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Sample records for self-healing polymer composite

  1. Multifunctional Polymers and Composites for Self-Healing Applications

    DTIC Science & Technology

    2006-09-30

    30 September 2006 4 . TITLE AND SUBTITLE 5a. CONTRACT NUMBER Multifunctional Polymers and Composites for Self-Healing Applications 5b. GRANT NUMBER...Multifunctional Polymers and Composites for Self-Healing Applications FINAL TECHNICAL REPORT AFOSR GRANT # F49620-03-1-0179 4 /1/2003-9/30/2006 Scott R. White...copolymerization strategies, "• develop new mechanochemical triggering concepts for self-healing polymers. STATUS This project began 4 /1/03 and

  2. Photoresponsive Self-Healing Polymer Composite with Photoabsorbing Hybrid Microcapsules.

    PubMed

    Gao, Lei; He, Jinliang; Hu, Jun; Wang, Chao

    2015-11-18

    Microcapsule-based self-healing polymer materials are highly desirable because they can heal large-volume cracks without changing the original chemical structures of polymers. However, they are limited by processing difficulties and inhomogeneous distributions of two components. Herein, we report a one-component photoresponsive self-healing polymer composite with photoabsorbing hybrid microcapsules (PAHM), which gives the microcapsules photoabsorbing properties by introducing nano-TiO2 particles as photoabsorbing and emulsified agents in the poly(urea-formaldehyde)/TiO2 hybrid shells. Upon mechanical damage and then exposure to light, the photoresponsive healing agents in the cracks will be solidified to allow for self-healing, while the healing agents in the unbroken PAHM will be protected and remain unreacted, which endows this photoresponsive microcapsule-based self-healing composite with self-healing properties like those found in the conventional two-component microcapsule-based systems. Given the universality of this hybrid polymerization method, incorporation of the photoabsorbing particles to conventional polymer shells may further broaden the scope of applications of these widely used materials.

  3. Nanostructured Self-Healing Polymers and Composites

    DTIC Science & Technology

    2010-10-31

    science and engineering of new processing routes for nanoencapsulation of healing chemistries and seamless integration of the self-healing functionality...healing with submicron and nanoscale consitutents. The research was driven by basic science and engineering of new processing routes for nanoencapsulation...polymerization of urea and formaldehyde using a modified process of Brown et al. [2]. The sonication horn of an ultrasonic homogenizer was placed in

  4. A self-healing polymer composite for extended fatigue life

    SciTech Connect

    Brown, E. N.; Jones, A. S.; White, S. R.; Sottos, Nancy R.

    2004-01-01

    A novel approach is explored for improving the fatigue life of thermosetting polymers through the addition of self-healing functionality. Thermosetting polymers are used in a wide variety of applications, but are susceptible to the initiation and propagation of small cracks deep within the structure where detection is difficult and repair is virtually impossible. The material under investigation is an epoxy matrix composite, which utilizes embedded microcapsules to store a healing agent and an embedded catalyst. A propagating crack exposes particles of catalyst and ruptures the microcapsules, which release healing agent into the crack plane. Polymerization of the healing agent is triggered by contact with the catalyst. Fatigue crack retardation and arrest from self-healing functionality result from crack-tip shielding mechanisms, such as hydrodynamic pressure and artificial-crack closure. In situ healing is observed to significantly extended fatigue life or permanently arrested fatigue crack growth over a wide range of loading conditions.

  5. Self-healing polymer composites: mimicking nature to enhance performance.

    PubMed

    Trask, R S; Williams, H R; Bond, I P

    2007-03-01

    Autonomic self-healing materials, where initiation of repair is integral to the material, are being developed for engineering applications. This bio-inspired concept offers the designer an ability to incorporate secondary functional materials capable of counteracting service degradation whilst still achieving the primary, usually structural, requirement. Most materials in nature are themselves self-healing composite materials. This paper reviews the various self-healing technologies currently being developed for fibre reinforced polymeric composite materials, most of which are bioinspired, inspired by observation of nature. The most recent self-healing work has attempted to mimic natural healing through the study of mammalian blood clotting and the design of vascular networks found in biological systems. A perspective on current and future self-healing approaches using this biomimetic technique is offered. The intention is to stimulate debate outside the engineering community and reinforce the importance of a multidisciplinary approach in this exciting field.

  6. Fatigue crack arrest in a self-healing polymer composite

    SciTech Connect

    Brown, E. N.; White, S. R.; Sottos, Nancy R.

    2004-01-01

    A comprehensive experimental program is performed to assess the in situ fatigue behavior of a self-healing polymer. A fatigue-life-extension protocol is established for characterizing healing efficiency of the self-healing epoxy under cyclic loading. At moderate {Delta}K{sub I} and at high {Delta}K{sub I}, when a rest period is employed, in situ healing extends fatigue life though temporary crack arrest and retardation. In situ self-healing permanently arrests crack growth at low {delta}K{sub I} and at moderate {Delta}K{sub I}, when a rest period is employed. Fatigue crack retardation and arrest result from two primary crack-tip shielding mechanisms: hydrodynamic pressure in the viscous healing agent and artificial crack closure. Application of self-healing functionality to fatigue slows the crack growth rate and increases the fatigue threshold.

  7. Self-healing polymers

    NASA Technical Reports Server (NTRS)

    Klein, Daniel J. (Inventor)

    2011-01-01

    A three dimensional structure fabricated from a self-healing polymeric material, comprising poly(ester amides) obtained from ethylene glycol, azelaic acid and 1,1-aminoundecanoic acid, wherein polymeric material has a melt index above 2.5 g/10 min. as determined by ASTM D1238 at 190.degree. C. and 2.16kg, impact resistance and ductility sufficient to resist cracking and brittle fracture upon impact by a 9 mm bullet fired at a temperature of about 29.degree. C. at subsonic speed in a range from about 800 feet/sec to about 1000 feet/sec. It has been determined that the important factors necessary for self-healing behavior of polymers include sufficient impact strength, control of the degree of crystallinity, low melting point and the ability to instantly melt at impacted area.

  8. Repeated self-healing of microvascular carbon fibre reinforced polymer composites

    NASA Astrophysics Data System (ADS)

    Coope, T. S.; Wass, D. F.; Trask, R. S.; Bond, I. P.

    2014-11-01

    A self-healing, high performance, carbon fibre reinforced polymer (CFRP) composite is demonstrated by embedding a Lewis-acid catalytic curing agent within a laminate, manufactured using out of autoclave (OOA) composite manufacturing methods. Two configurations of healing agent delivery, pre-mixed and autonomous mixing, are investigated via injection of a healing agent through bio-inspired microvascular channels exposed on Mode I fractured crack planes. Healing is effected when an epoxy resin-solvent healing agent mixture reaches the boundary of embedded solid-state scandium(III) triflate (Sc(OTf)3) catalyst, located on the crack plane, to initiate the ring-opening polymerisation (ROP) of epoxides. Tailored self-healing agents confer high healing efficiency values after multiple healing cycles (69-108%) to successfully mitigate against crack propagation within the composite microstructure.

  9. An Assessment of Self-Healing Fiber Reinforced Composites

    NASA Technical Reports Server (NTRS)

    Smith, Joseph G., Jr.

    2012-01-01

    Several reviews and books have been written concerning self-healing polymers over the last few years. These have focused primarily on the types of self-healing materials being studied, with minor emphasis given to composite properties. The purpose of this review is to assess the self-healing ability of these materials when utilized in fiber reinforced composites

  10. Self-Healing Polymer Networks

    NASA Astrophysics Data System (ADS)

    Tournilhac, Francois

    2012-02-01

    Supramolecular chemistry teaches us to control non-covalent interactions between organic molecules, particularly through the use of optimized building blocks able to establish several hydrogen bonds in parallel. This discipline has emerged as a powerful tool in the design of new materials through the concept of supramolecular polymers. One of the fascinating aspects of such materials is the possibility of controlling the structure, adding functionalities, adjusting the macroscopic properties of and taking profit of the non-trivial dynamics associated to the reversibility of H-bond links. Applications of these compounds may include adhesives, coatings, rheology additives, high performance materials, etc. However, the synthesis of such polymers at the industrial scale still remains a challenge. Our first ambition is to design supramolecular polymers with original properties, the second ambition is to devise simple and environmentally friendly methods for their industrial production. In our endeavours to create novel supramolecular networks with rubbery elasticity, self-healing ability and as little as possible creep, the strategy to prolongate the relaxation time and in the same time, keep the system flexible was to synthesize rather than a single molecule, an assembly of randomly branched H-bonding oligomers. We propose a strategy to obtain through a facile one-pot synthesis a large variety of supramolecular materials that can behave as differently as associating low-viscosity liquids, semi-crystalline or amorphous thermoplastics, viscoelastic melts or self-healing rubbers.

  11. Self-Healing Nanofiber-Reinforced Polymer Composites. 1. Tensile Testing and Recovery of Mechanical Properties.

    PubMed

    Lee, Min Wook; An, Seongpil; Jo, Hong Seok; Yoon, Sam S; Yarin, Alexander L

    2015-09-09

    The present work aims at development of self-healing materials capable of partially restoring their mechanical properties under the conditions of prolonged periodic loading and unloading, which is characteristic, for example, of aerospace applications. Composite materials used in these and many other applications frequently reveal multiple defects stemming from their original inhomogeneity, which facilitates microcracking and delamination at ply interfaces. Self-healing nanofiber mats may effectively prevent such damage without compromising material integrity. Two types of core-shell nanofibers were simultaneously electrospun onto the same substrate in order to form a mutually entangled mat. The first type of core-shell fibers consisted of resin monomer (dimethylsiloxane) within the core and polyacrylonitrile within the shell. The second type of core-shell nanofibers consisted of cure (dimethyl-methyl hydrogen-siloxane) within the core and polyacrylonitrile within the shell. These mutually entangled nanofiber mats were used for tensile testing, and they were also encased in polydimethylsiloxane to form composites that were also subsequently subjected to tensile testing. During tensile tests, the nanofibers can be damaged in stretching up to the plastic regime of deformation. Then, the resin monomer and cure was released from the cores and the polydimethylsiloxane resin was polymerized, which might be expected to result in the self-healing properties of these materials. To reveal and evaluate the self-healing properties of the polyacrylonitrile-resin-cure nanofiber mats and their composites, the results were compared to the tensile test results of the monolithic polyacrylonitrile nanofiber mats or composites formed by encasing polyacrylonitrile nanofibers in a polydimethylsiloxane matrix. The latter do not possess self-healing properties, and indeed, do not recover their mechanical characteristics, in contrast to the polyacrylonitrile-resin-cure nanofiber mats and

  12. Self-healing of damage in fibre-reinforced polymer-matrix composites.

    PubMed

    Hayes, S A; Zhang, W; Branthwaite, M; Jones, F R

    2007-04-22

    Self-healing resin systems have been discussed for over a decade and four different technologies had been proposed. However, little work on their application as composite matrices has been published although this was one of the stated aims of the earliest work in the field. This paper reports on the optimization of a solid-state self-healing resin system and its subsequent use as a matrix for high volume fraction glass fibre-reinforced composites. The resin system was optimized using Charpy impact testing and repeated healing, while the efficiency of healing in composites was determined by analysing the growth of delaminations following repeated impacts with or without a healing cycle. To act as a reference, a non-healing resin system was subjected to the same treatments and the results are compared with the healable system. The optimized resin system displays a healing efficiency of 65% after the first healing cycle, dropping to 35 and 30% after the second and third healing cycles, respectively. Correction for any healability due to further curing showed that approximately 50% healing efficiency could be achieved with the bisphenol A-based epoxy resin containing 7.5% of polybisphenol-A-co-epichlorohydrin. The composite, on the other hand, displays a healing efficiency of approximately 30%. It is therefore clear that the solid-state self-healing system is capable of healing transverse cracks and delaminations in a composite, but that more work is needed to optimize matrix healing within a composite and to develop a methodology for assessing recovery in performance.

  13. Self-healing coatings based on halloysite clay polymer composites for protection of copper alloys.

    PubMed

    Abdullayev, Elshad; Abbasov, Vagif; Tursunbayeva, Asel; Portnov, Vasiliy; Ibrahimov, Hikmat; Mukhtarova, Gulbaniz; Lvov, Yuri

    2013-05-22

    Halloysite clay nanotubes loaded with corrosion inhibitors benzotriazole (BTA), 2-mercaptobenzimidazole (MBI), and 2-mercaptobenzothiazole (MBT) were used as additives in self-healing composite paint coating of copper. These inhibitors form protective films on the metal surface and mitigate corrosion. Mechanisms involved in the film formation have been studied with optical and electron microscopy, UV-vis spectrometry, and adhesivity tests. Efficiency of the halloysite lumen loading ascended in the order of BTA < MBT < MBI; consequently, MBI and MBT halloysite formulations have shown the best protection. Inhibitors were kept in the tubes buried in polymeric paint layer for a long time and release was enhanced in the coating defects exposed to humid media with 20-50 h, sufficient for formation of protective layer. Anticorrosive performance of the halloysite-based composite acrylic and polyurethane coatings have been demonstrated for 110-copper alloy strips exposed to 0.5 M aqueous NaCl for 6 months.

  14. Self-healing polymers via supramolecular forces.

    PubMed

    Herbst, Florian; Döhler, Diana; Michael, Philipp; Binder, Wolfgang H

    2013-02-12

    As polymers and polymeric materials are "the" smart invention and technological driving force of the 20th century, the quest for self-healing or self-repairing polymers is strong. The concept of supramolecular self-healing materials relies on the use of noncovalent, transient bonds to generate networks, which are able to heal the damaged site, putting aspects of reversibility and dynamics of a network as crucial factors for the understanding and design of such self-healing materials. This Review describes recent examples and concepts of supramolecular polymers based on hydrogen bonding, π-π interactions, ionomers, and coordinative bonds, thus convincingly discussing the advantages and versatility of these supramolecular forces for the design and realization of self-healing polymers. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  15. Self-healing composites and applications thereof

    DOEpatents

    Tee, Chee Keong; Wang, Chao; Cui, Yi; Bao, Zhenan

    2016-11-08

    A battery electrode includes an electrochemically active material and a binder covering the electrochemically active material. The binder includes a self-healing polymer and conductive additives dispersed in the self-healing polymer to provide an electrical pathway across at least a portion of the binder.

  16. Self-Healing Composite of Thermoset Polymer and Programmed Super Contraction Fibers

    NASA Technical Reports Server (NTRS)

    Li, Guoqiang (Inventor); Meng, Harper (Inventor)

    2016-01-01

    A composition comprising thermoset polymer, shape memory polymer to facilitate macro scale damage closure, and a thermoplastic polymer for molecular scale healing is disclosed; the composition has the ability to resolve structural defects by a bio-mimetic close-then heal process. In use, the shape memory polymer serves to bring surfaces of a structural defect into approximation, whereafter use of the thermoplastic polymer for molecular scale healing allowed for movement of the thermoplastic polymer into the defect and thus obtain molecular scale healing. The thermoplastic can be fibers, particles or spheres which are used by heating to a level at or above the thermoplastic's melting point, then cooling of the composition below the melting temperature of the thermoplastic. Compositions of the invention have the ability to not only close macroscopic defects, but also to do so repeatedly even if another wound/damage occurs in a previously healed/repaired area.

  17. Self-healing Nanofiber-Reinforced Polymer Composites. 2. Delamination/Debonding and Adhesive and Cohesive Properties.

    PubMed

    Lee, Min Wook; An, Seongpil; Jo, Hong Seok; Yoon, Sam S; Yarin, Alexander L

    2015-09-09

    The capacity for core-shell nanofiber mats containing healing agents (resin monomer and cure) in their cores to adhere to a substrate was studied using blister testing. After extended periodic bending, the adhesion energy was measured, and the effect of self-healing on the composite's delamination from the substrate was considered. In addition, the cohesion of two layers of the self-healing nanofibers was examined using blister testing and compared to that of ordinary nanofiber mats. The damage inflicted by prolonged periodic bending to the interface of the two nanofiber mats was demonstrated to have self-healed, and the cohesion energy was measured.

  18. Chemistry of crosslinking processes for self-healing polymers.

    PubMed

    Billiet, Stijn; Hillewaere, Xander K D; Teixeira, Roberto F A; Du Prez, Filip E

    2013-02-25

    Recent developments in material design have seen an exponential increase of polymers and polymer composites that can repair themselves in response to damage. In this review, a distinction is made between extrinsic materials, where the self-healing property is obtained by adding healing agents to the material to be repaired, and intrinsic materials, where self-healing is achieved by the material itself through its chemical nature. An overview of the crosslinking chemistries used in self-healing materials will be given, discussing the advantages and drawbacks of each system. The review is not only aiming to enable researchers to compare their ongoing research with the state-of-the-art but also to serve as a guide for the newcomers, which allows for a selection of the most promising self-healing chemistries.

  19. Polydimethylsiloxane-based self-healing composite and coating materials

    NASA Astrophysics Data System (ADS)

    Cho, Soo Hyoun

    This thesis describes the science and technology of a new class of autonomic polymeric materials which mimic some of the functionalities of biological materials. Specifically, we demonstrate an autonomic self-healing polymer system which can heal damage in both coatings and bulk materials. The new self-healing system we developed greatly extends the capability of self-healing polymers by introducing tin catalyzed polycondensation of hydroxyl end-functionalited polydimethylsiloxane and polydiethoxysiloxane based chemistries. The components in this system are widely available and comparatively low in cost, and the healing chemistry also remains stable in humid or wet environments. These achievements significantly increase the probability that self-healing could be extended not only to polymer composites but also to coatings and thin films in harsh environments. We demonstrate the bulk self-healing property of a polymer composite composed of a phase-separated PDMS healing agent and a microencapsulated organotin catalyst by chemical and mechanical testing. Another significant research focus is on self-healing polymer coatings which prevent corrosion of a metal substrate after deep scratch damage. The anti-corrosion properties of the self-healing polymer on metal substrates are investigated by corrosion resistance and electrochemical tests. Even after scratch damage into the substrate, the coating is able to heal, while control samples which do not include all the necessary healing components reveal rapid corrosion propagation. This self-healing coating solution can be easily applied to most substrate materials, and is compatible with most common polymer matrices. Self-healing has the potential to extend the lifetime and increase the reliability of thermosetting polymers used in a wide variety of applications ranging from microelectronics to aerospace.

  20. Developing Flexible, High Performance Polymers with Self-Healing Capabilities

    NASA Technical Reports Server (NTRS)

    Jolley, Scott T.; Williams, Martha K.; Gibson, Tracy L.; Caraccio, Anne J.

    2011-01-01

    Flexible, high performance polymers such as polyimides are often employed in aerospace applications. They typically find uses in areas where improved physical characteristics such as fire resistance, long term thermal stability, and solvent resistance are required. It is anticipated that such polymers could find uses in future long duration exploration missions as well. Their use would be even more advantageous if self-healing capability or mechanisms could be incorporated into these polymers. Such innovative approaches are currently being studied at the NASA Kennedy Space Center for use in high performance wiring systems or inflatable and habitation structures. Self-healing or self-sealing capability would significantly reduce maintenance requirements, and increase the safety and reliability performance of the systems into which these polymers would be incorporated. Many unique challenges need to be overcome in order to incorporate a self-healing mechanism into flexible, high performance polymers. Significant research into the incorporation of a self-healing mechanism into structural composites has been carried out over the past decade by a number of groups, notable among them being the University of I1linois [I]. Various mechanisms for the introduction of self-healing have been investigated. Examples of these are: 1) Microcapsule-based healant delivery. 2) Vascular network delivery. 3) Damage induced triggering of latent substrate properties. Successful self-healing has been demonstrated in structural epoxy systems with almost complete reestablishment of composite strength being achieved through the use of microcapsulation technology. However, the incorporation of a self-healing mechanism into a system in which the material is flexible, or a thin film, is much more challenging. In the case of using microencapsulation, healant core content must be small enough to reside in films less than 0.1 millimeters thick, and must overcome significant capillary and surface

  1. Self-healing graphene-based composites with sensing capabilities.

    PubMed

    D'Elia, Eleonora; Barg, Suelen; Ni, Na; Rocha, Victoria G; Saiz, Eduardo

    2015-08-26

    A self-healing composite is fabricated by confining a supramolecular polymer in a graphene network. The network provides electrical conductivity. Upon damage, the polymer is released and flows to reform the material. Healing is repeatable and autonomous. The composite is sensitive to pressure and flexion and recovers its mechanical and electrical properties even when rejoining cut surfaces after long exposure times.

  2. Self-healing sandwich composite structures

    NASA Astrophysics Data System (ADS)

    Fugon, D.; Chen, C.; Peters, K.

    2012-04-01

    Previous research demonstrated that a thin self-healing layer is effective in recovering partial sandwich composite performance after an impact event. Many studies have been conducted that show the possibility of using Fiber Bragg Grating (FBG) sensors to monitor the cure of a resin through strain and temperature monitoring. For this experiment, FBG sensors were used to monitor the curing process of a self-healing layer within a twelve-layer fiberglass laminate after impact. First, five self-healing sandwich composite specimens were manufactured. FBG sensors were embedded between the fiberglass and foam core. Then the fiberglass laminate was impacted with the use of a drop tower and the curing process was monitored. The collected data was used to compare the cure of the resin and fiberglass alone to the cure of the resin from a self-healing specimen. For the low viscosity resin system tested, these changes were not sufficiently large to identify different polymerization states in the resin as it cured. These results indicate that applying different resin systems might increase the efficiency of the self-healing in the sandwich composites.

  3. Carbon Dots as Fillers Inducing Healing/Self-Healing and Anticorrosion Properties in Polymers.

    PubMed

    Zhu, Cheng; Fu, Yijun; Liu, Changan; Liu, Yang; Hu, Lulu; Liu, Juan; Bello, Igor; Li, Hao; Liu, Naiyun; Guo, Sijie; Huang, Hui; Lifshitz, Yeshayahu; Lee, Shuit-Tong; Kang, Zhenhui

    2017-08-01

    Self-healing is the way by which nature repairs damage and prolongs the life of bio entities. A variety of practical applications require self-healing materials in general and self-healing polymers in particular. Different (complex) methods provide the rebonding of broken bonds, suppressing crack, or local damage propagation. Here, a simple, versatile, and cost-effective methodology is reported for initiating healing in bulk polymers and self-healing and anticorrosion properties in polymer coatings: introduction of carbon dots (CDs), 5 nm sized carbon nanocrystallites, into the polymer matrix forming a composite. The CDs are blended into polymethacrylate, polyurethane, and other common polymers. The healing/self-healing process is initiated by interfacial bonding (covalent, hydrogen, and van der Waals bonding) between the CDs and the polymer matrix and can be optimized by modifying the functional groups which terminate the CDs. The healing properties of the bulk polymer-CD composites are evaluated by comparing the tensile strength of pristine (bulk and coatings) composites to those of fractured composites that are healed and by following the self-healing of scratches intentionally introduced to polymer-CD composite coatings. The composite coatings not only possess self-healing properties but also have superior anticorrosion properties compared to those of the pure polymer coatings. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  4. Self Healing Composite for Aircraft's Structural Application

    NASA Astrophysics Data System (ADS)

    Teoh, S. H.; Chia, H. Y.; Lee, M. S.; Nasyitah, A. J. N.; Luqman, H. B. S. M.; Nurhidayah, S.; Tan, Willy. C. K.

    When one cuts himself, it is amazing to watch how quickly the body acts to mend the wound. Immediately, the body works to pull the skin around the cut back together. The concept of repair by bleeding of enclosed functional agents serves as the biomimetic inspiration of synthetic self repair systems. Such synthetic self repair systems are based on advancement in polymeric materials; the process of human thrombosis is the inspiration for the application of self healing fibres within the composite materials. Results based on flexural 3 point bend test on the prepared samples have shown that the doubled layer healed hollow fibre laminate subjected to a healing regime of 3 weeks has a healed strength increase of 27% compared to the damaged baseline laminate. These results gave us confidence that there is a great potential to adopt such self healing mechanism on actual composite parts like in aircraft's composite structures.

  5. A self-healing PDMS polymer with solvatochromic properties.

    PubMed

    Jia, Xiao-Yong; Mei, Jin-Feng; Lai, Jian-Cheng; Li, Cheng-Hui; You, Xiao-Zeng

    2015-05-28

    Coordination bonds are effective for constructing functional self-healing materials due to their tunable bond strength and metal-ion-induced functionalities. In this work, we incorporate a cobalt(II) triazole complex into a polydimethylsiloxane (PDMS) matrix. The resulting polymers show solvatochromic behaviour as well as self-healing properties.

  6. Damage properties simulations of self-healing composites.

    PubMed

    Chen, Cheng; Ji, Hongwei; Wang, Huaiwen

    2013-10-01

    Self-healing materials are inspired by biological systems in which damage triggers an autonomic healing response. The damage properties of a self-healing polymer composite were investigated by numerical simulation in this paper. Unit cell models with single-edge centered crack and single-edge off-centered crack were employed to investigate the damage initiation and crack evolution by the extended finite element method (XFEM) modeling. The effect of microcapsule's Young's modulus on composites was investigated. Result indicates the microcapsule's Young's modulus has little effect on the unit cell's carrying capacity. It was found that during the crack propagation process, its direction is attracted toward the microcapsules, which makes it helpful for the microcapsules to be ruptured by the propagating crack fronts resulting in release of the healing agent into the cracks by capillary action.

  7. Self-healing composite sandwich structures

    NASA Astrophysics Data System (ADS)

    Williams, H. R.; Trask, R. S.; Bond, I. P.

    2007-08-01

    Impact damage can degrade the flexural strength of composite sandwich structures by over 50% due to a loss of skin support inducing localized skin buckling. Various self-healing methodologies have been applied to laminated composites but the concept of delivering a healing agent from a remote reservoir to a region of damage via a vascular network offers the potential for a robust and replenishable system housed in the core of a sandwich structure. In this pilot study a vascular sandwich structure that appears as a conventional sandwich composite has been developed and tested. The network has been shown to have negligible influence on the innate static mechanical properties of the host panel. Infiltration of the vascular network with a pre-mixed epoxy resin system after impact damage demonstrated a complete recovery of flexural failure mode and load. Infiltration with the same resin system from separate unmixed networks, where self-healing is initiated autonomously via mixing within the damage, has also been shown to fully recover undamaged failure load when both networks are successfully breached.

  8. Self-healing structural composites with electromagnetic functionality

    NASA Astrophysics Data System (ADS)

    Plaisted, Thomas A.; Vakil Amirkhizi, Alireza; Arbelaez, Diego; Nemat-Nasser, Syrus C.; Nemat-Nasser, Sia

    2003-08-01

    We have incorporated arrays of conductive electromagnetic scattering elements such as straight copper wires and copper coils into fiber-reinforced polymer composites, resulting in materials with required structural and further electromagnetic functionality. The scattering elements provide controlled electromagnetic response for tasks such as filtering and may be used to tune the overall index of refraction of the composite. Integration of these metallic elements into traditional fiber-reinforced polymer composites has introduced other opportunities for multifunctionality in terms of self-healing, thermal transport and perhaps sensing applications. Such functionalities are the result of fiber/wire integration through textile braiding and weaving, combined with a new polymer matrix that has the ability to heal internal cracking through thermo-reversible covalent bonds. Multifunctional composites of this kind enhance the role of structural materials from mere load-bearing systems to lightweight structures of good thermo-mechanical attributes that also have electromagnetic and other functionalities.

  9. Repeated Instant Self-healing Shape Memory Composites

    NASA Astrophysics Data System (ADS)

    Wang, C. C.; Ding, Z.; Purnawali, H.; Huang, W. M.; Fan, H.; Sun, L.

    2012-12-01

    We present a shape memory composite which is made of two types of shape memory materials, namely shape memory alloy (SMA) and shape memory hybrid. This composite has repeated instant self-healing function by means of not only shape recovery but also strength recovery (over 80%). The activation of the self-healing function is triggered by joule heating the embedded SMA.

  10. Puncture Self-Healing Polymers for Aerospace Applications

    NASA Technical Reports Server (NTRS)

    Gordon, Keith L.; Penner, Ronald K.; Bogert, Phil B.; Yost, W. T.; Siochi, Emilie J.

    2011-01-01

    Space exploration launch costs on the order of $10K per pound provide ample incentive to seek innovative, cost-effective ways to reduce structural mass without sacrificing safety and reliability. Damage-tolerant structural systems can provide a route to avoiding weight penalty while enhancing vehicle safety and reliability. Self-healing polymers capable of spontaneous puncture repair show great promise to mitigate potentially catastrophic damage from events such as micrometeoroid penetration. Effective self-repair requires these materials to heal instantaneously following projectile penetration while retaining structural integrity. Poly(ethylene-co-methacrylic acid) (EMMA), also known as Surlyn is an ionomer-based copolymer that undergoes puncture reversal (self-healing) following high impact puncture at high velocities. However EMMA is not a structural engineering polymer, and will not meet the demands of aerospace applications requiring self-healing engineering materials. Current efforts to identify candidate self-healing polymer materials for structural engineering systems are reported. Rheology, high speed thermography, and high speed video for self-healing semi-crystalline and amorphous polymers will be reported.

  11. Impression Testing of Self-Healing Polymers

    NASA Technical Reports Server (NTRS)

    Hinkley, Jeffrey A.; Huber, Amy

    2005-01-01

    As part of the BIOSANT program (biologically-inspired smart nanotechnology), scientists at NASA-Langley have identified a "self-healing" plastic that spontaneously closes the hole left by the passage of a bullet. To understand and generalize the phenomenon in question, the mechanical properties responsible for this ability are being explored. Low-rate impression testing was chosen to characterize post-yield material properties, and it turned out that materials that heal following ballistic puncture also show up to 80% healing of the low-rate impression. Preliminary results on the effects of temperature and rate of puncture are presented.

