant matrix resins

NASA Technical Reports Server (NTRS)

Chang, G. E.; Powell, S. H.; Jones, R. J.

1983-01-01

The objective was to develop organic matrix resins suitable for service at temperatures up to 644 K (700 F) and at air pressures up to 0.4 MPa (60 psia) for time durations of a minimum of 100 hours. Matrix resins capable of withstanding these extreme oxidative environmental conditions would lead to increased use of polymer matrix composites in aircraft engines and provide significant weight and cost savings. Six linear condensation, aromatic/heterocyclic polymers containing fluorinated and/or diphenyl linkages were synthesized. The thermo-oxidative stability of the resins was determined at 644 K and compressed air pressures up to 0.4 MPa. Two formulations, both containing perfluoroisopropylidene linkages in the polymer backbone structure, exhibited potential for 644 K service to meet the program objectives. Two other formulations could not be fabricated into compression molded zero defect specimens.

Corrigendum to “High-fidelity micro-scale modeling of the thermo-visco-plastic behavior of carbon fiber polymer matrix composites” [Compos Struct 134 (2015) 132–141

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bai, Xiaoming; Bessa, Miguel A.; Melro, Antonio R.

The authors would like to inform that one of the modifications proposed in the article “High-fidelity micro-scale modeling of the thermo-visco-plastic behavior of carbon fiber polymer matrix composites” [1] was found to be unnecessary: the paraboloid yield criterion is sufficient to describe the shear behavior of the epoxy matrix considered (Epoxy 3501-6). The authors recently noted that the experimental work [2] used to validate the pure matrix response considered engineering shear strain instead of its tensorial counter-part, which caused the apparent inconsistency with the paraboloid yield criterion. A recently proposed temperature dependency law for glassy polymers is evaluated herein, thusmore » better agreement with the experimental results for this epoxy is observed.« less

Polyhedral oligomeric silsesquioxane grafted polymer in polymeric foam

DOEpatents

King, Bruce A.; Patankar, Kshitish A.; Costeux, Stephane; Jeon, Hyun K.

2017-01-17

A polymeric foam article with a polymer matrix defining multiple cells therein has a polymer component with a first polymer that is a polyhedral oligomeric silsesquioxane grafted polymer that has a weight-average molecular weight of two kilograms per mole or higher and 200 kilograms per mole or lower.

A review on the cords & plies reinforcement of elastomeric polymer matrix

NASA Astrophysics Data System (ADS)

Mahmood, S. S.; Husin, H.; Mat-Shayuti, M. S.; Hassan, Z.

2016-06-01

Steel, polyester, nylon and rayon are the main materials of cords & plies that have been reinforced in the natural rubber to produce quality tyres but there is few research reported on cord and plies reinforcement in silicone rubber. Taking the innovation of tyres as inspiration, this review's first objective is to compile the comprehensive studies about the cords & plies reinforcement in elastomeric polymer matrix. The second objective is to gather information about silicone rubber that has a high potential as a matrix phase for cords and plies reinforcement. All the tests and findings are gathered and compiled in sections namely processing preparation, curing, physical and mechanical properties, and adhesion between cords-polymer.

Estimating the stability of electrical conductivity of filled polymers under the influence of negative temperatures

NASA Astrophysics Data System (ADS)

Minakova, N. N.; Ushakov, V. Ya.

2017-12-01

One of the key problems in modern materials technology is synthesis of materials for electrotechnical devices capable of operating under severe conditions. Electrical and power engineering, in particular, demands for electrically conductive composite materials operating at high and low temperatures, various mechanical loads, electric fields, etc. Chaotic arrangement of electrically conductive component in the matrix and its structural and geometrical inhomogeneity can increase the local electric and thermal energy flux densities up to critical values even when their average values remain moderate. Elastomers filled with technical carbon being a promising component for electrotechnical devices was chosen as an object of study.

Nitrogen--sulfur--carbon nanocomposites and their application as cathode materials in lithium--sulfur batteries

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dai, Sheng; Sun, Xiao-Guang; Guo, Bingkun

The invention is directed in a first aspect to electron-conducting porous compositions comprising an organic polymer matrix doped with nitrogen atoms and having elemental sulfur dispersed therein, particularly such compositions having an ordered framework structure. The invention is also directed to composites of such S/N-doped electron-conducting porous aromatic framework (PAF) compositions, or composites of an S/N-doped mesoporous carbon composition, which includes the S/N-doped composition in admixture with a binder, and optionally, conductive carbon. The invention is further directed to cathodes for a lithium-sulfur battery in which such composites are incorporated.

Manipulating polymers and composites from the nanoscopic to microscopic length scales

NASA Astrophysics Data System (ADS)

Gupta, Suresh

2008-10-01

This thesis focuses on the manipulation of polymers and composites on length scales ranging from the nanoscopic to microscopic. In particular, on the microscopic length scale electric fields were used to produce instabilities at the air surface and at polymer interfaces that lead to novel three dimensional structures and patterns. On the nanoscopic length scale, the interaction of ligands attached to nanoparticles and polymer matrix were used to induce self-assembly processes that, in turn, lead to systems that self-heal, self-corral, or are patterned. For manipulation at the micron length scale, electrohydrodynamic instabilities were used in trilayer system composed of a layer of poly(methyl methacrylate) (PMMA), a second layer of polystyrene (PS) and a third layer of air. Dewetting of the polymer at the substrate at the polymer/polymer interface under an applied electric field was used to generate novel three dimensional structures. Also, electrohydrodynamic instabilities were used to pattern thin polymer films in conjunction with ultrasonic vibrations and patterned upper electrodes. Self-assembly processes involving polymers and nanoparticles offer a unique means of generating pattern materials or materials that self heal. Simple polymer/nanoparticle composites were investigated. Here, in the absence of interactions between the poly(ethylene oxide) ligands attached to the nanoparticles and PMMA polymer matrix, the opportunity to generate self-healing systems was opened. The size of the nanoparticle was varied and the effect on diffusion of nanoparticle in the polymer matrix was studied. CdSe nanorods were also assembled on a substrate templated with or guided by microphase separated diblock copolymers. The nanorods were incorporated in the diblock copolymer thin films by spin coating the co-solution of nanorods and polymer, surface adsorption of nanorods on to the patterned diblock copolymer films and surface reconstruction of PS/PMMA diblock copolymer thin film. Further, the interactions between the PMMA polymer matrix and the tri n-octyl phosphine oxide ligands attached to an anisotropic nanoparticle, i.e. nanorods, were used to influence the dispersion of the nanorods in the polymer. This led to a novel assembly, termed self-corralling where under an applied electric field highly oriented, highly ordered arrays of nanorods form. Further, self corralling of nanorods was directed by chemically patterned substrates.

Bio-Based Nanocomposites: An Alternative to Traditional Composites

ERIC Educational Resources Information Center

Tate, Jitendra S.; Akinola, Adekunle T.; Kabakov, Dmitri

2009-01-01

Polymer matrix composites (PMC), often referred to as fiber reinforced plastics (FRP), consist of fiber reinforcement (E-glass, S2-glass, aramid, carbon, or natural fibers) and polymer matrix/resin (polyester, vinyl ester, polyurethane, phenolic, and epoxies). Eglass/ polyester and E-glass/vinyl ester composites are extensively used in the marine,…

Outgassing and dimensional changes of polymer matrix composites in space

NASA Technical Reports Server (NTRS)

Tennyson, R. C.; Matthews, R.

1993-01-01

A thermal-vacuum outgassing model and test protocol for predicting outgassing times and dimensional changes for polymer matrix composites is described. Experimental results derived from a 'control' sample are used to provide the basis for analytical predictions to compare with the outgassing response of Long Duration Exposure Facility (LDEF) flight samples.

Mechanically Strong Aerogels Formed by Templated Growth of Polymer Cross- Linkers on Inorganic Nanoparticles

NASA Technical Reports Server (NTRS)

Leventis, Nicholas; Fabrizio, Eve F.; Johnston, Chris; Meador, Maryann

2004-01-01

In the search for materials with better mechanical, thermal, and electrical properties, it is becoming evident that oftentimes dispersing ceramic nanoparticles in plastics improves performance. Along these lines, chemical bonding (both covalent and noncovalent) between a filler and a polymer improves their compatibility, and thus enhances certain properties of the polymeric matrix above and beyond what is accomplished by simple doping with the filler. When a similarly sized dopant and matrix are used, elementary building blocks may also have certain distinct advantages (e.g., in catalysis). In this context, researchers at the NASA Glenn Research Center reasoned that in the extreme case, where the dopant and the matrix (e.g., a filler and a polymer) are not only sized similarly, but their relative amounts are comparable, the relative roles of the dopant and matrix can be reversed. Then, if the "filler," or a certain form thereof, possesses desirable properties of its own, such properties could be magnified by cross-linking with a polymer. We at Glenn have identified silica as such a filler in its lowest-density form, namely the silica aerogel.

Damping mathematical modelling and dynamic responses for FRP laminated composite plates with polymer matrix

NASA Astrophysics Data System (ADS)

Liu, Qimao

2018-02-01

This paper proposes an assumption that the fibre is elastic material and polymer matrix is viscoelastic material so that the energy dissipation depends only on the polymer matrix in dynamic response process. The damping force vectors in frequency and time domains, of FRP (Fibre-Reinforced Polymer matrix) laminated composite plates, are derived based on this assumption. The governing equations of FRP laminated composite plates are formulated in both frequency and time domains. The direct inversion method and direct time integration method for nonviscously damped systems are employed to solve the governing equations and achieve the dynamic responses in frequency and time domains, respectively. The computational procedure is given in detail. Finally, dynamic responses (frequency responses with nonzero and zero initial conditions, free vibration, forced vibrations with nonzero and zero initial conditions) of a FRP laminated composite plate are computed using the proposed methodology. The proposed methodology in this paper is easy to be inserted into the commercial finite element analysis software. The proposed assumption, based on the theory of material mechanics, needs to be further proved by experiment technique in the future.

Mixed Matrix Membranes of Boron Icosahedron and Polymers of Intrinsic Microporosity (PIM-1) for Gas Separation

PubMed Central

Khan, Muntazim Munir; Shishatskiy, Sergey; Filiz, Volkan

2018-01-01

This work reports on the preparation and gas transport performance of mixed matrix membranes (MMMs) based on the polymer of intrinsic microporosity (PIM-1) and potassium dodecahydrododecaborate (K2B12H12) as inorganic particles (IPs). The effect of IP loading on the gas separation performance of these MMMs was investigated by varying the IP content (2.5, 5, 10 and 20 wt %) in a PIM-1 polymer matrix. The derived MMMs were characterized by scanning electron microscopy (SEM), thermogravimetric analysis (TGA), single gas permeation tests and sorption measurement. The PIM1/K2B12H12 MMMs show good dispersion of the IPs (from 2.5 to 10 wt %) in the polymer matrix. The gas permeability of PIM1/K2B12H12 MMMs increases as the loading of IPs increases (up to 10 wt %) without sacrificing permselectivity. The sorption isotherm in PIM-1 and PIM1/K2B12H12 MMMs demonstrate typical dual-mode sorption behaviors for the gases CO2 and CH4. PMID:29301312

In-situ preparation of poly(ethylene oxide)/Li3PS4 hybrid polymer electrolyte with good nanofiller distribution for rechargeable solid-state lithium batteries

NASA Astrophysics Data System (ADS)

Chen, Shaojie; Wang, Junye; Zhang, Zhihua; Wu, Linbin; Yao, Lili; Wei, Zhenyao; Deng, Yonghong; Xie, Dongjiu; Yao, Xiayin; Xu, Xiaoxiong

2018-05-01

Nano-sized fillers in a polymer matrix with good distribution can play a positive role in improving polymer electrolytes in the aspects of ionic conductivity, mechanical property and electrochemical performance of Li-ion cells. Herein, polyethylene oxide (PEO)/Li3PS4 hybrid polymer electrolyte is prepared via a new in-situ approach. The ionic conductivities of the novel hybrid electrolytes with variable proportions are measured, and the optimal electrolyte of PEO-2%vol Li3PS4 presents a considerable ionic conductivity of 8.01 × 10-4 S cm-1 at 60 °C and an electrochemical window up to 5.1 V. The tests of DSC and EDXS reveal that the Li3PS4 nanoparticles with better distribution, as active fillers scattering in the PEO, exhibit a positive effect on the transference of lithium ion and electrochemical interfacial stabilities. Finally, the assembled solid-state LiFePO4/Li battery presents a decent cycling performance (80.9% retention rate after 325 cycles at 60 °C) and excellent rate capacities with 153, 143, 139 and 127 mAh g-1 at the discharging rate of 0.1 C, 0.2 C, 0.5 C and 1 C at 60 °C. It is fully proved that it is an advanced strategy to preparing the new organic/inorganic hybrid electrolytes for lithium-ion batteries applications.

Controlled nucleation and growth of CdS nanoparticles in a polymer matrix.

PubMed

Di Luccio, Tiziana; Laera, Anna Maria; Tapfer, Leander; Kempter, Susanne; Kraus, Robert; Nickel, Bert

2006-06-29

In-situ synchrotron X-ray diffraction (XRD) was used to monitor the thermal decomposition (thermolysis) of Cd thiolates precursors embedded in a polymer matrix and the nucleation of CdS nanoparticles. A thiolate precursor/polymer solid foil was heated to 300 degrees C in the X-ray diffraction setup of beamline W1.1 at Hasylab, and the diffraction curves were each recorded at 10 degrees C. At temperatures above 240 degrees C, the precursor decomposition is complete and CdS nanoparticles grow within the polymer matrix forming a nanocomposite with interesting optical properties. The nanoparticle structural properties (size and crystal structure) depend on the annealing temperature. Transmission electron microscopy (TEM) and photoluminescence (PL) analyses were used to characterize the nanoparticles. A possible mechanism driving the structural transformation of the precursor is inferred from the diffraction features arising at the different temperatures.