  12. Assessment of Composite Delamination Self-Healing Under Cyclic Loading

    NASA Technical Reports Server (NTRS)

    O'Brien, T. Kevin

    2009-01-01

    Recently, the promise of self-healing materials for enhanced autonomous durability has been introduced using a micro-encapsulation technique where a polymer based healing agent is encapsulated in thin walled spheres and embedded into a base polymer along with a catalyst phase. For this study, composite skin-stiffener flange debonding specimens were manufactured from composite prepreg containing interleaf layers with a polymer based healing agent encapsulated in thin-walled spheres. Constant amplitude fatigue tests in three-point bending showed the effect of self-healing on the fatigue response of the skin-stiffener flange coupons. After the cycling that created debonding, fatigue tests were held at the mean load for 24 hours. For roughly half the specimens tested, when the cyclic loading was resumed a decrease in compliance (increase in stiffness) was observed, indicating that some healing had occurred. However, with continued cycling, the specimen compliance eventually increased to the original level before the hold, indicating that the damage had returned to its original state. As was noted in a prevoius study conducted with specimens tested under monotonically increasing loads to failure, healing achieved via the micro-encapsulation technique may be limited to the volume of healing agent available relative to the crack volume.

  13. The self-healing composite anticorrosion coating

    NASA Astrophysics Data System (ADS)

    Yang, Zhao; Wei, Zhang; Le-ping, Liao; Hong-mei, Wang; Wu-jun, Li

    Self-healing coatings, which autonomically repair and prevent corrosion of the underlying substrate, are of particular interest for the researchers. In the article, effectiveness of epoxy resin filled microcapsules was investigated for healing of cracks generated in coatings. Microcapsules were prepared by in situ polymerization of urea-formaldehyde resin to form shell over epoxy resindroplets. Characteristics of these capsules were studied by scanning electron microscope (SEM), thermo gravimetric analyzer (TGA) and particle size analyzer. The model system of self-healing antisepsis coating consists of an epoxy resin matrix, 10 wt% microencapsulated healing agent, 2wt% catalyst solution. The self-healing function of this coating system is evaluated through corrosion testing of damaged and healed coated steel samples compared to control samples. Electrochemical testing provides further evidence of passivation of the substrate by self-healing coatings.

  14. High Temperature Self-Healing Metallic Composite

    NASA Astrophysics Data System (ADS)

    Kutelia, E. R.; Bakhtiyarov, S. I.; Tsurtsumia, O. O.; Bakhtiyarov, A. S.; Eristavi, B.

    2012-01-01

    This work presents the possibility to realize the self healing mechanisms for heterogeneous architectural metal/ceramic high temperature sandwich thermal barrier coating systems on the surfaces refractory metals by analogy of wound healing in the skin.

  15. Inkjet Assisted Creation of Self-Healing Layers Between Composite Plies

    DTIC Science & Technology

    2013-07-29

    images of PMMA dots with fluorescein on CFRP prepreg under different conditions: (a) before curing cycle, (b) after heating to 100° C and (c) after the...of CFRP simultaneously, and without imparting any parasitic weight, restored the properties of the damaged and self-healed composite to a large...parameters for accurate deposition of inkjet printed polymers, suitable thermoplastic self-healing agents for high-temperature CFRP , and selection of

  16. Responsive Polymers as Sensors, Muscles, and Self-Healing Materials.

    PubMed

    Zhang, Qiang Matthew; Serpe, Michael J

    2015-01-01

    Responsive polymer-based materials can adapt to their surrounding environment by expanding and shrinking. This swelling and shrinking (mechanotransduction) can result in a number of functions. For example, the response can be used to lift masses, move objects, and can be used for sensing certain species in a system. Furthermore, responsive polymers can also yield materials capable of self-healing any damage affecting their mechanical properties. In this chapter we detail many examples of how mechanical responses can be triggered by external electric and/or magnetic fields, hygroscopicity, pH, temperature, and many other stimuli. We highlight how the specific responses can be used for artificial muscles, self-healing materials, and sensors, with particular focus on detailing the polymer response yielding desired effects.

  17. Self-healing nanocomposite using shape memory polymer and carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Liu, Yingtao; Rajadas, Abhishek; Chattopadhyay, Aditi

    2013-04-01

    Carbon fiber reinforced composites are used in a wide range of applications in aerospace, mechanical, and civil structures. Due to the nature of material, most damage in composites, such as delaminations, are always barely visible to the naked eye, which makes it difficult to detect and repair. The investigation of biological systems has inspired the development and characterization of self-healing composites. This paper presents the development of a new type of self-healing material in order to impede damage progression and conduct in-situ damage repair in composite structures. Carbon nanotubes, which are highly conductive materials, are mixed with shape memory polymer to develop self-healing capability. The developed polymeric material is applied to carbon fiber reinforced composites to automatically heal the delamination between different layers. The carbon fiber reinforced composite laminates are manufactured using high pressure molding techniques. Tensile loading is applied to double cantilever beam specimens using an MTS hydraulic test frame. A direct current power source is used to generate heat within the damaged area. The application of thermal energy leads to re-crosslinking in shape memory polymers. Experimental results showed that the developed composite materials are capable of healing the matrix cracks and delaminations in the bonded areas of the test specimens. The developed self-healing material has the potential to be used as a novel structural material in mechanical, civil, aerospace applications.

  18. A polymer scaffold for self-healing perovskite solar cells

    PubMed Central

    Zhao, Yicheng; Wei, Jing; Li, Heng; Yan, Yin; Zhou, Wenke; Yu, Dapeng; Zhao, Qing

    2016-01-01

    Advancing of the lead halide perovskite solar cells towards photovoltaic market demands large-scale devices of high-power conversion efficiency, high reproducibility and stability via low-cost fabrication technology, and in particular resistance to humid environment for long-time operation. Here we achieve uniform perovskite film based on a novel polymer-scaffold architecture via a mild-temperature process. These solar cells exhibit efficiency of up to ∼16% with small variation. The unencapsulated devices retain high output for up to 300 h in highly humid environment (70% relative humidity). Moreover, they show strong humidity resistant and self-healing behaviour, recovering rapidly after removing from water vapour. Not only the film can self-heal in this case, but the corresponding devices can present power conversion efficiency recovery after the water vapour is removed. Our work demonstrates the value of cheap, long chain and hygroscopic polymer scaffold in perovskite solar cells towards commercialization. PMID:26732479

  19. A polymer scaffold for self-healing perovskite solar cells

    NASA Astrophysics Data System (ADS)

    Zhao, Yicheng; Wei, Jing; Li, Heng; Yan, Yin; Zhou, Wenke; Yu, Dapeng; Zhao, Qing

    2016-01-01

    Advancing of the lead halide perovskite solar cells towards photovoltaic market demands large-scale devices of high-power conversion efficiency, high reproducibility and stability via low-cost fabrication technology, and in particular resistance to humid environment for long-time operation. Here we achieve uniform perovskite film based on a novel polymer-scaffold architecture via a mild-temperature process. These solar cells exhibit efficiency of up to ~16% with small variation. The unencapsulated devices retain high output for up to 300 h in highly humid environment (70% relative humidity). Moreover, they show strong humidity resistant and self-healing behaviour, recovering rapidly after removing from water vapour. Not only the film can self-heal in this case, but the corresponding devices can present power conversion efficiency recovery after the water vapour is removed. Our work demonstrates the value of cheap, long chain and hygroscopic polymer scaffold in perovskite solar cells towards commercialization.

  20. Multifunctional Self-Healing and Morphing Composites

    DTIC Science & Technology

    2006-11-01

    NMR) both proton (1H) and carbon (13C), Matrix Assisted Laser Desorption/Ionization ( MALDI - MS ), and Elemental Analysis. The mendomer-400 is...process is fully reversible and can be used to repair the cracks multiple times. When heated, ionic groups lose their attractions and the chains...ionomers in terms of ionic group re-attachment. These ionomers have been demonstrated to self-heal using embedded magnetic particles in a related

  1. Nature's Mechanisms for Tough, Self-healing Polymers and Polymer Adhesives

    NASA Astrophysics Data System (ADS)

    Hansma, Paul

    2007-03-01

    Spider silk^2 and the natural polymer adhesives in abalone shells^3 and bone^4,5 can give us insights into nature's mechanisms for tough, self-healing polymers and polymer adhesives. The natural polymer adhesives in biomaterials have been optimized by evolution. An optimized polymer adhesive has five characteristics. 1) It holds together the strong elements of the composite. 2) It yields just before the strong elements would otherwise break. 3) It dissipates large amounts of energy as it yields. 4) It self heals after it yields. 5) It takes just a few percent by weight. Both natural polymer adhesives and silk rely on sacrificial bonds and hidden length for toughness and self-healing.^6 A relatively large energy, of order 100eV, is required to stretch a polymer molecule after a weak bond, a sacrificial bond, breaks and liberates hidden length, which was previously hidden, typically in a loop or folded domain, from whatever was stretching the polymer. The bond is called sacrificial if it breaks at forces well below the forces that could otherwise break the polymer backbone, typically greater than 1nN. In many biological cases, the breaking of sacrificial bonds has been found to be reversible, thereby also providing a ``self-healing'' property to the material.^2-4 Individual polymer adhesive molecules based on sacrificial bonds and hidden length can supply forces of order 300pN over distances of 100s of nanometers. Model calculations show that a few percent by weight of adhesives based on these principles could be optimized adhesives for high performance composite materials including nanotube and graphene sheet composites. ^2N. Becker, E. Oroudjev, S. Mutz et al., Nature Materials 2 (4), 278 (2003). ^3B. L. Smith, T. E. Schaffer, M. Viani et al., Nature 399 (6738), 761 (1999). ^4J. B. Thompson, J. H. Kindt, B. Drake et al., Nature 414 (6865), 773 (2001). ^5G. E. Fantner, T. Hassenkam, J. H. Kindt et al., Nature Materials 4, 612 (2005). ^6G. E. Fantner, E. Oroudjev, G

  2. Self-Healing of Polymer Networks with Reversible Bonds

    NASA Astrophysics Data System (ADS)

    Rubinstein, Michael

    2015-03-01

    Self-healing polymeric materials are systems that after damage can revert to their original state with full or partial recovery of mechanical strength. Using scaling theory we study a simple model of autonomic self-healing of polymer networks. In this model one of the two end monomers of each polymer chain is fixed in space mimicking dangling chains attachment to a polymer network, while the sticky monomer at the other end of each chain can form pairwise reversible bond with the sticky end of another chain. We study the reaction kinetics of reversible bonds in this simple model and analyze the different stages in the self-repair process. The formation of bridges and the recovery of the material strength across the fractured interface during the healing period occur appreciably faster after shorter waiting time, during which the fractured surfaces are kept apart. We observe the slowest formation of bridges for self-adhesion after bringing into contact two bare surfaces with equilibrium (very low) density of open stickers in comparison with self-healing. The primary role of anomalous diffusion in material self-repair for short waiting times is established, while at long waiting times the recovery of bonds across fractured interface is due to hopping diffusion of stickers between different bonded partners. Acceleration in bridge formation for self-healing compared to self-adhesion is due to excess nonequilibrium concentration of open stickers. Full recovery of reversible bonds across fractured interface (formation of bridges) occurs after appreciably longer time than the equilibration time of the concentration of reversible bonds in the bulk. The model is extended to describe enhanced toughness of dual networks with both permanent and reversible cross-links. This work was done in collaboration with Drs. Ludwik Leibler, Li-Heng Cai, Evgeny B. Stukalin, N. Arun Kumar and supported by the National Science Foundation.

  3. Self-Healing of Unentangled Polymer Networks with Reversible Bonds

    PubMed Central

    Stukalin, Evgeny B.; Cai, Li-Heng; Kumar, N. Arun; Leibler, Ludwik; Rubinstein, Michael

    2013-01-01

    Self-healing polymeric materials are systems that after damage can revert to their original state with full or partial recovery of mechanical strength. Using scaling theory we study a simple model of autonomic self-healing of unentangled polymer networks. In this model one of the two end monomers of each polymer chain is fixed in space mimicking dangling chains attachment to a polymer network, while the sticky monomer at the other end of each chain can form pairwise reversible bond with the sticky end of another chain. We study the reaction kinetics of reversible bonds in this simple model and analyze the different stages in the self-repair process. The formation of bridges and the recovery of the material strength across the fractured interface during the healing period occur appreciably faster after shorter waiting time, during which the fractured surfaces are kept apart. We observe the slowest formation of bridges for self-adhesion after bringing into contact two bare surfaces with equilibrium (very low) density of open stickers in comparison with self-healing. The primary role of anomalous diffusion in material self-repair for short waiting times is established, while at long waiting times the recovery of bonds across fractured interface is due to hopping diffusion of stickers between different bonded partners. Acceleration in bridge formation for self-healing compared to self-adhesion is due to excess non-equilibrium concentration of open stickers. Full recovery of reversible bonds across fractured interface (formation of bridges) occurs after appreciably longer time than the equilibration time of the concentration of reversible bonds in the bulk. PMID:24347684

  4. Polydimethylsiloxane-based Self healing Composite and Coating Materials

    DTIC Science & Technology

    2006-01-01

    interfacial polymerization for catalyst microencapsulation . ...........26 Figure 2.14: Microscopic images of synthesized microcapsules : (a) Optical...control b, matrix, adhesion promoter, and microencapsulated tin catalyst (dimethyldineodecanoate tin, 3 wt% of total microcapsules ); control c... microencapsulated monomer, which can be dispersed through the matrix, is used. Using microcapsules enables self-healing polymer mass production, even

  5. Polymer Welding and Self-healing: Strength Through Entanglements

    NASA Astrophysics Data System (ADS)

    Ge, Ting; Robbins, Mark O.; Perahia, Dvora; Grest, Gary S.

    2013-03-01

    Polymer interfaces are crucial in determining the mechanical strength of many systems. A common means of welding joints or self-healing cracks is to apply heat and allow polymers to interdiffuse. As the microscopic mechanism of interface strengthening is difficult to isolate experimentally, we probe the molecular origins of interfacial strength using large scale molecular simulations of welding and self-healing of cut systems. Systems are heated well above the glass temperature Tg and then quenched below Tg for mechanical testing. The interfacial strength is characterized by the maximum shear stress σmax before failure. As strength grows, the dominant failure mode changes from chain pullout at the interface to chain scission, as in the bulk. In all simulations, σmax saturates long before polymers diffuse by their own size. Bulk strength is observed for miscible welds, while strength is suppressed for cut systems due to short chain segments that remain near the interface. Entanglements are tracked using the Primitive Path Analysis. We find that the bulk response is not fully recovered until the density of entanglements at the interface reaches the bulk value. Moreover, the increase of σmax beforesaturationisproportionaltothenumberofinterfacial entanglements between chains from opposite sides, which correlates linearly with the interdiffusion depth. This material is based upon work supported by NSF Grant DMR-1006805 and DMR-0907390.

  6. Self-Healing Metals and Metal Matrix Composites

    NASA Astrophysics Data System (ADS)

    Ferguson, J. B.; Schultz, Benjamin F.; Rohatgi, Pradeep K.

    2014-06-01

    Self-healing in inorganic materials is a relatively new area in materials science and engineering that draws inspiration from biological systems that can self-repair damage. This article reviews the preliminary attempts to impart self-healing behavior to metals. Several challenges yet exist in the development of metallic alloys that can self-repair damage, including surface bonding issues, such as liquid/solid contact angle (wetting) and oxidation, and practical issues, such as capillary pressure for delivery of a liquid metal to a damaged area or crack, and the overall mechanical properties of a composite system. Although the applied research approaches reviewed have obtained marginal success, the development of self-healing metallic systems has the potential to benefit a wide range of industrial applications and thus deserves greater investment in fundamental research.

  7. DYNAMERS: dynamic polymers as self-healing materials.

    PubMed

    Roy, Nabarun; Bruchmann, Bernd; Lehn, Jean-Marie

    2015-06-07

    Importing self-repair or self-healing features into inert materials is of great relevance to material scientists, since it is expected to eliminate the necessity of replenishing a damaged material. Be it material chemistry or more specifically polymer chemistry, such materials have attracted the imagination of both material scientists and chemists. A stroll down the memory lane 70 years back, this might have sounded utopian. However with the current progress in supramolecular chemistry and the emergence of dynamic covalent and non-covalent chemistries, novel perspectives have been opened up to materials science towards the development of dynamic materials (DYNAMATS) and in particular dynamic polymers (DYNAMERS), with the ability to produce such species by custom made designs. Chemistry took giant strides to gain control over the structure and features of materials and, besides basic progress, to apply it for tailor-making matter for applications in our daily life. In that applied perspective, materials science plays a paramount role in shaping our present and in contributing to a sustainable future. The goal is to develop materials, which would be dynamic enough to carry out certain functions as effectively as in biological systems with, however, the freedom to recruit the powers of chemistry on a wider scale, without the limitation imposed by life. Material scientists and in particular polymer chemists may build on chemistry, physics and biology for bridging the gap to develop dynamic materials presenting a wide range of novel functionalities and to convert dreams into reality. In this current review we will focus on developments in the area of dynamic polymers, as a class of dynamic materials presenting self-healing features and, more generally, the ability to undergo adaptation under the effect of physical and/or chemical agents, and thus function as adaptive polymers or ADAPTAMERS.

  8. Self-Healing Nanocomposites for Reusable Composite Cryotanks

    NASA Technical Reports Server (NTRS)

    Eberly, Daniel; Ou, Runqing; Karcz, Adam; Skandan, Ganesh

    2013-01-01

    Composite cryotanks, or composite overwrapped pressure vessels (COPVs), offer advantages over currently used aluminum-lithium cryotanks, particularly with respect to weight savings. Future NASA missions are expected to use COPVs in spaceflight propellant tanks to store fuels, oxidizers, and other liquids for launch and space exploration vehicles. However, reliability, reparability, and reusability of the COPVs are still being addressed, especially in cryogenic temperature applications; this has limited the adoption of COPVs in reusable vehicle designs. The major problem with composites is the inherent brittleness of the epoxy matrix, which is prone to microcrack formation, either from exposure to cryogenic conditions or from impact from different sources. If not prevented, the microcracks increase gas permeation and leakage. Accordingly, materials innovations are needed to mitigate microcrack damage, and prevent damage in the first place, in composite cryotanks. The self-healing technology being developed is capable of healing the microcracks through the use of a novel engineered nanocomposite, where a uniquely designed nanoparticle additive is incorporated into the epoxy matrix. In particular, this results in an enhancement in the burst pressure after cryogenic cycling of the nanocomposite COPVs, relative to the control COPVs. Incorporating a novel, self-healing, epoxy-based resin into the manufacture of COPVs allows repeatable self-healing of microcracks to be performed through the simple application of a low-temperature heat source. This permits COPVs to be reparable and reusable with a high degree of reliability, as microcracks will be remediated. The unique phase-separated morphology that was imparted during COPV manufacture allows for multiple self-healing cycles. Unlike single-target approaches where one material property is often improved at the expense of another, robustness has been introduced to a COPV by a combination of a modified resin and

  9. Effects of self-healing microcapsules on bending performance in composite brake pads

    NASA Astrophysics Data System (ADS)

    Zhang, Li; Dong, Xiu-ping; Wang, Hui

    2009-07-01

    For the purpose of reducing self-weight, friction noise and cost, improving shock absorption, enhancing corrosion and wear resistance, brake pads made of composite materials with self-healing function are prepared to substitute metal ones by designing ingredients and applying optimized production technology. As self-healing capsules are chosen, new method with technology of self-healing microcapsules, dicyclpentadiene (DCPD) microcapsules coated with poly (urea-formaldehyde), is put forward in this paper. In the crack's extending process, the stress is concentrated at the crack end, where the microcapsule is designed to be located. When the stress goes through the microcapsules and causes them to break, the self-healing liquid runs out to fill the crack by the capillary and it will poly-react with catalyst in the composite. As a result, the crack is healed. In this paper, polymer matrix composite brake pads with 6 prescriptions are prepared and studied. Three-point bending tests are carried out according to standards in GB/T 3356-1999 and the elastic constants of these polymer matrix composites are obtained by experiments. In accordance with the law of the continuous fiber composite, elastic constants of the short-fiber composite can be calculated by proportions of each ingredient. Results show that the theoretical expected results and the experimental values are consistent. 0.3-1.2 % mass proportion of microcapsules has little effects on the composite's bending intensity and modulus of elasticity. These studies also show that self-healing microcapsules used in composite brake pads is feasible.

  10. Highly Elastic and Self-Healing Composite Colloidal Gels.

    PubMed

    Diba, Mani; Wang, Huanan; Kodger, Thomas E; Parsa, Shima; Leeuwenburgh, Sander C G

    2017-03-01

    Composite colloidal gels are formed by the pH-induced electrostatic assembly of silica and gelatin nanoparticles. These injectable and moldable colloidal gels are able to withstand substantial compressive and tensile loads, and exhibit a remarkable self-healing efficiency. This study provides new, critical insight into the structural and mechanical properties of composite colloidal gels and opens up new avenues for practical application of colloidal gels.

  11. Self-healing in tough graphene oxide composite hydrogels.

    PubMed

    Liu, Jiaqi; Song, Guoshan; He, Changcheng; Wang, Huiliang

    2013-06-25

    Polymer hydrogels that are capable of spontaneously healing injury are being developed at a rapid pace because of their great potential in biomedical applications. Here, the self-healing property of tough graphene nanocomposite hydrogels fabricated by using graphene peroxide as polyfunctional initiating and cross-linking centers is reported. The hydrogels show excellent self-healing ability at ambient temperature or even lower temperatures for a short time and very high recovery degrees (up to 88% tensile strength) can be achieved at a prolonged healing time. The healed gels exhibit very high tensile strengths (up to 0.35 MPa) and extremely high elongations (up to 4900%). The strong interactions between the polyacrylamide chains and the graphene oxide sheets are essential to the mechanical strengths of the healed gels. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  12. Frustrated Lewis Pair Polymers as Responsive Self-Healing Gels.

    PubMed

    Wang, Meng; Nudelman, Fabio; Matthes, Rebecca R; Shaver, Michael P

    2017-09-27

    Steric bulk prevents the formation of strong bonds between Lewis acids and bases in frustrated Lewis pairs (FLPs), where latent reactivity makes these reagents transformative in small molecule activations and metal-free catalysis. However, their use as a platform for developing materials chemistry is unexplored. Here we report a fully macromolecular FLP, built from linear copolymers that containing either a sterically encumbered Lewis base or Lewis acid as a pendant functional group. The target functional copolymers were prepared by a controlled radical copolymerization of styrene with designer boron or phosphorus containing monomers. Mixtures of the B- and P-functionalized polystyrenes do not react, with the steric bulk of the functional monomers preventing the favorable Lewis acid base interaction. Addition of a small molecule (diethyl azodicarboxylate) promotes rapid network formation, cross-linking the reactive polymer chains. The resulting gel is dynamic, can self-heal, is heat responsive, and can be reshaped by postgelation processing.

  13. Thermally responsive polymer systems for self-healing, reversible adhesion and shape memory applications

    NASA Astrophysics Data System (ADS)

    Luo, Xiaofan

    Responsive polymers are "smart" materials that are capable of performing prescribed, dynamic functions under an applied stimulus. In this dissertation, we explore several novel design strategies to develop thermally responsive polymers and polymer composites for self-healing, reversible adhesion and shape memory applications. In the first case described in Chapters 2 and 3, a thermally triggered self-healing material was prepared by blending a high-temperature epoxy resin with a thermoplastic polymer, poly(epsilon-caprolactone) (PCL). The initially miscible system undergoes polymerization induced phase separation (PIPS) during the curing of epoxy and yields a variety of compositionally dependent morphologies. At a particular PCL loading, the cured blend displays a "bricks-and-mortar" morphology in which epoxy exists as interconnected spheres ("bricks") within a continuous PCL matrix ("mortar"). A heat induced "bleeding" phenomenon was observed in the form of spontaneous wetting of all free surfaces by the molten PCL, and is attributed to the volumetric thermal expansion of PCL above its melting point in excess of epoxy brick expansion, which we term differential expansive bleeding (DEB). This DEB is capable of healing damage such as cracks. In controlled self-healing experiments, heating of a cracked specimen led to PCL bleeding from the bulk that yields a liquid layer bridging the crack gap. Upon cooling, a "scar" composed of PCL crystals was formed at the site of the crack, restoring a significant portion of mechanical strength. We further utilized DEB to enable strong and thermally-reversible adhesion of the material to itself and to metallic substrates, without any requirement for macroscopic softening or flow. After that, Chapters 4--6 present a novel composite strategy for the design and fabrication of shape memory polymer composites. The basic approach involves physically combining two or more functional components into an interpenetrating fiber

  14. Autonomous self-healing structural composites with bio-inspired design

    NASA Astrophysics Data System (ADS)

    D'Elia, Eleonora; Eslava, Salvador; Miranda, Miriam; Georgiou, Theoni K.; Saiz, Eduardo

    2016-05-01

    Strong and tough natural composites such as bone, silk or nacre are often built from stiff blocks bound together using thin interfacial soft layers that can also provide sacrificial bonds for self-repair. Here we show that it is possible exploit this design in order to create self-healing structural composites by using thin supramolecular polymer interfaces between ceramic blocks. We have built model brick-and-mortar structures with ceramic contents above 95 vol% that exhibit strengths of the order of MPa (three orders of magnitude higher than the interfacial polymer) and fracture energies that are two orders of magnitude higher than those of the glass bricks. More importantly, these properties can be fully recovered after fracture without using external stimuli or delivering healing agents. This approach demonstrates a very promising route towards the design of strong, ideal self-healing materials able to self-repair repeatedly without degradation or external stimuli.

  15. Autonomous self-healing structural composites with bio-inspired design.

    PubMed

    D'Elia, Eleonora; Eslava, Salvador; Miranda, Miriam; Georgiou, Theoni K; Saiz, Eduardo

    2016-05-05

    Strong and tough natural composites such as bone, silk or nacre are often built from stiff blocks bound together using thin interfacial soft layers that can also provide sacrificial bonds for self-repair. Here we show that it is possible exploit this design in order to create self-healing structural composites by using thin supramolecular polymer interfaces between ceramic blocks. We have built model brick-and-mortar structures with ceramic contents above 95 vol% that exhibit strengths of the order of MPa (three orders of magnitude higher than the interfacial polymer) and fracture energies that are two orders of magnitude higher than those of the glass bricks. More importantly, these properties can be fully recovered after fracture without using external stimuli or delivering healing agents. This approach demonstrates a very promising route towards the design of strong, ideal self-healing materials able to self-repair repeatedly without degradation or external stimuli.

  16. Autonomous self-healing structural composites with bio-inspired design

    PubMed Central

    D’Elia, Eleonora; Eslava, Salvador; Miranda, Miriam; Georgiou, Theoni K.; Saiz, Eduardo

    2016-01-01

    Strong and tough natural composites such as bone, silk or nacre are often built from stiff blocks bound together using thin interfacial soft layers that can also provide sacrificial bonds for self-repair. Here we show that it is possible exploit this design in order to create self-healing structural composites by using thin supramolecular polymer interfaces between ceramic blocks. We have built model brick-and-mortar structures with ceramic contents above 95 vol% that exhibit strengths of the order of MPa (three orders of magnitude higher than the interfacial polymer) and fracture energies that are two orders of magnitude higher than those of the glass bricks. More importantly, these properties can be fully recovered after fracture without using external stimuli or delivering healing agents. This approach demonstrates a very promising route towards the design of strong, ideal self-healing materials able to self-repair repeatedly without degradation or external stimuli. PMID:27146382

  17. Biomimetic self-healing of advanced composite structures using hollow glass fibres

    NASA Astrophysics Data System (ADS)

    Trask, R. S.; Bond, I. P.

    2006-06-01

    The use of functional repair components stored inside hollow reinforcing fibres is being considered as a self-repair system for future composite structures. The incorporation of a self-healing capability within a variety of materials, including fibre reinforced polymers (FRPs), has been investigated by a number of workers previously. This paper considers the placement of self-healing plies within an FRP to mitigate damage occurrence and restore mechanical strength. The flexural strength results indicate that the inclusion of hollow fibres results in an initial strength reduction of 16% from a baseline FRP laminate. However, the effect of impact damage on the performance of the baseline FRP laminate and the laminate containing the hollow fibre layers was comparable, with a flexural strength typically 72-74% of the undamaged state. Self-healing of the damage site saw the laminate recover 87% of the undamaged baseline FRP laminate's strength. This study provides clear evidence that an FRP laminate containing hollow fibre layers can successfully self-heal. This result suggests that biomimetic repair is now possible for advanced composite structures.

  18. Novel Diels-Alder based self-healing epoxies for aerospace composites

    NASA Astrophysics Data System (ADS)

    Coope, T. S.; Turkenburg, D. H.; Fischer, H. R.; Luterbacher, R.; van Bracht, H.; Bond, I. P.