Flexible and conductive waste tire-derived carbon/polymer composite paper as pseudocapacitive electrode

DOE Office of Scientific and Technical Information (OSTI.GOV)

Naskar, Amit K.; Paranthaman, Mariappan Parans; Boota, Muhammad

A method of making a supercapacitor from waste tires, includes the steps of providing rubber pieces and contacting the rubber pieces with a sulfonation bath to produce sulfonated rubber; pyrolyzing the sulfonated rubber to produce a tire-derived carbon composite comprising carbon black embedded in rubber-derived carbon matrix comprising graphitized interface portions; activating the tire-derived carbon composite by contacting the tire-derived carbon composite with a specific surface area-increasing composition to increase the specific surface area of the carbon composite to provide an activated tire-derived carbon composite; and, mixing the activated tire-derived carbon composite with a monomer and polymerizing the monomer tomore » produce a redox-active polymer coated, activated tire-derived carbon composite. The redox-active polymer coated, activated tire-derived carbon composite can be formed into a film. An electrode and a supercapacitor are also disclosed.« less

Process for derivatizing carbon nanotubes with diazonium species and compositions thereof

NASA Technical Reports Server (NTRS)

Bahr, Jeffrey L. (Inventor); Tour, James M. (Inventor); Yang, Jiping (Inventor)

2011-01-01

Methods for the chemical modification of carbon nanotubes involve the derivatization of multi- and single-wall carbon nanotubes, including small diameter (ca. 0.7 nm) single-wall carbon nanotubes, with diazonium species. The method allows the chemical attachment of a variety of organic compounds to the side and ends of carbon nanotubes. These chemically modified nanotubes have applications in polymer composite materials, molecular electronic applications, and sensor devices. The methods of derivatization include electrochemical induced reactions, thermally induced reactions, and photochemically induced reactions. Moreover, when modified with suitable chemical groups, the derivatized nanotubes are chemically compatible with a polymer matrix, allowing transfer of the properties of the nanotubes (such as, mechanical strength or electrical conductivity) to the properties of the composite material as a whole. Furthermore, when modified with suitable chemical groups, the groups can be polymerized to form a polymer that includes carbon nanotubes.

Effect of monomer composition of polymer matrix on flexural properties of glass fibre-reinforced orthodontic archwire.

PubMed

Ohtonen, J; Vallittu, P K; Lassila, L V J

2013-02-01

To compare force levels obtained from glass fibre-reinforced composite (FRC) archwires. Specifically, FRC wires were compared with polymer matrices having different dimethacrylate monomer compositions. FRC material (E-glass provided by Stick Tech Ltd, Turku, Finland) with continuous unidirectional glass fibres and four different types of dimethacrylate monomer compositions for the resin matrix were tested. Cross-sectionally round FRC archwires fitting into the 0.3 mm slot of a bracket were divided into 16 groups with six specimens in each group. Glass fibres were impregnated by the manufacturer, and they were initially light-cured by hand light-curing unit or additionally post-cured in light-curing oven. The FRC archwire specimens were tested at 37°C according to a three-point bending test in dry and wet conditions using a span length of 10 mm and a crosshead speed of 1.0 mm/minute. The wires were loaded until final failure. The data were statistically analysed using analysis of variance (ANOVA). The dry FRC archwire specimens revealed higher load values than water stored ones, regardless of the polymer matrix. A majority of the FRC archwires showed higher load values after being post-cured. ANOVA revealed that the polymer matrix, curing method, and water storage had a significant effect (P < 0.05) on the flexural behaviour of the FRC archwire. Polymer matrix composition, curing method, and water storage affected the flexural properties and thus, force level and working range which could be obtained from the FRC archwire.

Introducing catalyst in alkaline membrane for improved performance direct borohydride fuel cells

NASA Astrophysics Data System (ADS)

Qin, Haiying; Lin, Longxia; Chu, Wen; Jiang, Wei; He, Yan; Shi, Qiao; Deng, Yonghong; Ji, Zhenguo; Liu, Jiabin; Tao, Shanwen

2018-01-01

A catalytic material is introduced into the polymer matrix to prepare a novel polymeric alkaline electrolyte membrane (AEM) which simultaneously increases ionic conductivity, reduces the fuel cross-over. In this work, the hydroxide anion exchange membrane is mainly composed of poly(vinylalcohol) and alkaline exchange resin. CoCl2 is added into the poly(vinylalcohol) and alkaline exchange resin gel before casting the membrane to introduce catalytic materials. CoCl2 is converted into CoOOH after the reaction with KOH solution. The crystallinity of the polymer matrix decreases and the ionic conductivity of the composite membrane is notably improved by the introduction of Co-species. A direct borohydride fuel cell using the composite membrane exhibits an open circuit voltage of 1.11 V at 30 °C, which is notably higher than that of cells using other AEMs. The cell using the composite membrane achieves a maximum power density of 283 mW cm-2 at 60 °C while the cell using the membrane without Co-species only reaches 117 mW cm-2 at the same conditions. The outstanding performance of the cell using the composite membrane benefits from impregnation of the catalytic Co-species in the membrane, which not only increases the ionic conductivity but also reduces electrode polarization thus improves the fuel cell performance. This work provides a new approach to develop high-performance fuel cells through adding catalysts in the electrolyte membrane.

Quantitative evaluation of polymer concentration profile during swelling of hydrophilic matrix tablets using 1H NMR and MRI methods.

PubMed

Baumgartner, Sasa; Lahajnar, Gojmir; Sepe, Ana; Kristl, Julijana

2005-02-01

Many pharmaceutical tablets are based on hydrophilic polymers, which, after exposure to water, form a gel layer around the tablet that limits the dissolution and diffusion of the drug and provides a mechanism for controlled drug release. Our aim was to determine the thickness of the swollen gel layer of matrix tablets and to develop a method for calculating the polymer concentration profile across the gel layer. MR imaging has been used to investigate the in situ swelling behaviour of cellulose ether matrix tablets and NMR spectroscopy experiments were performed on homogeneous hydrogels with known polymer concentration. The MRI results show that the thickest gel layer was observed for hydroxyethylcellulose tablets, followed by definitely thinner but almost equal gel layer for hydroxypropylcellulose and hydroxypropylmethylcellulose of both molecular weights. The water proton NMR relaxation parameters were combined with the MRI data to obtain a quantitative description of the swelling process on the basis of the concentrations and mobilities of water and polymer as functions of time and distance. The different concentration profiles observed after the same swelling time are the consequence of the different polymer characteristics. The procedure developed here could be used as a general method for calculating polymer concentration profiles on other similar polymeric systems.

Development and evaluation of Ketoprofen sustained release matrix tablet using Hibiscus rosa-sinensis leaves mucilage.

PubMed

Kaleemullah, M; Jiyauddin, K; Thiban, E; Rasha, S; Al-Dhalli, S; Budiasih, S; Gamal, O E; Fadli, A; Eddy, Y

2017-07-01

Currently, the use of natural gums and mucilage is of increasing importance in pharmaceutical formulations as valuable drug excipient. Natural plant-based materials are economic, free of side effects, biocompatible and biodegradable. Therefore, Ketoprofen matrix tablets were formulated by employing Hibiscus rosa-sinensis leaves mucilage as natural polymer and HPMC (K100M) as a synthetic polymer to sustain the drug release from matrix system. Direct compression method was used to develop sustained released matrix tablets. The formulated matrix tablets were evaluated in terms of physical appearance, weight variation, thickness, diameter, hardness, friability and in vitro drug release. The difference between the natural and synthetic polymers was investigated concurrently. Matrix tablets developed from each formulation passed all standard physical evaluation tests. The dissolution studies of formulated tablets revealed sustained drug release up to 24 h compared to the reference drug Apo Keto® SR tablets. The dissolution data later were fitted into kinetic models such as zero order equation, first order equation, Higuchi equation, Hixson Crowell equation and Korsmeyer-Peppas equation to study the release of drugs from each formulation. The best formulations were selected based on the similarity factor ( f 2 ) value of 50% and more. Through the research, it is found that by increasing the polymers concentration, the rate of drug release decreased for both natural and synthetic polymers. The best formulation was found to be F3 which contained 40% Hibiscus rosa-sinensis mucilage polymer and showed comparable dissolution profile to the reference drug with f 2 value of 78.03%. The release kinetics of this formulation has shown to follow non-Fickian type which involved both diffusion and erosion mechanism. Additionally, the statistical results indicated that there was no significant difference (p > 0.05) between the F3 and reference drug in terms of MDT and T50% with p-values of 1.00 and 0.995 respectively.

Synthesis, Biodegradability, and Biocompatibility of Lysine Diisocyanate–Glucose Polymers

PubMed Central

ZHANG, JIAN-YING; BECKMAN, ERIC J.; HU, JING; YANG, GUO-GUANG; AGARWAL, SUDHA; HOLLINGER, JEFFREY O.

2016-01-01

The success of a tissue-engineering application depends on the use of suitable biomaterials that degrade in a timely manner and induce the least immunogenicity in the host. With this purpose in mind, we have attempted to synthesize a novel nontoxic biodegradable lysine diisocyanate (LDI)-and glucose-based polymer via polymerization of highly purified LDI with glucose and its subsequent hydration to form a spongy matrix. The LDI–glucose polymer was degradable in aqueous solutions at 37, 22, and 4°C, and yielded lysine and glucose as breakdown products. The degradation products of the LDI–glucose polymer did not significantly affect the pH of the solution. The physical properties of the polymer were found to be adequate for supporting cell growth in vitro, as evidenced by the fact that rabbit bone marrow stromal cells (BMSCs) attached to the polymer matrix, remained viable on its surface, and formed multilayered confluent cultures with retention of their phenotype over a period of 2 to 4 weeks. These observations suggest that the LDI–glucose polymer and its degradation products were nontoxic in vitro. Further examination in vivo over 8 weeks revealed that subcutaneous implantation of hydrated matrix degraded in vivo three times faster than in vitro. The implanted polymer was not immunogenic and did not induce antibody responses in the host. Histological analysis of the implanted polymer showed that LDI–glucose polymer induced a minimal foreign body reaction, with formation of a capsule around the degrading polymer. The results suggest that biodegradable peptide-based polymers can be synthesized, and may potentially find their way into biomedical applications because of their biodegradability and biocompatibility. PMID:12459056

Nanostructured pseudocapacitive materials decorated 3D graphene foam electrodes for next generation supercapacitors.

PubMed

Patil, Umakant; Lee, Su Chan; Kulkarni, Sachin; Sohn, Ji Soo; Nam, Min Sik; Han, Suhyun; Jun, Seong Chan

2015-04-28

Nowadays, advancement in performance of proficient multifarious electrode materials lies conclusively at the core of research concerning energy storage devices. To accomplish superior capacitance performance the requirements of high capacity, better cyclic stability and good rate capability can be expected from integration of electrochemical double layer capacitor based carbonaceous materials (high power density) and pseudocapacitive based metal hydroxides/oxides or conducting polymers (high energy density). The envisioned three dimensional (3D) graphene foams are predominantly advantageous to extend potential applicability by offering a large active surface area and a highly conductive continuous porous network for fast charge transfer with decoration of nanosized pseudocapacitive materials. In this article, we review the latest methodologies and performance evaluation for several 3D graphene based metal oxides/hydroxides and conducting polymer electrodes with improved electrochemical properties for next-generation supercapacitors. The most recent research advancements of our and other groups in the field of 3D graphene based electrode materials for supercapacitors are discussed. To assess the studied materials fully, a careful interpretation and rigorous scrutiny of their electrochemical characteristics is essential. Auspiciously, both nano-structuration as well as confinement of metal hydroxides/oxides and conducting polymers onto a conducting porous 3D graphene matrix play a great role in improving the performance of electrodes mainly due to: (i) active material access over large surface area with fast charge transportation; (ii) synergetic effect of electric double layer and pseudocapacitive based charge storing.

Metal coordination polymer derived mesoporous Co3O4 nanorods with uniform TiO2 coating as advanced anodes for lithium ion batteries

NASA Astrophysics Data System (ADS)

Geng, Hongbo; Ang, Huixiang; Ding, Xianguang; Tan, Huiteng; Guo, Guile; Qu, Genlong; Yang, Yonggang; Zheng, Junwei; Yan, Qingyu; Gu, Hongwei

2016-01-01

In this work, a one-dimensional Co3O4@TiO2 core-shell electrode material with superior electrochemical performance is fabricated by a convenient and controllable route. The approach involves two main steps: the homogeneous deposition of polydopamine and TiO2 layers in sequence on the cobalt coordination polymer and the thermal decomposition of the polymer matrix. The as-prepared electrode material can achieve excellent electrochemical properties and stability as an anode material for lithium ion batteries, such as a high specific capacity of 1279 mA h g-1, good cycling stability (around 803 mA h g-1 at a current density of 200 mA g-1 after 100 cycles), and stable rate performance (around 520 mA h g-1 at a current density of 1000 mA g-1). This dramatic electrochemical performance is mainly attributed to the excellent structural characteristics, which could improve the electrical conductivity and lithium ion mobility, as well as electrolyte permeability and architectural stability during cycling.In this work, a one-dimensional Co3O4@TiO2 core-shell electrode material with superior electrochemical performance is fabricated by a convenient and controllable route. The approach involves two main steps: the homogeneous deposition of polydopamine and TiO2 layers in sequence on the cobalt coordination polymer and the thermal decomposition of the polymer matrix. The as-prepared electrode material can achieve excellent electrochemical properties and stability as an anode material for lithium ion batteries, such as a high specific capacity of 1279 mA h g-1, good cycling stability (around 803 mA h g-1 at a current density of 200 mA g-1 after 100 cycles), and stable rate performance (around 520 mA h g-1 at a current density of 1000 mA g-1). This dramatic electrochemical performance is mainly attributed to the excellent structural characteristics, which could improve the electrical conductivity and lithium ion mobility, as well as electrolyte permeability and architectural stability during cycling. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr08570e

Interpenetrating polymer network approach to tougher and more microcracking resistant high temperature polymers. I - LaRC-RP40

NASA Technical Reports Server (NTRS)

Pater, Ruth H.; Morgan, Cassandra D.

1988-01-01

Interpenetrating polymer networks in the form of the LaRC-RP40 resin, prepared by the in situ polymerization of a thermosetting imide prepolymer and thermoplastic monomer reactants, are presently used to obtain toughness and microcracking resistance in a high-temperature polymer. Attention is presently given to the processing, physical, and mechanical properties, as well as the thermooxidative stability, of both the neat resin and the resin as a graphite fiber-reinforced matrix. Microcracking after thermal cycling was also tested. LaRC-RP40 exhibits significant resin fracture toughness improvements over the PMR-15 high-temperature matrix resin.

Interpenetrating polymer network approach to tougher and more microcracking resistant high temperature polymers. I. LaRC-RP40

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pater, R.H.; Morgan, C.D.

1988-10-01

Interpenetrating polymer networks in the form of the LaRC-RP40 resin, prepared by the in situ polymerization of a thermosetting imide prepolymer and thermoplastic monomer reactants, are presently used to obtain toughness and microcracking resistance in a high-temperature polymer. Attention is presently given to the processing, physical, and mechanical properties, as well as the thermooxidative stability, of both the neat resin and the resin as a graphite fiber-reinforced matrix. Microcracking after thermal cycling was also tested. LaRC-RP40 exhibits significant resin fracture toughness improvements over the PMR-15 high-temperature matrix resin. 16 references.

Transparent and High Refractive Index Thermoplastic Polymer Glasses Using Evaporative Ligand Exchange of Hybrid Particle Fillers.

PubMed

Wang, Zongyu; Lu, Zhao; Mahoney, Clare; Yan, Jiajun; Ferebee, Rachel; Luo, Danli; Matyjaszewski, Krzysztof; Bockstaller, Michael R

2017-03-01

Development of high refractive index glasses on the basis of commodity polymer thermoplastics presents an important requisite to further advancement of technologies ranging from energy efficient lighting to cost efficient photonics. This contribution presents a novel particle dispersion strategy that enables uniform dispersion of zinc oxide (ZnO) particles in a poly(methyl methacrylate) (PMMA) matrix to facilitate hybrid glasses with inorganic content exceeding 25% by weight, optical transparency in excess of 0.8/mm, and a refractive index greater than 1.64 in the visible wavelength range. The method is based on the application of evaporative ligand exchange to synthesize poly(styrene-r-acrylonitrile) (PSAN)-tethered zinc oxide (ZnO) particle fillers. Favorable filler-matrix interactions are shown to enable the synthesis of isomorphous blends with high molecular PMMA that exhibit improved thermomechanical stability compared to that of the pristine PMMA matrix. The concurrent realization of high refractive index and optical transparency in polymer glasses by modification of a thermoplastic commodity polymer could present a viable alternative to expensive specialty polymers in applications where high costs or demands for thermomechanical stability and/or UV resistance prohibit the application of specialty polymer solutions.

A Review on Grafting of Biofibers for Biocomposites

PubMed Central

Wei, Liqing; McDonald, Armando G.

2016-01-01

A recent increase in the use of biofibers as low-cost and renewable reinforcement for the polymer biocomposites has been seen globally. Biofibers are classified into: lignocellulosic fibers (i.e., cellulose, wood and natural fibers), nanocellulose (i.e., cellulose nanocrystals and cellulose nanofibrils), and bacterial cellulose, while polymer matrix materials can be petroleum based or bio-based. Green biocomposites can be produced using both biobased fibers and polymers. Incompatibility between the hydrophilic biofibers and hydrophobic polymer matrix can cause performance failure of resulting biocomposites. Diverse efforts have focused on the modification of biofibers in order to improve the performances of biocomposites. “Grafting” copolymerization strategy can render the advantages of biofiber and impart polymer properties onto it and the performance of biocomposites can be tuned through changing grafting parameters. This review presents a short overview of various “grafting” methods which can be directly or potentially employed to enhance the interaction between biofibers and a polymer matrix for biocomposites. Major grafting techniques, including ring opening polymerization, grafting via coupling agent and free radical induced grafting, have been discussed. Improved properties such as mechanical, thermal, and water resistance have provided grafted biocomposites with new opportunities for applications in specific industries. PMID:28773429

Carbon nanotube-polymer composite actuators

DOEpatents

Gennett, Thomas [Denver, CO; Raffaelle, Ryne P [Honeoye Falls, NY; Landi, Brian J [Rochester, NY; Heben, Michael J [Denver, CO

2008-04-22

The present invention discloses a carbon nanotube (SWNT)-polymer composite actuator and method to make such actuator. A series of uniform composites was prepared by dispersing purified single wall nanotubes with varying weight percents into a polymer matrix, followed by solution casting. The resulting nanotube-polymer composite was then successfully used to form a nanotube polymer actuator.

Electrical and mechanical behavior of polymethyl methacrylate/cadmium sulphide composites

NASA Astrophysics Data System (ADS)

Kaur, Rajdeep; Samra, Kawaljeet Singh

2018-06-01

In the present investigation, electrical and mechanical behavior of cadmium sulphide (CdS) doped polymethyl methacrylate (PMMA) have been studied using different techniques. Dip casting technique was used for preparing free standing films of pristine and CdS doped PMMA at different compositions (i.e. 1 and 5 wt%). Optical absorbance as a function of wavelength was studied, by UV-visible spectroscopy, to find the impact of CdS doping on the optical band gap of synthesized PMMA/CdS composite. DC and AC conductivities were measured as a function of dopant concentration and temperature. Considerable increase in electrical conductivity was observed with the increase of CdS contents in polymer matrix. Overall electrical conduction mechanism in PMMA/CdS composites was attributed to movement of electrons through the uniformly distributed CdS aggregates within the matrix of PMMA. Mechanical properties, such as Young's modulus, tensile strength, elongation and ductility, of PMMA/CdS composites were determined and relevant responsible phenomena were discussed.

Physical solid-state properties and dissolution of sustained-release matrices of polyvinylacetate.

PubMed

Gonzalez Novoa, Gelsys Ananay; Heinämäki, Jyrki; Mirza, Sabir; Antikainen, Osmo; Colarte, Antonio Iraizoz; Paz, Alberto Suzarte; Yliruusi, Jouko

2005-02-01

Solid-state compatibility and in vitro dissolution of direct-compressed sustained-release matrices of polyvinylacetate (PVAc) and polyvinylpyrrolidone (PVP) containing ibuprofen as a model drug were studied. Polyvinylalcohol (PVA) was used as an alternative water-soluble polymer to PVP. Differential scanning calorimetry (DSC) and powder X-ray diffractometry (PXRD) were used for characterizing solid-state polymer-polymer and drug-polymer interactions. The mechanical treatment for preparing physical mixtures of polyvinyl polymers and the drug (i.e. simple blending or stressed cogrinding) was shown not to affect the physical state of the drug and the polymers. With the drug-polymer mixtures the endothermic effect due to drug melting was always evident, but a considerable modification of the melting point of the drug in physical binary mixtures (drug:PVP) was observed, suggesting some interaction between the two. On the other hand, the lack of a significant shift of the melting endothermic peak of the drug in physical tertiary drug-polymer mixtures revealed no evidence of solid-state interaction between the drug and the present polymers. Sustained-release dissolution profiles were achieved from the direct-compressed matrices made from powder mixtures of the drug and PVAc combined with PVP, and the proportion of PVAc in the mixture clearly altered the drug release profiles in vitro. The drug release from the present matrix systems is controlled by both diffusion of the drug through the hydrate matrix and the erosion of the matrix itself.

Biofunctional polymer nanoparticles for intra-articular targeting and retention in cartilage

NASA Astrophysics Data System (ADS)

Rothenfluh, Dominique A.; Bermudez, Harry; O'Neil, Conlin P.; Hubbell, Jeffrey A.

2008-03-01

The extracellular matrix of dense, avascular tissues presents a barrier to entry for polymer-based therapeutics, such as drugs encapsulated within polymeric particles. Here, we present an approach by which polymer nanoparticles, sufficiently small to enter the matrix of the targeted tissue, here articular cartilage, are further modified with a biomolecular ligand for matrix binding. This combination of ultrasmall size and biomolecular binding converts the matrix from a barrier into a reservoir, resisting rapid release of the nanoparticles and clearance from the tissue site. Phage display of a peptide library was used to discover appropriate targeting ligands by biopanning on denuded cartilage. The ligand WYRGRL was selected in 94 of 96 clones sequenced after five rounds of biopanning and was demonstrated to bind to collagen II α1. Peptide-functionalized nanoparticles targeted articular cartilage up to 72-fold more than nanoparticles displaying a scrambled peptide sequence following intra-articular injection in the mouse.

High rate deposition system for metal-cluster/SiO x C y H z -polymer nanocomposite thin films

NASA Astrophysics Data System (ADS)

Peter, T.; Rehders, S.; Schürmann, U.; Strunskus, T.; Zaporojtchenko, V.; Faupel, F.

2013-06-01

A system for deposition of nanocomposite materials consisting of a SiO x C y H z -polymer matrix and Ag nanoclusters is presented. Ag nanoclusters with sizes between 2 and 20 nm are produced in a gas aggregation cluster source and are deposited through a focused beam at a high rate. This cluster source is presented in detail and the characteristics of the produced nanoclusters are shown. Simultaneously, a SiO x C y H z -polymer matrix is grown from the precursor hexamethyldisiloxane in an RF plasma. The beam of clusters is deposited into the growing polymer, forming the composite material. This process allows the rapid deposition of composite material with varying metal nanocluster concentrations and properties. Since the cluster generation is separated from the matrix growth, the properties of both can be controlled independently. In this study, we present two types of nanocomposite samples, in the first the Ag nanoclusters are homogeneously distributed in the matrix, in the second type the Ag nanoclusters form a layer which is covered by the matrix. These samples are investigated using transmission electron micrography to determine the morphology. Furthermore, the optical properties are probed using optical transmission spectroscopy and the plasmonic resonance behavior is discussed.

Study of drug release and tablet characteristics of silicone adhesive matrix tablets.

PubMed

Tolia, Gaurav; Li, S Kevin

2012-11-01

Matrix tablets of a model drug acetaminophen (APAP) were prepared using a highly compressible low glass transition temperature (T(g)) polymer silicone pressure sensitive adhesive (PSA) at various binary mixtures of silicone PSA/APAP ratios. Matrix tablets of a rigid high T(g) matrix forming polymer ethyl cellulose (EC) were the reference for comparison. Drug release study was carried out using USP Apparatus 1 (basket), and the relationship between the release kinetic parameters of APAP and polymer/APAP ratio was determined to estimate the excipient percolation threshold. The critical points attributed to both silicone PSA and EC tablet percolation thresholds were found to be between 2.5% and 5% w/w. For silicone PSA tablets, satisfactory mechanical properties were obtained above the polymer percolation threshold; no cracking or chipping of the tablet was observed above this threshold. Rigid EC APAP tablets showed low tensile strength and high friability. These results suggest that silicone PSA could eliminate issues related to drug compressibility in the formulation of directly compressed oral controlled release tablets of poorly compressible drug powder such as APAP. No routinely used excipients such as binders, granulating agents, glidants, or lubricants were required for making an acceptable tablet matrix of APAP using silicone PSA. Copyright © 2012 Elsevier B.V. All rights reserved.

Vascularization and tissue infiltration of a biodegradable polyurethane matrix

PubMed Central

Ganta, Sudhakar R.; Piesco, Nicholas P.; Long, Ping; Gassner, Robert; Motta, Luis F.; Papworth, Glenn D.; Stolz, Donna B.; Watkins, Simon C.; Agarwal, Sudha

2016-01-01

Urethanes are frequently used in biomedical applications because of their excellent biocompatibility. However, their use has been limited to bioresistant polyurethanes. The aim of this study was to develop a nontoxic biodegradable polyurethane and to test its potential for tissue compatibility. A matrix was synthesized with pentane diisocyanate (PDI) as a hard segment and sucrose as a hydroxyl group donor to obtain a microtextured spongy urethane matrix. The matrix was biodegradable in an aqueous solution at 37°C in vitro as well as in vivo. The polymer was mechanically stable at body temperatures and exhibited a glass transition temperature (Tg) of 67°C. The porosity of the polymer network was between 10 and 2000 µm, with the majority of pores between 100 and 300 µm in diameter. This porosity was found to be adequate to support the adherence and proliferation of bone-marrow stromal cells (BMSC) and chondrocytes in vitro. The degradation products of the polymer were nontoxic to cells in vitro. Subdermal implants of the PDI–sucrose matrix did not exhibit toxicity in vivo and did not induce an acute inflammatory response in the host. However, some foreign-body giant cells did accumulate around the polymer and in its pores, suggesting its degradation is facilitated by hydrolysis as well as by giant cells. More important, subdermal implants of the polymer allowed marked infiltration of vascular and connective tissue, suggesting the free flow of fluids and nutrients in the implants. Because of the flexibility of the mechanical strength that can be obtained in urethanes and because of the ease with which a porous microtexture can be achieved, this matrix may be useful in many tissue-engineering applications. PMID:12522810

The effects of lactate and acid on articular chondrocytes function: Implications for polymeric cartilage scaffold design.