    2016-08-01

    Epoxy resins containing Diels-Alder (DA) furan and maleimide moieties are presented with the capability to self-heal after exposure to an external heat source. A conventional epoxy amine system has been combined with furfuryl and maleimide functional groups in a two-step process, to avoid major side-reactions, and the concentration of a thermo-reversibly binding cross-linker was considered to balance thermoset and thermoplastic behaviours, and the subsequent self-healing performance. In the context of self-repair technologies an inbuilt ‘intrinsic’ self-healing system is deemed favourable as the healing agent can be placed in known ‘hot spot’ regions (i.e. skin-stringer run outs, ply drops and around drilled holes) where operational damage predominately occurs in load bearing aerospace structures. In this study, the mechanical and self-healing performance of furan functionalised epoxy resins containing varying amounts (10, 20, 30 or 40 pph) of bismaleimide were investigated using a bulk epoxy polymer tapered double cantilever beam test specimen geometry. Two forms, a thin film and a bulk material, were evaluated to account for future integration methods into fibre reinforced polymer (FRP) composites. The highest healing efficiency, with respect to the obtained initial load value, was observed from the 20 pph bulk material derivative. The polymers were successful in achieving consistent multiple (three) healing cycles when heated at 150 °C for 5 min. This novel investigated DA material exhibits favourable processing characteristics for FRP composites as preliminary studies have shown successful coextrution with reinforcing fibres to form free standing films and dry fibre impregnation.

  19. Design and development of self-healing dental composites.

    PubMed

    Huyang, George; Debertin, Anne E; Sun, Jirun

    2016-03-15

    The purpose of this project is to design and develop a clinically applicable self-healing dental composite (SHDC). The value of resin-based dental restorations could be improved by increasing their service lives. One way to improve longevity is to obturate micro-cracks that form during or after the composite hardens in the dental cavity. Toward this end, we introduce here a new type of SHDC made with contemporary dental components plus two additional ingredients: a healing powder (HP, strongtium fluoroaluminosilicate particles) and a healing liquid (HL, aqueous solutions of polyacrylic acids) that is enclosed within silica microcapsules. As micro-cracks develop, they will break the microcapsules in their propagation path, thereby releasing HL. This liquid will then react with particles of HP exposed by the crack formation, forming an insoluble reaction product that fills and seals the cracks. The key factors to achieve this self-healing of cracks are discussed. The elastic modulus of a SHDC appeared to be satisfactory. The healing process was confirmed by means of mechanical, morphological, and chemical methods. The SHDC restored micro-cracks without external intervention, thereby showing potential for increasing the service lives of dental restorations. Importantly, this SHDC contains only clinically-tested, biocompatible materials, making it readily applicable.

  20. Modified rheokinetic technique to enhance the understanding of microcapsule-based self-healing polymers.

    PubMed

    Mauldin, Timothy C; Leonard, Joshua; Earl, Kelly; Lee, Jong Keun; Kessler, Michael R

    2012-03-01

    A modified rheokinetic technique was developed to monitor the polymerization of healing monomers in a microcapsule-based, self-healing mimicking environment. Using this modified technique, monomers active toward ring-opening metathesis polymerization (ROMP) were either identified or disregarded as candidates for incorporation in self-healing polymers. The effect of initiator loading on the quality and speed of healing was also studied. It was observed that self-healing polymers have upper and lower temperature limits between which the healing mechanism performs at optimal levels. Also, a study of the quality of healing cracks of different thicknesses was performed, and it was discovered that above a critical crack thickness value, the quality of self-healing diminishes substantially; reasons for this phenomenon are discussed in detail. © 2012 American Chemical Society

  1. Bio-inspired Self-healing Composite Hydrogel with Iron Oxide Nanoparticle as Coordination Crosslinker

    NASA Astrophysics Data System (ADS)

    Li, Qiaochu; Barret, Devin G.; Messersmith, Phillip B.; Holten-Andersen, Niels

    2014-03-01

    Polymer-nanoparticle (NP) composites have attracted renewed attention due to enhanced mechanical strength combined with various functionalities, but controlling the interfacial chemistry between NPs and polymer matrix, which is crucial for the composite's mechanical behavior, remains a major challenge. Inspired by the adhesion chemistry of mussel fibers, we investigated a novel approach to incorporate Fe3O4 NPs into hydrogel matrix. A polyethylene glycol polymer is designed with both ends conjugated by catechol groups, which have strong coordination affinity to Fe. The polymer network is crosslinked via coordination bonding at the surface of Fe3O4 NPs, yielding a stiff nanocomposite hydrogel. Due to the reversible nature of coordination bonding, the hydrogel presents self-healing behavior. Oscillatory rheology allows comparative kinetic studies of self-healing driven by catechol bonding at Fe3O4 NP interfaces and by catechol-Fe3+ coordination complexes. Furthermore, the superparamagnetic property of Fe3O4 NP is preserved after gelation, allowing for response to external stimuli. This gelation motif can serve as a versatile platform for tuning functional and mechanical properties for future polymer nanocomposite materials.

  2. Design of a biomimetic self-healing superalloy composite

    NASA Astrophysics Data System (ADS)

    Files, Bradley Steven

    1997-10-01

    Use of systems engineering concepts to design technologically advanced materials has allowed ambitious goals of self-healing alloys to be realized. Shape memory alloy reinforcements are embedded in an alloy matrix to demonstrate concepts of stable crack growth and matrix crack closure. Computer methods are used to design thermodynamically compatible iron-based alloys using bio-inspired concepts of crack bridging and self-healing. Feasibility of crack closure and stable crack growth is shown in a prototype system with a Sn-Bi matrix and TiNi fibers. Design of Fe-Ni-Co-Ti-Al alloys using thermodynamic models to determine stabilities and phase equilibria allows for a methodical system designing compatible multicomponent alloys for composite systems. Final alloy computations for this project led to the alloy Fe-27.6Ni-18.2Co-4.1Ti-1.6Al as a compatible shape memory a with a 650sp°C 90 minute heat treatment leading to martensite and austenite start temperatures (Msbs and Asbs) near room temperature. Thin slices of this alloy were able to fully recover at least 5% strain upon unloading heating. Composites made from the designed shape memory alloy and a compatible Fe-based B2 matrix were used to test self-healing concepts in the superalloy system. Diffusion couple experiments verified thermodynamic compatibility between matrix and reinforcement alloys at the solution treatment temperature of 1100sp°C. Concepts of stable crack growth and crack bridging were demonstrated in the composite, leading to enhanced toughness of the brittle matrix. However, healing behavior in this system was limited by intergranular fracture of the reinforcement alloy. It is believed that use of rapidly solidified powders could eliminate intergranular fracture, leading to greatly enhanced properties of toughening and healing. Crack clamping and stable crack growth were achieved in a feasibility study using a Sn-Bi matrix reinforced with TiNi fibers. Tensile specimens with less than 1% fibers

  3. Evaluation of tungsten hexachloride as a ROMP active catalyst precursor for self-healing polymers

    NASA Astrophysics Data System (ADS)

    Kamphaus, Jason M.

    Self-healing polymers and composites have been demonstrated via a microencapsulated healing agent and catalytic trigger within the matrix material. The microcapsules are ruptured by a propagating crack and healing agent is released into the crack plane by capillary action. Contact with the catalyst initiates a chemical reaction and the resulting solid polymer bonds the crack faces together. Initial work using the microcapsule/catalytic trigger concept focused on the ring-opening-metathesis-polymerization (ROMP) of endo-dicyclopentadiene with Grubbs' catalyst. Monotonic fracture recovery in excess of 90% and extended fatigue life have been reported. A novel self-healing system based on the ROMP active catalyst tungsten (VI) chloride (WCl6) shows great promise for addressing the limitations of Grubbs' catalyst, specifically the high cost and low thermal stability. The healing chemistry utilizes WCl6 in solid phase and exo-dicyclopentadiene (exo-DCPD) monomer. The exo-DCPD monomer is the same molecule as used in previously self-healing materials, but is a different isomer and exhibits much higher ROMP reactivity and kinetics. The effect of two different initiators, phenylacetylene and 1-decyne, was explored, as well as an alternative monomer, 5-ethylidene-2-norbornene (ENB). Three catalyst forms (as-received, recrystallized, and wax-protected) were investigated to address the known sensitivity of WCl6 to moisture and amine curing agents. Fracture experiments were performed to evaluate the healing efficiency of each catalyst type. A tapered double cantilever beam (TDCB) specimen geometry was used to evaluate the virgin and healed fracture toughness of the material. Fracture recovery of ca. 90% was achieved in both the recrystallized and as-received WCl6 cases at 12 wt% catalyst loading. The wax-protected form of the catalyst gives healing efficiencies of ca. 50% at only 4 wt% overall catalyst loading. In situ samples achieved healing efficiencies of up to 30% for

  4. Effects of water-aging on self-healing dental composite containing microcapsules

    PubMed Central

    Wu, Junling; Weir, Michael D.; Melo, Mary Anne S.; Strassler, Howard E.; Xu, Hockin H. K.

    2016-01-01

    Objectives The objectives of this study were to develop a self-healing dental composite containing poly(urea-formaldehyde) (PUF) shells with triethylene glycol dimethacrylate (TEGDMA) and N,N-dihydroxyethyl-p-toluidine (DHEPT) as healing liquid, and to investigate the mechanical properties of the composite and its self-healing efficacy after water-aging for 6 months. Methods PUF microspheres were synthesized encapsulating a TEGDMA-DHEPT healing liquid. Composite containing 30% of a resin matrix and 70% of glass fillers by mass was incorporated with 0%, 2.5%, 5%, 7.5% and 10% of microcapsules. A flexural test was used to measure flexural strength and elastic modulus. A single edge V-notched beam method was used to measure fracture toughness (KIC) and self-healing efficacy. Specimens were water-aged at 37 °C for 1 d to 6 months and then tested for self-healing. Fractured specimens were healed while being immersed in water to examine self-healing efficacy, in comparison with that in air. Results Incorporation of up to 7.5% of microcapsules into the resin composite achieved effective self-healing, without adverse effects on the virgin mechanical properties of the composite (p > 0.1). An excellent self-healing efficacy of 64%–77% recovery was obtained (mean ± sd; n = 6). Six months of water-aging did not decrease the self-healing efficacy compared to 1 d (p > 0.1). Exposure to water did not decrease the healing efficacy, compared to that healed in air (p > 0.1). Conclusions A composite was developed with excellent self-healing efficacy even while being immersed in water. The self-healing efficacy did not decrease with increasing water-aging time for 6 months. Clinical significance The novel self-healing composite may be promising for dental applications to heal cracks, resist fracture, and increase the durability and longevity. PMID:26808158

  5. Effects of water-aging on self-healing dental composite containing microcapsules.

    PubMed

    Wu, Junling; Weir, Michael D; Melo, Mary Anne S; Strassler, Howard E; Xu, Hockin H K

    2016-04-01

    The objectives of this study were to develop a self-healing dental composite containing poly(urea-formaldehyde) (PUF) shells with triethylene glycol dimethacrylate (TEGDMA) and N,N-dihydroxyethyl-p-toluidine (DHEPT) as healing liquid, and to investigate the mechanical properties of the composite and its self-healing efficacy after water-aging for 6 months. PUF microspheres were synthesized encapsulating a TEGDMA-DHEPT healing liquid. Composite containing 30% of a resin matrix and 70% of glass fillers by mass was incorporated with 0%, 2.5%, 5%, 7.5% and 10% of microcapsules. A flexural test was used to measure flexural strength and elastic modulus. A single edge V-notched beam method was used to measure fracture toughness (KIC) and self-healing efficacy. Specimens were water-aged at 37 °C for 1 day to 6 months and then tested for self-healing. Fractured specimens were healed while being immersed in water to examine self-healing efficacy, in comparison with that in air. Incorporation of up to 7.5% of microcapsules into the resin composite achieved effective self-healing, without adverse effects on the virgin mechanical properties of the composite (p>0.1). An excellent self-healing efficacy of 64-77% recovery was obtained (mean±sd; n=6). Six months of water-aging did not decrease the self-healing efficacy compared to 1 day (p>0.1). Exposure to water did not decrease the healing efficacy, compared to that healed in air (p>0.1). A composite was developed with excellent self-healing efficacy even while being immersed in water. The self-healing efficacy did not decrease with increasing water-aging time for 6 months. The novel self-healing composite may be promising for dental applications to heal cracks, resist fracture, and increase the durability and longevity. Copyright © 2016 Elsevier Ltd. All rights reserved.

  6. Light-triggered self-healing and shape-memory polymers.

    PubMed

    Habault, Damien; Zhang, Hongji; Zhao, Yue

    2013-09-07

    In this review, we highlight the recent progress made in light-controlled self-healing and shape memory polymers. We analyse the materials design, underlying mechanisms and chemistries involved in the different methods developed for these two types of emerging photoresponsive materials. We show that these two seemingly different groups of functional materials are linked by a number of common approaches enabling their optical control, particularly the approaches based on the photothermal effect and photochemical reactions of photoswitching groups incorporated in polymer structures. Possible future developments and perspectives of using light as a unique trigger for polymer self-healing and shape-memory are also discussed.

  7. Bioinspired engineering study of Plantae vascules for self-healing composite structures

    PubMed Central

    Trask, R. S.; Bond, I. P.

    2010-01-01

    This paper presents the first conceptual study into creating a Plantae-inspired vascular network within a fibre-reinforced polymer composite laminate, which provides an ongoing self-healing functionality without incurring a mass penalty. Through the application of a ‘lost-wax’ technique, orthogonal hollow vascules, inspired by the ‘ray cell’ structures found in ring porous hardwoods, were successfully introduced within a carbon fibre-reinforced epoxy polymer composite laminate. The influence on fibre architecture and mechanical behaviour of single vascules (located on the laminate centreline) when aligned parallel and transverse to the local host ply was characterized experimentally using a compression-after-impact test methodology. Ultrasonic C-scanning and high-resolution micro-CT X-ray was undertaken to identify the influence of and interaction between the internal vasculature and impact damage. The results clearly show that damage morphology is influenced by vascule orientation and that a 10 J low-velocity impact damage event is sufficient to breach the vasculature; a prerequisite for any subsequent self-healing function. The residual compressive strength after a 10 J impact was found to be dependent upon vascule orientation. In general, residual compressive strength decreased to 70 per cent of undamaged strength when vasculature was aligned parallel to the local host ply and a value of 63 per cent when aligned transverse. This bioinspired engineering study has illustrated the potential that a vasculature concept has to offer in terms of providing a self-healing function with minimum mass penalty, without initiating premature failure within a composite structure. PMID:19955122

  8. Bioinspired engineering study of Plantae vascules for self-healing composite structures.

    PubMed

    Trask, R S; Bond, I P

    2010-06-06

    This paper presents the first conceptual study into creating a Plantae-inspired vascular network within a fibre-reinforced polymer composite laminate, which provides an ongoing self-healing functionality without incurring a mass penalty. Through the application of a 'lost-wax' technique, orthogonal hollow vascules, inspired by the 'ray cell' structures found in ring porous hardwoods, were successfully introduced within a carbon fibre-reinforced epoxy polymer composite laminate. The influence on fibre architecture and mechanical behaviour of single vascules (located on the laminate centreline) when aligned parallel and transverse to the local host ply was characterized experimentally using a compression-after-impact test methodology. Ultrasonic C-scanning and high-resolution micro-CT X-ray was undertaken to identify the influence of and interaction between the internal vasculature and impact damage. The results clearly show that damage morphology is influenced by vascule orientation and that a 10 J low-velocity impact damage event is sufficient to breach the vasculature; a prerequisite for any subsequent self-healing function. The residual compressive strength after a 10 J impact was found to be dependent upon vascule orientation. In general, residual compressive strength decreased to 70 per cent of undamaged strength when vasculature was aligned parallel to the local host ply and a value of 63 per cent when aligned transverse. This bioinspired engineering study has illustrated the potential that a vasculature concept has to offer in terms of providing a self-healing function with minimum mass penalty, without initiating premature failure within a composite structure.

  9. Adhesion promotion via noncovalent interactions in self-healing polymers.

    PubMed

    Wilson, Gerald O; Caruso, Mary M; Schelkopf, Stuart R; Sottos, Nancy R; White, Scott R; Moore, Jeffrey S

    2011-08-01

    Dimethylnorbornene ester (DNE) is successfully used as a noncovalent adhesion promoter. DNE was confirmed to copolymerize with dicyclopentadiene (DCPD) to yield a copolymer with better adhesion to an EPON 828 epoxy matrix relative to poly(DCPD) alone. The mechanical properties of the copolymer were comparable to that of poly(DCPD) alone. An optimized blend of the monomers was encapsulated using a urea-formaldheyde microencapsulation procedure and the resulting capsules were used for in situ self-healing experiments. Improved healing efficiency was observed for samples containing the DCPD/DNE capsules under conditions in which the monomers were efficiently polymerized.

  10. Autonomous stimulus triggered self-healing in smart structural composites

    NASA Astrophysics Data System (ADS)

    Norris, C. J.; White, J. A. P.; McCombe, G.; Chatterjee, P.; Bond, I. P.; Trask, R. S.

    2012-09-01

    Inspired by the ability of biological systems to sense and autonomously heal damage, this research has successfully demonstrated the first autonomous, stimulus triggered, self-healing system in a structural composite material. Both the sensing and healing mechanisms are reliant on microvascular channels incorporated within a laminated composite material. For the triggering mechanism, a single air filled vessel was pressurized, sealed and monitored. Upon drop weight impact (10 J), delamination and microcrack connectivity between the pressurized vessel and those open to ambient led to a pressure loss which, with the use of a suitable sensor, triggered a pump to deliver a healing agent to the damage zone. Using this autonomous healing approach, near full recovery of post-impact compression strength was achieved (94% on average). A simplified alternative system with healing agent continuously flowing through the vessels, akin to blood flow, was found to offer 100% recovery of the material’s virgin strength. Optical microscopy and ultrasonic C-scanning provided further evidence of large-scale infusion of matrix damage with the healing agent. The successful implementation of this bioinspired technology could substantially enhance the integrity and reliability of aerospace structures, whilst offering benefits through improved performance/weight ratios and extended lifetimes.

  11. Effect of 3D-Printed Microvascular Network Design on the Self-Healing Behavior of Cross-Linked Polymers.

    PubMed

    Postiglione, G; Alberini, M; Leigh, S; Levi, M; Turri, S

    2017-04-12

    This article describes the manufacturing procedure and the characterization of self-healing polymers based on embedded microvascular networks. The samples were realized by resin casting into water-soluble PVA molds, fabricated via 3D printing. This technology allowed us to exploit the 3D printers' ability to produce complex structures with high resolution for the creation of independent microchannels networks. The two reacting components of a two-part resin could be stored separately within the microstructure. The materials' self-healing ability resulted from their reaction when severe damage caused the healing liquids to leak out, wetting the sample cross section and diffusing one into the other. The mechanical properties of healed samples were investigated by means of uniaxial tensile tests and compared to those of undamaged samples. The effect of microchannel density and different network designs on self-healing efficiency was determined. The different microstructures used were characterized using computerized X-ray microtomography. The versatility of the fabrication technique presented in this work allows conversion of any water-resistant resin into a fully functional self-healing polymeric composite.

  12. Redox-responsive self-healing materials formed from host–guest polymers

    PubMed Central

    Nakahata, Masaki; Takashima, Yoshinori; Yamaguchi, Hiroyasu; Harada, Akira

    2011-01-01

    Expanding the useful lifespan of materials is becoming highly desirable, and self-healing and self-repairing materials may become valuable commodities. The formation of supramolecular materials through host–guest interactions is a powerful method to create non-conventional materials. Here we report the formation of supramolecular hydrogels and their redox-responsive and self-healing properties due to host–guest interactions. We employ cyclodextrin (CD) as a host molecule because it is environmentally benign and has diverse applications. A transparent supramolecular hydrogel quickly forms upon mixing poly(acrylic acid) (pAA) possessing β-CD as a host polymer with pAA possessing ferrocene as a guest polymer. Redox stimuli induce a sol−gel phase transition in the supramolecular hydrogel and can control self-healing properties such as re-adhesion between cut surfaces. PMID:22027591

  13. Redox-responsive self-healing materials formed from host-guest polymers.

    PubMed

    Nakahata, Masaki; Takashima, Yoshinori; Yamaguchi, Hiroyasu; Harada, Akira

    2011-10-25

    Expanding the useful lifespan of materials is becoming highly desirable, and self-healing and self-repairing materials may become valuable commodities. The formation of supramolecular materials through host-guest interactions is a powerful method to create non-conventional materials. Here we report the formation of supramolecular hydrogels and their redox-responsive and self-healing properties due to host-guest interactions. We employ cyclodextrin (CD) as a host molecule because it is environmentally benign and has diverse applications. A transparent supramolecular hydrogel quickly forms upon mixing poly(acrylic acid) (pAA) possessing β-CD as a host polymer with pAA possessing ferrocene as a guest polymer. Redox stimuli induce a sol-gel phase transition in the supramolecular hydrogel and can control self-healing properties such as re-adhesion between cut surfaces.

  14. Imaging the Molecular Motions of Autonomous Repair in a Self-Healing Polymer.

    PubMed

    van der Kooij, Hanne M; Susa, Arijana; García, Santiago J; van der Zwaag, Sybrand; Sprakel, Joris

    2017-07-01

    Self-healing polymers can significantly extend the service life of materials and structures by autonomously repairing damage. Intrinsic healing holds great promise as a design strategy to mitigate the risks of damage by delaying or preventing catastrophic failure. However, experimentally resolving the microscopic mechanisms of intrinsic repair has proven highly challenging. This work demonstrates how optical micromechanical mapping enables the quantitative imaging of these molecular-scale dynamics with high spatiotemporal resolution. This approach allows disentangling delocalized viscoplastic relaxation and localized cohesion-restoring rebonding processes that occur simultaneously upon damage to a self-healing polymer. Moreover, frequency- and temperature-dependent imaging provides a way to pinpoint the repair modes in the relaxation spectrum of the quiescent material. These results give rise to a complete picture of autonomous repair that will guide the rational design of improved self-healing materials. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  15. Dynamic sulfur chemistry as a key tool in the design of self-healing polymers

    NASA Astrophysics Data System (ADS)

    Martin, Roberto; Rekondo, Alaitz; Ruiz de Luzuriaga, Alaitz; Casuso, Pablo; Dupin, Damien; Cabañero, Germán; Grande, Hans J.; Odriozola, Ibon

    2016-08-01

    The rich variety of reversible or dynamic covalent chemistries based on sulfur offers a unique opportunity for the design of self-healing polymer networks. The reversibility of such chemical bonds can be used to create soft systems which can self-mend at ambient conditions. Here we focus on the mechanism of three different dynamic sulfur chemistries which have been used for the development of self-healing elastomers and hydrogels: thiolate/nanoparticle exchange, aromatic disulfide exchange and gold(I)-thiolate/disulfide exchange.

  16. Self-healing multiphase polymers via dynamic metal-ligand interactions.

    PubMed

    Mozhdehi, Davoud; Ayala, Sergio; Cromwell, Olivia R; Guan, Zhibin

    2014-11-19

    A new self-healing multiphase polymer is developed in which a pervasive network of dynamic metal-ligand (zinc-imidazole) interactions are programmed in the soft matrix of a hard/soft two-phase brush copolymer system. The mechanical and dynamic properties of the materials can be tuned by varying a number of molecular parameters (e.g., backbone/brush degree of polymerization and brush density) as well as the ligand/metal ratio. Following mechanical damage, these thermoplastic elastomers show excellent self-healing ability under ambient conditions without any intervention.

  17. Malleable and Self-Healing Covalent Polymer Networks through Tunable Dynamic Boronic Ester Bonds.

    PubMed

    Cromwell, Olivia R; Chung, Jaeyoon; Guan, Zhibin

    2015-05-27

    Despite numerous strategies involving dynamic covalent bond exchange for dynamic and self-healing materials, it remains a challenge to be able to tune the malleability and self-healing properties of bulk materials through simple small molecule perturbations. Here we describe the use of tunable rates of boronic ester transesterification to tune the malleability and self-healing efficiencies of bulk materials. Specifically, we used two telechelic diboronic ester small molecules with variable transesterification kinetics to dynamically cross-link 1,2-diol-containing polymer backbones. The sample cross-linked with fast-exchanging diboronic ester showed enhanced malleability and accelerated healing compared to the slow-exchanging variant under the same conditions. Our report demonstrates the possibility of transferring small molecule kinetics to dynamic properties of bulk solid material and may serve as a guide for the rational design of tunable dynamic materials.

  18. A rapidly self-healing supramolecular polymer hydrogel with photostimulated room-temperature phosphorescence responsiveness.

    PubMed

    Chen, Hui; Ma, Xiang; Wu, Shuaifan; Tian, He

    2014-12-15

    Development of self-healing and photostimulated luminescent supramolecular polymeric materials is important for artificial soft materials. A supramolecular polymeric hydrogel is reported based on the host-guest recognition between a β-cyclodextrin (β-CD) host polymer (poly-β-CD) and an α-bromonaphthalene (α-BrNp) polymer (poly-BrNp) without any additional gelator, which can self-heal within only about one minute under ambient atmosphere without any additive. This supramolecular polymer system can be excited to engender room-temperature phosphorescence (RTP) signals based on the fact that the inclusion of β-CD macrocycle with α-BrNp moiety is able to induce RTP emission (CD-RTP). The RTP signal can be adjusted reversibly by competitive complexation of β-CD with azobenzene moiety under specific irradiation by introducing another azobenzene guest polymer (poly-Azo). © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  19. Life extension of self-healing polymers with rapidly growing fatigue cracks.

    PubMed

    Jones, A S; Rule, J D; Moore, J S; Sottos, N R; White, S R

    2007-04-22

    Self-healing polymers, based on microencapsulated dicyclopentadiene and Grubbs' catalyst embedded in the polymer matrix, are capable of responding to propagating fatigue cracks by autonomic processes that lead to higher endurance limits and life extension, or even the complete arrest of the crack growth. The amount of fatigue-life extension depends on the relative magnitude of the mechanical kinetics of crack propagation and the chemical kinetics of healing. As the healing kinetics are accelerated, greater fatigue life extension is achieved. The use of wax-protected, recrystallized Grubbs' catalyst leads to a fourfold increase in the rate of polymerization of bulk dicyclopentadiene and extends the fatigue life of a polymer specimen over 30 times longer than a comparable non-healing specimen. The fatigue life of polymers under extremely fast fatigue crack growth can be extended through the incorporation of periodic rest periods, effectively training the self-healing polymeric material to achieve higher endurance limits.

  20. An electrically and mechanically self-healing composite with pressure- and flexion-sensitive properties for electronic skin applications

    NASA Astrophysics Data System (ADS)

    Tee, Benjamin C.-K.; Wang, Chao; Allen, Ranulfo; Bao, Zhenan

    2012-12-01

    Pressure sensitivity and mechanical self-healing are two vital functions of the human skin. A flexible and electrically conducting material that can sense mechanical forces and yet be able to self-heal repeatably can be of use in emerging fields such as soft robotics and biomimetic prostheses, but combining all these properties together remains a challenging task. Here, we describe a composite material composed of a supramolecular organic polymer with embedded nickel nanostructured microparticles, which shows mechanical and electrical self-healing properties at ambient conditions. We also show that our material is pressure- and flexion-sensitive, and therefore suitable for electronic skin applications. The electrical conductivity can be tuned by varying the amount of nickel particles and can reach values as high as 40 S cm-1. On rupture, the initial conductivity is repeatably restored with ~90% efficiency after 15 s healing time, and the mechanical properties are completely restored after ~10 min. The composite resistance varies inversely with applied flexion and tactile forces. These results demonstrate that natural skin's repeatable self-healing capability can be mimicked in conductive and piezoresistive materials, thus potentially expanding the scope of applications of current electronic skin systems.

  1. An electrically and mechanically self-healing composite with pressure- and flexion-sensitive properties for electronic skin applications.

    PubMed

    Tee, Benjamin C-K; Wang, Chao; Allen, Ranulfo; Bao, Zhenan

    2012-12-01

    Pressure sensitivity and mechanical self-healing are two vital functions of the human skin. A flexible and electrically conducting material that can sense mechanical forces and yet be able to self-heal repeatably can be of use in emerging fields such as soft robotics and biomimetic prostheses, but combining all these properties together remains a challenging task. Here, we describe a composite material composed of a supramolecular organic polymer with embedded nickel nanostructured microparticles, which shows mechanical and electrical self-healing properties at ambient conditions. We also show that our material is pressure- and flexion-sensitive, and therefore suitable for electronic skin applications. The electrical conductivity can be tuned by varying the amount of nickel particles and can reach values as high as 40 S cm(-1). On rupture, the initial conductivity is repeatably restored with ∼90% efficiency after 15 s healing time, and the mechanical properties are completely restored after ∼10 min. The composite resistance varies inversely with applied flexion and tactile forces. These results demonstrate that natural skin's repeatable self-healing capability can be mimicked in conductive and piezoresistive materials, thus potentially expanding the scope of applications of current electronic skin systems.

  2. Using nanoparticles to create self-healing composites

    NASA Astrophysics Data System (ADS)

    Lee, Jae Youn; Buxton, Gavin A.; Balazs, Anna C.

    2004-09-01

    The need for viable materials for optical communications, display technologies, and biomedical engineering is driving the creation of multilayer composites that combine brittle materials, such as glass, with moldable polymers. However, crack formation is a critical problem in composites where thin brittle films lie in contact with deformable polymer layers. Using computer simulations, we show that adding nanoparticles to the polymers yields materials in which the particles become localized at nanoscale cracks and effectively form "patches" to repair the damaged regions. Through micromechanics simulations, we evaluate the properties of these systems in the undamaged, damaged, and healed states and determine optimal conditions for harnessing nanoparticles to act as responsive, self-assembled "band aids" for composite materials. The results reveal situations where the mechanical properties of the repaired composites can potentially be restored to 75%-100% of the undamaged material.