PubMed

Zhang, Xiaolei; Wu, Yan; Pan, Zongyou; Sun, Heng; Wang, Junjuan; Yu, Dongsheng; Zhu, Shouan; Dai, Jun; Chen, Yishan; Tian, Naifeng; Heng, Boon Chin; Coen, Noelle D; Xu, Huazi; Ouyang, Hongwei

2016-09-15

Poly (lactic-co-glycolic acid) (PLGA) and poly-l-lactate acid (PLLA) are biodegradable polymers widely utilized as scaffold materials for cartilage tissue engineering. Their acid degradation products have been widely recognized as being detrimental to cell function. However, the biological effects of lactate, rather than lactic acid, on chondrocytes have never been investigated. This is the major focus of this study. The amounts of lactate and the pH value (acid) of the PLGA and PLLA degradation medium were measured. The effects of PLGA and PLLA degradation medium, as well as different lactate concentrations and timing of exposure on chondrocytes proliferation and cartilage-specific matrix synthesis were investigated by various techniques including global gene expression profiling and gene knockdown experiments. It was shown that PLGA and PLLA degradation medium differentially regulated chondrocyte proliferation and matrix synthesis. Acidic pH caused by lactate inhibited chondrocyte proliferation and matrix synthesis. The effect of lactate on chondrocyte matrix synthesis was both time and dose dependent. A lactate concentration of 100mM and exposure duration of 8h significantly enhanced matrix synthesis. Lactate could also inhibit expression of cartilage matrix degradation genes in osteoarthritic chondrocytes, such as the major aggrecanase ADAMTS5, whilst promoting matrix synthesis simultaneously. Pulsed addition of lactate was shown to be more efficient in promoting COL2A1 expression. Global gene expression data and gene knock down experiments demonstrated that lactate promote matrix synthesis through up-regulation of HIF1A. These observed differential biological effects of lactate on chondrocytes would have implications for the future design of polymeric cartilage scaffolds. Lactic acid is a widely used substrate for polymers synthesis, PLGA and PLLA in particular. Although physical and biological modifications have been made on these polymers to make them be better cartilage scaffolds, little concern has been given on the biological effect of lactic acid, the main degradation product of these polymers, on chondrocytes. Our finding illustrates the differential biological function of lactate and acid on chondrocytes matrix synthesis. These results can facilitate future design of lactate polymers-based cartilage scaffolds. Copyright © 2016 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Polymer/clay/wood nanocomposites: The effect of incorporation of nanoclay into the wood/polymer composites

NASA Astrophysics Data System (ADS)

Hetzer, Max E.

Thermoplastic composites play an important role in our society. The uses of these composites range from cookware to components for the space shuttle. In recent years, researchers at Toyota developed numerous methods of preparation for composites made from olefins and inorganic fillers such as clay and calcium carbonate. Wood fibers have been used as reinforcing filler in polymer matrices for the past several decades. The advantages of using wood fibers as reinforcing fillers are: the low cost of the fibers (or flour), low density, and resistance to breakage. The disadvantage of using wood as a filler is the thermal instability of wood above 200 °C. The majority of thermoplastics exhibit melting points between 160 and 220 °C, which is in the range of thermal decomposition of wood. Nanoclay was first successfully used as a filler in polyolefin materials by the Toyota research team in early 90s. It was found that the addition of a small amount (< 5 wt.%) of nanoclay increased the mechanical properties of a Nylon-6 matrix dramatically. Since Nylon-6 is a hydrophilic material no compatibilizer was necessary to exfoliate the nanoclay. The use of compatibilizers such as maleic modified polyethylenes (MAPEs) is necessary upon addition of nanoclay to a hydrophobic polyolefin systems such polyethylene (PE) or polypropylene (PP). Few researchers have attempted to reinforce the polymer matrix via the use of the nanoclay for use as a matrix in wood/polymer composites. High molecular weight and low molecular weight MAPEs have been used to enhance the bonding between the nanoclay and the polymer matrix as well as between the wood flour and the polymer matrix. The effects of combinations of the high and low molecular weight MAPEs on the mechanical and thermal properties of polymer/clay nanocomposites (PCNs) and of wood/polymer/clay composites (WPCs) were investigated. The effects of adding nanoclay to wood/polymer systems on the mechanical and thermal properties of the composites were also investigated. A model based on the Halpin-Tsai model was developed that predicts the (Young's) modulus-temperature relationship of the composites based on discontinuous fillers. It was found that the molecular weight of the compatibilizer significantly affects the exfoliation/dispersion of the nanoclay within the polymer matrix. A compatibilizer containing a high Mw fraction based on high density polyethylene (HDPE) and a low Mw fraction based on linear low density polyethylene (LLDPE) was found to be the most effective at enhancing the thermal and mechanical properties of PCNs and WPCs. A compatibilizer containing greater than 60 wt.% high Mw fraction resulted in a 30% increase of the modulus and a 15°C increase of the heat deflection temperature (HDT). The addition of the nanoclay had a detrimental effect on the moduli of PCNs and WPCs when a low Mw compatibilizer based on LLDPE was used. The moduli of these composites increased with increasing high Mw content of the compatibilizer and increasing nanoclay content. The addition of the nanoclay to wood/polymer composites resulted in an increased modulus of elasticity and HDT of these composites. The developed model quantitatively predicts the modulus-temperature relationship of the fiber containing composites. It was found that the modulus of the composites varies linearly with temperature and was highly dependent on the exfoliation of the nanoclay within the polymer matrix.

Carbon Nanotube Sheet Scrolled Fiber Composite for Enhanced Interfacial Mechanical Properties

NASA Astrophysics Data System (ADS)

Kokkada Ravindranath, Pruthul

The high tensile strength of Polymer Matrix Composites (PMC) is derived from the high tensile strength of the embedded carbon fibers. However, their compressive strength is significantly lower than their tensile strength, as they tend to fail through micro-buckling, under compressive loading. Fiber misalignment and the presence of voids created during the manufacturing processes, add to the further reduction in the compressive strength of the composites. Hence, there is more scope for improvement. Since, the matrix is primarily responsible for the shear load transfer and dictating the critical buckling load of the fibers by constraining the fibers from buckling, to improve the interfacial mechanical properties of the composite, it is important to modify the polymer matrix, fibers and/or the interface. In this dissertation, a novel approach to enhance the polymer matrix-fiber interface region has been discussed. This approach involves spiral wrapping carbon nanotube (CNT) sheet around individual carbon fiber or fiber tow, at room temperature at a prescribed wrapping angle (bias angle), and then embed the scrolled fiber in a resin matrix. The polymer infiltrates into the nanopores of the multilayer CNT sheet to form CNT/polymer nanocomposite surrounding fiber, and due to the mechanical interlocking, provides reinforcement to the interface region between fiber and polymer matrix. This method of nano-fabrication has the potential to improve the mechanical properties of the fiber-matrix interphase, without degrading the fiber properties. The effect of introducing Multi-Walled Carbon Nanotubes (MWNT) in the polymer matrix was studied by analyzing the atomistic model of the epoxy (EPON-862) and the embedded MWNTs. A multi-scale method was utilized by using molecular dynamics (MD) simulations on the nanoscale model of the epoxy with and without the MWNTs to calculate compressive strength of the composite and predict the enhancement in the composite material. The influence of the bias/over wrapping angle of the MWNT sheets on the carbon fiber was also studied. The predicted compressive strength from the MD results and the multiscale approach for baseline Epoxy case was shown to be in good relation with the experimental results for Epon-862. On adding MWNTs to the epoxy system, a significant improvement in the compressive strength of the PMC was observed. Further, the effect of bias angle of MWNT wrapped over carbon fiber was compared for 0°, 45° and 90°. This is further verified by making use of the Halpin-Tsai.

Organic-inorganic nano-composite films for photonic applications made by multi-beam multi-target pulsed laser deposition with remote control of the plume directions

NASA Astrophysics Data System (ADS)

Darwish, Abdalla M.; Moore, Shaelynn; Mohammed, Aziz; Alexander, Deonte'; Bastian, Tyler; Dorlus, Wydglif; Sarkisov, Sergey S.; Patel, Darayas N.; Mele, Paolo; Koplitz, Brent

2016-09-01

There has been an explosive interest in the technique of laser assisted deposition of polymer nano-composite films exploiting the matrix assisted pulsed laser evaporation (MAPLE) with regard to the polymer host as can be judged form recent publications.1-4 In MAPLE, a frozen solution of a polymer in a relatively volatile solvent is used as a laser target. The solvent and concentration are selected so that first, the polymer of interest can dissolve to form a dilute, particulate free solution, second, the majority of the laser energy is initially absorbed by the solvent molecules and not by the solute molecules, and third, there is no photochemical reaction between the solvent and the solute. The light-material interaction in MAPLE can be described as a photothermal process. The photon energy absorbed by the solvent is converted to thermal energy that causes the polymer to be heated but the solvent to vaporize. As the surface solvent molecules are evaporated into the gas phase, polymer molecules are exposed at the gas-target matrix interface. The polymer molecules attain sufficient kinetic energy through collective collisions with the evaporating solvent molecules, to be transferred into the gas phase. By careful optimization of the MAPLE deposition conditions (laser wavelength, repetition rate, solvent type, concentration, temperature, and background gas and gas pressure), this process can occur without any significant polymer decomposition. The MAPLE process proceeds layer-by-layer, depleting the target of solvent and polymer in the same concentration as the starting matrix. When a substrate is positioned directly in the path of the plume, a coating starts to form from the evaporated polymer molecules, while the volatile solvent molecules are evacuated by the pump from the deposition chamber. In case of fabrication of polymer nanocomposites, MAPLE targets are usually prepared as nano-colloids of the additives of interest in the initial polymer solutions. Mixing the components of different nature, organic polymers and inorganic dopants, in the same target at a certain proportion and exposing them to the same laser beam not necessarily brings good quality nano-composite films. The laser pulse energy and wavelength cannot be optimized for each component individually. Also, the mixing proportion in the composite film is dictated by the initial proportion of the target and thus cannot be changed in the process. These limitations were removed in the recently proposed method of multi-beam and multi-target deposition (in its doublebeam/ dual-target variation) using a MAPLE polymer target and one inorganic target, each being concurrently exposed to laser beams of different wavelengths.5-14 Using the method, nano-composite films of polymer poly(methyl methacrylate) known as PMMA doped with a rare earth (RE) inorganic upconversion phosphor compounds were prepared. Also, a nano-composite film of thermoelectric film of inorganic aluminum-doped ZnO known as AZO was impregnated with PMMA nano-fillers with the purpose of improving electrical conductivity and thermoelectric performance.10, 14 The polymer target was a frozen (to a temperature of liquid nitrogen) PMMA solution in chlorobenzene exposed to a 1064- nm laser beam from a Q-switched Nd:YAG pulsed laser. The inorganic targets were the pellets made of the compressed micro-powders of highly efficient RE-doped NaYF4 or the sintered powder of AZO concurrently ablated with the

Compositions containing borane or carborane cage compounds and related applications

DOEpatents

Bowen, III, Daniel E; Eastwood, Eric A

2013-05-28

Compositions comprising a polymer-containing matrix and a filler comprising a cage compound selected from borane cage compounds, carborane cage compounds, metal complexes thereof, residues thereof, mixtures thereof, and/or agglomerations thereof, where the cage compound is not covalently bound to the matrix polymer. Methods of making and applications for using such compositions are also disclosed.

Magnetic nanofiber composite materials and devices using same

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chen, Xing; Zhou, Ziyao

2017-04-11

A nonreciprocal device is described. It includes a housing, a waveguide layer and at least one layer of magnetic nanofiber composite. The magnetic nanofiber composite layer is made up of a polymer base layer, a dielectric matrix comprising magnetic nanofibers. The nanofibers have a high aspect ratio and wherein said dielectric matrix is embedded in the polymer base layer.

Effect of Coconut, Sisal and Jute Fibers on the Properties of Starch/Gluten/Glycerol Matrix

USDA-ARS?s Scientific Manuscript database

Coconut, sisal and jute fibers were added as reinforcement materials in a biodegradable polymer matrix comprised of starch/gluten/glycerol. The content of fibers used in the composites varied from 5% to 30% by weight of the total polymers (starch and gluten). Materials were processed in a Haake torq...

Compositions containing borane or carborane cage compounds and related applications

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bowen, III, Daniel E; Eastwood, Eric A

2014-11-11

Compositions comprising a polymer-containing matrix and a filler comprising a cage compound selected from borane cage compounds, carborane cage compounds, metal complexes thereof, residues thereof, mixtures thereof, and/or agglomerations thereof, where the cage compound is not covalently bound to the matrix polymer. Methods of making and applications for using such compositions are also disclosed.

Compositions containing borane or carborane cage compounds and related applications

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bowen, III, Daniel E.; Eastwood, Eric A.

2015-09-15

Compositions comprising a polymer-containing matrix and a filler comprising a cage compound selected from borane cage compounds, carborane cage compounds, metal complexes thereof, residues thereof, mixtures thereof, and/or agglomerations thereof, where the cage compound is not covalently bound to the matrix polymer. Methods of making and applications for using such compositions are also disclosed.

Zeolite-imidazolate framework (ZIF-8) membrane synthesis on a mixed-matrix substrate.

PubMed

Barankova, Eva; Pradeep, Neelakanda; Peinemann, Klaus-Viktor

2013-10-21

A thin, dense, compact and hydrogen selective ZIF-8 membrane was synthesized on a polymer/metal oxide mixed-matrix support by a secondary seeding method. The new concept of incorporating ZnO particles into the support and PDMS coating of the ZIF-8 layer is introduced to improve the preparation of ZIF-polymer composite membranes.

Process of Making Boron-Fiber Reinforced Composite Tape

NASA Technical Reports Server (NTRS)

Belvin, Harry L. (Inventor); Cano, Roberto J. (Inventor); Johnston, Norman J. (Inventor); Marchello, Joseph M. (Inventor)

2002-01-01

The invention is an apparatus and method for producing a hybrid boron reinforced polymer matrix composition from powder pre-impregnated fiber tow bundles and a linear array of boron fibers. The boron fibers are applied onto the powder pre-impregnated fiber tow bundles and then are processed within a processing component having an impregnation bar assembly. After passing through variable-dimension forming nip-rollers, the powder pre-impregnated fiber tow bundles with the boron fibers become a hybrid boron reinforced polymer matrix composite tape. A driving mechanism pulls the powder pre-impregnated fiber tow bundles with boron fibers through the processing line of the apparatus and a take-up spool collects the formed hybrid boron-fiber reinforced polymer matrix composite tape.

Variable-Resistivity Material For Memory Circuits

NASA Technical Reports Server (NTRS)

Nagasubramanian, Ganesan; Distefano, Salvador; Moacanin, Jovan

1989-01-01

Nonvolatile memory elements packed densely. Electrically-erasable, programmable, read-only memory matrices made with newly-synthesized organic material of variable electrical resistivity. Material, polypyrrole doped with tetracyanoquinhydrone (TCNQ), changes reversibly between insulating or higher-resistivity state and conducting or low-resistivity state. Thin film of conductive polymer separates layer of row conductors from layer of column conductors. Resistivity of film at each intersection and, therefore, resistance of memory element defined by row and column, increased or decreased by application of suitable switching voltage. Matrix circuits made with this material useful for experiments in associative electronic memories based on models of neural networks.