  3. Using nanoparticles to create self-healing composites.

    PubMed

    Lee, Jae Youn; Buxton, Gavin A; Balazs, Anna C

    2004-09-15

    The need for viable materials for optical communications, display technologies, and biomedical engineering is driving the creation of multilayer composites that combine brittle materials, such as glass, with moldable polymers. However, crack formation is a critical problem in composites where thin brittle films lie in contact with deformable polymer layers. Using computer simulations, we show that adding nanoparticles to the polymers yields materials in which the particles become localized at nanoscale cracks and effectively form "patches" to repair the damaged regions. Through micromechanics simulations, we evaluate the properties of these systems in the undamaged, damaged, and healed states and determine optimal conditions for harnessing nanoparticles to act as responsive, self-assembled "band aids" for composite materials. The results reveal situations where the mechanical properties of the repaired composites can potentially be restored to 75%-100% of the undamaged material.

  4. Development of novel self-healing and antibacterial dental composite containing calcium phosphate nanoparticles

    PubMed Central

    Wu, Junling; Weir, Michael D.; Melo, Mary Anne S.; Xu, Hockin H. K.

    2015-01-01

    Objectives Fracture and secondary caries are the primary reasons for dental restoration failure. The objective of this study was to develop a self-healing composite to heal cracks, while containing dimethylaminohexadecyl methacrylate (DMAHDM) for antibacterial function and nanoparticles of amorphous calcium phosphate (NACP) for remineralization. Methods Microcapsules were synthesized with poly(urea-formaldehyde) (PUF) shells containing triethylene glycol dimethacrylate (TEGDMA) and N,N-dihydroxyethyl-p-toluidine (DHEPT) as healing liquid. Composite contained 20 mass% of NACP and 35% glass fillers. In addition, composite contained 0%, 2.5%, 5%, 7.5%, or 10% of microcapsules. A single edge V-notched beam method measured fracture toughness (KIC) and self-healing efficiency. A dental plaque microcosm biofilm model was used to test the antibacterial properties. Results Incorporation of microcapsules up to 7.5% into the composite did not adversely affect the mechanical properties (p > 0.1). Successful self-healing was achieved, with KIC recovery of 65–81% (mean ± sd; n = 6) to regain the load-bearing capability after composite fracture. The self-healing DMAHDM-NACP composite displayed a strong antibacterial potency, inhibiting biofilm viability and lactic acid production, and reducing colony-forming units by 3–4 orders of magnitude, compared to control composite without DMAHDM. Conclusions A dental composite was developed with triple benefits of self-healing after fracture, antibacterial activity, and remineralization capability for the first time. Clinical significance The self-healing, antibacterial and remineralizing composite may be promising for tooth cavity restorations to combat bulk fracture and secondary caries. The method of using triple agents (self-healing microcapsules, DMAHDM, and NACP) may have wide applicability to other dental composites, adhesives, sealants and cements. PMID:25625674

  5. Development of novel self-healing and antibacterial dental composite containing calcium phosphate nanoparticles.

    PubMed

    Wu, Junling; Weir, Michael D; Melo, Mary Anne S; Xu, Hockin H K

    2015-03-01

    Fracture and secondary caries are the primary reasons for dental restoration failure. The objective of this study was to develop a self-healing composite to heal cracks, while containing dimethylaminohexadecyl methacrylate (DMAHDM) for antibacterial function and nanoparticles of amorphous calcium phosphate (NACP) for remineralization. Microcapsules were synthesized with poly(urea-formaldehyde) (PUF) shells containing triethylene glycol dimethacrylate (TEGDMA) and N,N-dihydroxyethyl-p-toluidine (DHEPT) as healing liquid. Composite contained 20 mass% of NACP and 35% glass fillers. In addition, composite contained 0%, 2.5%, 5%, 7.5%, or 10% of microcapsules. A single edge V-notched beam method measured fracture toughness (KIC) and self-healing efficiency. A dental plaque microcosm biofilm model was used to test the antibacterial properties. Incorporation of microcapsules up to 7.5% into the composite did not adversely affect the mechanical properties (p > 0.1). Successful self-healing was achieved, with KIC recovery of 65-81% (mean ± sd; n = 6) to regain the load-bearing capability after composite fracture. The self-healing DMAHDM-NACP composite displayed a strong antibacterial potency, inhibiting biofilm viability and lactic acid production, and reducing colony-forming units by 3-4 orders of magnitude, compared to control composite without DMAHDM. A dental composite was developed with triple benefits of self-healing after fracture, antibacterial activity, and remineralization capability for the first time. The self-healing, antibacterial and remineralizing composite may be promising for tooth cavity restorations to combat bulk fracture and secondary caries. The method of using triple agents (self-healing microcapsules, DMAHDM, and NACP) may have wide applicability to other dental composites, adhesives, sealants and cements. Copyright © 2015 Elsevier Ltd. All rights reserved.

  6. Seawater-Assisted Self-Healing of Catechol Polymers via Hydrogen Bonding and Coordination Interactions.

    PubMed

    Li, Jincai; Ejima, Hirotaka; Yoshie, Naoko

    2016-07-27

    It is highly desirable to prevent crack formation in polymeric materials at an early stage and to extend their lifespan, particularly when repairs to these materials would be difficult for humans. Here, we designed and synthesized catechol-functionalized polymers that can self-heal in seawater through hydrogen bonding and coordination. These bioinspired acrylate polymers are originally viscous materials, but after coordination with environmentally safe, common metal cations in seawater, namely, Ca(2+) and Mg(2+), the mechanical properties of the polymers were greatly enhanced from viscous to tough, hard materials. Reduced swelling in seawater compared with deionized water owing to the higher osmotic pressure resulted in greater toughness (∼5 MPa) and self-healing efficiencies (∼80%).

  7. Piezoelectric and mechanical properties of fatigue resistant, self-healing PZT-ionomer composites

    NASA Astrophysics Data System (ADS)

    James, N. K.; Lafont, U.; van der Zwaag, S.; Groen, W. A.

    2014-05-01

    Piezoelectric ceramic-polymer composites with 0-3 connectivity were fabricated using lead zirconium titanate (PZT) powder dispersed in an ionomer (Zn ionomer) and its reference ethylene methacrylic acid copolymer (EMAA) polymer matrix. The PZT-Zn ionomer and PZT-EMAA composites were prepared by melt extrusion followed by hot pressing. The effects of poling conditions such as temperature, time and electric field on the piezoelectric properties of the composites were investigated. The experimentally observed piezoelectric charge coefficient and dielectric constant of the composites were compared with theoretical models. The results show that PZT-Zn ionomer composites have better piezoelectric properties compared to PZT-EMAA composites. The static and fatigue properties of the composites were investigated. The PZT-Zn ionomer composites were found to have excellent fatigue resistance even at strain levels of 4%. Due to the self-healing capabilities of the ionomer matrix, the loss of piezoelectric properties after high strain tensile cyclic loading could be partially recovered by thermal healing.

  8. Hierarchical Nacre Mimetics with Synergistic Mechanical Properties by Control of Molecular Interactions in Self-Healing Polymers.

    PubMed

    Zhu, Baolei; Jasinski, Nils; Benitez, Alejandro; Noack, Manuel; Park, Daesung; Goldmann, Anja S; Barner-Kowollik, Christopher; Walther, Andreas

    2015-07-20

    Designing the reversible interactions of biopolymers remains a grand challenge for an integral mimicry of mechanically superior biological composites. Yet, they are the key to synergistic combinations of stiffness and toughness by providing sacrificial bonds with hidden length scales. To address this challenge, dynamic polymers were designed with low glass-transition temperature T(g) and bonded by quadruple hydrogen-bonding motifs, and subsequently assembled with high-aspect-ratio synthetic nanoclays to generate nacre-mimetic films. The high dynamics and self-healing of the polymers render transparent films with a near-perfectly aligned structure. Varying the polymer composition allows molecular control over the mechanical properties up to very stiff and very strong films (E≈45 GPa, σ(UTS)≈270 MPa). Stable crack propagation and multiple toughening mechanisms occur in situations of balanced dynamics, enabling synergistic combinations of stiffness and toughness. Excellent gas barrier properties complement the multifunctional property profile.

  9. Polymer damage mitigation---predictive lifetime models of polymer insulation degradation and biorenewable thermosets through cationic polymerization for self-healing applications

    NASA Astrophysics Data System (ADS)

    Hondred, Peter Raymond

    Over the past 50 years, the industrial development and applications for polymers and polymer composites has become expansive. However, as with any young technology, the techniques for predicting material damage and resolving material failure are in need of continued development and refinement. This thesis work takes two approaches to polymer damage mitigation---material lifetime prediction and spontaneous damage repair through self-healing while incorporating bio-renewable feedstock. First, material lifetime prediction offers the benefit of identifying and isolating material failures before the effects of damage results in catastrophic failure. Second, self-healing provides a systematic approach to repairing damaged polymer composites, specifically in applications where a hands-on approach or removing the part from service are not feasible. With regard to lifetime prediction, we investigated three specific polymeric materials---polytetrafluoroethylene (PTFE), poly(ethylene-alt-tetrafluoroethylene) (ETFE), and Kapton. All three have been utilized extensively in the aerospace field as a wire insulation coating. Because of the vast amount of electrical wiring used in aerospace constructions and the potential for electrical and thermal failure, this work develops mathematical models for both the thermal degradation kinetics as well as a lifetime prediction model for electrothermal breakdown. Isoconversional kinetic methods, which plot activation energy as a function of the extent of degradation, present insight into the development each kinetic model. The models for PTFE, ETFE, and Kapton are one step, consecutive three-step, and competitive and consecutive five-step respectively. Statistical analysis shows that an nth order autocatalytic reaction best defined the reaction kinetics for each polymer's degradation. Self-healing polymers arrest crack propagation through the use of an imbedded adhesive that reacts when cracks form. This form of damage mitigation focuses on

  10. CuAAC-Based Click Chemistry in Self-Healing Polymers.

    PubMed

    Döhler, Diana; Michael, Philipp; Binder, Wolfgang H

    2017-09-11

    )branched polymers, autocatalysis, or internal chelation concepts enable efficient click cross-linking already at 5 °C with a simultaneously reduced amount of Cu(I) catalyst and increased reaction rates, culminating in the first reported self-healing system based on click cycloaddition reactions. Via tailor-made nanocarbon/Cu(I) catalysts we can further improve the click cross-linking reaction in view of efficiency and kinetics, leading to the generation of self-healing graphene-based epoxy nanocomposites. Additionally, we have designed special CuAAC click methods for chemical reporting and visualization systems based on the detection of ruptured capsules via a fluorogenic click reaction, which can be combined with CuAAC cross-linking reactions to obtain simultaneous stress detection and self-healing within polymeric materials. In a similar concept, we have prepared polymeric Cu(I)-biscarbene complexes to detect (mechanical) stress within self-healing polymeric materials via a triggered fluorogenic reaction, thus using a destructive force for a constructive chemical response.

  11. Processing and damage recovery of intrinsic self-healing glass fiber reinforced composites

    NASA Astrophysics Data System (ADS)

    Sordo, Federica; Michaud, Véronique

    2016-08-01

    Glass fiber reinforced composites with a self-healing, supramolecular hybrid network matrix were produced using a modified vacuum assisted resin infusion moulding process adapted to high temperature processing. The quality and fiber volume fraction (50%) of the obtained materials were assessed through microscopy and matrix burn-off methods. The thermo-mechanical properties were quantified by means of dynamic mechanical analysis, revealing very high damping properties compared to traditional epoxy-based glass fiber reinforced composites. Self-healing properties were assessed by three-point bending tests. A high recovery of the flexural properties, around 72% for the elastic modulus and 65% of the maximum flexural stress, was achieved after a resting period of 24 h at room temperature. Recovery after low velocity impact events was also visually observed. Applications for this intrinsic and autonomic self-healing highly reinforced composite material point towards semi-structural applications where high damping and/or integrity recovery after impact are required.

  12. Correlated aggregate model of self-healing in dye-doped polymers

    NASA Astrophysics Data System (ADS)

    Kuzyk, Mark G.; Ramini, Shiva

    2012-10-01

    Self healing of chromophores in a dye-doped polymer after photodegradation is a counterintuitive process based on the nearly universal observation that molecular damage is a thermodynamically irreversible process. We propose a new simple model of this phenomenon that takes into account all observations, including the effects of concentration, temperature, and bystander states. Critical to this model are correlations between chromophores, perhaps mediated by the polymer, which actively favors the undamaged species in analogy to Bose-Einstein condensation. We use this model to predict the behavior of decay and recovery experiments as measured with amplified spontaneous emission and absorption spectroscopy.

  13. A multiple-responsive self-healing supramolecular polymer gel network based on multiple orthogonal interactions.

    PubMed

    Zhan, Jiayi; Zhang, Mingming; Zhou, Mi; Liu, Bin; Chen, Dong; Liu, Yuanyuan; Chen, Qianqian; Qiu, Huayu; Yin, Shouchun

    2014-08-01

    Supramolecular polymer networks have attracted considerable attention not only due to their topological importance but also because they can show some fantastic properties such as stimuli-responsiveness and self-healing. Although various supramolecular networks are constructed by supramolecular chemists based on different non-covalent interactions, supramolecular polymer networks based on multiple orthogonal interactions are still rare. Here, a supramolecular polymer network is presented on the basis of the host-guest interactions between dibenzo-24-crown-8 (DB24C8) and dibenzylammonium salts (DBAS), the metal-ligand coordination interactions between terpyridine and Zn(OTf)2 , and between 1,2,3-triazole and PdCl2 (PhCN)2 . The topology of the networks can be easily tuned from monomer to main-chain supramolecular polymer and then to the supramolecular networks. This process is well studied by various characterization methods such as (1) H NMR, UV-vis, DOSY, viscosity, and rheological measurements. More importantly, a supramolecular gel is obtained at high concentrations of the supramolecular networks, which demonstrates both stimuli-responsiveness and self-healing properties. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  14. Three-dimensional percolation modeling of self-healing composites.

    PubMed

    Dementsov, Alexander; Privman, Vladimir

    2008-08-01

    We study the self-healing process of materials with embedded "glue"-carrying cells, in the regime of the onset of the initial fatigue. Three-dimensional numerical simulations within the percolation-model approach are reported. The main numerical challenge taken up in the present work has been to extend the calculation of the conductance to three-dimensional lattices. Our results confirm the general features of the process: The onset of material fatigue is delayed, by development of a plateaulike time dependence of the material quality. We demonstrate that, in this low-damage regime, the changes in the conductance and thus in similar transport and response properties of the material can be used as measures of the material quality degradation. A new feature found for three dimensions, where it is much more profound than in earlier-studied two-dimensional systems, is the competition between the healing cells. Even for low initial densities of the healing cells, they interfere with each other and reduce each other's effective healing efficiency.

  15. Self-Healing of Polyethylene Oxide

    NASA Astrophysics Data System (ADS)

    Chipara, Dorina Magdalena; Flores, Maritza; Puente, Nancy; Lozano, Karen

    2011-03-01

    Autonomic self-healing is expected to enhance the lifetime of polymeric materials, resins, and composites subjected to long term mechanical stresses. The self-healing process is initiated by the rupture of some polyurea-formaldehyde microcapsules filled with monomer. The self-healing polymer is actually a compound containing microcapsules filled with monomer and catalyst particles. The monomer released from these broken microcapsules is diffusing within the polymer, reacting with the catalyst and starting a polymerization reaction. This new polymer, growing within the propagating crack, stops the mechanical failure. While the process is pretty slow (timescale of the order of 10 to 100 s), there are many important technological applications that would benefit from the availability of self-healing polymers. We report about the addition of self-healing capabilities to polyethylene oxide by using polyurea formaldehyde microcapsules filled with dicyclopentadiene and first generation Grubbs catalysts. Details regarding the physical and chemical steps used to add self-healing capabilities to polyethylene oxide will be presented. Self-healing efficiency was assessed by fatigues tests.

  16. Processing and Damage Tolerance of Continuous Carbon Fiber Composites Containing Puncture Self-Healing Thermoplastic Matrix

    NASA Technical Reports Server (NTRS)

    Grimsley, Brian W.; Gordon, Keith L.; Czabaj, Michael W.; Cano, Roberto J.; Siochi, Emilie J.

    2012-01-01

    Research at NASA Langley Research Center (NASA LaRC) has identified several commercially available thermoplastic polymers that self-heal after ballistic impact and through-penetration. One of these resins, polybutadiene graft copolymer (PB(sub g)), was processed with unsized IM7 carbon fibers to fabricate reinforced composite material for further evaluation. Temperature dependent characteristics, such as the degradation point, glass transition (T(sub g)), and viscosity of the PBg polymer were characterized by thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and dynamic parallel plate rheology. The PBg resin was processed into approximately equal to 22.0 cm wide unidirectional prepreg tape in the NASA LaRC Advanced Composites Processing Research Laboratory. Data from polymer thermal characterization guided the determination of a processing cycle used to fabricate quasi-isotropic 32-ply laminate panels in various dimensions up to 30.5cm x 30.5cm in a vacuum press. The consolidation quality of these panels was analyzed by optical microscopy and acid digestion. The process cycle was further optimized based on these results and quasi-isotropic, [45/0/-45/90]4S, 15.24cm x 15.24cm laminate panels were fabricated for mechanical property characterization. The compression strength after impact (CAI) of the IM7/pBG composites was measured both before and after an elevated temperature and pressure healing cycle. The results of the processing development effort of this composite material as well as the results of the mechanical property characterization are presented in this paper.

  17. Glass fibre polyester composite with in vivo vascular channel for use in self-healing

    NASA Astrophysics Data System (ADS)

    Fifo, Omosola; Ryan, Kevin; Basu, Biswajit

    2014-09-01

    The embedment of adhesive-filled hollow glass fibres (HGF) has been reported as a way of combating micro-crack development in fibre-reinforced polymer (FRP) structures. However, hollow fibres can critically undermine the effectiveness of self-healing systems and have been reported to be a potential impediment to the healing agent flow path. On the other hand, attempting to use non-hollow vascular systems in higher dimensions has largely been restricted to bulk polymers that lack reinforcing fibres. This paper investigates an alternative technique where a simple two-dimensional (2D) network of hollow channels is created within a glass-fibre-reinforced polyester-composite structure. The network is created using a fugitive preforming material at the ply level of interest, similar to a direct ink writing procedure. The temporary structure is extracted as a part of the curing and post-curing processes. The channels formed are used to deliver cyanoacrylate adhesive (CA) to areas that have been damaged under a flexural three-point bending test. Subsequent post-repair mechanical testing, under the same mode, evaluates the success of the repair process. The results show good recovery of the stiffness, a paramount mechanical property, and indicate how the grade of the repairing agent used influences the recovered loading strength of the FRP samples.

  18. Effective Crack Control of Concrete by Self-Healing of Cementitious Composites Using Synthetic Fiber.

    PubMed

    Choi, Heesup; Inoue, Masumi; Kwon, Sukmin; Choi, Hyeonggil; Lim, Myungkwan

    2016-03-30

    Although concrete is one of the most widely used construction materials, it is characterized by substantially low tensile strength in comparison to its compression strength, and the occurrence of cracks is unavoidable. In addition, cracks progress due to environmental conditions including damage by freezing, neutralization, and salt, etc. Moreover, detrimental damage can occur in concrete structures due to the permeation of deteriorating elements such as Cl(-) and CO₂. Meanwhile, under an environment in which moisture is being supplied and if the width of the crack is small, a phenomenon of self-healing, in which a portion of the crack is filled in due to the rehydration of the cement particles and precipitation of CaCO₃, is been confirmed. In this study, cracks in cementitious composite materials are effectively dispersed using synthetic fibers, and for cracks with a width of more than 0.1 mm, a review of the optimal self-healing conditions is conducted along with the review of a diverse range of self-healing performance factors. As a result, it was confirmed that the effective restoration of watertightness through the production of the majority of self-healing products was achieved by CaCO₃ and the use of synthetic fibers with polarity, along with the effect of inducing a multiple number of hairline cracks. In addition, it was confirmed that the self-healing conditions of saturated Ca(OH)₂ solution, which supplied CO₂ micro-bubbles, displayed the most effective self-healing performance in the surface and internal sections of the cracks.

  19. Effective Crack Control of Concrete by Self-Healing of Cementitious Composites Using Synthetic Fiber

    PubMed Central

    Choi, Heesup; Inoue, Masumi; Kwon, Sukmin; Choi, Hyeonggil; Lim, Myungkwan

    2016-01-01

    Although concrete is one of the most widely used construction materials, it is characterized by substantially low tensile strength in comparison to its compression strength, and the occurrence of cracks is unavoidable. In addition, cracks progress due to environmental conditions including damage by freezing, neutralization, and salt, etc. Moreover, detrimental damage can occur in concrete structures due to the permeation of deteriorating elements such as Cl− and CO2. Meanwhile, under an environment in which moisture is being supplied and if the width of the crack is small, a phenomenon of self-healing, in which a portion of the crack is filled in due to the rehydration of the cement particles and precipitation of CaCO3, is been confirmed. In this study, cracks in cementitious composite materials are effectively dispersed using synthetic fibers, and for cracks with a width of more than 0.1 mm, a review of the optimal self-healing conditions is conducted along with the review of a diverse range of self-healing performance factors. As a result, it was confirmed that the effective restoration of watertightness through the production of the majority of self-healing products was achieved by CaCO3 and the use of synthetic fibers with polarity, along with the effect of inducing a multiple number of hairline cracks. In addition, it was confirmed that the self-healing conditions of saturated Ca(OH)2 solution, which supplied CO2 micro-bubbles, displayed the most effective self-healing performance in the surface and internal sections of the cracks. PMID:28773372

  20. Self-healing antimicrobial polymer coating with efficacy in the presence of organic matter

    NASA Astrophysics Data System (ADS)

    Bastarrachea, Luis J.; Goddard, Julie M.

    2016-08-01

    A method to prepare a self-healing, antimicrobial polymer coating that retains efficacy against Escherichia coli O157:H7 in the presence of organic matter is reported. A coating composed of branched polyethyleneimine (PEI) and styrene maleic anhydride copolymer (SMA) was applied to a maleic anhydride functionalized polypropylene support. The chemistry of the polymer coating was designed to impart hydrophobicity due to the styrene subunits, intrinsic antimicrobial character (>99.9% reduction) from the cationic primary amine groups, and enhanced antimicrobial character (> 99.99% reduction) after chlorination of N-halamine forming groups. Antimicrobial effectiveness was demonstrated under conditions of increasing organic load. Up to 500 ppm horse serum, chlorinated coatings retained full antimicrobial character (>99.99% reduction). Even at 50,000 ppm of horse serum, the coating provided ∼90% reduction as prepared, and between ∼75% and ∼80% reduction in the form of N-halamines. Microscopy confirmed no evidence of bacterial adhesion on the coating surface. Finally, the coating exhibited self-healing properties after exposure to acid and alkaline solutions and restoration by heat, as confirmed through spectroscopy from the rebuilding of characteristic chemical bonds. Such robust antimicrobial polymer coatings with efficacy under conditions of increasing organic load may support reducing microbial cross-contamination in food and biomedical industries.

  1. Solvent-based self-healing approaches for fiber-reinforced composites

    NASA Astrophysics Data System (ADS)

    Jones, Amanda R.

    Damage in composite materials spans many length scales and is often difficult to detect or costly to repair. The incorporation of self-healing functionality in composite materials has the potential to greatly extend material lifetime and reliability. Although there has been remarkable progress in self-healing polymers over the past decade, self-repair in fiber-reinforced composite materials presents significant technical challenges due to stringent manufacturing and performance requirements. For high performance, fiber-reinforced composites, the self-healing components need to survive high temperature processing, reside in matrix interstitial regions to retain a high fiber volume fraction, and have minimal impact on the mechanical properties of the host material. This dissertation explores several microencapsulated solvent-based self-healing approaches for fiber-reinforced composites at the fiber/ matrix interface size scale as well as matrix cracking. Systems are initially developed for room temperature cured epoxies/ glass fiber interfaces and successfully transitioned to carbon fibers and high temperature-cured, thermoplastic-toughened matrices. Full recovery of interfacial bond strength after complete fiber/matrix debonding is achieved with a microencapsulated solvent-based healing chemistry. The surface of a glass fiber is functionalized with microcapsules containing varying concentrations of reactive epoxy resin and ethyl phenyl acetate (EPA) solvent. Microbond specimens consisting of a single fiber and a microdroplet of epoxy are cured at 35°C, tested, and the interfacial shear strengths (IFSS) during the initial (virgin) debonding and subsequent healing events are measured. Debonding of the fiber/matrix interface ruptures the capsules, releasing resin and solvent into the crack plane. The solvent swells the matrix, initiating transport of residual amine functionality for further curing with the epoxy resin delivered to the crack plane. Using a resin

  2. Experimental Study on Mechanical Properties and Porosity of Organic Microcapsules Based Self-Healing Cementitious Composite.

    PubMed

    Wang, Xianfeng; Sun, Peipei; Han, Ningxu; Xing, Feng

    2017-01-01

    Encapsulation of healing agents embedded in a material matrix has become one of the major approaches for achieving self-healing function in cementitious materials in recent years. A novel type of microcapsules based self-healing cementitious composite was developed in Guangdong Provincial Key Laboratory of Durability for Marine Civil Engineering, Shenzhen University. In this study, both macro performance and the microstructure of the composite are investigated. The macro performance was evaluated by employing the compressive strength and the dynamic modulus, whereas the microstructure was represented by the pore structure parameters such as porosity, cumulative-pore volume, and average-pore diameter, which are significantly correlated to the pore-size distribution and the compressive strength. The results showed that both the compressive strength and the dynamic modulus, as well as the pore structure parameters such as porosity, cumulative-pore volume, and average-pore diameter of the specimen decrease to some extent with the amount of microcapsules. However, the self-healing rate and the recovery rate of the specimen performance and the pore-structure parameters increase with the amount of microcapsules. The results should confirm the self-healing function of microcapsules in the cementitious composite from macroscopic and microscopic viewpoints.

  3. Experimental Study on Mechanical Properties and Porosity of Organic Microcapsules Based Self-Healing Cementitious Composite

    PubMed Central

    Wang, Xianfeng; Sun, Peipei; Han, Ningxu; Xing, Feng

    2017-01-01

    Encapsulation of healing agents embedded in a material matrix has become one of the major approaches for achieving self-healing function in cementitious materials in recent years. A novel type of microcapsules based self-healing cementitious composite was developed in Guangdong Provincial Key Laboratory of Durability for Marine Civil Engineering, Shenzhen University. In this study, both macro performance and the microstructure of the composite are investigated. The macro performance was evaluated by employing the compressive strength and the dynamic modulus, whereas the microstructure was represented by the pore structure parameters such as porosity, cumulative-pore volume, and average-pore diameter, which are significantly correlated to the pore-size distribution and the compressive strength. The results showed that both the compressive strength and the dynamic modulus, as well as the pore structure parameters such as porosity, cumulative-pore volume, and average-pore diameter of the specimen decrease to some extent with the amount of microcapsules. However, the self-healing rate and the recovery rate of the specimen performance and the pore-structure parameters increase with the amount of microcapsules. The results should confirm the self-healing function of microcapsules in the cementitious composite from macroscopic and microscopic viewpoints. PMID:28772382

  4. Surface-initiated self-healing of polymers in aqueous media

    NASA Astrophysics Data System (ADS)

    Ahn, B. Kollbe; Lee, Dong Woog; Israelachvili, Jacob N.; Waite, J. Herbert

    2014-09-01

    Polymeric materials that intrinsically heal at damage sites under wet or moist conditions are urgently needed for biomedical and environmental applications. Although hydrogels with self-mending properties have been engineered by means of mussel-inspired metal-chelating catechol-functionalized polymer networks, biological self-healing in wet conditions, as occurs in self-assembled holdfast proteins in mussels and other marine organisms, is generally thought to involve more than reversible metal chelates. Here we demonstrate self-mending in metal-free water of synthetic polyacrylate and polymethacrylate materials that are surface-functionalized with mussel-inspired catechols. Wet self-mending of scission in these polymers is initiated and accelerated by hydrogen bonding between interfacial catechol moieties, and consolidated by the recruitment of other non-covalent interactions contributed by subsurface moieties. The repaired and pristine samples show similar mechanical properties, suggesting that the triggering of complete self-healing is enabled underwater by the formation of extensive catechol-mediated interfacial hydrogen bonds.

  5. Surface-initiated self-healing of polymers in aqueous media.

    PubMed

    Ahn, B Kollbe; Lee, Dong Woog; Israelachvili, Jacob N; Waite, J Herbert

    2014-09-01

    Polymeric materials that intrinsically heal at damage sites under wet or moist conditions are urgently needed for biomedical and environmental applications. Although hydrogels with self-mending properties have been engineered by means of mussel-inspired metal-chelating catechol-functionalized polymer networks, biological self-healing in wet conditions, as occurs in self-assembled holdfast proteins in mussels and other marine organisms, is generally thought to involve more than reversible metal chelates. Here we demonstrate self-mending in metal-free water of synthetic polyacrylate and polymethacrylate materials that are surface-functionalized with mussel-inspired catechols. Wet self-mending of scission in these polymers is initiated and accelerated by hydrogen bonding between interfacial catechol moieties, and consolidated by the recruitment of other non-covalent interactions contributed by subsurface moieties. The repaired and pristine samples show similar mechanical properties, suggesting that the triggering of complete self-healing is enabled underwater by the formation of extensive catechol-mediated interfacial hydrogen bonds.

  6. Photothermal triggering of self-healing processes applied to the reparation of bio-based polymer networks

    NASA Astrophysics Data System (ADS)

    Altuna, F. I.; Antonacci, J.; Arenas, G. F.; Pettarin, V.; Hoppe, C. E.; Williams, R. J. J.