Adsorption of copolymers at polymer/air and polymer/solid interfaces

NASA Astrophysics Data System (ADS)

Oslanec, Robert

Using mainly low-energy forward recoil spectrometry (LE-FRES) and neutron reflectivity (NR), copolymer behavior at polymer/air and polymer/solid interfaces is investigated. For a miscible blend of poly(styrene-ran-acrylonitrile) copolymers, the volume fraction profile of the copolymer with lower acrylonitrile content is flat near the surface in contrast to mean field predictions. Including copolymer polydispersity into a self consistent mean field (SCMF) model does not account for this profile shape. LE-FRES and NR is also used to study poly(deuterated styrene-block-methyl-methacrylate) (dPS-b-PMMA) adsorption from a polymer matrix to a silicon oxide substrate. The interfacial excess, zsp*, layer thickness, L, and layer-matrix width, w, depend strongly on the number of matrix segments, P, for P 2N, the matrix chains are repelled from the adsorbed layer and the layer characteristics become independent of P. An SCMF model of block copolymer adsorption is developed. SCMF predictions are in qualitative agreement with the experimental behavior of zsp*, L, and w as a function of P. Using this model, the interaction energy of the MMA block with the oxide substrate is found to be -8ksb{B}T. In a subsequent experiment, the matrix/dPS interaction is made increasingly unfavorable by increasing the 4-bromostyrene mole fraction, x, in a poly(styrene-ran-4-bromostyrene) (PBrsbxS) matrix. Whereas experiments show that zsp* slightly decreases as x increases, the SCMF model predicts that zsp* should increase as the matrix becomes more unfavorable. Upon including a small matrix attraction for the substrate, the SCMF model shows that zsp* decreases with x because of competition between PBrsbxS and dPS-b-PMMA for adsorbing sites. In thin film dewetting experiments on silicon oxide, the addition of dPS-b-PMMA to PS coatings acts to slow hole growth and prevent holes from impinging. Dewetting studies show that longer dPS-b-PMMA chains are more effective stabilizing agents than shorter ones and that 3 volume percent dPS-b-PMMA is the optimum additive concentration for this system. For a dPS-b-PMMA:PS blend, atomic force microscopy of the hole floor reveals mounds of residual polymer and a modulated contact line where the rim meets the substrate.

Proton exchange membrane based on chitosan and solvent-free carbon nanotube fluids for fuel cells applications.

PubMed

Wang, Jie; Gong, Chunli; Wen, Sheng; Liu, Hai; Qin, Caiqin; Xiong, Chuanxi; Dong, Lijie

2018-04-15

Poor dispersion and inert ionic conduction are two major obstacles towards using carbon nanotubes (CNTs) to modify polymer electrolyte membranes (PEMs) in energy conversion devices. In this work, solvent-free carbon nanotube fluids (CNT fluids) with liquid-like behavior are prepared through an ion exchange method and incorporated into a chitosan (CS) matrix to fabricate composite membranes. The electrostatic interactions between SO 3 - groups in the CNT fluids and NH 2 groups in the CS matrix, in addition to the unique flow properties of the CNT fluids, promote the uniform dispersion of CNT fluids in the CS matrix. Markedly, the CS/CNT fluid-3 composite membrane is simultaneously reinforced and toughened by 180% and 300% compared to pure CS membrane, respectively. Moreover, the SO 3 - groups in the CNT fluids facilitate the proton transfer such that the proton conductivity of CS/CNT fluid-3 composite membrane reaches a maximum value of 0.044 S cm -1 at 80 °C. Copyright © 2018 Elsevier Ltd. All rights reserved.

Modeling of Interfacial Modification Effects on Thermal Conductivity of Carbon Nanotube Composites

NASA Technical Reports Server (NTRS)

Clancy, Thomas C.; Gates, Thomas S.

2006-01-01

The effect of functionalization of carbon nanotubes on the thermal conductivity of nanocomposites has been studied using a multi-scale modeling approach. These results predict that grafting linear hydrocarbon chains to the surface of a single wall carbon nanotube with covalent chemical bonds should result in a significant increase in the thermal conductivity of these nanocomposites. This is due to the decrease in the interfacial thermal (Kapitza) resistance between the single wall carbon nanotube and the surrounding polymer matrix upon chemical functionalization. The nanocomposites studied here consist of single wall carbon nanotubes in a bulk poly(ethylene vinyl acetate) matrix. The nanotubes are functionalized by end-grafting linear hydrocarbon chains of varying length to the surface of the nanotube. The effect which this functionalization has on the interfacial thermal resistance is studied by molecular dynamics simulation. Interfacial thermal resistance values are calculated for a range of chemical grafting densities and with several chain lengths. These results are subsequently used in an analytical model to predict the resulting effect on the bulk thermal conductivity of the nanocomposite.

Development of electroactive polymer nanocomposites with porous structured materials

NASA Astrophysics Data System (ADS)

Lopes, Ana Catarina Teixeira Castro

Electroactive polymer composites are interesting materials for advance technological applications due to the possibility to combine the electroactive properties of the polymer matrix with a large variety of fillers that allow tailored responses for specific applications. The best all-around electroactive polymers are poly(vinylidene fluoride) (PVDF) and its copolymers which allied with the properties of porous zeolite materials, with tailored shape, size and Si/Al ratio, among others, leads to the possibility of development of promising PVDF/zeolite composites. In this way, a study of the structural, thermal and electrical properties of PVDF composites prepared with different framework zeolite types (LTL, LTA, FAU and MFI), different polymer solvents (DMF, DMSO, TEP) and different zeolite (NaY) concentrations (4, 16, 24 and 32 wt %) was performed. Further, the dielectric response, electrical conductivity and electric modulus of the composites were investigated as a function of NaYzeolite content. The zeolite influence on the electroactive gamma-phase crystallization of PVDF was explored, as well as the effect of clay layered structure (Montmorillonite, Kaolinite and Laponite) on the electroactive gamma-phase nucleation and on the optical transparency of the composite. It was found that the obtained composites showed an electrical response dependence on the pore structure and chemical content of the inorganic host. The dielectric response of the composites is directly related to the Si/Al ratio, leading zeolites with lower Si/Al ratios to larger dielectric responses and encapsulation efficiencies in the composites. It was also found that the zeolite content strongly influences the macroscopic response of dielectric response, which increases for increasing filler content. The dielectric constant at room temperature reaches values larger than 1000 for the 32 wt.% composite at 1 kHz what is mainly attributed to restricted ion mobility and interfacial polarization effects due to the zeolite inclusion, leading also to high dielectric losses. For the higher zeolite concentrations the composite d.c. electrical conductivity is characterized by two conducting regimes separated by a concentration independent breaking voltage of 4 V, which is associated to an intrazeolite charge transport. Dielectric relaxation studies show that the main relaxation process (?-relaxation) of the amorphous phase of the polymer matrix is not affected by the presence of the zeolite and, in a similar way, the zeolite low temperature relaxation is not significantly affected by the polymer phase. On the other hand, the electric modulus formalism reveals significant contributions of the fillers to the electrical permittivity and conductivity of the composites. The presence of the zeolite particles increases a.c. conductivity and the Maxwell-Wagner-Sillars contribution that is predominant at low frequencies with respect to the ohmic contribution to permittivity. The ability of zeolites to induce the eletroactive gamma-phase nucleation of PVDF is directly dependent on the Si/Al ratio and zeolite content; however it only occurs when the composite is melted at temperatures below 200 ºC. The complete ?-phase crystallization of the polymer crystalline phase occurs for a filler content of 16 wt% of LTA or FAU zeolite structure. The even higher surface interaction of clays when exfoliated leads to the same phenomenon with an amount of 0.50 % of Montmorillonite clay content. The electroactivity of the material has been proven by measuring the piezoelectric d33 response of the material, which presents a value of -7 pC/N, lower than for beta-PVDF obtained by mechanical stretching but still among the largest coefficients obtained for polymers. Further, the optical transmittance in the visible range is strongly enhanced with respect to the transmittance of the pure polymer. The development, characterization and physical-chemical understanding of these PVDF/zeolite and PVDF/clay composites resulted in suitable materials for applications in diverse areas including battery separator membranes and biomedical applications.

Analysis of mechanical properties anisotropy of nanomodified carbon fibre-reinforced woven composites

NASA Astrophysics Data System (ADS)

Ruslantsev, A. N.; Portnova, Ya M.; Tairova, L. P.; Dumansky, A. M.

2016-10-01

The polymer binder cracking problem arises while designing and maintaining polymer composite-based aircraft load-bearing members. Some technological methods are used to solve this problem. In particular the injection of nanoagents can block the initiation and growth of microscopic cracks. Crack propagation can also be blocked if the strain energy release is not related with fracturing. One of the possible ways for such energy release is creep. Testing of the anisotropy of the woven carbon fibre reinforced plastic elastic characteristics and creep have been conducted. The samples with different layouts have been made of woven carbon fibre laminate BMI-3/3692 with nanomodified bismaleimide matrix. This matrix has a higher glass transition temperature and improved mechanical properties. The deformation regularities have been analyzed, layer elastic characteristics have been determined. The constitutive equations describing composite material creep have been obtained and its parameters have been defined. Experimental and calculated creep curves have been plotted. It was found that the effects of rheology arise as the direction of load does not match the direction of reinforcing fibres of the material.

Preparation and characterization of PVP-PVA–ZnO blend polymer nano composite films

DOE Office of Scientific and Technical Information (OSTI.GOV)

Divya, S., E-mail: divi.fysics@gmail.com; Saipriya, G.; Hemalatha, J., E-mail: hemalatha@nitt.edu

Flexible self-standing films of PVP-PVA blend composites are prepared by using ZnO as a nano filler at different concentrations. The structural, compositional, morphological and optical studies made with the help of X-ray diffraction (XRD), Fourier Transform Infra-Red spectroscopy (FTIR), Scanning electron microscope (SEM), Atomic Force Microscopy (AFM), Ultraviolet-visible spectroscopy (UV-vis) and Photoluminescence (PL) spectra are presented in this paper. The results of XRD indicate that ZnO nanoparticles are formed with hexagonal phase in the polymeric matrix. SEM images show the dispersion of ZnO nano filler in the polymer matrix. UV–vis spectra reveal that the absorption peak is centered around 235more » nm and 370 nm for the nano composite films. The blue shift is observed with decrease in the concentration of the nano filler. PL spectra shows the excitation wavelength is given at 320 nm.The emission peaks were observed at 383 nm ascribing to the electronic transitions between valence band and conduction band and the peak at 430 nm.« less

Preparation and characterization of composites based on poly(lactic acid) and CaCO{sub 3} nanofiller

DOE Office of Scientific and Technical Information (OSTI.GOV)

Moreno, Janaína Fernandes; Silva, Ana Lúcia N. da, E-mail: janamoreno.quim@gmail.com, E-mail: ananazareth@ima.ufrj.br; Silva, Antonio Henrique Monteiro da Fonseca T. da, E-mail: antoniohmfts@id.uff.br

In recent years, extensive studies have been conducted on the study of the poly(lactic acid) (PLA) properties, because of its being a typical biobased and biodegradable polymer, with good mechanical properties. However, its toughness and gas barrier properties are not satisfactory and can be improved by the addition of nanofillers, such as calcium carbonate (n-CaCO{sub 3}). The present work PLA composites with nano-sized precipitated calcium carbonate (n-NPCC) were prepared by melt extrusion. Thermal, mechanical and flow properties of the composites were evaluated by using a factorial design.The results showed that the addition of the nanofiller in the PLA matrix didn’tmore » improve thethermal and mechanical properties of the matrix significantly. This behavior is probably due to the presence of the stearic acid that is coating on the n-NPCC particles, resulting in a weak polymer-particle interaction. Beyond this, it was also observed a decrease in MFI of the composites when nanofiller was added and at a higher screw speed.« less

Suspensions of polymer-grafted nanoparticles with added polymers-Structure and effective pair-interactions.

PubMed

Chandran, Sivasurender; Saw, Shibu; Kandar, A K; Dasgupta, C; Sprung, M; Basu, J K

2015-08-28

We present the results of combined experimental and theoretical (molecular dynamics simulations and integral equation theory) studies of the structure and effective interactions of suspensions of polymer grafted nanoparticles (PGNPs) in the presence of linear polymers. Due to the absence of systematic experimental and theoretical studies of PGNPs, it is widely believed that the structure and effective interactions in such binary mixtures would be very similar to those of an analogous soft colloidal material-star polymers. In our study, polystyrene-grafted gold nanoparticles with functionality f = 70 were mixed with linear polystyrene (PS) of two different molecular weights for obtaining two PGNP:PS size ratios, ξ = 0.14 and 2.76 (where, ξ = Mg/Mm, Mg and Mm being the molecular weights of grafting and matrix polymers, respectively). The experimental structure factor of PGNPs could be modeled with an effective potential (Model-X), which has been found to be widely applicable for star polymers. Similarly, the structure factor of the blends with ξ = 0.14 could be modeled reasonably well, while the structure of blends with ξ = 2.76 could not be captured, especially for high density of added polymers. A model (Model-Y) for effective interactions between PGNPs in a melt of matrix polymers also failed to provide good agreement with the experimental data for samples with ξ = 2.76 and high density of added polymers. We tentatively attribute this anomaly in modeling the structure factor of blends with ξ = 2.76 to the questionable assumption of Model-X in describing the added polymers as star polymers with functionality 2, which gets manifested in both polymer-polymer and polymer-PGNP interactions especially at higher fractions of added polymers. The failure of Model-Y may be due to the neglect of possible many-body interactions among PGNPs mediated by matrix polymers when the fraction of added polymers is high. These observations point to the need for a new framework to understand not only the structural behavior of PGNPs but also possibly their dynamics and thermo-mechanical properties as well.

Carbon Nanotube Purification and Functionalization

NASA Technical Reports Server (NTRS)

Lebron, Marisabel; Mintz, Eric; Smalley, Richard E.; Meador, Michael A.