    2016-04-01

    Green laser irradiation successfully activated self-healing processes in epoxy-acid networks modified with low amounts of gold nanoparticles (NPs). A bio-based polymer matrix, obtained by crosslinking epoxidized soybean oil (ESO) with an aqueous citric acid (CA) solution, was self-healed through molecular rearrangements produced by transesterification reactions of β-hydroxyester groups generated in the polymerization reaction. The temperature increase required for the triggering of these thermally activated reactions was attained by green light irradiation of the damaged area. Compression force needed to assure a good contact between crack faces was achieved by volume dilatation generated by the same temperature rise. Gold NPs dispersed in the polymer efficiently generated heat in the presence of electromagnetic radiation under plasmon resonance, acting as nanometric heating sources and allowing remote activation of the self-healing in the crosslinked polymer.

  7. Assessment of Composite Delamination Self-Healing Via Micro-Encapsulation

    NASA Technical Reports Server (NTRS)

    O'Brien, T. Kevin; White, Scott R.

    2008-01-01

    Composite skin/stringer flange debond specimens manufactured from composite prepreg containing interleaf layers with a polymer based healing agent encapsulated in thin walled spheres were tested. As a crack develops and grows in the base polymer, the spheres fracture releasing the healing agent. The agent reacts with catalyst and polymerizes healing the crack. In addition, through-thickness reinforcement, in the form of pultruded carbon z-pins were included near the flange tips to improve the resistance to debonding. Specimens were manufactured with 14 plies in the skin and 10 plies in the stiffener flange. Three-point bend tests were performed to measure the skin/stiffener debonding strength and the recovered strength after healing. The first three tests performed indicated no healing following unloading and reloading. Micrographs showed that delaminations could migrate to the top of the interleaf layer due to the asymmetric loading, and hence, bypass most of the embedded capsules. For two subsequent tests, specimens were clamped in reverse bending before reloading. In one case, healing was observed as evidenced by healing agent that leaked to the specimen edge forming a visible "scar". The residual strength measured upon reloading was 96% of the original strength indicating healing had occurred. Hence, self-healing is possible in fiber reinforced composite material under controlled conditions, i.e., given enough time and contact with pressure on the crack surfaces. The micro-encapsulation technique may prove more robust when capsule sizes can be produced that are small enough to be embedded in the matrix resin without the need for using an interleaf layer. However, in either configuration, the amount of healing that can occur may be limited to the volume of healing agent available relative to the crack volume that must be filled.

  8. Self-Healing of Microcracks in Engineered Cementitious Composites (ECC) Under a Natural Environment.

    PubMed

    Herbert, Emily N; Li, Victor C

    2013-07-15

    This paper builds on previous self-healing engineered cementitious composites (ECC) research by allowing ECC to heal outdoors, in the natural environment, under random and sometimes extreme environmental conditions. Development of an ECC material that can heal itself in the natural environment could lower infrastructure maintenance costs and allow for more sustainable development in the future by increasing service life and decreasing the amount of resources and energy needed for repairs. Determining to what extent current ECC materials self-heal in the natural environment is the first step in the development of an ECC that can completely heal itself when exposed to everyday environmental conditions. This study monitored outdoor ECC specimens for one year using resonant frequency (RF) and mechanical reloading to determine the rate and extent of self-healing in the natural environment. It was found that the level of RF, stiffness, and first cracking strength recovery increased as the duration of natural environment exposure increased. For specimens that underwent multiple damage cycles, it was found that the level of recovery was highly dependent on the average temperature and amount of precipitation between each damage event. However, RF, stiffness, and first cracking strength recovery data for specimens that underwent multiple loading cycles suggest that self-healing functionality can be maintained under multiple damage events.

  9. A computational model for the flow of resin in self-healing composites

    NASA Astrophysics Data System (ADS)

    Hall, J.; Qamar, I. P. S.; Rendall, T. C. S.; Trask, R. S.

    2015-03-01

    To explore the flow characteristics of healing agent leaving a vascular network and infusing a damage site within a fibre reinforced polymer composite, a numerical model of healing agent flow from an orifice has been developed using smoothed particle hydrodynamics. As an initial validation the discharge coefficient for low Reynolds number flow from a cylindrical tank is calculated numerically, using two different viscosity formulations, and compared to existing experimental data. Results of this comparison are very favourable; the model is able to reproduce experimental results for the discharge coefficient in the high Reynolds number limit, together with the power-law behaviour for low Reynolds numbers. Results are also presented for a representative delamination geometry showing healing fluid behaviour and fraction filled inside the delamination for a variety of fluid viscosities. This work provides the foundations for the vascular self-healing community in calculating not only the flow rate through the network, but also, by simulating a representative damage site, the final location of the healing fluid within the damage site in order to assess the improvement in local and global mechanical properties and thus healing efficiency.

  10. Dynamic urea bond for the design of reversible and self-healing polymers.

    PubMed

    Ying, Hanze; Zhang, Yanfeng; Cheng, Jianjun

    2014-01-01

    Polymers bearing dynamic covalent bonds may exhibit dynamic properties, such as self-healing, shape memory and environmental adaptation. However, most dynamic covalent chemistries developed so far require either catalyst or change of environmental conditions to facilitate bond reversion and dynamic property change in bulk materials. Here we report the rational design of hindered urea bonds (urea with bulky substituent attached to its nitrogen) and the use of them to make polyureas and poly(urethane-urea)s capable of catalyst-free dynamic property change and autonomous repairing at low temperature. Given the simplicity of the hindered urea bond chemistry (reaction of a bulky amine with an isocyanate), incorporation of the catalyst-free dynamic covalent urea bonds to conventional polyurea or urea-containing polymers that typically have stable bulk properties may further broaden the scope of applications of these widely used materials.

  11. Dynamic urea bond for the design of reversible and self-healing polymers

    NASA Astrophysics Data System (ADS)

    Ying, Hanze; Zhang, Yanfeng; Cheng, Jianjun

    2014-02-01

    Polymers bearing dynamic covalent bonds may exhibit dynamic properties, such as self-healing, shape memory and environmental adaptation. However, most dynamic covalent chemistries developed so far require either catalyst or change of environmental conditions to facilitate bond reversion and dynamic property change in bulk materials. Here we report the rational design of hindered urea bonds (urea with bulky substituent attached to its nitrogen) and the use of them to make polyureas and poly(urethane-urea)s capable of catalyst-free dynamic property change and autonomous repairing at low temperature. Given the simplicity of the hindered urea bond chemistry (reaction of a bulky amine with an isocyanate), incorporation of the catalyst-free dynamic covalent urea bonds to conventional polyurea or urea-containing polymers that typically have stable bulk properties may further broaden the scope of applications of these widely used materials.

  12. Dynamic urea bond for the design of reversible and self-healing polymers

    PubMed Central

    Ying, Hanze; Zhang, Yanfeng; Cheng, Jianjun

    2014-01-01

    Polymers bearing dynamic covalent bonds may exhibit dynamic properties, such as self-healing, shape memory and environmental adaptation. However, most dynamic covalent chemistries developed so far require either catalyst or change of environmental conditions to facilitate bond reversion and dynamic property change in bulk materials. Here we report the rational design of hindered urea bonds (urea with bulky substituent attached to its nitrogen) and the use of them to make polyureas and poly(urethane-ureas) capable of catalyst-free dynamic property change and autonomous repairing at low temperature. Given the simplicity of the hindered urea bond chemistry (reaction of a bulky amine with an isocyanate), incorporation of the catalyst-free dynamic covalent urea bonds to conventional polyurea or urea-containing polymers that typically have stable bulk properties may further broaden the scope of applications of these widely used materials. PMID:24492620

  13. Exploiting Bisphosphonate-Bioactive-Glass Interactions for the Development of Self-Healing and Bioactive Composite Hydrogels.

    PubMed

    Diba, Mani; An, Jie; Schmidt, Stephan; Hembury, Mathew; Ossipov, Dmitri; Boccaccini, Aldo R; Leeuwenburgh, Sander C G

    2016-12-01

    Hydrogels are widely recognized as promising candidates for various biomedical applications, such as tissue engineering. Recently, extensive research efforts have been devoted to the improvement of the biological and mechanical performance of hydrogel systems by incorporation of functional groups and/or inorganic particles in their composition. Bisphosphonates are a class of drugs, commonly used for treatment of osteoporosis, which exhibit a strong binding affinity for hydroxyapatite. In this study, the binding affinity of a bisphosphonate-functionalized polymer, hyaluronan, toward a bioactive glass (i.e., 45S5 Bioglass) is evaluated using force-distance measurements with atomic force microscopy. The strong interaction between bisphosphonate and bioactive glass is then exploited to develop organic-inorganic composite hydrogels and the viscoelastic and self-healing ability of these materials are investigated. Finally, the stability and mineralization behavior of these hydrogels are evaluated in simulated body fluid. Following this approach, injectable, bioactive and self-healing organic-inorganic composite hydrogels are produced, which mineralize abundantly and rapidly in simulated body fluid. These properties render these composite gels suitable for applications in bone-tissue engineering.

  14. Microencapsulation of Polyfunctional Amines for Self-Healing of Epoxy-Based Composites

    DTIC Science & Technology

    2008-01-01

    MICROENCAPSULATION OF POLYFUNCTIONAL AMINES FOR SELF-HEALING OF EPOXY-BASED COMPOSITES David A. McIlroy*§, Ben J. Blaiszik,¥ Paul V. Braun... microcapsules containing an amine hardener (DEH-52, Dow Chemical) for use as the hardener in a 2-part epoxy healing system consisting of epoxy...microscope. Scanning electron microscopy was performed on a Philips XL30 ESEM-FEG instrument. Microencapsulation Procedure. 10 g of a 2:1 v/v

  15. X-ray computed microtomography of three-dimensional microcracks and self-healing in engineered cementitious composites

    NASA Astrophysics Data System (ADS)

    Fan, Shuai; Li, Mo

    2015-01-01

    Concrete cracking and deterioration can potentially be addressed by innovative self-healing cementitious materials, which can autogenously regain transport properties and mechanical characteristics after the damage self-healing process. For the development of such materials, it is crucial, but challenging, to precisely characterize the extent and quality of self-healing due to a variety of factors. This study adopted x-ray computed microtomography (μCT) to derive three-dimensional morphological data on microcracks before and after healing in engineered cementitious composite (ECC). Scanning electron microscope and energy dispersive x-ray spectroscopy were also used to morphologically and chemically analyze the healing products. This work showed that the evolution of the microcrack 3D structure due to self-healing in cementitious materials can be directly and quantitatively characterized by μCT. A detailed description of the μCT image analysis method applied to ECC self-healing was presented. The results revealed that the self-healing extent and rate strongly depended on initial surface crack width, with smaller crack width favoring fast and robust self-healing. We also found that the self-healing mechanism in cementitious materials is dependent on crack depth. The region of a crack close to the surface (from 0 to around 50-150 μm below the surface) can be sealed quickly with crystalline precipitates. However, at greater depths the healing process inside the crack takes a significantly longer time to occur, with healing products more likely resulting from continued hydration and pozzolanic reactions. Finally, the μCT method was compared with other self-healing characterization methods, with discussions on its importance in generating new scientific knowledge for the development of robust self-healing cementitious materials.

  16. Robust superhydrophobic PDMS/camphor based composite coatings with self-cleaning and self-healing properties

    NASA Astrophysics Data System (ADS)

    Mitra, Sushanta; Sahoo, Bichitra; Nanda, Sonil; Kozinski, Janusz

    2016-11-01

    We report a novel process for the preparation of self-cleaning polymer composite with self-healing ability to self-repair from chemical and mechanical damages using readily available materials like Polydimethylsiloxane (PDMS) and camphor soot particles. When the camphor soot particles loading attained a critical level, the composite coating on glass and stainless steel surfaces reveals self-cleaning property with water contact angle of 1710. We also demonstrate that any degradation of its surface energy under the oxygen plasma etching can be recuperated, illustrating that the obtained superhydrophobic surface has a good self-healing ability. The fabricated PDMS/Camphor soot hybrid coating exhibited excellent retention of superhydrophobicity against impact of sand particles from a height of 10-70 cm. In addition, after being damaged chemically by strong acid treatment (2M HNO3 solution), the coating can also restore its properties after a short thermal cycle. Such versatile superhydrophobic surfaces can have wide applications ranging from under-water marine vessels to coating for surfaces to protect them from moisture and unwanted penetration of water.

  17. Self-healing materials.

    PubMed

    Hager, Martin D; Greil, Peter; Leyens, Christoph; van der Zwaag, Sybrand; Schubert, Ulrich S

    2010-12-14

    Self-healing materials are able to partially or completely heal damage inflicted on them, e.g., crack formation; it is anticipated that the original functionality can be restored. This article covers the design and generic principles of self-healing materials through a wide range of different material classes including metals, ceramics, concrete, and polymers. Recent key developments and future challenges in the field of self-healing materials are summarised, and generic, fundamental material-independent principles and mechanism are discussed and evaluated.

  18. Functional Metal Matrix Composites: Self-lubricating, Self-healing, and Nanocomposites-An Outlook

    NASA Astrophysics Data System (ADS)

    Dorri Moghadam, Afsaneh; Schultz, Benjamin F.; Ferguson, J. B.; Omrani, Emad; Rohatgi, Pradeep K.; Gupta, Nikhil

    2014-06-01

    Many different types of advanced metal matrix composites are now available, some of which possess functional properties. Recent work on particle-reinforced, self-lubricating and self-healing metals and metal matrix nanocomposites (MMNCs) synthesized by solidification synthesis is reviewed. Particle-based MMNCs have been developed by several modern processing tools based on either solid- or liquid-phase synthesis techniques that are claimed to exhibit exciting mechanical properties including improvements of modulus, yield strength, and ultimate tensile strength. This article presents a brief and objective review of the work done over the last decade to identify the challenges and future opportunities in the area of functional nanocomposites. Increasing interest in lightweight materials has resulted in studies on hollow particle-filled metal matrix syntactic foams. Syntactic foams seem especially suitable for development with functional properties such as self-healing and self-lubrication. The metal matrix micro and nanocomposites, and syntactic foams having combinations of ultrahigh strength and wear resistance, self-lubricating, and/or self-healing properties can lead to increased energy efficiency, reliability, comfort of operation, reparability, and safety of vehicles. The focus of the present review is aluminum and magnesium matrix functional materials.

  19. Self-healing biomaterials.

    PubMed

    Brochu, Alice B W; Craig, Stephen L; Reichert, William M

    2011-02-01

    The goal of this review is to introduce the biomaterials community to the emerging field of self-healing materials, and also to suggest how one could utilize and modify self-healing approaches to develop new classes of biomaterials. A brief discussion of the in vivo mechanical loading and resultant failures experienced by biomedical implants is followed by presentation of the self-healing methods for combating mechanical failure. If conventional composite materials that retard failure may be considered zeroth generation self-healing materials, then taxonomically speaking, first generation self-healing materials describe approaches that "halt" and "fill" damage, whereas second generation self-healing materials strive to "fully restore" the prefailed material structure. In spite of limited commercial use to date, primarily because the technical details have not been suitably optimized, it is likely from a practical standpoint that first generation approaches will be the first to be employed commercially, whereas second generation approaches may take longer to implement. For self-healing biomaterials the optimization of technical considerations is further compounded by the additional constraints of toxicity and biocompatibility, necessitating inclusion of separate discussions of design criteria for self-healing biomaterials. 2010 Wiley Periodicals, Inc.

  20. Effect of polymer porosity on aqueous self-healing encapsulation of proteins in PLGA microspheres.

    PubMed

    Reinhold, Samuel E; Schwendeman, Steven P

    2013-12-01

    Self-healing (SH) poly(lactic-co-glycolic acid) (PLGA) microspheres are a unique class of functional biomaterials capable of microencapsulating process-sensitive proteins by simple mixing and heating the drug-free polymer in aqueous protein solution. Drug-free SH microspheres of PLGA 50/50 with percolating pore networks of varying porosity (ϵ = 0.49-73) encapsulate increasing lysozyme (≈1 to 10% w/w) with increasing ϵ, with typically ≈20 to 25% pores estimated accessible to entry by the enzyme from the external solution. Release kinetics of lysozyme under physiological conditions is continuous over more than two weeks and most strongly influenced by ϵ and protein loading before reaching a lag phase until 28 d at the study completion. Recovered enzyme after release is typically predominantly monomeric and active. Formulations containing acid-neutralizing MgCO3 at ≥ 4.3% exhibit >97% monomeric and active protein after the release with full mass balance recovery. Hence, control of SH polymer ϵ is a key parameter to development of this new class of biomaterials.

  1. Self-Healing composites for Mitigation of Impact Damage in US Army Applications

    DTIC Science & Technology

    1976-12-01

    triggering mechanism for self-healing, rupturing the embedded microcapsules and releasing healing agent into In this study, fiber-reinforced...through the inclusion of urea-formaldehyde properties in self-healing materials have focused on microcapsules containing dicyclopentadiene (DCPD) monotonic...systems, healing is Figure 1: (a) Optical micrograph and (b) schematic demonstrating accomplished by incorporating a microencapsulated the self-healing

  2. Microfluidic encapsulation for self-healing material and investigation of its impacts on composite performance

    NASA Astrophysics Data System (ADS)

    Lemmens, Ryan J.

    Encapsulation is a key enabling technology of self-healing materials for which incorporation of reactive materials into a composite, without loss of functionality, is required for damage repair. The functionalized particles resulting from such processes must be readily incorporable into a composite and have minimal detrimental impact on its undamaged properties. At the same time, their morphology must preferentially promote the release of their content during a damage event. However, there is still a need for new techniques capable of fine tuning particle properties for the controlled design of composite performance. To introduce superior processing control, two microfluidics based encapsulation processes have been developed, one each for the individual components of a two-part chemical healing system, namely dicyclopentadiene and Grubb's catalyst. These processes have enabled significantly enhanced performance of self-healing epoxy composites by introducing unprecedented control over particle morphology. The microfluidics based encapsulation platform is first demonstrated by emulsification, using droplet microfluidics, and subsequent encapsulation of dicyclopentadiene. The reported approach allows for facile control of mean microcapsule diameter thru variation of fluid flow rates. The microcapsules exhibit coefficients of variation (CV) of diameter in the range 1-3 (i.e. monodisperse is typically defined as CV smaller than 5), an order of magnitude reduction when compared with conventional batch emulsification methods whose typical CV is 20-40. This control over microcapsule uniformity has led to significant improvement in self-healing composite performance as exemplified by ˜25% higher undamaged fracture toughness. A microfluidic solution spinning process is then developed to encapsulate Grubb's catalyst, the most expensive component of this particular material system, in a novel fibrous morphology. The continuous, on-chip fiber production allows for

  3. Fatigue of Self-Healing Nanofiber-based Composites: Static Test and Subcritical Crack Propagation.

    PubMed

    Lee, Min Wook; Sett, Soumyadip; Yoon, Sam S; Yarin, Alexander L

    2016-07-20

    Here, we studied the self-healing of composite materials filled with epoxy-containing nanofibers. An initial incision in the middle of a composite sample stretched in a static fatigue test can result in either crack propagation or healing. In this study, crack evolution was observed in real time. A binary epoxy, which acted as a self-healing agent, was encapsulated in two separate types of interwoven nano/microfibers formed by dual-solution blowing, with the core containing either epoxy or hardener and the shell being formed from poly(vinylidene fluoride)/ poly(ethylene oxide) mixture. The core-shell fibers were encased in a poly(dimethylsiloxane) matrix. When the fibers were damaged by a growing crack in this fiber-reinforced composite material because of static stretching in the fatigue test, they broke and released the healing agent into the crack area. The epoxy used in this study was cured and solidified for approximately an hour at room temperature, which then conglutinated and healed the damaged location. The observations were made for at least several hours and in some cases up to several days. It was revealed that the presence of the healing agent (the epoxy) in the fibers successfully prevented the propagation of cracks in stretched samples subjected to the fatigue test. A theoretical analysis of subcritical cracks was performed, and it revealed a jumplike growth of subcritical cracks, which was in qualitative agreement with the experimental results.

  4. Ultra-thin Solid-State Li-Ion Electrolyte Membrane Facilitated by a Self-Healing Polymer Matrix.

    PubMed

    Whiteley, Justin M; Taynton, Philip; Zhang, Wei; Lee, Se-Hee

    2015-11-18

    Thin solid membranes are formed by a new strategy, whereby an in situ derived self-healing polymer matrix that penetrates the void space of an inorganic solid is created. The concept is applied as a separator in an all-solid-state battery with an FeS2 -based cathode and achieves tremendous performance for over 200 cycles. Processing in dry conditions represents a paradigm shift for incorporating high active-material mass loadings into mixed-matrix membranes.

  5. Self-healing of covalently cross-linked polymers by reshuffling thiuram disulfide moieties in air under visible light.

    PubMed

    Amamoto, Yoshifumi; Otsuka, Hideyuki; Takahara, Atsushi; Matyjaszewski, Krzysztof

    2012-08-02

    Self-healing of covalently cross-linked polymers under an ambient visible light in the bulk state, in air, at room temperature using radical exchange of thiuram disulfide units is reported. The successful attachment of surfaces of cut pieces proceeded under ambient conditions under exposure to visible light from a commercial tabletop lamp, as confirmed by bending and tensile tests. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  6. Use of composite materials, health monitoring and self-healing concepts to refurbish our civil and military infrastructure.

    SciTech Connect

    Roach, Dennis Patrick; Delong, Waylon Anthony; White, Scott; Yepez, Esteban; Rackow, Kirk A.; Reedy, Earl David, Jr.

    2007-09-01

    An unavoidable by-product of a metallic structure's use is the appearance of crack, corrosion, erosion and other flaws. Economic barriers to the replacement of these structures have created an aging civil and military infrastructure and placed even greater demands on efficient and safe repair and inspection methods. As a result of Homeland Security issues and these aging infrastructure concerns, increased attention has been focused on the rapid repair and preemptive reinforcement of structures such as buildings and bridges. This Laboratory Directed Research and Development (LDRD) program established the viability of using bonded composite patches to repair metallic structures. High modulus fiber-reinforced polymer (FRP) material may be used in lieu of mechanically fastened metallic patches or welds to reinforce or repair damaged structures. Their use produces a wide array of engineering and economic advantages. Current techniques for strengthening steel structures have several drawbacks including requiring heavy equipment for installation, poor fatigue performance, and the need for ongoing maintenance due to continued corrosion attack or crack growth. The use of bonded composite doublers has the potential to correct the difficulties associated with current repair techniques and the ability to be applied where there are currently no rehabilitation options. Applications include such diverse structures as: buildings, bridges, railroad cars, trucks and other heavy machinery, steel power and communication towers, pipelines, factories, mining equipment, ships, tanks and other military vehicles. This LDRD also proved the concept of a living infrastructure by developing custom sensors and self-healing chemistry and linking this technology with the application of advanced composite materials. Structural Health Monitoring (SHM) systems and mountable, miniature sensors were designed to continuously or periodically assess structural integrity. Such systems are able to detect

  7. Dynamic Iminoboronate-Based Boroxine Chemistry for the Design of Ambient Humidity-Sensitive Self-Healing Polymers.

    PubMed

    Delpierre, Sébastien; Willocq, Bertrand; De Winter, Julien; Dubois, Philippe; Gerbaux, Pascal; Raquez, Jean-Marie

    2017-05-17

    Developing intrinsic self-healing polymeric materials is of great interest nowadays to extend material lifetime and/or prevent the replacement of damaged pieces. Spontaneously humidity-sensitive healable polymer network built around dynamic covalent B-O bonds was templated by using iminoboronate-based boroxine derivatives. Taking advantage of the dynamic boroxine/boronic acid equilibrium and iminoboronate chemistry, it is possible to construct polymeric materials able to self-heal without requiring any energy-demanding external activation. Interestingly, this novel family of iminoboronate adduct-based materials can be readily produced by a relatively simple and straightforward synthesis between boronic acid and diamine-based compounds, paving the way to coatings that are self-healable at ambient humidity. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  8. Characterization of self-healing glassy composites by high-temperature environmental scanning electron microscopy (HT-ESEM).

    PubMed

    Coillot, Daniel; Podor, Renaud; Méar, François O; Montagne, Lionel

    2010-01-01

    In situ high-temperature healing of cracks in composites made of glass and vanadium boride (VB) particles was observed using an environmental scanning electron microscope equipped with a high-temperature chamber (HT-ESEM). HT-ESEM is an adequate tool for studying the self-healing property of these materials. The change in crack length as a function of redox atmospheric conditions is reported. No self-healing behaviour was observed under reducing conditions, while a complete and rapid healing of the cracks was measured under oxidizing conditions. HT-ESEM image analyses enabled the monitoring of the healing effect. The self-healing mechanism was identified as a consequence of the VB active particles oxidation and subsequent pouring of fluid oxides into the cracks. These innovative composites offer an interesting potential in the domain of solid oxide fuel cell sealants.

  9. Unveiling the molecular mechanism of self-healing in a telechelic, supramolecular polymer network

    NASA Astrophysics Data System (ADS)

    Yan, Tingzi; Schröter, Klaus; Herbst, Florian; Binder, Wolfgang H.; Thurn-Albrecht, Thomas

    2016-09-01

    Reversible polymeric networks can show self-healing properties due to their ability to reassemble after application of stress and fracture, but typically the relation between equilibrium molecular dynamics and self-healing kinetics has been difficult to disentangle. Here we present a well-characterized, self-assembled bulk network based on supramolecular assemblies, that allows a clear distinction between chain dynamics and network relaxation. Small angle x-ray scattering and rheological measurements provide evidence for a structurally well-defined, dense network of interconnected aggregates giving mechanical strength to the material. Different from a covalent network, the dynamic character of the supramolecular bonds enables macroscopic flow on a longer time scale and the establishment of an equilibrium structure. A combination of linear and nonlinear rheological measurements clearly identifies the terminal relaxation process as being responsible for the process of self-healing.

  10. Unveiling the molecular mechanism of self-healing in a telechelic, supramolecular polymer network

    PubMed Central

    Yan, Tingzi; Schröter, Klaus; Herbst, Florian; Binder, Wolfgang H.; Thurn-Albrecht, Thomas

    2016-01-01

    Reversible polymeric networks can show self-healing properties due to their ability to reassemble after application of stress and fracture, but typically the relation between equilibrium molecular dynamics and self-healing kinetics has been difficult to disentangle. Here we present a well-characterized, self-assembled bulk network based on supramolecular assemblies, that allows a clear distinction between chain dynamics and network relaxation. Small angle x-ray scattering and rheological measurements provide evidence for a structurally well-defined, dense network of interconnected aggregates giving mechanical strength to the material. Different from a covalent network, the dynamic character of the supramolecular bonds enables macroscopic flow on a longer time scale and the establishment of an equilibrium structure. A combination of linear and nonlinear rheological measurements clearly identifies the terminal relaxation process as being responsible for the process of self-healing. PMID:27581380

  11. Self-healing polymeric materials.

    PubMed

    Yang, Ying; Urban, Marek W

    2013-09-07

    Inspired by nature, self-healing materials represent the forefront of recent developments in materials chemistry and engineering. This review outlines the recent advances in the field of self-healing polymers. The first part discusses thermodynamic requirements for self-healing networks in the context of conformation changes that contribute to the Gibbs free energy. The chain flexibility significantly contributes to the entropy changes, whereas the heat of reaction and the external energy input are the main contributors to enthalpy changes. The second part focuses on chemical reactions that lead to self-healing, and the primary classes are the covalent bonding, supramolecular assemblies, ionic interactions, chemo-mechanical self-healing, and shape memory polymers. The third part outlines recent advances using encapsulation, remote self-healing and the role of shape memory polymers. Recent developments in the field of self-healing polymers undeniably indicate that the main challenge will be the designing of high glass transition (Tg) functional materials, which also exhibit stimuli-responsive attributes. Build-in controllable hierarchical heterogeneousness at various length scales capable of remote self-healing by physical and chemical responses will be essential in designing future materials of the 21st century.

  12. High Temperature Lightweight Self-Healing Ceramic Composites for Aircraft Engine Applications

    NASA Technical Reports Server (NTRS)

    Raj, Sai V.; Singh, Mrityunjay; Bhatt, Ramakrishna T.

    2014-01-01

    The present research effort was undertaken to develop a new generation of SiC fiber- reinforced engineered matrix composites (EMCs) with sufficient high temperature plasticity to reduce crack propagation and self-healing capabilities to fill surface-connected cracks to prevent the oxygen ingress to the fibers. A matrix engineered with these capabilities is expected to increase the load bearing capabilities of SiCSiC CMCs at high temperatures. Several matrix compositions were designed to match the coefficient of thermal expansion (CTE) of the SiC fibers using a rule of mixture (ROM) approach. The CTE values of these matrices were determined and it was demonstrated that they were generally in good agreement with that of monolithic SiC between room temperature and 1525 K. The parameters to hot press the powders were optimized, and specimens were fabricated for determining bend strength, CTE, oxidation and microstructural characteristics of the engineered matrices. The oxidation tests revealed that some of the matrices exhibited catastrophic oxidation, and therefore, these were eliminated from further consideration. Two promising compositions were down selected based on these results for further development. Four-point bend tests were conducted on these two promising matrices between room temperature and 1698 K. Although theses matrices were brittle and failed at low stresses at room temperature, they exhibited high temperature ductility and higher stresses at the higher temperatures. The effects of different additives on the self-healing capabilities of these matrices were investigated. The results of preliminary studies conducted to slurry and melt infiltration trials with CrSi2 are described.