2003-01-01

Carbon nanotubes have the potential to significantly enhance the mechanical, thermal, and electrical properties of polymers. However, dispersion of carbon nanotubes in a polymer matrix is hindered by the electrostatic forces that cause them to agglomerate. Chemical modification of the nanotubes is necessary to minimize these electrostatic forces and promote adhesion between the nanotubes and the polymer matrix. In a collaborative research program between Clark Atlanta University, Rice University, and NASA Glenn Research Center several approaches are being explored to chemically modify carbon nanotubes. The results of this research will be presented.

Properties and Residual Stresses in Angle-Ply Polymer Matrix Composites

DTIC Science & Technology

1982-03-01

AMMRC TR 82-12 PROPERTIES AND RES l DUAL STRESSES IN ANGLE-PLY POLYMER MATR l X COMPOSITES March 1982 ABDEL A. FAHMY,, HARVEY A. WEST, and MARK...m D.e. Enl.r.d) PROPERTIES AND RESIDUAL STRESSES I N ANGLE-PLY F i n a l Report POLYMER MATRIX COMPOSITES REPORTDOCUMENTATlON PAGE I 7. AUTHOR...SUPPLEMENTARV NOTES L 19. KEY WORDS (Comclrm. m r.r.r. wd. 11 ner..sw and idenllfy by blocb nmb-r) Composites Thermal expansion Epoxy l a m i n a t e s

Raw materials for wood-polymer composites.

Treesearch

Craig Clemons

2008-01-01

To understand wood-plastic composites (WPCs) adequately, we must first understand the two main constituents. Though both are polymer based, they are very different in origin, structure, and performance. Polymers are high molecular weight materials whose performance is largely determined by its molecular architecture. In WPCs, a polymer matrix forms the continuous phase...

Optically transparent semiconducting polymer nanonetwork for flexible and transparent electronics

PubMed Central

Yu, Kilho; Park, Byoungwook; Kim, Geunjin; Kim, Chang-Hyun; Park, Sungjun; Kim, Jehan; Jung, Suhyun; Jeong, Soyeong; Kwon, Sooncheol; Kang, Hongkyu; Kim, Junghwan; Yoon, Myung-Han; Lee, Kwanghee

2016-01-01

Simultaneously achieving high optical transparency and excellent charge mobility in semiconducting polymers has presented a challenge for the application of these materials in future “flexible” and “transparent” electronics (FTEs). Here, by blending only a small amount (∼15 wt %) of a diketopyrrolopyrrole-based semiconducting polymer (DPP2T) into an inert polystyrene (PS) matrix, we introduce a polymer blend system that demonstrates both high field-effect transistor (FET) mobility and excellent optical transparency that approaches 100%. We discover that in a PS matrix, DPP2T forms a web-like, continuously connected nanonetwork that spreads throughout the thin film and provides highly efficient 2D charge pathways through extended intrachain conjugation. The remarkable physical properties achieved using our approach enable us to develop prototype high-performance FTE devices, including colorless all-polymer FET arrays and fully transparent FET-integrated polymer light-emitting diodes. PMID:27911774

Ultra-high dispersion of graphene in polymer composite via solvent free fabrication and functionalization

PubMed Central

Noh, Ye Ji; Joh, Han-Ik; Yu, Jaesang; Hwang, Soon Hyoun; Lee, Sungho; Lee, Cheol Ho; Kim, Seong Yun; Youn, Jae Ryoun

2015-01-01

The drying process of graphene-polymer composites fabricated by solution-processing for excellent dispersion is time consuming and suffers from a restacking problem. Here, we have developed an innovative method to fabricate polymer composites with well dispersed graphene particles in the matrix resin by using solvent free powder mixing and in-situ polymerization of a low viscosity oligomer resin. We also prepared composites filled with up to 20 wt% of graphene particles by the solvent free process while maintaining a high degree of dispersion. The electrical conductivity of the composite, one of the most significant properties affected by the dispersion, was consistent with the theoretically obtained effective electrical conductivity based on the mean field micromechanical analysis with the Mori-Tanaka model assuming ideal dispersion. It can be confirmed by looking at the statistical results of the filler-to-filler distance obtained from the digital processing of the fracture surface images that the various oxygenated functional groups of graphene oxide can help improve the dispersion of the filler and that the introduction of large phenyl groups to the graphene basal plane has a positive effect on the dispersion. PMID:25771823

Bismaleimides and related maleimido polymers as matrix resins

NASA Technical Reports Server (NTRS)

Parker, J. A.; Kourtides, D. A.; Fohlen, G. M.

1985-01-01

Significant processing and property improvements can be achieved by copolymerization of state-of-the-art bisimides with various vinyl stilbazole derivatives to give both fire resistance and high-temperature properties from hot-melt compositions. Significant improvement in mechanical properties is achieved through these modifications, which may make these new matrix resins ideal candidates for fireworthy secondary graphite composite structures. Phosphorous modifications of maleimido polymers through phosphonate structure and tricyclophosphazene derivatives provide families of new matrix resins for short-time applications in severe thermo-oxidative environments. With further research these may provide matrix resins for long-term thermo-oxidative stability of advanced composites at temperatures up to 400 to 500 C.

Study of piezoelectric filler on the properties of PZT-PVDF composites

NASA Astrophysics Data System (ADS)

Matei, Alina; Å¢ucureanu, Vasilica; Vlǎzan, Paulina; Cernica, Ileana; Popescu, Marian; RomaniÅ£an, Cosmin

2017-12-01

The ability to obtain composites with desired functionalities is based on advanced knowledge of the processes synthesis and of the structure of piezoceramic materials, as well the incorporation of different fillers in selected polymer matrix. Polyvinylidene fluoride (PVDF) is a fluorinated polymer with excellent mechanical and electric properties, which it was chosen as matrix due to their applications in a wide range of industrial fields [1-4]. The present paper focuses on the development of composites based on PZT particles as filler obtained by conventional methods and PVDF as polymer matrix. The synthesis of PVDF-PZT composites was obtained by dispersing the ceramic powders in a solution of PVDF in N-methyl-pyrrolidone (NMP) under mechanical mixing and ultrasonication, until a homogenous mixture is obtained. The properties of the piezoceramic fillers before and after embedding into the polymeric matrix were investigated by Fourier transform infrared spectrometry, field emission scanning electron microscopy and X-ray diffraction. In the FTIR spectra, appear a large number of absorption bands which are exclusive of the phases from PVDF matrix confirming the total embedding of PZT filler into matrix. Also, the XRD pattern of the composites has confirmed the presence of crystalline phases of PVDF and the ceramic phase of PZT. The SEM results showed a good distribution of fillers in the matrix.

Self-healing polymers and composites based on thermal activation

NASA Astrophysics Data System (ADS)

Wang, Ying; Bolanos, Ed; Wudl, Fred; Hahn, Thomas; Kwok, Nathan

2007-04-01

Structural polymer composites are susceptible to premature failure in the form of microcracks in the matrix. Although benign initially when they form, these matrix cracks tend to coalesce and lead in service to critical damage modes such as ply delamination. The matrix cracks are difficult to detect and almost impossible to repair because they form inside the composite laminate. Therefore, polymers with self-healing capability would provide a promising potential to minimize maintenance costs while extending the service lifetime of composite structures. In this paper we report on a group of polymers and their composites which exhibit mendable property upon heating. The failure and healing mechanisms of the polymers involve Diels-Alder (DA) and retro-Diels-Alder (RDA) reactions on the polymer back-bone chain, which are thermally reversible reactions requiring no catalyst. The polymers exhibited good healing property in bulk form. Composite panels were prepared by sandwiching the monomers between carbon fiber fabric layers and cured in autoclave. Microcracks were induced on the resin-rich surface of composite with Instron machine at room temperature by holding at 1% strain for 1 min. The healing ability of the composite was also demonstrated by the disappearance of microcracks after heating. In addition to the self-healing ability, the polymers and composites also exhibited shape memory property. These unique properties may provide the material multi-functional applications. Resistance heating of traditional composites and its applicability in self-healing composites is also studied to lay groundwork for a fully integrated self-healing composite.

Conservative Exposure Predictions for Rapid Risk Assessment of Phase-Separated Additives in Medical Device Polymers.

PubMed

Chandrasekar, Vaishnavi; Janes, Dustin W; Saylor, David M; Hood, Alan; Bajaj, Akhil; Duncan, Timothy V; Zheng, Jiwen; Isayeva, Irada S; Forrey, Christopher; Casey, Brendan J

2018-01-01

A novel approach for rapid risk assessment of targeted leachables in medical device polymers is proposed and validated. Risk evaluation involves understanding the potential of these additives to migrate out of the polymer, and comparing their exposure to a toxicological threshold value. In this study, we propose that a simple diffusive transport model can be used to provide conservative exposure estimates for phase separated color additives in device polymers. This model has been illustrated using a representative phthalocyanine color additive (manganese phthalocyanine, MnPC) and polymer (PEBAX 2533) system. Sorption experiments of MnPC into PEBAX were conducted in order to experimentally determine the diffusion coefficient, D = (1.6 ± 0.5) × 10 -11  cm 2 /s, and matrix solubility limit, C s  = 0.089 wt.%, and model predicted exposure values were validated by extraction experiments. Exposure values for the color additive were compared to a toxicological threshold for a sample risk assessment. Results from this study indicate that a diffusion model-based approach to predict exposure has considerable potential for use as a rapid, screening-level tool to assess the risk of color additives and other small molecule additives in medical device polymers.

Thermoset molecular composites

DOEpatents

Benicewicz, Brian C.; Douglas, Elliot P.; Hjelm, Jr., Rex P.

1996-01-01

A polymeric composition including a liquid crystalline polymer and a thermosettable liquid crystalline monomer matrix, said polymeric composition characterized by a phase separation on the scale of less than about 500 Angstroms and a polymeric composition including a liquid crystalline polymer and a liquid crystalline thermoset matrix, said polymeric composition characterized by a phase separation on the scale of less than about 500 Angstroms are disclosed.

Fluorescent Water Soluble Polymers for Isozyme-Selective Interactions with Matrix Metalloproteinase-9

PubMed Central

Dutta, Rinku; Scott, Michael D.; Haldar, Manas K.; Ganguly, Bratati; Srivastava, D. K.; Friesner, Daniel L.; Mallik, Sanku

2011-01-01

Matrix metalloproteinases (MMPs) are overexpressed in various pathological conditions, including various cancers. Although these isozymes have similar active sites, the patterns of exposed amino acids on their surfaces are different. Herein, we report the synthesis and molecular interactions of two water-soluble, fluorescent polymers which demonstrate selective interactions with MMP-9 compared to MMP-7 and -10. PMID:21367603

A study on mechanical properties of PBT nano-composites reinforced with microwave functionalized MWCNTs

NASA Astrophysics Data System (ADS)

Deshpande, Revati; Naik, Garima; Chopra, Swamini; Deshmukh, Kavita A.; Deshmukh, Abhay D.; Peshwe, D. R.

2018-04-01

Polybutylene Terephthalate (PBT) is a synthetic thermoplastic polymer with fast crystallization rate; and is extensively used in many automobile applications where it is prone to continuous wear. Carbon Nanotubes (CNTs) as reinforcements are most ideal and promising reinforcement in enhancing mechanical properties of polymers. Owing to strong van der Waals’ interaction between the nanotubes; they tend to aggregate. To overcome this behavior, CNTs are generally functionalized in acid solutions to help stabilize the dispersion and allow interaction with polymer matrix. Thus, the present study focuses on the effect of reinforcing microwave-functionalized CNTs on the mechanical and tribological properties of PBT polymer matrix. The homogenous dispersion of CNTs in PBT matrix was successfully achieved by functionalizing the CNTs. DSC and XRD analysis confirms better crystallization and reduced crystallite size due to improved nucleation. Apart; an increase in the hardness and MFI value was also noted, which again hinted towards improved dispersion. However, the reduction in tensile strength and % elongation indicated embrittlement of the PBT matrix after addition of functionalized CNTs. Furthermore, the peeling and scuffing phenomenon observed for virgin PBT, during sliding wear, was suppressed after CNT addition.

Process and Microstructure to Achieve Ultra-high Dielectric Constant in Ceramic-Polymer Composites.

PubMed

Zhang, Lin; Shan, Xiaobing; Bass, Patrick; Tong, Yang; Rolin, Terry D; Hill, Curtis W; Brewer, Jeffrey C; Tucker, Dennis S; Cheng, Z-Y

2016-10-21

Influences of process conditions on microstructure and dielectric properties of ceramic-polymer composites are systematically studied using CaCu 3 Ti 4 O 12 (CCTO) as filler and P(VDF-TrFE) 55/45 mol.% copolymer as the matrix by combining solution-cast and hot-pressing processes. It is found that the dielectric constant of the composites can be significantly enhanced-up to about 10 times - by using proper processing conditions. The dielectric constant of the composites can reach more than 1,000 over a wide temperature range with a low loss (tan δ ~ 10 -1 ). It is concluded that besides the dense structure of composites, the uniform distribution of the CCTO particles in the matrix plays a key role on the dielectric enhancement. Due to the influence of the CCTO on the microstructure of the polymer matrix, the composites exhibit a weaker temperature dependence of the dielectric constant than the polymer matrix. Based on the results, it is also found that the loss of the composites at low temperatures, including room temperature, is determined by the real dielectric relaxation processes including the relaxation process induced by the mixing.

Process and Microstructure to Achieve Ultra-high Dielectric Constant in Ceramic-Polymer Composites

NASA Astrophysics Data System (ADS)

Zhang, Lin; Shan, Xiaobing; Bass, Patrick; Tong, Yang; Rolin, Terry D.; Hill, Curtis W.; Brewer, Jeffrey C.; Tucker, Dennis S.; Cheng, Z.-Y.

2016-10-01

Influences of process conditions on microstructure and dielectric properties of ceramic-polymer composites are systematically studied using CaCu3Ti4O12 (CCTO) as filler and P(VDF-TrFE) 55/45 mol.% copolymer as the matrix by combining solution-cast and hot-pressing processes. It is found that the dielectric constant of the composites can be significantly enhanced-up to about 10 times - by using proper processing conditions. The dielectric constant of the composites can reach more than 1,000 over a wide temperature range with a low loss (tan δ ~ 10-1). It is concluded that besides the dense structure of composites, the uniform distribution of the CCTO particles in the matrix plays a key role on the dielectric enhancement. Due to the influence of the CCTO on the microstructure of the polymer matrix, the composites exhibit a weaker temperature dependence of the dielectric constant than the polymer matrix. Based on the results, it is also found that the loss of the composites at low temperatures, including room temperature, is determined by the real dielectric relaxation processes including the relaxation process induced by the mixing.

Process and Microstructure to Achieve Ultra-high Dielectric Constant in Ceramic-Polymer Composites

PubMed Central

Zhang, Lin; Shan, Xiaobing; Bass, Patrick; Tong, Yang; Rolin, Terry D.; Hill, Curtis W.; Brewer, Jeffrey C.; Tucker, Dennis S.; Cheng, Z.-Y.

2016-01-01

Influences of process conditions on microstructure and dielectric properties of ceramic-polymer composites are systematically studied using CaCu3Ti4O12 (CCTO) as filler and P(VDF-TrFE) 55/45 mol.% copolymer as the matrix by combining solution-cast and hot-pressing processes. It is found that the dielectric constant of the composites can be significantly enhanced–up to about 10 times – by using proper processing conditions. The dielectric constant of the composites can reach more than 1,000 over a wide temperature range with a low loss (tan δ ~ 10−1). It is concluded that besides the dense structure of composites, the uniform distribution of the CCTO particles in the matrix plays a key role on the dielectric enhancement. Due to the influence of the CCTO on the microstructure of the polymer matrix, the composites exhibit a weaker temperature dependence of the dielectric constant than the polymer matrix. Based on the results, it is also found that the loss of the composites at low temperatures, including room temperature, is determined by the real dielectric relaxation processes including the relaxation process induced by the mixing. PMID:27767184

Improvement of mechanical properties of polymeric composites: Experimental methods and new systems

NASA Astrophysics Data System (ADS)

Nguyen, Felix Nhanchau

Filler- (e.g., particulate or fiber) reinforced structural polymers or polymeric composites have changed the way things are made. Today, they are found, for example, in air/ground transportation vehicles, sporting goods, ballistic barrier applications and weapons, electronic packaging, musical instruments, fashion items, and more. As the demand increases, so does the desire to have not only well balanced mechanical properties, but also light weight and low cost. This leads to a constant search for novel constituents and additives, new fabrication methods and analytical techniques. To achieve new or improved composite materials requires more than the identification of the right reinforcements to be used with the right polymer matrix at the right loading. Also, an optimized adhesion between the two phases and a toughened matrix system are needed. This calls for new methods to predict, modify and assess the level of adhesion, and new developments in matrix tougheners to minimize compromises in other mechanical/thermal properties. Furthermore, structural optimization, associated with fabrication (e.g., avoidance of fiber-fiber touching or particle aggregation), and sometimes special properties, such as electrical conductivity or magnetic susceptibility are necessary. Finally, the composite system's durability, often under hostile conditions, is generally mandatory. The present study researches new predictive and experimental methods for optimizing and characterizing filler-matrix adhesion and develops a new type of epoxy tougheners. Specifically, (1) a simple thermodynamic parameter evaluated by UNIFAC is applied successfully to screen out candidate adhesion promoters, which is necessary for optimization of the physio-chemical interactions between the two phases; (2) an optical-acoustical mechanical test assisted with an acoustic emission technique is developed to de-convolute filler debonding/delamination among many other micro failure events, and (3) novel core (thermoplastic)-shell (dendrimer) nanoparticles are synthesized and incorporated in epoxy to enhance both stiffness and the polymer's fracture toughness or resistance to crack growth. This unique dendrimer has the possibility of acting both as an adhesion promoter and filler spacer, when applied to the filler surface, and as a matrix enhancer, when combined with other materials, with the unique ability to improve mechanical/thermal/electrical properties. These developments should help in the creation of the next generation of polymeric composites.

Molecular dynamics simulation of diffusion of gases in a carbon-nanotube-polymer composite

NASA Astrophysics Data System (ADS)

Lim, Seong Y.; Sahimi, Muhammad; Tsotsis, Theodore T.; Kim, Nayong

2007-07-01

Extensive molecular dynamics (MD) simulations were carried out to compute the solubilities and self-diffusivities of CO2 and CH4 in amorphous polyetherimide (PEI) and mixed-matrix PEI generated by inserting single-walled carbon nanotubes into the polymer. Atomistic models of PEI and its composites were generated using energy minimizations, MD simulations, and the polymer-consistent force field. Two types of polymer composite were generated by inserting (7,0) and (12,0) zigzag carbon nanotubes into the PEI structure. The morphologies of PEI and its composites were characterized by their densities, radial distribution functions, and the accessible free volumes, which were computed with probe molecules of different sizes. The distributions of the cavity volumes were computed using the Voronoi tessellation method. The computed self-diffusivities of the gases in the polymer composites are much larger than those in pure PEI. We find, however, that the increase is not due to diffusion of the gases through the nanotubes which have smooth energy surfaces and, therefore, provide fast transport paths. Instead, the MD simulations indicate a squeezing effect of the nanotubes on the polymer matrix that changes the composite polymers’ free-volume distributions and makes them more sharply peaked. The presence of nanotubes also creates several cavities with large volumes that give rise to larger diffusivities in the polymer composites. This effect is due to the repulsive interactions between the polymer and the nanotubes. The solubilities of the gases in the polymer composites are also larger than those in pure PEI, hence indicating larger gas permeabilities for mixed-matrix PEI than PEI itself.

Environmental durability of polymer concrete

DOE Office of Scientific and Technical Information (OSTI.GOV)

Palmese, G.R.; Chawalwala, A.J.

1996-12-31

Over the past two decades, polymer concrete has increasingly been used for a number of applications including piping, machine bases, chemically resistant flooring, and bridge overlays. Currently, the use of polymer concrete as a wear surface for polymeric composite bridge decks is being investigated. Polymer concrete is a particulate composite comprised of mineral aggregate bound by a polymeric matrix. Such materials possess significantly higher mechanical properties than Portland cement concrete. However, the mechanical characteristics and environmental durability of polymer concrete are influenced by a number of factors. Among these are the selection of aggregate and resin, surface treatment, and curemore » conditions. In this work the influence of matrix selection and cure history on the environmental durability of polymer concrete was investigated. Particular attention was given to the effects of water on composite properties and to the mechanisms by which degradation occurs. The basalt-based polymer concrete systems investigated were susceptible to attack by water. Furthermore, results suggest that property loss associated with water exposure was primarily a result of interfacial weakening.« less

Nanoparticle-assisted high photoconductive gain in polymer/fullerene matrix

PubMed Central

Chen, Hsiang-Yu; Lo, Michael K. F.; Yang, Guanwen; Monbouquette, Harold G.; Yang, Yang

2014-01-01

Polymer/inorganic nanocrystal composites1–10 offer an attractive means to combine the merits of organic and inorganic materials into novel electronic and photonic systems. However, many applications of these composites are limited by the solubility11 and distribution of nanocrystals (NCs) in polymer matrices. Here, a high photoconductive gain has been achieved by blending cadmium telluride (CdTe) nanoparticles (NPs) into a polymer/fullerene matrix followed by a solvent annealing12 process. The NP surface capping ligand, N-phenyl-N’-methyldithiocarbamate, renders the NPs highly soluble in the polymer blend thereby enabling high nanocrystal loadings. An external quantum efficiency (EQE) as high as ~8000% (at 350nm) is reached at −4.5V. Hole-dominant devices coupled with AFM images are studied to uncover the probable mechanism. We observe a higher concentration of CdTe NPs is located near the cathode/polymer interface. These NPs with trapped electrons assist hole injection into the polymer under reverse bias, which contributes to greater than 100% EQE. PMID:18772915

A Fully Non-Metallic Gas Turbine Engine Enabled by Additive Manufacturing Part I: System Analysis, Component Identification, Additive Manufacturing, and Testing of Polymer Composites

NASA Technical Reports Server (NTRS)

Grady, Joseph E.; Haller, William J.; Poinsatte, Philip E.; Halbig, Michael C.; Schnulo, Sydney L.; Singh, Mrityunjay; Weir, Don; Wali, Natalie; Vinup, Michael; Jones, Michael G.;

Designing Solvent Exchange-Induced In Situ Forming Gel from Aqueous Insoluble Polymers as Matrix Base for Periodontitis Treatment.

PubMed

Srichan, Tharatree; Phaechamud, Thawatchai

2017-01-01

An in situ forming gel is a dosage form which is promised for site-specific therapy such as periodontal pocket of periodontitis treatment. Ethylcellulose, bleached shellac, and Eudragit RS were applied in this study as a polymeric matrix for in situ forming gel employing N-methyl pyrrolidone (NMP) as solvent. Solutions comprising ethylcellulose, bleached shellac, and Eudragit RS in NMP were evaluated for viscosity, rheology, and rate of water penetration. Ease of administration by injection was determined as the force required to expel polymeric solutions through a needle using texture analyzer. In vitro gel formation and in vitro gel degradation were conducted after injection into phosphate buffer solution pH 6.8. Ethylcellulose, bleached shellac, and Eudragit RS could form the in situ gel, in vitro. Gel viscosity and pH value depended on percentage amount of the polymer, whereas the water diffusion at early period likely relied on types of polymer. Furthermore, the solutions containing higher polymer concentration exhibited the lower degree of degradation. All the preparations were acceptable as injectable dosage forms because the applied force was lower than 50 N. All of them inhibited Staphylococcus aureus, Escherichia coli, Candida albicans, Streptococcus mutans, and Porphyrommonas gingivalis growth owing to antimicrobial activity of NMP which exhibited a potential use for periodontitis treatment. Moreover, the developed systems presented as the solvent exchange induced in situ forming gel and showed capability to be incorporated with the suitable antimicrobial active compounds for periodontitis treatment which should be further studied.

Tough and Conductive Hybrid Hydrogels Enabling Facile Patterning.

PubMed

Zhu, Fengbo; Lin, Ji; Wu, Zi Liang; Qu, Shaoxing; Yin, Jun; Qian, Jin; Zheng, Qiang

2018-04-25

Conductive polymer hydrogels (CPHs) that combine the unique properties of hydrogels and electronic properties of conductors have shown their great potentials in wearable/implantable electronic devices, where materials with remarkable mechanical properties, high conductivity, and easy processability are demanding. Here, we have developed a new type of polyion complex/polyaniline (PIC/PAni) hybrid hydrogels that are tough, conductive, and can be facilely patterned. The incorporation of conductive phase (PAni) into PIC matrix through phytic acid resulted in hybrid gels with ∼65 wt % water; high conductivity while maintaining the key viscoelasticity of the tough matrix. The gel prepared from 1 M aniline (Ani) exhibited the breaking strain, fracture stress, tensile modulus, and electrical conductivity of 395%, 1.15 MPa, 5.31 MPa, and 0.7 S/m, respectively, superior to the most existing CPHs. The mechanical and electrical performance of PIC/PAni hybrid hydrogels exhibited pronounced rate-dependent and self-recovery behaviors. The hybrid gels can effectively detect subtle human motions as strain sensors. Alternating conductive/nonconductive patterns can be readily achieved by selective Ani polymerization using stencil masks. This facile patterning method based on PIC/PAni gels can be readily scaled up for fast fabrication of wavy gel circuits and multichannel sensor arrays, enabling real-time monitoring of the large-extent and large-area deformations with various sensitivities.

Chemically modified graphene/polyimide composite films based on utilization of covalent bonding and oriented distribution.

PubMed

Huang, Ting; Lu, Renguo; Su, Chao; Wang, Hongna; Guo, Zheng; Liu, Pei; Huang, Zhongyuan; Chen, Haiming; Li, Tongsheng

2012-05-01

Herein, we have developed a rather simple composite fabrication approach to achieving molecular-level dispersion and planar orientation of chemically modified graphene (CMG) in the thermosetting polyimide (PI) matrix as well as realizing strong adhesion at the interfacial regions between reinforcing filler and matrix. The covalent adhesion of CMG to PI matrix and oriented distribution of CMG were carefully confirmed and analyzed by detailed investigations. Combination of covalent bonding and oriented distribution could enlarge the effectiveness of CMG in the matrix. Efficient stress transfer was found at the CMG/PI interfaces. Significant improvements in the mechanical performances, thermal stability, electrical conductivity, and hydrophobic behavior were achieved by addition of only a small amount of CMG. Furthermore, it is noteworthy that the hydrophilic-to-hydrophobic transition and the electrical percolation were observed at only 0.2 wt % CMG in this composite system. This facile methodology is believed to afford broad application potential in graphene-based polymer nanocomposites, especially other types of high-performance thermosetting systems.

Carbon nanotubes/fluorinated polymers nanocomposite thin films for electrical contacts lubrication

NASA Astrophysics Data System (ADS)

Benedetto, A.; Viel, P.; Noël, S.; Izard, N.; Chenevier, P.; Palacin, S.

2007-09-01

The need to operate in extreme environmental conditions (ultra high vacuum, high temperatures, aerospatial environment, …) and the miniaturization toward micro electromechanical systems is demanding new materials in the field of low-level electrical contacts lubrication. Dry and chemically immobilized lubrication is expected to be an alternative to the traditional wet lubricants oils. With the goal to conciliate electrical conductivity and lubricant properties we designed nanocomposite thin films composed of a 2D carbon nanotubes network embedded in an organic matrix. The nanotubes networks were deposited on gold surfaces modified by electrochemical cathodic grafting of poly(acrylonitrile). The same substrate served for covalently bonding the low-friction organic matrix. Three different matrixes were tested: a perfluorinated oligomer chemically grafted and two different polyfluorinated acrylates electrochemically grafted. The nanocomposite thin films have been characterized by ATR FT-IR, XPS and Raman spectroscopy. We measured the effects of the different matrixes and the nanotubes addition on the tribological properties and on the contact resistances of the films.

Dielectric relaxations and conduction mechanisms in polyether-clay composite polymer electrolytes under high carbon dioxide pressure.