  13. [Development of novel self-healing and antibacterial resin composite containing microcapsules filled with polymerizable healing monomer].

    PubMed

    Wu, Junling; Zhang, Qiang; Zhu, Ting; Ge, Jianhua; Zhou, Chuanjian

    2015-08-01

    To develop novel self- healing and antibacterial resin composite containing microcapsules filled with polymerizable healing monomer, and to measure its properties for further clinical application. Microcapsules filled with healing monomer of triethylene glycol dimethacrylate were synthesized according to methods introduced in the previous research. Microcapsules were added into novel resin composite containing nano-antibacterial silica fillers grafted with long chain alkyl quaternary ammonium at mass fractions of 0, 2.5%, 5.0%, 7.5% or 10.0%. A commercial resin composite (Tetric N-Ceram) was used as control. Flexural test was used to measure resin composite flexural strength and elastic modulus. The single edge V-notched beam method was used to measure fracture toughness and self-healing efficiency. Scanning electron microscope (SEM) was used to examine the fractured surface of selected specimen for investigation of fracture mechanisms. The flexural strength and elastic modulus of the resin composite were (96.4 ± 14.3) MPa and (6.2 ± 1.1) GPa respectively after incorporation of microcapsules up to 7.5%, and no significant difference was found between the experimental group and the control group [(99.1 ± 11.9) MPa and (6.1 ± 1.1) GPa] (P>0.05). The self-healing efficiency of (66.8 ± 7.0)% and (79.3 ± 9.7)% were achieved for resin composite with microcapsule mass fractions at 7.5% and 10.0%. SEM image showed that irregular films covered the fractured surface. Conclusions This novel self-healing and antibacterial resin composite containing microcapsules filled with polymerizable healing monomer exhibited a promising self- healing ability, which enabled itself well up for combating bulk fracture and secondary caries in clinical application.

  14. Synthesis of a Self-Healing Polymer Based on Reversible Diels-Alder Reaction: An Advanced Undergraduate Laboratory at the Interface of Organic Chemistry and Materials Science

    ERIC Educational Resources Information Center

    Weizman, Haim; Nielsen, Christian; Weizman, Or S.; Nemat-Nasser, Sia

    2011-01-01

    This laboratory experiment exposes students to the chemistry of self-healing polymers based on a Diels-Alder reaction. Students accomplish a multistep synthesis of a monomer building block and then polymerize it to form a cross-linked polymer. The healing capability of the polymer is verified by differential scanning calorimetry (DSC) experiments.…

  15. Synthesis of a Self-Healing Polymer Based on Reversible Diels-Alder Reaction: An Advanced Undergraduate Laboratory at the Interface of Organic Chemistry and Materials Science

    ERIC Educational Resources Information Center

    Weizman, Haim; Nielsen, Christian; Weizman, Or S.; Nemat-Nasser, Sia

    2011-01-01

    This laboratory experiment exposes students to the chemistry of self-healing polymers based on a Diels-Alder reaction. Students accomplish a multistep synthesis of a monomer building block and then polymerize it to form a cross-linked polymer. The healing capability of the polymer is verified by differential scanning calorimetry (DSC) experiments.…

  16. Self-Healing Laminate System

    NASA Technical Reports Server (NTRS)

    Beiermann, Brett A. (Inventor); Keller, Michael W. (Inventor); White, Scott R. (Inventor); Sottos, Nancy R. (Inventor)

    2016-01-01

    A laminate material may include a first flexible layer, and a self-healing composite layer in contact with the first flexible layer. The composite layer includes an elastomer matrix, a plurality of first capsules including a polymerizer, and a corresponding activator for the polymerizer. The laminate material may self-heal when subjected to a puncture or a tear.

  17. Cationic polymer lubricant (CPL): A new bond and mobile boundary lubricant with self-healing capabilities

    NASA Astrophysics Data System (ADS)

    Liao, Erik Hsiao

    The boundary film formation and lubrication effects of low-molecular-weight silicone molecules with cationic side groups were studied. Poly-(N,N,N-trimethylamine-3- propylmethylsiloxane-co-dimethylsiloxane) iodide was synthesized and deposited on silicon oxide surfaces to form a bound-and-mobile lubricant film. The effects of the ionically bound layer and mobile multilayers were investigated. Both nano- and macro-scale tribological tests revealed superior lubrication performance of the silicon molecule with cationic side chains over the neutral silicon molecule (which was modeled with polydimethylsiloxane with the same molecule weight). The multilayer films exhibited characteristic topographic features due to ionic interactions within the polymeric film. In the macro-scale, the effects of ionic content, environmental condition, and advantage of the bound layer on self-healing will be discussed to demonstrate the wear resistance and selfhealing capability. The multilayer spreading rates were estimated to be ~10-11 m2/s. In the nanoscale, the results of disjoining pressure and viscosity measurements help understand the lateral spreading of the mobile layer and identify the mobile species. The mobile species are the reduced tertiary amine form of CPL. The hydrophobic but hygroscopic properties of CPL are also investigated with SFG and ATR-IR. The CPL-coated surfaces are hydrophobic which prevents the detrimental effects of humidity on wear of silicon. In addition, the hygroscopic nature of CPL allows humidity to be absorbed into the film, which enhances the self-healing capabilities. Finally, by texturing the silicon surface with nanowells, self-healing is enhanced when the nanowells are filled with CPL. The nanowells serve as CPL reservoirs that are readily available for self-healing within the wear track for faster cycle intervals. However, the nanowells deteriorate the self-healing from surrounding the contact region due to the refilling of the empty nanowells.

  18. Self-Healing Software

    NASA Astrophysics Data System (ADS)

    Frei, Regina; Serugendo, Giovanna Di Marzo

    The following sections are included: * Introduction * Self-Awareness as an Aspect of Self-Healing * A Working Taxonomy for Software Self-Healing * Failures, errors and faults * Approaches to Software Self-Healing * Self-healing at code level * Self-healing through self-organisation * Self-healing based on policies * Architectures for self-healing * Model-based solutions for self-healing * Discussion and Conclusion

  19. Self-healing polymers---The importance of choosing an adequate healing monomer, and the olefin metathesis polymerization of agricultural oils

    NASA Astrophysics Data System (ADS)

    Mauldin, Timothy C.

    Modern society's immense and ill-fated reliance on petrochemical-based polymeric materials will likely necessitate a shift in polymer production paradigms in the near future. The work presented herein attempts to address this issue via a two-pronged approach. First, efforts to improve the duration of composite materials by incorporation of a self-healing function are discussed, the fruitful application of which can potentially reduce or eliminate the massive carbon footprints associated with the repair/replacement of damaged materials. And second, polymeric materials derived predominately from natural and renewable feedstock---namely vegetable oils---are developed. Early microcapsule-based self-healing materials utilized dicyclopentadiene-filled microcapsules and Grubbs' olefin metathesis catalyst to initiate the healing mechanism. However, the patent-protected catalyst, made from the precious metal ruthenium and sometimes costly ligands, will likely never be inexpensive and therefore limit large-scale applications. Hence, clever approaches to reduce the healing catalyst loading in self-healing polymers are of great interest. To this end, our efforts have revolved around solving the problem of the relatively inefficient use of Grubbs' catalyst during the healing mechanism. Given that the mismatch of the olefin metathesis polymerization and Grubbs' catalyst dissolution (in monomer) kinetics is a known cause of this inefficient use of the catalyst, we attempted to tune the "latency" (i.e. pot life) of the olefin metathesis polymerization to ensure more complete dissolution of catalyst in monomer. In an alternative approach to improving efficient catalyst dissolution, we developed a simple model to predict relative dissolution rates of Grubbs' catalyst in a small library of healing monomers. This model was shown experimentally to be able to aid in the selection of, for example, reactive monomer additives that can yield impressive improvements in catalyst dissolution

  20. Optimal Reactivity and Improved Self-Healing Capability of Structurally Dynamic Polymers Grafted on Janus Nanoparticles Governed by Chain Stiffness and Spatial Organization.

    PubMed

    Xu, Guoxi; Huang, Zihan; Chen, Pengyu; Cui, Tianqi; Zhang, Xinghua; Miao, Bing; Yan, Li-Tang

    2017-01-16

    Structurally dynamic polymers are recognized as a key potential to revolutionize technologies ranging from design of self-healing materials to numerous biomedical applications. Despite intense research in this area, optimizing reactivity and thereby improving self-healing ability at the most fundamental level pose urgent issue for wider applications of such emerging materials. Here, the authors report the first mechanistic investigation of the fundamental principle for the dependence of reactivity and self-healing capabilities on the properties inherent to dynamic polymers by combining large-scale computer simulation, theoretical analysis, and experimental discussion. The results allow to reveal how chain stiffness and spatial organization regulate reactivity of dynamic polymers grafted on Janus nanoparticles and mechanically mediated reaction in their reverse chemistry, and, particularly, identify that semiflexible dynamic polymers possess the optimal reactivity and self-healing ability. The authors also develop an analytical model of blob theory of polymer chains to complement the simulation results and reveal essential scaling laws for optimal reactivity. The findings offer new insights into the physical mechanism in various systems involving reverse/dynamic chemistry. These studies highlight molecular engineering of polymer architecture and intrinsic property as a versatile strategy in control over the structural responses and functionalities of emerging materials with optimized self-healing capabilities.

  1. Facile synthesis of supramolecular ionic polymers that combine unique rheological, ionic conductivity, and self-healing properties.

    PubMed

    Aboudzadeh, M Ali; Muñoz, M Eugenia; Santamaría, Antxon; Marcilla, Rebeca; Mecerreyes, David

    2012-02-27

    A new family of supramolecular ionic polymers is synthesized by a simple method using (di-/tri-)carboxylic acids and (di-/tri-)alkyl amines. These polymers are formed by carboxylate and ammonium molecules that are weakly bonded together by a combination of ionic and hydrogen bonds, becoming solid at room temperature. The supramolecular ionic polymers show a sharp rheological transition from a viscoelastic gel to a viscous liquid between 30 and 80 °C. This sharp viscosity decrease is responsible for an unprecedented jump in ionic conductivity of four orders of magnitude in that temperature range. As a potential application, this chemistry can be used to develop polymeric materials with self-healing properties, since it combines properties from supramolecular polymers and ionomers into the same material. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  2. High-Temperature, Lightweight, Self-Healing Ceramic Composites for Aircraft Engine Applications

    NASA Technical Reports Server (NTRS)

    Raj, Sai V.; Bhatt, Ramkrishna

    2013-01-01

    The use of reliable, high-temperature, lightweight materials in the manufacture of aircraft engines is expected to result in lower fossil and biofuel consumption, thereby leading to cost savings and lower carbon emissions due to air travel. Although nickel-based superalloy blades and vanes have been successfully used in aircraft engines for several decades, there has been an increased effort to develop high-temperature, lightweight, creep-resistant substitute materials under various NASA programs over the last two decades. As a result, there has been a great deal of interest in developing SiC/SiC ceramic matrix composites (CMCs) due to their higher damage tolerance compared to monolithic ceramics. Current-generation SiC/SiC ceramic matrix composites rely almost entirely on the SiC fibers to carry the load, owing to the premature cracking of the matrix during loading. Thus, the high-temperature usefulness of these CMCs falls well below their theoretical capabilities. The objective of this work is to develop a new class of high-temperature, lightweight, self-healing, SiC fiber-reinforced, engineered matrix ceramic composites.

  3. Advanced Materials for Use in Soft Self-Healing Devices.

    PubMed

    Huynh, Tan-Phat; Sonar, Prashant; Haick, Hossam

    2017-05-01

    Devices integrated with self-healing ability can benefit from long-term use as well as enhanced reliability, maintenance and durability. This progress report reviews the developments in the field of self-healing polymers/composites and wearable devices thereof. One part of the progress report presents and discusses several aspects of the self-healing materials chemistry (from non-covalent to reversible covalent-based mechanisms), as well as the required main approaches used for functionalizing the composites to enhance their electrical conductivity, magnetic, dielectric, electroactive and/or photoactive properties. The second and complementary part of the progress report links the self-healing materials with partially or fully self-healing device technologies, including wearable sensors, supercapacitors, solar cells and fabrics. Some of the strong and weak points in the development of each self-healing device are clearly highlighted and criticized, respectively. Several ideas regarding further improvement of soft self-healing devices are proposed. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  4. A seawater triggered dynamic coordinate bond and its application for underwater self-healing and reclaiming of lipophilic polymer.

    PubMed

    Xia, Nan Nan; Xiong, Xiao Min; Wang, Junhu; Rong, Min Zhi; Zhang, Ming Qiu

    2016-04-21

    In this work, water triggered dynamic catechol-Fe(3+) coordinate bonds are revealed and studied at atomic, molecular and macroscopic levels using Mössbauer spectroscopy, rheological analysis, etc. DOPA-iron complexation is found to be dynamic in the presence of water, and this dynamic manner is immobilized after removing water. Accordingly, a water saturated lipophilic polymer containing catechol-Fe(3+) crosslinks, rather than the dry version, exhibits dynamic coordination-dissociation behavior. In addition, a migration of iron proves to be enabled in the catechol-Fe(3+) crosslinked polymer immersed in seawater. Rearrangement of the dynamic catechol-Fe(3+) coordinate bonds among different molecules is thus favored. Based on these results, we develop a bulk lipophilic polymer solid capable of repeated autonomic recovery of strength in seawater without manual intervention. When the polymer is damaged in seawater, reshuffling of the mobile hyperbranched polymer networks across the crack interface, owing to the dynamic catechol-Fe(3+) crosslinkages activated by the alkaline circumstances, rebinds the damaged site. By taking advantage of the same mechanism, the polymer can be remolded with the help of seawater and this recycled polymer is still self-healable in seawater. Unlike in the case of conventional polymers where water would shield macromolecules from interacting, here, seawater is a necessary environmental assistant for the material interaction to take effect. The outcomes are beneficial for deepening the understanding of coordinate bonds, and the development of robust underwater self-healing lipophilic polymers.

  5. Imaging studies of temperature dependent photodegradation and self-healing in disperse orange 11 dye-doped polymers

    NASA Astrophysics Data System (ADS)

    Anderson, Benjamin R.; Hung, Sheng-Ting; Kuzyk, Mark G.

    2016-07-01

    Using confocal transmission imaging microscopy, we measure the temperature dependence of photodegradation and self-healing in disperse orange 11 (DO11) dye-doped (poly)methyl-methacrylate (PMMA) and polystyrene (PS). In both dye-doped polymers, an increase in sample temperature results in a greater photodegradation rate and degree of degradation, while also resulting in a slower recovery rate and larger recovery fraction. These results confirm the temperature dependence predictions of the modified correlated chromophore domain model (mCCDM) [B. R. Anderson and M. G. Kuzyk, Phys. Rev. E 89, 032601 (2014)]. Additionally, using quantitative fitting of the imaging data for DO11/PMMA, we determine the domain density parameter to be ρ = 1.19 (±0.25) × 10-2 and the domain free energy advantage to be λ = 0.282 ± 0.015 eV, which are within the uncertainty of the values previously determined using amplified spontaneous emission as the probe method [S. K. Ramini et al., Polym. Chem. 4, 4948 (2013)]. Finally, while we find photodegradation and self-healing of DO11/PS to be qualitatively consistent with the mCCDM, we find that it is quantitatively incompatible with the mCCDM as recovery in DO11/PS is found to behave as a stretched (or double) exponential as a function of time.

  6. Imaging studies of temperature dependent photodegradation and self-healing in disperse orange 11 dye-doped polymers.

    PubMed

    Anderson, Benjamin R; Hung, Sheng-Ting; Kuzyk, Mark G

    2016-07-14

    Using confocal transmission imaging microscopy, we measure the temperature dependence of photodegradation and self-healing in disperse orange 11 (DO11) dye-doped (poly)methyl-methacrylate (PMMA) and polystyrene (PS). In both dye-doped polymers, an increase in sample temperature results in a greater photodegradation rate and degree of degradation, while also resulting in a slower recovery rate and larger recovery fraction. These results confirm the temperature dependence predictions of the modified correlated chromophore domain model (mCCDM) [B. R. Anderson and M. G. Kuzyk, Phys. Rev. E 89, 032601 (2014)]. Additionally, using quantitative fitting of the imaging data for DO11/PMMA, we determine the domain density parameter to be ρ = 1.19 (±0.25) × 10(-2) and the domain free energy advantage to be λ = 0.282 ± 0.015 eV, which are within the uncertainty of the values previously determined using amplified spontaneous emission as the probe method [S. K. Ramini et al., Polym. Chem. 4, 4948 (2013)]. Finally, while we find photodegradation and self-healing of DO11/PS to be qualitatively consistent with the mCCDM, we find that it is quantitatively incompatible with the mCCDM as recovery in DO11/PS is found to behave as a stretched (or double) exponential as a function of time.

  7. Self healing properties of Cu-Pt coated ionic polymer actuators

    NASA Astrophysics Data System (ADS)

    Johanson, Urmas; Punning, Andres; Kruusmaa, Maarja; Aabloo, Alvo

    2008-03-01

    Composite actuators consisting of sheets of the solid polymer electrolyte (similar to Nafion (R)) with Cu 2+ counter-ions inserted and coated with platinum and copper metal layers (so-called Ionomeric Polymer-Metal Composites; IPMCs) have been synthesised and their electromechanical performance upon actuation has been monitored. Resistance measurements on the electrodes show that the electrical conductivity of the membranes metal surface increases on the cathode side during the actuation process, contradictory to the situation when Cu is absent from the metal coating. This phenomenon is explained by the subsequent reduction of Cu 2+ ions on the cathode upon actuation; Cu layer growth in this side prevents it from cracking and decreases its electrode resistance. The phenomenon opens up for longer life-times for Cu-based IPMCs. However, additional problems with Cu layer oxidation and Cu dendrite growth on the electrodes should be considered.

  8. Characterization and modeling of three-dimensional self-healing shape memory alloy-reinforced metal-matrix composites

    SciTech Connect

    Zhu, Pingping; Cui, Zhiwei; Kesler, Michael S.; Newman, John A.; Manuel, Michele V.; Wright, M. Clara; Brinson, L. Catherine

    2016-09-10

    In this paper, three-dimensional metal-matrix composites (MMCs) reinforced by shape memory alloy (SMA) wires are modeled and simulated, by adopting an SMA constitutive model accounting for elastic deformation, phase transformation and plastic behavior. A modeling method to create composites with pre-strained SMA wires is also proposed to improve the self-healing ability. Experimental validation is provided with a composite under three-point bending. This modeling method is applied in a series of finite element simulations to investigate the self-healing effects in pre-cracked composites, especially the role of the SMA reinforcement, the softening property of the matrix, and the effect of pre-strain in the SMA. The results demonstrate that SMA reinforcements provide stronger shape recovery ability than other, non-transforming materials. The softening property of the metallic matrix and the pre-strain in SMA are also beneficial to help crack closure and healing. This modeling approach can serve as an efficient tool to design SMA-reinforced MMCs with optimal self-healing properties that have potential applications in components needing a high level of reliability.

  9. Sustainable self-healing at ultra-low temperatures in structural composites incorporating hollow vessels and heating elements

    NASA Astrophysics Data System (ADS)

    Wang, Yongjing; Pham, Duc Truong; Zhang, Zhichun; Li, Jinjun; Ji, Chunqian; Liu, Yanju; Leng, Jinsong

    2016-09-01

    Self-healing composites are able to restore their properties automatically. Impressive healing efficiencies can be achieved when conditions are favourable. On the other hand, healing might not be possible under adverse circumstances such as very low ambient temperature. Here, we report a structural composite able to maintain its temperature to provide a sustainable self-healing capability-similar to that in the natural world where some animals keep a constant body temperature to allow enzymes to stay active. The composite embeds three-dimensional hollow vessels with the purpose of delivering and releasing healing agents, and a porous conductive element to provide heat internally to defrost and promote healing reactions. A healing efficiency over 100% at around -60°C was obtained. The effects of the sheets on the interlaminar and tensile properties have been investigated experimentally. The proposed technique can be implemented in a majority of extrinsic self-healing composites to enable automatic recovery at ultra-low temperatures.

  10. Sustainable self-healing at ultra-low temperatures in structural composites incorporating hollow vessels and heating elements.

    PubMed

    Wang, Yongjing; Pham, Duc Truong; Zhang, Zhichun; Li, Jinjun; Ji, Chunqian; Liu, Yanju; Leng, Jinsong

    2016-09-01

    Self-healing composites are able to restore their properties automatically. Impressive healing efficiencies can be achieved when conditions are favourable. On the other hand, healing might not be possible under adverse circumstances such as very low ambient temperature. Here, we report a structural composite able to maintain its temperature to provide a sustainable self-healing capability-similar to that in the natural world where some animals keep a constant body temperature to allow enzymes to stay active. The composite embeds three-dimensional hollow vessels with the purpose of delivering and releasing healing agents, and a porous conductive element to provide heat internally to defrost and promote healing reactions. A healing efficiency over 100% at around -60°C was obtained. The effects of the sheets on the interlaminar and tensile properties have been investigated experimentally. The proposed technique can be implemented in a majority of extrinsic self-healing composites to enable automatic recovery at ultra-low temperatures.

  11. Sustainable self-healing at ultra-low temperatures in structural composites incorporating hollow vessels and heating elements

    PubMed Central

    Pham, Duc Truong; Zhang, Zhichun; Li, Jinjun; Ji, Chunqian; Liu, Yanju; Leng, Jinsong

    2016-01-01

    Self-healing composites are able to restore their properties automatically. Impressive healing efficiencies can be achieved when conditions are favourable. On the other hand, healing might not be possible under adverse circumstances such as very low ambient temperature. Here, we report a structural composite able to maintain its temperature to provide a sustainable self-healing capability—similar to that in the natural world where some animals keep a constant body temperature to allow enzymes to stay active. The composite embeds three-dimensional hollow vessels with the purpose of delivering and releasing healing agents, and a porous conductive element to provide heat internally to defrost and promote healing reactions. A healing efficiency over 100% at around −60°C was obtained. The effects of the sheets on the interlaminar and tensile properties have been investigated experimentally. The proposed technique can be implemented in a majority of extrinsic self-healing composites to enable automatic recovery at ultra-low temperatures. PMID:27703711

  12. Self-healing biomaterials(3)

    PubMed Central

    Brochu, Alice B. W.; Craig, Stephen L.; Reichert, William M.

    2010-01-01

    The goal of this review is to introduce the biomaterials community to the emerging field of self-healing materials, and also to suggest how one could utilize and modify self-healing approaches to develop new classes of biomaterials. A brief discussion of the in vivo mechanical loading and resultant failures experienced by biomedical implants is followed by presentation of the self-healing methods for combating mechanical failure. If conventional composite materials that retard failure may be considered zeroth generation self-healing materials, then taxonomically-speaking, first generation self-healing materials describe approaches that “halt” and “fill” damage, whereas second generation self-healing materials strive to “fully restore” the pre-failed material structure. In spite of limited commercial use to date, primarily because the technical details have not been suitably optimized, it is likely from a practical standpoint that first generation approaches will be the first to be employed commercially, whereas second generation approaches may take longer to implement. For self-healing biomaterials the optimization of technical considerations is further compounded by the additional constraints of toxicity and biocompatibility, necessitating inclusion of separate discussions of design criteria for self-healing biomaterials. PMID:21171168

  13. Self-Healing Wire Insulation

    NASA Technical Reports Server (NTRS)

    Parrish, Clyde F. (Inventor)

    2012-01-01

    A self-healing system for an insulation material initiates a self-repair process by rupturing a plurality of microcapsules disposed on the insulation material. When the plurality of microcapsules are ruptured, reactants within the plurality of microcapsules react to form a replacement polymer in a break of the insulation material. This self-healing system has the ability to repair multiple breaks in a length of insulation material without exhausting the repair properties of the material.

  14. Mechanical Characterization of High-Performance Steel-Fiber Reinforced Cement Composites with Self-Healing Effect

    PubMed Central

    Kim, Dong Joo; Kang, Seok Hee; Ahn, Tae-Ho

    2014-01-01

    The crack self-healing behavior of high-performance steel-fiber reinforced cement composites (HPSFRCs) was investigated. High-strength deformed steel fibers were employed in a high strength mortar with very fine silica sand to decreasing the crack width by generating higher interfacial bond strength. The width of micro-cracks, strongly affected by the type of fiber and sand, clearly produced the effects on the self-healing behavior. The use of fine silica sand in HPSFRCs with high strength deformed steel fibers successfully led to rapid healing owing to very fine cracks with width less than 20 μm. The use of very fine silica sand instead of normal sand produced 17%–19% higher tensile strength and 51%–58% smaller width of micro-cracks. PMID:28788471

  15. Microcapsule-Type Self-Healing Protective Coating for Cementitious Composites with Secondary Crack Preventing Ability

    PubMed Central

    Kim, Dong-Min; Yu, Hwan-Chul; Yang, Hye-In; Cho, Yu-Jin; Lee, Kwang-Myong; Chung, Chan-Moon

    2017-01-01

    A microcapsule-type self-healing protective coating with secondary crack preventing capability has been developed using a silanol-terminated polydimethylsiloxane (STP)/dibutyltin dilaurate (DD) healing agent. STP undergoes condensation reaction in the presence of DD to give a viscoelastic substance. STP- and DD-containing microcapsules were prepared by in-situ polymerization and interfacial polymerization methods, respectively. The microcapsules were characterized by Fourier-transform infrared (FT-IR) spectroscopy, optical microscopy, and scanning electron microscopy (SEM). The microcapsules were integrated into commercial enamel paint or epoxy coating formulations, which were applied on silicon wafers, steel panels, and mortar specimens to make dual-capsule self-healing protective coatings. When the STP/DD-based coating was scratched, self-healing of the damaged region occurred, which was demonstrated by SEM, electrochemical test, and water permeability test. It was also confirmed that secondary crack did not occur in the healed region upon application of vigorous vibration to the self-healing coating. PMID:28772475

  16. Multichannel and repeatable self-healing of mechanical enhanced graphene-thermoplastic polyurethane composites.

    PubMed

    Huang, Lu; Yi, Ningbo; Wu, Yingpeng; Zhang, Yi; Zhang, Qian; Huang, Yi; Ma, Yanfeng; Chen, Yongsheng

    2013-04-18

    A novel self-healing material, which was fabricated using few-layered graphene (FG) and thermoplastic polyurethane (TPU) via a facile method, not only exhibits a mechanical enhanced property, but also can be repeatedly healed by various methods including infrared (IR) light, electricity and electromagnetic wave with healing efficiencies higher than 98%.

  17. A novel methodology for self-healing at the nanoscale in CNT/epoxy composites

    NASA Astrophysics Data System (ADS)

    Quigley, E.; Datta, S.; Chattopadhyay, A.

    2016-04-01

    Self-healing materials have the potential to repair induced damage and extend the service life of aerospace or civil components as well as prevent catastrophic failure. A novel technique to provide self-healing capabilities at the nanoscale in carbon nanotube/epoxy nanocomposites is presented in this paper. Carbon nanotubes (CNTs) functionalized with the healing agent (dicyclopentadiene) were used to fabricate self-healing CNT/epoxy nanocomposite films. The structure of CNTs was considered suitable for this application since they are nanosized, hollow, and provide a more consistent size distribution than polymeric nanocapsules. Specimens with different weight fractions of the functionalized CNTs were fabricated to explore the effect of weight fraction of functionalized CNTs on the extent of healing. Optical micrographs with different fluorescent filters showed partial or complete healing of damage approximately two to three weeks after damage was induced. Results indicate that by using CNTs to encapsulate a healing agent, crack growth in self-healing CNT/epoxy nanocomposites can be retarded, leading to safer materials that can autonomously repair itself.

  18. A Highly Stretchable and Autonomous Self-Healing Polymer Based on Combination of Pt···Pt and π-π Interactions.

    PubMed

    Mei, Jin-Feng; Jia, Xiao-Yong; Lai, Jian-Cheng; Sun, Yang; Li, Cheng-Hui; Wu, Jun-Hua; Cao, Yi; You, Xiao-Zeng; Bao, Zhenan

    2016-10-01

    A new self-healing polymer has been obtained by incorporating a cyclometalated platinum(II) complex Pt(C(∧) N(∧) N)Cl (C(∧) N(∧) N = 6-phenyl-2,2'-bipyridyl) into a polydimethylsiloxane (PDMS) backbone. The molecular interactions (a combination of Pt···Pt and π-π interactions) between cyclometalated platinum(II) complexes are strong enough to crosslink the linear PDMS polymer chains into an elastic film. The as prepared polymer can be stretched to over 20 times of its original length. When damaged, the polymer can be healed at room temperature without any healants or external stimuli. Moreover, the self-healing is insensitive to surface aging. This work represents the first example where the attractive metallophilic inter-actions are utilized to design self-healing materials. Moreover, our results suggest that the stretchability and self-healing properties can be obtained simultaneously without any conflict by optimizing the strength of crosslinking interactions. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  19. Feasibility investigation of self-healing cementitious composite using oil core/silica gel shell passive smart microcapsules

    NASA Astrophysics Data System (ADS)

    Yang, Zhengxian; Hollar, John; He, Xiaodong; Shi, Xianming

    2009-07-01

    This paper presents our work in the concept exploration of a new family of self-healing materials that hold promise for "crack-free" cementitious composites. This innovative system features the design of passive smart microcapsules with oil core and silica gel shell, prepared through an interfacial self-assembly process and sol-gel reaction. Methylmethacrylate monomer and triethylborane were chosen as the healing agent and the catalyst, and were microencapsulated respectively. The microcapsules were dispersed in fresh cement mortar along with carbon microfibers. For the hardened mortar, self-healing can be triggered by crack propagation through the microcapsules, which then releases the healing agent and the catalyst into the microcracks. Polymerization of the healing agent is initiated by contact with the catalyst, bonding the crack faces. Surface analytical tools such as optical microscope and field emission scanning electron microscope were used to examine the localized morphology and encapsulation of the passive smart microcapsules. The self-healing effect was evaluated using gas permeability and electrochemical impedance measurements.