PubMed

Kitajima, Shunsuke; Bertasi, Federico; Vezzù, Keti; Negro, Enrico; Tominaga, Yoichi; Di Noto, Vito

2013-10-21

The composite material P(EO/EM)-Sa consisting of synthetic saponite (Sa) dispersed in poly[ethylene oxide-co-2-(2-methoxyethoxy)ethyl glycidyl ether] (P(EO/EM)) is studied by "in situ" measurements using broadband electrical spectroscopy (BES) under pressurized CO2 to characterize the dynamic behavior of conductivity and the dielectric relaxations of the ion host polymer matrix. It is revealed that there are three dielectric relaxation processes associated with: (I) the dipolar motions in the short oxyethylene side chains of P(EO/EM) (β); and (II) the segmental motion of the main chains comprising the polyether components (αfast, αslow). αslow is attributed to the slow α-relaxation of P(EO/EM) macromolecules, which is hindered by the strong coordination interactions with the ions. Two conduction processes are observed, σDC and σID, which are attributed, respectively, to the bulk conductivity and the interdomain conductivity. The temperature dependence of conductivity and relaxation processes reveals that αfast and αslow are strongly correlated with σDC and σID. The "in situ" BES measurements under pressurized CO2 indicate a fast decrease in σDC at the initial CO2 treatment time resulting from the decrease in the concentration of polyether-M(n+) complexes, which is driven by the CO2 permeation. The relaxation frequency (fR) of αslow at the initial CO2 treatment time increases and shows a steep rise with time with the same behavior of the αfast mode. It is demonstrated that the interactions between polyether chains of P(EO/EM) and cations in the polymer electrolyte layers embedded in Sa are probably weakened by the low permittivity of CO2 (ε = 1.08). Thus, the formation of ion pairs in the polymer electrolyte domains of P(EO/EM)-Sa occurs, with a corresponding reduction in the concentration of ion carriers.

Non-Newtonian behavior observed via dynamic rheology for various particle types in energetic materials and simulant composites

NASA Astrophysics Data System (ADS)

Choi, Jong Han; Lee, Sangmook; Lee, Jae Wook

2017-02-01

The rheological properties of polymer composites highly filled with different filler materials were examined using a stress-controlled rheometer with a parallel-plate configuration, for particle characterization of the filler materials in plastic (polymer) bonded explosive (PBX). Ethylene vinyl acetate (EVA) with dioctyl adipate (DOA) was used as the matrix phase, which was shown to exhibit Newtonian-like behavior. The dispersed phase consisted of one of two energetic materials, i.e., explosive cyclotrimethylene trinitramine (RDX) or cyclotetramethylene tetranitramine (HMX), or a simulant (Dechlorane) in a bimodal size distribution. Before the test, preshearing was conducted to identify the initial condition of each sample. All examined filled polymer specimens exhibited yield stress and shear-thinning behavior over the investigated frequency range. The complex viscosity dependence on the dynamic oscillation frequency was also fitted using an appropriate rheological model, suggesting the model parameters. Furthermore, the temperature dependency of the different filler particle types was determined for different filler volume fractions. These comparative studies revealed the influence of the particle characteristics on the rheological properties of the filled polymer.

Studying the orientation of bio-objects by nematic liquid crystals

NASA Astrophysics Data System (ADS)

Zubtsova, Yu. A.; Kamanin, A. A.; Kamanina, N. V.

2017-05-01

We have studied the ability of a liquid-crystal (LC) matrix to visualize and orient DNA molecules. It is established that the relief of the interface between the LC mesophase and conducting contact can be improved without using an additional high-ohmic polymer layer. Spectroscopic and ellipsometric techniques revealed changes in the refractive properties and structure of composites. The obtained results can be used in creating devices for rapid DNA testing with retained form of biostructures.

Sustained release of antimicrobial drugs from polyvinylalcohol and gum arabica blend matrix.

PubMed

Kushwaha, V; Bhowmick, A; Behera, B K; Ray, A R

1998-03-01

Synthetic polymers are widely used in biomedical applications. Polymer blends have recently paved their way in this field. An attempt to prepare blend of synthetic polymer polyvinylalcohol and natural macromolecule gum arabica is made in this paper. Characterization of these blends by NMR, DSC and viscoelastic studies reveal preparation of a blend composition with synergistic properties. The blend composition with synergistic properties was used to release various antimicrobial drugs. The duration and release of the drug depends on the amount of drug loaded in the matrix and solubility of the drug in the matrix and release medium. The advantage of this system is that the release kinetics of the drug from the system can be tailored by adjusting plasticizer, homopolymer and crosslinker composition depending on the drug to be released.

Iron oxide/cassava starch-supported Ziegler-Natta catalysts for in situ ethylene polymerization.

PubMed

Chancharoenrith, Sittikorn; Kamonsatikul, Choavarit; Namkajorn, Montree; Kiatisevi, Supavadee; Somsook, Ekasith

2015-03-06

Iron oxide nanoparticles were used as supporters for in situ polymerization to produce polymer nanocomposites with well-dispersed fillers in polymer matrix. Iron oxide could be sustained as colloidal solutions by cassava starch to produce a good dispersion of iron oxide in the matrix. New supports based on iron oxide/cassava starch or cassava starch for Ziegler-Natta catalysts were utilized as heterogeneous supporters for partially hydrolyzed triethylaluminum. Then, TiCl4 was immobilized on the supports as catalysts for polymerization of ethylene. High-density polyethylene (HDPE) composites were obtained by the synthesized catalysts. A good dispersion of iron oxide/cassava starch particles was observed in the synthesized polymer matrix promoting to good mechanical properties of HDPE. Copyright © 2014 Elsevier Ltd. All rights reserved.

Nonlinearity and Strain-Rate Dependence in the Deformation Response of Polymer Matrix Composites Modeled

NASA Technical Reports Server (NTRS)

Goldberg, Robert K.

2000-01-01

There has been no accurate procedure for modeling the high-speed impact of composite materials, but such an analytical capability will be required in designing reliable lightweight engine-containment systems. The majority of the models in use assume a linear elastic material response that does not vary with strain rate. However, for containment systems, polymer matrix composites incorporating ductile polymers are likely to be used. For such a material, the deformation response is likely to be nonlinear and to vary with strain rate. An analytical model has been developed at the NASA Glenn Research Center at Lewis Field that incorporates both of these features. A set of constitutive equations that was originally developed to analyze the viscoplastic deformation of metals (Ramaswamy-Stouffer equations) was modified to simulate the nonlinear, rate-dependent deformation of polymers. Specifically, the effects of hydrostatic stresses on the inelastic response, which can be significant in polymers, were accounted for by a modification of the definition of the effective stress. The constitutive equations were then incorporated into a composite micromechanics model based on the mechanics of materials theory. This theory predicts the deformation response of a composite material from the properties and behavior of the individual constituents. In this manner, the nonlinear, rate-dependent deformation response of a polymer matrix composite can be predicted.

Microwave absorption properties of reduced graphene oxide strontium hexaferrite/poly(methyl methacrylate) composites

NASA Astrophysics Data System (ADS)

Acharya, Sanghamitra; Ray, J.; Patro, T. U.; Alegaonkar, Prashant; Datar, Suwarna

2018-03-01

The key factors to consider when designing microwave absorber materials for eradication of electromagnetic (EM) pollution are absorption of incident EM waves and good impedance matching. By keeping these things in mind, flexible microwave absorber composite films can be fabricated by simple gel casting techniques using reduced graphene oxide (RGO) and strontium ferrite (SF) in a poly(methyl methacrylate) (PMMA) matrix. SF nanoparticles are synthesized by the well known sol-gel method. Subsequently, reduced graphene oxide (RGO) and SF nanocomposite (RGOSF) are prepared through a chemical reduction method using hydrazine. The structure, morphology, chemical composition, thermal stability and magnetic properties of the nanocomposite are characterized in detail by various techniques. The SF particles are found to be nearly 500 nm and decorated on RGO sheets as revealed by field emission scanning electron microscopy and transmission electron microscopy analysis. Fourier transform infrared and and Raman spectroscopy clearly show the presence of SF in the graphene sheet by the lower peak positions. Finally, ternary polymer composites of RGO/SF/PMMA are prepared by an in situ polymerization method. Magnetic and dielectric studies of the composite reveal that the presence of RGO/SF/PMMA lead to polarization effects contributing to dielectric loss. Also, RGO surrounding SF provides a conductive network in the polymer matrix which is in turn responsible for the magnetic loss in the composite. Thus, the permittivity as well as the permeability of the composite can be controlled by an appropriate combination of RGO and SF in PMMA. More than 99% absorption efficiency is achieved by a suitable combination of magneto-dielectric coupling in the X-band frequency range by incorporating 9 wt% of RGO and 1 wt% of SF in the polymer matrix.

Water hyacinth: a possible alternative rate retarding natural polymer used in sustained release tablet design

PubMed Central

Khatun, Sabera; Sutradhar, Kumar B.

2014-01-01

In recent years natural polymers have been widely used because of their effectiveness and availability over synthetic polymers. In this present investigation matrix tablets of Metformin hydrochloride were formulated using Water hyacinth powder and its rate retardant activity was studied. Tablets were prepared using wet granulation method with 8% starch as granulating agent and 5, 10, 15, 20, 25 and 30% of Water hyacinth powder to the drug. In preformulation study, angle of repose, Carr's Index and Hausner ratio were calculated. Fourier Transform Infrared Spectroscopy (FTIR), Differential Scanning Calorimetry (DSC), and Scanning Electron Microscopy (SEM) studies were performed and no interactions were found between drug and excipients. Weight variation, friability, hardness, thickness, diameter, and in vitro release study were performed with the prepared matrix tablets. Dissolution studies were conducted using USP type II apparatus at a speed of 100 rpm at 37°C ± 0.5 temperature for 8 h. Though all the formulations comply with both BP and USP requirements, formulation F-1 (5% of Water hyacinth) was the best fitted formula. The drug release patterns were explained in different kinetic models such as Zero order, First order, Higuchi, Hixson Crowell, and Korsmeyer-Peppas equations. The current investigation implies that Water hyacinth has the potential to be used as a rate-retarding agent in sustained release drug formulations. PMID:24966835

Multi-walled carbon nanotubes/polymer composites in absence and presence of acrylic elastomer (ACM).

PubMed

Kumar, S; Rath, T; Mahaling, R N; Mukherjee, M; Khatua, B B; Das, C K

2009-05-01

Polyetherimide/Multiwall carbon nanotube (MWNTs) nanocomposites containing as-received and modified (COOH-MWNT) carbon nanotubes were prepared through melt process in extruder and then compression molded. Thermal properties of the composites were characterized by thermo-gravimetric analysis (TGA). Field emission scanning electron microscopy (FESEM) images showed that the MWNTs were well dispersed and formed an intimate contact with the polymer matrix without any agglomeration. However the incorporation of modified carbon nanotubes formed fascinating, highly crosslinked, and compact network structure throughout the polymer matrix. This showed the increased adhesion of PEI with modified MWNTs. Scanning electron microscopy (SEM) also showed high degree of dispersion of modified MWNTs along with broken ends. Dynamic mechanical analysis (DMA) results showed a marginal increase in storage modulus (E') and glass transition temperature (T(g)) with the addition of MWNTs. Increase in tensile strength and impact strength of composites confirmed the use the MWNTs as possible reinforcement agent. Both thermal and electrical conductivity of composites increased, but effect is more pronounced on modification due to formation of network of carbon nanotubes. Addition of acrylic elastomer to developed PEI/MWNTs (modified) nanocomposites resulted in the further increase in thermal and electrical properties due to the formation of additional bond between MWNTs and acrylic elastomers at the interface. All the results presented are well corroborated by SEM and FESEM studies.

Double emulsions for the compatibilization of hydrophilic nanocellulose with non-polar polymers and validation in the synthesis of composite fibers.

PubMed

Carrillo, Carlos A; Nypelö, Tiina; Rojas, Orlando J

2016-03-14

A route for the compatibilization of aqueous dispersions of cellulose nanofibrils (CNFs) with a non-polar polymer matrix is proposed to overcome a major challenge in CNF-based material synthesis. Non-ionic surfactants were used in CNF aqueous dispersions equilibrated with an organic phase (for demonstration, a polystyrene solution, PS, was used). Stable water-in-oil-in-water (W/O/W) double emulsions were produced as a result of the compromise between composition and formulation variables. Most remarkably, the proposed route for CNF integration with hydrophobic polymers removed the need for drying or solvent-exchange of the CNF aqueous dispersion prior to processing. The rheological behavior of the double emulsions showed strong shear thinning behavior and facilitated CNF-PS co-mixing in solid nanofibers upon electrospinning. The morphology and thermal properties of the resultant nanofibers revealed that CNFs were efficiently integrated in the hydrophobic matrix which was consistent with the high interfacial area of the precursor double emulsion. In addition, the morphology and quality of the composite nanofibers can be controlled by the conductivity (ionic strength) of the CNF dispersion. Overall, double emulsion systems are proposed as a novel, efficient and scalable platform for CNF co-processing with non-polar systems and they open up the possibility for the redispersion of CNFs after removal of the organic phase.

Nanofiber Based Optical Sensors for Oxygen Determination

NASA Astrophysics Data System (ADS)

Xue, Ruipeng

Oxygen sensors based on luminescent quenching of nanofibers were developed for measurement of both gaseous and dissolved oxygen concentrations. Electrospinning was used to fabricate "core-shell" fiber configurations in which oxygen-sensitive transition metal complexes are embedded into a polymer 'core' while a synthetic biocompatible polymer provides a protective 'shell.' Various matrix polymers and luminescent probes were studied in terms of their sensitivity, linear calibration, reversibility, response time, stability and probe-matrix interactions. Due to the small size and high surface area of these nanofibers, all samples showed rapid response and a highly linear response to oxygen. The sensitivity and photostability of the sensors were controlled by the identity of both the probe molecule and the polymer matrix. Such nanofiber sensor forms are particularly suitable in biological applications due to the fact that they do not consume oxygen, are biocompatible and biomimetic and can be easily incorporated into cell culture. Applications of these fibers in cancer cell research, wound healing, breath analysis and waste water treatment were explored.