  20. Multifunctional Polymers and Composites for Self-Healing Applications

    DTIC Science & Technology

    2006-09-30

    plane and analyzed by Fourier transform infrared spectroscopy ( FTIR ). By monitoring the spectra and observing the characteristic peak at 965 cm·1...DCC) was obtained from Avocado . Reagent grade ether was purchased from Malinckrodt and anhydrous methylene chloride was purchased from Acros and

  1. Molecular dynamics simulation of cross-linked urea-formaldehyde polymers for self-healing nanocomposites: prediction of mechanical properties and glass transition temperature.

    PubMed

    Arab, Behrouz; Shokuhfar, Ali

    2013-11-01

    Urea-formaldehyde polymers, which are utilized in the adhesives industry, have recently been shown to be suitable materials for synthesizing micro/nanocapsules for use in self-healing (nano)composites. In this study, molecular dynamics was employed to simulate the process in which urea and formaldehyde are cross-linked via methylene and ether cross linkers, and to study the structure and mechanical/thermal properties of simulated poly(urea-formaldehyde)s (PUFs). The elastic stiffness constants of the simulated materials were calculated using the constant-strain (static) method. A temperature cycle was applied to the cross-linked PUFs, and the glass transition behavior of each material was investigated through the mean squared displacement (MSD) and temperature evolution of the energy and the specific volume of the polymer. The simulation results confirmed that there was considerable improvement in the properties of the poly(UF) materials upon cross linking. The radial distribution function was also used to study the local structures of the polymers, and this revealed that increasing the temperature and cross linking density results in a significant drop in hydrogen bonding intensity in the cross-linked PUF systems.

  2. Development and characterization of self-healing carbon fabric/ionomer composite through stitched polymeric artificial muscle

    NASA Astrophysics Data System (ADS)

    Gabriel, Mark Joseph

    Typical cracks in composite materials are hard to detect, because they may be very small or occur inside the material. This study investigates the development and characterization of carbon fiber and an ionomer, self-healing, laminate composite, enhanced with stitched artificial muscle elements. Although the carbon fiber is used as a structural reinforcement, the carbon fiber can also act as a resistive heating element in order to activate the healing elements in a Close-Then-Heal (CTH) approach. However in this study, hot air in an oven was used to activate the, SurlynRTM 8940, self-healing matrix. Artificial muscle was prepared from commercial fishing line to stitch reinforce the carbon laminate composite in the Z plane. Holes were drilled into the final composite and the muscle was stitched into the composite for active reinforcement. Differential scanning calorimetry was used to characterize the matrix and fishing line properties. The resulting smart composite was subjected to low velocity impact tests and consequential damage before healing in an oven, followed by three point bending flexure tests. Cracks in the carbon fiber reinforcement formed more easily than expected after impact because the holes were drilled to facilitate the muscle stitching. The matrix material could heal, but the reinforcement carbon could not. Several equipment issues and failures limited the amount of samples that could be created to continue testing with new parameters.

  3. Digital Manufacturing of Gradient Meshed SOFC Sealing Composites with Self-Healing Capabilities

    SciTech Connect

    Kathy Lu; Christopher Story; W.T. Reynolds

    2007-12-21

    Solid oxide fuel cells (SOFC) hold great promise for clean power generation. However, high temperature stability and long term durability of the SOFC components have presented serious problems in SOFC technological advancement and commercialization. The seals of the fuel cells are the most challenging area to address. A high temperature gas seal is highly needed which is durable against cracking and gas leakage during thermal cycling and extended operation. This project investigates a novel composite seal by integrating 3D printed shape memory alloy (SMA) wires into a glass matrix. The SMA we use is TiNiHf and the glass matrix we use is SrO-La{sub 2}O{sub 3}-Al{sub 2}O{sub 3}-B{sub 2}O{sub 3}-SiO{sub 2} (SLABS). Dilatometry shows to be an extremely useful tool in providing the CTEs. It pinpoints regions of different CTEs under simulated SOFC thermal cycles for the same glass. For the studied SLABS glass system, the region with the greatest CTE mismatch between the glass seal and the adjacent components is 40-500 C, the typical heating and cooling regions for SOFCs. Even for low temperature SOFC development, this region is still present and needs to be addressed. We have demonstrated that the proposed SLABS glass has great potential in mitigating the thermal expansion mismatch issues that are limiting the operation life of SOFCs. TiNiHf alloy has been successfully synthesized with the desired particle size for the 3DP process. The TiNiHf SMA shape memory effect very desirably overlaps with the problematic low CTE region of the glass. This supports the design intent that the gradient structure transition, phase transformation toughening, and self-healing of the SMA can be utilized to mitigate/eliminate the seal problem. For the 3DP process, a new binder has been identified to match with the specific chemistry of the SMA particles. This enables us to directly print SMA particles. Neutron diffraction shows to be an extremely useful tool in providing information

  4. A Conductive Self-Healing Hybrid Gel Enabled by Metal-Ligand Supramolecule and Nanostructured Conductive Polymer.

    PubMed

    Shi, Ye; Wang, Ming; Ma, Chongbo; Wang, Yaqun; Li, Xiaopeng; Yu, Guihua

    2015-09-09

    Self-healing materials emerge as a fascinating class of materials important for various technological applications. However, achieving the synergistic characteristics of high conductivity, room-temperature self-healing ability, and decent mechanical properties still remains a critical challenge. Here we develop for the first time a hybrid gel based on self-assembled supramolecular gel and nanostructured polypyrrole that synergizes the dynamic assembly/disassembly nature of metal-ligand supramolecule and the conductive nanostructure of polypyrrole hydrogel and exhibits features of high conductivity (12 S m(-1)), appealing mechanical and electrical self-healing property without any external stimuli, and enhanced mechanical strength and flexibility. The attractive characteristics of the hybrid gel are further demonstrated by a flexible yet self-healable electrical circuit. Our work shows the great potential of self-healing hybrid gel system in flexible electronics and provides a useful strategy to design multifunctional self-healing materials.

  5. Conductive elastomers with autonomic self-healing properties.

    PubMed

    Guo, Kun; Zhang, Da-Li; Zhang, Xiao-Mei; Zhang, Jian; Ding, Li-Sheng; Li, Bang-Jing; Zhang, Sheng

    2015-10-05

    Healable, electrically conductive materials are highly desirable and valuable for the development of various modern electronics. But the preparation of a material combining good mechanical elasticity, functional properties, and intrinsic self-healing ability remains a great challenge. Here, we design composites by connecting a polymer network and single-walled carbon nanotubes (SWCNTs) through host-guest interactions. The resulting materials show bulk electrical conductivity, proximity sensitivity, humidity sensitivity and are able to self-heal without external stimulus under ambient conditions rapidly. Furthermore, they also possess elasticity comparable to commercial rubbers. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  6. Advanced self-healing asphalt composites in the pavement performance field: mechanisms at the nano level and new repairing methodologies.

    PubMed

    Agzenai, Yahya; Pozuelo, Javier; Sanz, Javier; Perez, Ignacio; Baselga, Juan

    2015-01-01

    In an effort to give a global view of this field of research, in this mini-review we highlight the most recent publications and patents focusing on modified asphalt pavements that contain certain reinforcing nanoparticles which impart desirable thermal, electrical and mechanical properties. In response to the increasing cost of asphalt binder and road maintenance, there is a need to look for alternative technologies and new asphalt composites, able to self-repair, for preserving and renewing the existing pavements. First, we will focus on the self-healing property of asphalt, the evidences that support that healing takes place immediately after the contact between the faces of a crack, and how the amount of healing can be measured in both the laboratory and the field. Next we review the hypothetical mechanisms of healing to understand the material behaviour and establish models to quantify the damage-healing process. Thereafter, we outline different technologies, nanotechnologies and methodologies used for self-healing paying particular attention to embedded micro-capsules, new nano-materials like carbon nanotubes and nano-fibres, ionomers, and microwave and induction heating processes.

  7. Application of a silver-olefin coordination polymer as a catalytic curing agent for self-healing epoxy polymers

    NASA Astrophysics Data System (ADS)

    Everitt, D. T.; Coope, T. S.; Trask, R. S.; Wass, D. F.; Bond, I. P.

    2015-05-01

    A silver-olefin based coordination polymer was prepared in a simple, one step process to act as an initiator to facilitate the ring-opening polymerization of epoxides. Thermal analysis found the complex to be capable of curing a range of commercially available epoxy resins used in the manufacture of conventional composite materials. Curing of the oligomeric diglycidyl ether bisphenol A resin, Epon 828, in combination with a non-toxic solvent, ethyl phenylacetate, was studied by differential scanning calorimetry. The mechanical characterization of the resultant cured polymers was conducted by single lap shear tests. Tapered double cantilever beam (TDCB) test specimens containing 2.5 pph of silver-olefin initiator, both with and without embedded microcapsules, were analyzed for their healing performance. Healing efficiency values were found to be strongly dependent on the applied healing temperature. A mean recovery of 74% fracture load was found in TDCB samples after being healed at 70 °C for 48 h.

  8. Synthetic Self-Healing Methods

    SciTech Connect

    Bello, Mollie

    2014-06-02

    Given enough time, pressure, temperature fluctuation, and stress any material will fail. Currently, synthesized materials make up a large part of our everyday lives, and are used in a number of important applications such as; space travel, under water devices, precise instrumentation, transportation, and infrastructure. Structural failure of these material scan lead to expensive and dangerous consequences. In an attempt to prolong the life spans of specific materials and reduce efforts put into repairing them, biologically inspired, self-healing systems have been extensively investigated. The current review explores recent advances in three methods of synthesized self-healing: capsule based, vascular, and intrinsic. Ideally, self-healing materials require no human intervention to promote healing, are capable of surviving all the steps of polymer processing, and heal the same location repeatedly. Only the vascular method holds up to all of these idealities.

  9. Self-healing mortar with pH-sensitive superabsorbent polymers: testing of the sealing efficiency by water flow tests

    NASA Astrophysics Data System (ADS)

    Gruyaert, Elke; Debbaut, Brenda; Snoeck, Didier; Díaz, Pilar; Arizo, Alejandro; Tziviloglou, Eirini; Schlangen, Erik; De Belie, Nele

    2016-08-01

    Superabsorbent polymers (SAPs) have potential to be used as healing agent in self-healing concrete due to their property to attract moisture from the environment and their capacity to promote autogenous healing. A possible drawback, however, is their uptake of mixing water during concrete manufacturing, resulting in an increased volume of macro-pores in the hardened concrete. To limit this drawback, newly developed SAPs with a high swelling and pH-sensitiveness were developed and tested within the FP7 project HEALCON. Evaluation of their self-sealing performance occurred through a water permeability test via water flow, a test method also developed within HEALCON. Three different sizes of the newly developed SAP were compared with a commercial SAP. Swelling tests in cement filtrate solution indicated that the commercial and in-house synthesized SAPs performed quite similar, but the difference between the swelling capacity at pH 9 and pH 13 is more pronounced for the self-synthesized SAPs. Moreover, in comparison to the commercial SAPs, less macro-pores are formed in the cement matrix of mixes with self-synthesized SAPs and the effect on the mechanical properties is lower, but not negligible, when using high amounts of SAPs. Although the immediate sealing effect of cracks in mortar was the highest for the commercial SAPs, the in-house made SAPs with a particle size between 400 and 600 μm performed the best with regard to crack closure (mainly CaCO3 precipitation) and self-sealing efficiency, after exposing the specimens to 28 wet-dry cycles. Some specimens could even withstand a water pressure of 2 bar.

  10. Self-Healing of biocompatible polymeric nanocomposities

    NASA Astrophysics Data System (ADS)

    Espino, Omar; Chipara, Dorina

    2014-03-01

    Polymers are vulnerable to damage in form of cracks deep within the structure, where detection is difficult and repair is near to impossible. These cracks lead to mechanical degradation of the polymer. A method has been created to solve this problem named polymeric self healing. Self healing capabilities implies the dispersion within the polymeric matrix of microcapsules filled with a monomer and of catalyst. Poly urea-formaldehyde microcapsules used in this method are filled with dicyclopentadiene that is liberated after being ruptured by the crack propagation in the material. Polymerization is assisted by a catalyst FGGC that ignites the self healing process. Nanocomposites, such as titanium oxide, will be used as an integration of these polymers that will be tested by rupturing mechanically slowly. In order to prove the self healing process, Raman spectroscopy, FTIR, and SEM are used.

  11. The Effect of 4-Octyldecyloxybenzoic Acid on Liquid-Crystalline Polyurethane Composites with Triple-Shape Memory and Self-Healing Properties.

    PubMed

    Ban, Jianfeng; Zhu, Linjiang; Chen, Shaojun; Wang, Yiping

    2016-09-21

    To better understand shape memory materials and self-healing materials, a new series of liquid-crystalline shape memory polyurethane (LC-SMPU) composites, named SMPU-OOBAm, were successfully prepared by incorporating 4-octyldecyloxybenzoic acid (OOBA) into the PEG-based SMPU. The effect of OOBA on the structure, morphology, and properties of the material has been carefully investigated. The results demonstrate that SMPU-OOBAm has liquid crystalline properties, triple-shape memory properties, and self-healing properties. The incorporated OOBA promotes the crystallizability of both soft and hard segments of SMPU, and the crystallization rate of the hard segment of SMPU decreases when the OOBA-content increases. Additionally, the SMPU-OOBAm forms a two-phase separated structure (SMPU phase and OOBA phase), and it shows two-step modulus changes upon heating. Therefore, the SMPU-OOBAm exhibits triple-shape memory behavior, and the shape recovery ratio decreases with an increase in the OOBA content. Finally, SMPU-OOBAm exhibits self-healing properties. The new mechanism can be ascribed to the heating-induced "bleeding" of OOBA in the liquid crystalline state and the subsequent re-crystallization upon cooling. This successful combination of liquid crystalline properties, triple-shape memory properties, and self-healing properties make the SMPU-OOBAm composites ideal for many promising applications in smart optical devices, smart electronic devices, and smart sensors.

  12. The Effect of 4-Octyldecyloxybenzoic Acid on Liquid-Crystalline Polyurethane Composites with Triple-Shape Memory and Self-Healing Properties

    PubMed Central

    Ban, Jianfeng; Zhu, Linjiang; Chen, Shaojun; Wang, Yiping

    2016-01-01

    To better understand shape memory materials and self-healing materials, a new series of liquid-crystalline shape memory polyurethane (LC-SMPU) composites, named SMPU-OOBAm, were successfully prepared by incorporating 4-octyldecyloxybenzoic acid (OOBA) into the PEG-based SMPU. The effect of OOBA on the structure, morphology, and properties of the material has been carefully investigated. The results demonstrate that SMPU-OOBAm has liquid crystalline properties, triple-shape memory properties, and self-healing properties. The incorporated OOBA promotes the crystallizability of both soft and hard segments of SMPU, and the crystallization rate of the hard segment of SMPU decreases when the OOBA-content increases. Additionally, the SMPU-OOBAm forms a two-phase separated structure (SMPU phase and OOBA phase), and it shows two-step modulus changes upon heating. Therefore, the SMPU-OOBAm exhibits triple-shape memory behavior, and the shape recovery ratio decreases with an increase in the OOBA content. Finally, SMPU-OOBAm exhibits self-healing properties. The new mechanism can be ascribed to the heating-induced “bleeding” of OOBA in the liquid crystalline state and the subsequent re-crystallization upon cooling. This successful combination of liquid crystalline properties, triple-shape memory properties, and self-healing properties make the SMPU-OOBAm composites ideal for many promising applications in smart optical devices, smart electronic devices, and smart sensors. PMID:28773914

  13. Two-dimensional Raman correlation spectroscopy reveals molecular structural changes during temperature-induced self-healing in polymers based on the Diels-Alder reaction.

    PubMed

    Geitner, R; Kötteritzsch, J; Siegmann, M; Bocklitz, T W; Hager, M D; Schubert, U S; Gräfe, S; Dietzek, B; Schmitt, M; Popp, J

    2015-09-21

    The thermally healable polymer P(LMA-co-FMA-co-MIMA) has been studied by temperature-dependent FT-Raman spectroscopy, two-dimensional Raman correlation analysis and density functional theory (DFT) calculations. To the best of our knowledge this study reports for the first time on the investigation of a self-healing polymer by means of two-dimensional correlation techniques. The synchronous correlation spectrum reveals that the spectrally overlapping C[double bond, length as m-dash]C stretching vibrations at 1501, 1575, 1585 and 1600 cm(-1) are perfect marker bands to monitor the healing process which is based on a Diels-Alder reaction of furan and maleimide. The comparison between experimental and calculated Raman spectra as well as their correlation spectra showed a good agreement between experiment and theory. The data presented within this study nicely demonstrate that Raman correlation analysis combined with a band assignment based on DFT calculations presents a powerful tool to study the healing process of self-healing polymers.

  14. Progress in the remote-controlled activation of self-healing processes

    NASA Astrophysics Data System (ADS)

    Shaaban, Ahmad; Schmidt, Annette M.

    2016-08-01

    Self-healing materials, able to heal themselves either spontaneously or after activation, and ultimately restore diverse properties such as mechanical, optical or electrical properties, are under intense investigation for various classes of material, including polymers, cementous materials, asphalts, metals, composites, and more. Among these, on-command self-healing systems can be classified as an approach towards a spatially resolved, externally controlled activation of self-healing behavior. Towards this goal, the last decade has experienced significant progress. Various methods, mainly based on indirect heating mechanisms, such as resistive, induction, or photo-induced heating, have been presented, depending on different antenna materials and energy sources, and tailored for different applications. This review discusses the up-to-date achievements in the field of on-command self-healing materials with a focus on electromagnetic and mechanochemical activation.

  15. Fracture Toughness of Carbon Fiber Composites Containing Various Fiber Sizings and a Puncture Self-Healing Thermoplastic Matrix

    NASA Technical Reports Server (NTRS)

    Cano, Roberto J.; Grimsley, Brian W.; Ratcliffe, James G.; Gordon, Keith L.; Smith, Joseph G.; Siochi, Emilie J.

    2015-01-01

    Ongoing efforts at NASA Langley Research Center (LaRC) have resulted in the identification of several commercially available thermoplastic resin systems which self-heal after ballistic impact and through penetration. One of these resins, polybutylene graft copolymer (PBg), was selected as a matrix for processing with unsized carbon fibers to fabricate reinforced composites for further evaluation. During process development, data from thermo-physical analyses was utilized to determine a processing cycle to fabricate laminate panels, which were analyzed by photo microscopy and acid digestion. The process cycle was further optimized based on these results to fabricate panels for mechanical property characterization. The results of the processing development effort of this composite material, as well as the results of the mechanical property characterization, indicated that bonding between the fiber and PBg was not adequate. Therefore, three sizings were investigated in this work to assess their potential to improve fiber/matrix bonding compared to previously tested unsized IM7 fiber. Unidirectional prepreg was made at NASA LaRC from three sized carbon fibers and utilized to fabricate test coupons that were tested in double cantilever beam configurations to determine GIc fracture toughness.

  16. Self Healing Percolation

    NASA Astrophysics Data System (ADS)

    Scala, Antonio

    2015-03-01

    We introduce the concept of self-healing in the field of complex networks modelling; in particular, self-healing capabilities are implemented through distributed communication protocols that exploit redundant links to recover the connectivity of the system. Self-healing is a crucial in implementing the next generation of smart grids allowing to ensure a high quality of service to the users. We then map our self-healing procedure in a percolation problem and analyse the interplay between redundancies and topology in improving the resilience of networked infrastructures to multiple failures. We find exact results both for planar lattices and for random lattices, hinting the role of duality in the design of resilient networks. Finally, we introduce a cavity method approach to study the recovery of connectivity after damage in self-healing networks. CNR-PNR National Project ``Crisis-Lab,'' EU HOME/2013/CIPS/AG/4000005013 project CI2C and EU FET project MULTIPLEX nr.317532.

  17. Redox-responsive self-healing for corrosion protection.

    PubMed

    Vimalanandan, Ashokanand; Lv, Li-Ping; Tran, The Hai; Landfester, Katharina; Crespy, Daniel; Rohwerder, Michael

    2013-12-23

    Raspberry-shaped redox-responsive capsules for storing corrosion inhibitors are introduced, targeted to solve the drawbacks of conducting-polymer-based coating systems for corrosion protection. These capsules synthesized via the miniemulsion technique have a remarkable release property upon reduction (onset of corrosion) and cease release upon reoxidation (passivation of the defect). The self-healing capability is demonstrated by application of these capsules as part of a composite coating on zinc.

  18. Numerical Modelling of Self Healing Mechanisms

    NASA Astrophysics Data System (ADS)

    Remmers, Joris J. C.; de Borst, René

    A number of self healing mechanisms for composite materials have been presented in the previous chapters of this book. These methods vary from the classical concept of micro-encapsulating of healing agents in polymer systems to the autonomous healing of concrete. The key feature of these self healing mechanisms is the transport of material to the damaged zone in order to establish the healing process. Generally, this material is a fluid and its motion is driven by capillary action which enables transportation over relatively large distances requiring little or no work. In the microencapsulated polymers as developed by White et al. [1], this liquid material is a healing agent, which is enclosed in the material by micro-encapsulation. When the capsule is ruptured by a crack, the healing agent will flow into the crack, driven by capillary action. Polymerisation of this healing agent is triggered by contact with catalysts which are inserted in the material and whose position is fixed. The new polymerised material will rebond the crack surfaces.

  19. Combining Through-Thickness Reinforcement and Self-Healing for Improved Damage Tolerance and Durability of Composites

    NASA Technical Reports Server (NTRS)

    O'Brien, T. Kevin; Czabaj, Michael W.; Hinkley, Jeffrey A.; Tsampas, Spiros; Greenhalgh, Emile S.; McCombe, Gregory; Bond, Ian P.; Trask, Richard

    2013-01-01

    A study was undertaken to develop a prototype method for adding through-thickness hollow glass tubes infused with uncured resin and hardener in a carbon Z-pin through-thickness reinforcement field embedded in a composite laminate. Two types of tube insertion techniques were attempted in an effort to ensure the glass tubes survived the panel manufacturing process. A self-healing resin was chosen with a very low viscosity, two component, liquid epoxy resin system designed to be mixed at a 2-to-1 ratio of epoxy to hardener. IM7/8552 carbon epoxy double cantilever beam (DCB) specimens were cut from the hybrid Z-pin and glass tube reinforced panels and tested. In-situ injection of resin and hardener directly into glass tubes, in a staggered pattern to allow for 2-to-1 ratio mixing, resulted in partial healing of the fracture plane, but only if the injection was performed while the specimen was held at maximum load after initial fracture. Hence, there is some potential for healing delamination via resin and hardener delivered through a network of through-thickness glass tubes, but only if the tubes are connected to a reservoir where additional material may be injected as needed.

  20. Multifunctional Carbon Nanotube-Based Sensors for Damage Detection and Self Healing in Structural Composites

    DTIC Science & Technology

    2010-10-29

    system has been used to detect damage accumulation in composite laminates in situ under quasi-static uniaxial and cyclic loading conditions. Large... coating on the surface of two E-glass fibers is shown in Fig. 5. Fig. 5. (a) Carbon nanotube agglomerates on the surface of glass fibers in the...unidirectional E-glass composites in which the center ply of the laminate was cut in the middle of the specimen to promote ply delamination during tensile

  1. pH-induced metal-ligand cross-links inspired by mussel yield self-healing polymer networks with near-covalent elastic moduli.

    PubMed

    Holten-Andersen, Niels; Harrington, Matthew J; Birkedal, Henrik; Lee, Bruce P; Messersmith, Phillip B; Lee, Ka Yee C; Waite, J Herbert

    2011-02-15

    Growing evidence supports a critical role of metal-ligand coordination in many attributes of biological materials including adhesion, self-assembly, toughness, and hardness without mineralization [Rubin DJ, Miserez A, Waite JH (2010) Advances in Insect Physiology: Insect Integument and Color, eds Jérôme C, Stephen JS (Academic Press, London), pp 75-133]. Coordination between Fe and catechol ligands has recently been correlated to the hardness and high extensibility of the cuticle of mussel byssal threads and proposed to endow self-healing properties [Harrington MJ, Masic A, Holten-Andersen N, Waite JH, Fratzl P (2010) Science 328:216-220]. Inspired by the pH jump experienced by proteins during maturation of a mussel byssus secretion, we have developed a simple method to control catechol-Fe(3+) interpolymer cross-linking via pH. The resonance Raman signature of catechol-Fe(3+) cross-linked polymer gels at high pH was similar to that from native mussel thread cuticle and the gels displayed elastic moduli (G') that approach covalently cross-linked gels as well as self-healing properties.

  2. pH-induced metal-ligand cross-links inspired by mussel yield self-healing polymer networks with near-covalent elastic moduli

    PubMed Central

    Holten-Andersen, Niels; Harrington, Matthew J.; Birkedal, Henrik; Lee, Bruce P.; Messersmith, Phillip B.; Lee, Ka Yee C.; Waite, J. Herbert

    2011-01-01

    Growing evidence supports a critical role of metal-ligand coordination in many attributes of biological materials including adhesion, self-assembly, toughness, and hardness without mineralization [Rubin DJ, Miserez A, Waite JH (2010) Advances in Insect Physiology: Insect Integument and Color, eds Jérôme C, Stephen JS (Academic Press, London), pp 75–133]. Coordination between Fe and catechol ligands has recently been correlated to the hardness and high extensibility of the cuticle of mussel byssal threads and proposed to endow self-healing properties [Harrington MJ, Masic A, Holten-Andersen N, Waite JH, Fratzl P (2010) Science 328:216–220]. Inspired by the pH jump experienced by proteins during maturation of a mussel byssus secretion, we have developed a simple method to control catechol-Fe3+ interpolymer cross-linking via pH. The resonance Raman signature of catechol-Fe3+ cross-linked polymer gels at high pH was similar to that from native mussel thread cuticle and the gels displayed elastic moduli (G′) that approach covalently cross-linked gels as well as self-healing properties. PMID:21278337

  3. Highly flexible transparent self-healing composite based on electrospun core-shell nanofibers produced by coaxial electrospinning for anti-corrosion and electrical insulation.

    PubMed

    An, Seongpil; Liou, Minho; Song, Kyo Yong; Jo, Hong Seok; Lee, Min Wook; Al-Deyab, Salem S; Yarin, Alexander L; Yoon, Sam S

    2015-11-14

    Coaxial electrospinning was used to fabricate two types of core-shell fibers: the first type with liquid resin monomer in the core and polyacrylonitrile in the shell, and the second type with liquid curing agent in the core and polyacrylonitrile in the shell. These two types of core-shell fibers were mutually entangled and embedded into two flexible transparent matrices thus forming transparent flexible self-healing composite materials. Such materials could be formed before only using emulsion electrospinning, rather than coaxial electrospinning. The self-healing properties of such materials are associated with release of healing agents (resin monomer and cure) from nanofiber cores in damaged locations with the subsequent polymerization reaction filing the micro-crack with polydimethylsiloxane. Transparency of these materials is measured and the anti-corrosive protection provided by them is demonstrated in electrochemical experiments.

  4. Highly flexible transparent self-healing composite based on electrospun core-shell nanofibers produced by coaxial electrospinning for anti-corrosion and electrical insulation

    NASA Astrophysics Data System (ADS)

    An, Seongpil; Liou, Minho; Song, Kyo Yong; Jo, Hong Seok; Lee, Min Wook; Al-Deyab, Salem S.; Yarin, Alexander L.; Yoon, Sam S.

    2015-10-01

    Coaxial electrospinning was used to fabricate two types of core-shell fibers: the first type with liquid resin monomer in the core and polyacrylonitrile in the shell, and the second type with liquid curing agent in the core and polyacrylonitrile in the shell. These two types of core-shell fibers were mutually entangled and embedded into two flexible transparent matrices thus forming transparent flexible self-healing composite materials. Such materials could be formed before only using emulsion electrospinning, rather than coaxial electrospinning. The self-healing properties of such materials are associated with release of healing agents (resin monomer and cure) from nanofiber cores in damaged locations with the subsequent polymerization reaction filing the micro-crack with polydimethylsiloxane. Transparency of these materials is measured and the anti-corrosive protection provided by them is demonstrated in electrochemical experiments.

  5. Self-healing materials with microvascular networks.

    PubMed

    Toohey, Kathleen S; Sottos, Nancy R; Lewis, Jennifer A; Moore, Jeffrey S; White, Scott R

    2007-08-01

    Self-healing polymers composed of microencapsulated healing agents exhibit remarkable mechanical performance and regenerative ability, but are limited to autonomic repair of a single damage event in a given location. Self-healing is triggered by crack-induced rupture of the embedded capsules; thus, once a localized region is depleted of healing agent, further repair is precluded. Re-mendable polymers can achieve multiple healing cycles, but require external intervention in the form of heat treatment and applied pressure. Here, we report a self-healing system capable of autonomously repairing repeated damage events. Our bio-inspired coating-substrate design delivers healing agent to cracks in a polymer coating via a three-dimensional microvascular network embedded in the substrate. Crack damage in the epoxy coating is healed repeatedly. This approach opens new avenues for continuous delivery of healing agents for self-repair as well as other active species for additional functionality.

  6. The role of non-covalent interactions in the self-healing mechanism of disulfide-based polymers.

    PubMed

    Formoso, Elena; Asua, José M; Matxain, Jon M; Ruipérez, Fernando

    2017-07-19

    In this work, a theoretical protocol based on classical molecular dynamics has been defined, in order to study weak non-covalent interactions in diphenyl disulfide based compounds. This protocol is then used to study the influence of hydrogen bonds and π-π stacking in four selected cases, namely, monosubstituted and amine ortho trisubstituted urea and urethane-based diphenyl disulfides. In all cases, it has been observed that hydrogen bonds are much more relevant than π-π stacking, which has little influence. In addition, hydrogen bonds are the responsible to maintain the polymeric chains close, so that the disulfides may reach the reacting region, even in urethane-based materials, where the lower amount of hydrogen bonds formed make the chains more flexible and mobile. Combining the results obtained by classical molecular dynamics with those obtained earlier by means of quantum mechanics, we conclude that there are two main factors that are relevant to the self-healing properties of disulfide-based materials: firstly, the capacity to generate sulfenyl radicals by breaking the disulfide S-S bond and, secondly, the ability of these radicals to attack neighboring disulfides. The former is dominated by the bond dissociation energy of the S-S bond, while the latter is strongly influenced by two other factors. On the one hand, the hydrogen bonding interactions established between chains, and on the other, the energy barriers for the attack of sulfur radicals to neighbor disulfides. We have defined three new parameters to estimate the influence of these features, with the aim of predicting the self-healing capacity of disulfides and related materials, which will help experimentalists in the development of improved materials.

  7. Magnetic Field Triggered Multicycle Damage Sensing and Self Healing

    NASA Astrophysics Data System (ADS)

    Ahmed, Anansa S.; Ramanujan, R. V.

    2015-09-01

    Multifunctional materials inspired by biological structures have attracted great interest, e.g. for wearable/ flexible “skin” and smart coatings. A current challenge in this area is to develop an artificial material which mimics biological skin by simultaneously displaying color change on damage as well as self healing of the damaged region. Here we report, for the first time, the development of a damage sensing and self healing magnet-polymer composite (Magpol), which actively responds to an external magnetic field. We incorporated reversible sensing using mechanochromic molecules in a shape memory thermoplastic matrix. Exposure to an alternating magnetic field (AMF) triggers shape recovery and facilitates damage repair. Magpol exhibited a linear strain response upto 150% strain and complete recovery after healing. We have demonstrated the use of this concept in a reusable biomedical device i.e., coated guidewires. Our findings offer a new synergistic method to bestow multifunctionality for applications ranging from medical device coatings to adaptive wing structures.

  8. Investigation of the Self-Healing Behaviors of Microcapsules/Bitumen Composites by a Repetitive Direct Tension Test

    PubMed Central

    Su, Jun-Feng; Yang, Peng; Wang, Ying-Yuan; Han, Shan; Han, Ning-Xu; Li, Wei

    2016-01-01

    The aim of this work was to evaluate the self-healing behaviors of bitumen using microcapsules containing rejuvenator by a modified fracture healing–refracture method through a repetitive tension test. Microcapsules had mean size values of 10, 20 and 30 μm with a same core/shell ratio of 1/1. Various microcapsules/bitumen samples were fabricated with microcapsule contents of 1.0, 3.0 and 5.0 wt. %, respectively. Tension strength values of microcapsules/bitumen samples were measured by a reparative fracture-healing process under different temperatures. It was found that these samples had tensile strength values larger than the data of pure bitumen samples under the same conditions after the four tensile fracture-healing cycles. Fracture morphology investigation and mechanism analysis indicated that the self-healing process was a process consisting of microcapsules being broken, penetrated and diffused. Moreover, the crack healing of bitumen can be considered as a viscosity driven process. The self-healing ability partly repaired the damage of bitumen during service life by comparing the properties of virgin and rejuvenated bitumen. PMID:28773722

  9. Multiphase design of autonomic self-healing thermoplastic elastomers

    NASA Astrophysics Data System (ADS)

    Chen, Yulin; Kushner, Aaron M.; Williams, Gregory A.; Guan, Zhibin

    2012-06-01

    The development of polymers that can spontaneously repair themselves after mechanical damage would significantly improve the safety, lifetime, energy efficiency and environmental impact of man-made materials. Most approaches to self-healing materials require the input of external energy, healing agents, solvent or plasticizer. Despite intense research in this area, the synthesis of a stiff material with intrinsic self-healing ability remains a key challenge. Here, we show a design of multiphase supramolecular thermoplastic elastomers that combine high modulus and toughness with spontaneous healing capability. The designed hydrogen-bonding brush polymers self-assemble into a hard-soft microphase-separated system, combining the enhanced stiffness and toughness of nanocomposites with the self-healing capability of dynamic supramolecular assemblies. In contrast to previous self-healing polymers, this new system spontaneously self-heals as a single-component solid material at ambient conditions, without the need for any external stimulus, healing agent, plasticizer or solvent.

  10. Multiphase design of autonomic self-healing thermoplastic elastomers.

    PubMed

    Chen, Yulin; Kushner, Aaron M; Williams, Gregory A; Guan, Zhibin

    2012-04-01

    The development of polymers that can spontaneously repair themselves after mechanical damage would significantly improve the safety, lifetime, energy efficiency and environmental impact of man-made materials. Most approaches to self-healing materials require the input of external energy, healing agents, solvent or plasticizer. Despite intense research in this area, the synthesis of a stiff material with intrinsic self-healing ability remains a key challenge. Here, we show a design of multiphase supramolecular thermoplastic elastomers that combine high modulus and toughness with spontaneous healing capability. The designed hydrogen-bonding brush polymers self-assemble into a hard-soft microphase-separated system, combining the enhanced stiffness and toughness of nanocomposites with the self-healing capability of dynamic supramolecular assemblies. In contrast to previous self-healing polymers, this new system spontaneously self-heals as a single-component solid material at ambient conditions, without the need for any external stimulus, healing agent, plasticizer or solvent.

  11. Autonomic self-healing in epoxidized natural rubber.

    PubMed

    Rahman, Arifur; Sartore, Luciana; Bignotti, Fabio; Di Landro, Luca

    2013-02-01

    The development of polymers that can repair damage autonomously would be useful to improve the lifetime of polymeric materials. To date, limited attention has been dedicated to developing elastomers with autonomic self-healing ability, which can recover damages without need for an external or internal source of healing agents. This work investigates the self-healing behavior of epoxidized natural rubber (ENR) with two different epoxidation levels (25 and 50 mol % epoxidation) and of the corresponding unfunctionalized rubber, cis-1,4-polyisoprene (PISP). A self-adhesion assisted self-healing behavior was revealed by T-peel tests on slightly vulcanized rubbers. A higher epoxidation level was found to enhance self-healing. Self-healing of rubbers following ballistic damages was also investigated. A pressurized air flow test setup was used to evaluate the self-healing of ballistic damages in rubbers. Microscope (OM, SEM, and TEM) analyses were carried out to provide further evidence of healing in the impact zones. Self-healing of ballistic damages was observed only in ENR with 50 mol % epoxidation and it was found to be influenced significantly by the cross-link density. Finally, self-healing of ballistic damages was also observed in ENR50/PISP blends only when the content of the healing component (i.e., ENR50) was at least 25 wt %. From an analysis of the results, it was concluded that a synergistic effect between interdiffusion and interaction among polar groups leads to self-healing in ENR.

  12. Biomimetic Self-Healing.

    PubMed

    Diesendruck, Charles E; Sottos, Nancy R; Moore, Jeffrey S; White, Scott R

    2015-09-01

    Self-healing is a natural process common to all living organisms which provides increased longevity and the ability to adapt to changes in the environment. Inspired by this fitness-enhancing functionality, which was tuned by billions of years of evolution, scientists and engineers have been incorporating self-healing capabilities into synthetic materials. By mimicking mechanically triggered chemistry as well as the storage and delivery of liquid reagents, new materials have been developed with extended longevity that are capable of restoring mechanical integrity and additional functions after being damaged. This Review describes the fundamental steps in this new field of science, which combines chemistry, physics, materials science, and mechanical engineering. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  13. Self-healing minefield

    NASA Astrophysics Data System (ADS)

    Rolader, Glenn E.; Rogers, John; Batteh, Jad

    2004-07-01

    The Self Healing Minefield (SHM) is comprised of a networked system of mobile anti-tank landmines. When the mines detect a breach, each calculates an appropriate response, and some fire small rockets to "hop" into the breach path, healing the breach. The purpose of the SHM is to expand the capabilities of traditional obstacles and provide an effective anti-tank obstacle that does not require Anti-Personnel (AP) submunitions. The DARPA/ATO sponsored program started in June 2000 and culminated in a full 100-unit demonstration at Fort Leonard Wood, MO in April 2003. That program went from "a concept" to a prototype system demonstration in approximately 21 months and to a full tactically significant demonstration in approximately 33 months. Significant accomplishments included the following: (1) Demonstration of a working, scalable (order of a hundred nodes), ad hoc, self-healing RF network. (2) Demonstration of an innovative distributed time synchronization scheme that does not rely on GPS. (3) Demonstration of a non-GPS based, self-mapping, relative geolocation system. (4) Development of an innovative distributed safe, arm, and fire system that allows for independent firing of eight rockets within a single node. (5) Development of a small rocket design with a novel geometry that meets the propulsion requirements.

  14. Ballistic Puncture Self-Healing Polymeric Materials

    NASA Technical Reports Server (NTRS)

    Gordon, Keith L.; Siochi, Emilie J.; Yost, William T.; Bogert, Phil B.; Howell, Patricia A.; Cramer, K. Elliott; Burke, Eric R.

    2017-01-01

    Space exploration launch costs on the order of $10,000 per pound provide an incentive to seek ways to reduce structural mass while maintaining structural function to assure safety and reliability. Damage-tolerant structural systems provide a route to avoiding weight penalty while enhancing vehicle safety and reliability. Self-healing polymers capable of spontaneous puncture repair show promise to mitigate potentially catastrophic damage from events such as micrometeoroid penetration. Effective self-repair requires these materials to quickly heal following projectile penetration while retaining some structural function during the healing processes. Although there are materials known to possess this capability, they are typically not considered for structural applications. Current efforts use inexpensive experimental methods to inflict damage, after which analytical procedures are identified to verify that function is restored. Two candidate self-healing polymer materials for structural engineering systems are used to test these experimental methods.

  15. An Electrically and Mechanically Autonomic Self-healing Hybrid Hydrogel with Tough and Thermoplastic Properties.

    PubMed

    He, Xiaoyan; Zhang, Caiyun; Wang, Meng; Zhang, Yunlei; Liu, Liqin; Yang, Wu

    2017-03-29

    Conductive hydrogels are a class of composite materials that usually comprise hydrated polymers and conductive materials. Practical application requires the conductive hydrogels to have various properties such as high conductivity, toughness, self-healing, facile processing ability, and so on. Although challenging to have all the above-mentioned properties, a composite material composed of polymer hydrogel with embedded Au nanoparticles (i.e., P(NaSS)/P(VBIm-Cl)/PVA@Au) was found to show the comprehensive properties above in this paper. For example, P(NaSS)/P(VBIm-Cl)/PVA@Au exhibits mechanical and electrical self-healing properties at ambient conditions. In addition, P(NaSS)/P(VBIm-Cl)/PVA@Au is tough and thermoplastic, potentially making it useful for a variety of applications.

  16. A Self-Healing Aqueous Lithium-Ion Battery.

    PubMed

    Zhao, Yang; Zhang, Ye; Sun, Hao; Dong, Xiaoli; Cao, Jingyu; Wang, Lie; Xu, Yifan; Ren, Jing; Hwang, Yunil; Son, In Hyuk; Huang, Xianliang; Wang, Yonggang; Peng, Huisheng

    2016-11-07

    Flexible lithium-ion batteries are critical for the next-generation electronics. However, during the practical application, they may break under deformations such as twisting and cutting, causing their failure to work or even serious safety problems. A new family of all-solid-state and flexible aqueous lithium ion batteries that can self-heal after breaking has been created by designing aligned carbon nanotube sheets loaded with LiMn2 O4 and LiTi2 (PO4 )3 nanoparticles on a self-healing polymer substrate as electrodes, and a new kind of lithium sulfate/sodium carboxymethylcellulose serves as both gel electrolyte and separator. The specific capacity, rate capability, and cycling performance can be well maintained after repeated cutting and self-healing. These self-healing batteries are demonstrated to be promising for wearable devices. © 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  17. Magnetic Field Triggered Multicycle Damage Sensing and Self Healing

    PubMed Central

    Ahmed, Anansa S.; Ramanujan, R. V.

    2015-01-01

    Multifunctional materials inspired by biological structures have attracted great interest, e.g. for wearable/ flexible “skin” and smart coatings. A current challenge in this area is to develop an artificial material which mimics biological skin by simultaneously displaying color change on damage as well as self healing of the damaged region. Here we report, for the first time, the development of a damage sensing and self healing magnet-polymer composite (Magpol), which actively responds to an external magnetic field. We incorporated reversible sensing using mechanochromic molecules in a shape memory thermoplastic matrix. Exposure to an alternating magnetic field (AMF) triggers shape recovery and facilitates damage repair. Magpol exhibited a linear strain response upto 150% strain and complete recovery after healing. We have demonstrated the use of this concept in a reusable biomedical device i.e., coated guidewires. Our findings offer a new synergistic method to bestow multifunctionality for applications ranging from medical device coatings to adaptive wing structures. PMID:26348284

  18. Bioconcrete: next generation of self-healing concrete.

    PubMed

    Seifan, Mostafa; Samani, Ali Khajeh; Berenjian, Aydin

    2016-03-01

    Concrete is one of the most widely used construction materials and has a high tendency to form cracks. These cracks lead to significant reduction in concrete service life and high replacement costs. Although it is not possible to prevent crack formation, various types of techniques are in place to heal the cracks. It has been shown that some of the current concrete treatment methods such as the application of chemicals and polymers are a source of health and environmental risks, and more importantly, they are effective only in the short term. Thus, treatment methods that are environmentally friendly and long-lasting are in high demand. A microbial self-healing approach is distinguished by its potential for long-lasting, rapid and active crack repair, while also being environmentally friendly. Furthermore, the microbial self-healing approach prevails the other treatment techniques due to the efficient bonding capacity and compatibility with concrete compositions. This study provides an overview of the microbial approaches to produce calcium carbonate (CaCO3). Prospective challenges in microbial crack treatment are discussed, and recommendations are also given for areas of future research.

  19. Nanoparticle polymer composites: where two small worlds meet.

    PubMed

    Balazs, Anna C; Emrick, Todd; Russell, Thomas P

    2006-11-17

    The mixing of polymers and nanoparticles is opening pathways for engineering flexible composites that exhibit advantageous electrical, optical, or mechanical properties. Recent advances reveal routes to exploit both enthalpic and entropic interactions so as to direct the spatial distribution of nanoparticles and thereby control the macroscopic performance of the material. For example, by tailoring the particle coating and size, researchers have created self-healing materials for improved sustainability and self-corralling rods for photovoltaic applications. A challenge for future studies is to create hierarchically structured composites in which each sublayer contributes a distinct function to yield a mechanically integrated, multifunctional material.

  20. Creep Behavior in Interlaminar Shear of a SiC/SiC Ceramic Composite with a Self-healing Matrix

    NASA Astrophysics Data System (ADS)

    Ruggles-Wrenn, M. B.; Pope, M. T.

    2014-02-01

    Creep behavior in interlaminar shear of a non-oxide ceramic composite with a multilayered matrix was investigated at 1,200 °C in laboratory air and in steam environment. The composite was produced via chemical vapor infiltration (CVI). The composite had an oxidation inhibited matrix, which consisted of alternating layers of silicon carbide and boron carbide and was reinforced with laminated Hi-Nicalon™ fibers woven in a five-harness-satin weave. Fiber preforms had pyrolytic carbon fiber coating with boron carbide overlay applied. The interlaminar shear properties were measured. The creep behavior was examined for interlaminar shear stresses in the 16-22 MPa range. Primary and secondary creep regimes were observed in all tests conducted in air and in steam. In air and in steam, creep run-out defined as 100 h at creep stress was achieved at 16 MPa. Larger creep strains were accumulated in steam. However, creep strain rates and creep lifetimes were only moderately affected by the presence of steam. The retained properties of all specimens that achieved run-out were characterized. Composite microstructure, as well as damage and failure mechanisms were investigated.

  1. Self healing of defected graphene

    SciTech Connect

    Chen, Jianhui; Shi, Tuwan; Cai, Tuocheng; Wu, Xiaosong; Yu, Dapeng; Xu, Tao; Sun, Litao

    2013-03-11

    For electronics applications, defects in graphene are usually undesirable because of their ability to scatter charge carriers, thereby reduce the carrier mobility. It would be extremely useful if the damage can be repaired. In this work, we employ Raman spectroscopy, X-ray photoemission spectroscopy, transmission electron microscopy, and electrical measurements to study defects in graphene introduced by argon plasma bombardment. We have found that majority of these defects can be cured by a simple thermal annealing process. The self-healing is attributed to recombination of mobile carbon adatoms with vacancies. With increasing level of plasma induced damage, the self-healing becomes less effective.

  2. Polylactic acid with improved heat deflection temperatures and self-healing properties for durable goods applications.

    PubMed

    Wertz, J T; Mauldin, T C; Boday, D J

    2014-11-12

    A method to recover fracture toughness after failure and increase thermal properties of polylactic acid (PLA) for use within durable goods applications is presented. Microcapsules were incorporated into PLA to form a composite material in which the microcapsules served the dual purpose of (1) releasing self-healing additives to fracture regions and (2) serving as nucleating agents to improve the PLA composite's thermal tolerance. Self-healing was achieved though embedment of dicyclopentadiene-filled microcapsules and Grubbs' first generation ruthenium metathesis catalyst, the former being autonomically released into damage volumes and undergoing polymerization in the presence of the catalyst. This approach led to up to 84% recovery of the polymer composite's initial fracture toughness. Additionally, PLA's degree of crystallinity and heat deflection temperature were improved by ∼ 11% and ∼ 21 °C, respectively, relative to nonfilled virgin PLA, owing to microcapsule-induced nucleation. The self-healing system developed here overcomes many property limitations of PLA that can potentially lead to its incorporation into various durable goods.

  3. Polymer composites containing nanotubes

    NASA Technical Reports Server (NTRS)

    Bley, Richard A. (Inventor)

    2008-01-01

    The present invention relates to polymer composite materials containing carbon nanotubes, particularly to those containing singled-walled nanotubes. The invention provides a polymer composite comprising one or more base polymers, one or more functionalized m-phenylenevinylene-2,5-disubstituted-p-phenylenevinylene polymers and carbon nanotubes. The invention also relates to functionalized m-phenylenevinylene-2,5-disubstituted-p-phenylenevinylene polymers, particularly to m-phenylenevinylene-2,5-disubstituted-p-phenylenevinylene polymers having side chain functionalization, and more particularly to m-phenylenevinylene-2,5-disubstituted-p-phenylenevinylene polymers having olefin side chains and alkyl epoxy side chains. The invention further relates to methods of making polymer composites comprising carbon nanotubes.

  4. A rapid and efficient self-healing thermo-reversible elastomer crosslinked with graphene oxide.

    PubMed

    Wang, Chao; Liu, Nan; Allen, Ranulfo; Tok, Jeffrey B-H; Wu, Yunpeng; Zhang, Fan; Chen, Yongsheng; Bao, Zhenan

    2013-10-25

    A self-healing thermo-reversible elastomer is synthesized by cross-linking a hydrogen bonding polymer network with chemically-modified graphene oxide. This nanocomposite allows for both rapid and efficient self-healing (in only several minutes) at room temperature, without the need for any external stimuli (e.g., heating or light exposure), healing agents, plasticizers or solvents.

  5. Rapid self-healing hydrogels

    PubMed Central

    Phadke, Ameya; Zhang, Chao; Arman, Bedri; Hsu, Cheng-Chih; Mashelkar, Raghunath A.; Lele, Ashish K.; Tauber, Michael J.; Arya, Gaurav; Varghese, Shyni

    2012-01-01

    Synthetic materials that are capable of autonomous healing upon damage are being developed at a rapid pace because of their many potential applications. Despite these advancements, achieving self-healing in permanently cross-linked hydrogels has remained elusive because of the presence of water and irreversible cross-links. Here, we demonstrate that permanently cross-linked hydrogels can be engineered to exhibit self-healing in an aqueous environment. We achieve this feature by arming the hydrogel network with flexible-pendant side chains carrying an optimal balance of hydrophilic and hydrophobic moieties that allows the side chains to mediate hydrogen bonds across the hydrogel interfaces with minimal steric hindrance and hydrophobic collapse. The self-healing reported here is rapid, occurring within seconds of the insertion of a crack into the hydrogel or juxtaposition of two separate hydrogel pieces. The healing is reversible and can be switched on and off via changes in pH, allowing external control over the healing process. Moreover, the hydrogels can sustain multiple cycles of healing and separation without compromising their mechanical properties and healing kinetics. Beyond revealing how secondary interactions could be harnessed to introduce new functions to chemically cross-linked polymeric systems, we also demonstrate various potential applications of such easy-to-synthesize, smart, self-healing hydrogels. PMID:22392977

  6. Self Healing Coating/Film Project

    NASA Technical Reports Server (NTRS)

    Summerfield, Burton; Thompson, Karen; Zeitlin, Nancy; Mullenix, Pamela; Calle, Luz; Williams, Martha

    2015-01-01

    Kennedy Space Center (KSC) has been developing self healing materials and technologies. This project seeks to further develop self healing functionality in thin films for applications such as corrosion protective coatings, inflatable structures, space suit materials, and electrical wire insulation.

  7. Microcapsule-Type Organogel-Based Self-Healing System Having Secondary Damage Preventing Capability.

    PubMed

    Yang, Hye-In; Kim, Dong-Min; Yu, Hwan-Chul; Chung, Chan-Moon

    2016-05-04

    We have developed a novel microcapsule-type organogel-based self-healing system in which secondary damage does not occur in the healed region. A mixture of an organogelator, poor and good solvents for the gelator is used as the healing agent; when the good solvent evaporates from this agent, a viscoelastic organogel forms. The healing agent is microencapsulated with urea-formaldehyde polymer, and the resultant microcapsules are integrated into a polymer coating to prepare self-healing coatings. When the coatings are scratched, they self-heal, as demonstrated by means of corrosion testing, electrochemical testing, optical microscopy, and scanning electron microscopy (SEM). After the healed coatings are subjected to vigorous vibration, it is demonstrated that no secondary damage occurs in the healed region. The secondary damage preventing capability of the self-healing coating is attributable to the viscoelasticity of the organogel. The result can give insight into the development of a "permanent" self-healing system.

  8. Self-healing fuse development

    NASA Technical Reports Server (NTRS)

    Jones, N. D.; Kinsinger, R. E.; Harris, L. P.

    1973-01-01

    The mercury-filled self-healing fuses developed for this program afford very good protection from circuit faults with rapid reclosure. Fuse performance and design parameters have been characterized. Life tests indicate a capability of 500 fuse operations. Fuse ratings are 150 v at 5, 15, 25 and 50 circuit A. A series of sample fuses using alumina and beryllia insulation have been furnished to NASA for circuit evaluation.

  9. Polyfibroblast: A Self-Healing and Galvanic Protection Additive

    DTIC Science & Technology

    2012-09-12

    self-healing and galvanic protection capacity to the primer (Figure 1). Polyfibroblast consists of paint-filled microcapsules and zinc powder. It has...significant added cost. Microcapsule Figure 1. Polyfibroblast contains fresh paint encapsulated in polymer shells plus Zn powder. When scratched, resin...from the broken microcapsules fills the crack to form a polymer scar. Zn powder supplies galvanic protection in the event of incomplete healing

  10. Damage initiated self-healing in ionomer blends

    NASA Astrophysics Data System (ADS)

    Rahman, Md. Arifur; Penco, Maurizio; Spagnoli, Gloria; Peroni, Isabella; Ramorino, Giorgio; Sartore, Luciana; Bignotti, Fabio; Landro, Luca Di

    2012-07-01

    The development and understanding of self-healing mechanisms have been investigated in blends of ionomers (Poly(ethyelene-co-methacrylic acid), sodium & zinc ions) (EMNa & EMZn) containing both elastomers (Epoxidized natural rubbers (ENR) and cis-1,4-Polyisoprene (PISP)) and crystalline component (Poly(vinly alcohol-co-ethylene) [PVAcE]) as secondary phases. All the blends were prepared by melt-blending and self-healing behavior was studied in ballistic puncture tests. Self-healing behavior of each material was evaluated by observing the impact zones under a stereo-optical microscope and the micrographic results were further supported by the fluid flow test in the punctured zones. Interestingly, ENR50 blends of sodium ion containing ionomers exhibited complete self-repairing behavior while zinc ion containing ionomer showed limited mending but EMNa/ENR25 and EMNa/PISP blends did not show any self-healing behavior following the damage. On the other hand, a composition dependent healing behavior was observed in the EMNa/PVAcE blends where healing was observed up to 30wt% PVAcE containing blends. The chemical structure studied by FTIR analysis showed that both ion content of ionomer and functionality of ENR have significant influence on the self-repairing behavior of blends. TEM analysis revealed that self-healing occurs in the blends when the dispersed phase has a dimension of 100 to 400 nm.

  11. Solid polymer electrolyte compositions

    DOEpatents

    Garbe, James E.; Atanasoski, Radoslav; Hamrock, Steven J.; Le, Dinh Ba

    2001-01-01

    An electrolyte composition is featured that includes a solid, ionically conductive polymer, organically modified oxide particles that include organic groups covalently bonded to the oxide particles, and an alkali metal salt. The electrolyte composition is free of lithiated zeolite. The invention also features cells that incorporate the electrolyte composition.

  12. Enhancing mechanical performance of a covalent self-healing material by sacrificial noncovalent bonds.

    PubMed

    Neal, James A; Mozhdehi, Davoud; Guan, Zhibin

    2015-04-15

    Polymers that repair themselves after mechanical damage can significantly improve their durability and safety. A major goal in the field of self-healing materials is to combine robust mechanical and efficient healing properties. Here, we show that incorporation of sacrificial bonds into a self-repairable network dramatically improves the overall mechanical properties. Specifically, we use simple secondary amide side chains to create dynamic energy dissipative hydrogen bonds in a covalently cross-linked polymer network, which can self-heal via olefin cross-metathesis. We envision that this straightforward sacrificial bonding strategy can be employed to improve mechanical properties in a variety of self-healing systems.

  13. Development of Micro and Nanostructured Materials for Interfacial Self-Healing

    ERIC Educational Resources Information Center

    Blaiszik, Benjamin James

    2009-01-01

    Damage in polymeric coatings, adhesives, microelectronic components, and composites spans many length scales. For small scale damage, autonomic self-healing can repair multiple damage modes without manual intervention. In autonomic self-healing materials, a healing response is triggered by damage to the material. Size scale considerations, such as…

  14. Development of Micro and Nanostructured Materials for Interfacial Self-Healing

    ERIC Educational Resources Information Center

    Blaiszik, Benjamin James

    2009-01-01

    Damage in polymeric coatings, adhesives, microelectronic components, and composites spans many length scales. For small scale damage, autonomic self-healing can repair multiple damage modes without manual intervention. In autonomic self-healing materials, a healing response is triggered by damage to the material. Size scale considerations, such as…

  15. Self-Healing Spongy Coating for Drug "Cocktail" Delivery.

    PubMed

    Chen, Xia-chao; Ren, Ke-feng; Lei, Wen-xi; Zhang, Jia-hui; Martins, M Cristina L; Barbosa, Mário A; Ji, Jian

    2016-02-01

    Optimized ratio in the codelivery of therapeutics is of crucial importance to promote the synergism rather than the antagonistic effects. In this study, a self-healing spongy coating was described to facilitate the surface-mediated delivery of drug "cocktails" proportionally. The formation of spongy structures within the coating was achieved by acidic treatment and freeze-drying. Various drug combinations can be readily integrated through wicking method and subsequent micropore self-healing. The ratio of drug loading can be precisely regulated by the composition of loading solution and the embedded drugs were released in proportion according to the initial ratio of drug combination.

  16. Self-healing sandwich structures incorporating an interfacial layer with vascular network

    NASA Astrophysics Data System (ADS)

    Chen, Chunlin; Peters, Kara; Li, Yulong

    2013-02-01

    A self-healing capability specifically targeted for sandwich composite laminates based on interfacial layers with built-in vascular networks is presented. The self-healing occurs at the facesheet-core interface through an additional interfacial layer to seal facesheet cracks and rebond facesheet-core regions. The efficacy of introducing the self-healing system at the facesheet-core interface is evaluated through four-point bend and edgewise compression testing of representative foam core sandwich composite specimens with impact induced damage. The self-healing interfacial layer partially restored the specific initial stiffness, doubling the residual initial stiffness as compared to the control specimen after the impact event. The restoration of the ultimate specific skin strength was less successful. The results also highlight the critical challenge in self-healing of sandwich composites, which is to rebond facesheets which have separated from the core material.

  17. Light-Switchable Self-Healing Hydrogel Based on Host-Guest Macro-Crosslinking.

    PubMed

    Yang, Qiaofeng; Wang, Ping; Zhao, Chuanzhuang; Wang, Wenqin; Yang, Jingfa; Liu, Qiao

    2017-03-01

    A self-healing hydrogel is prepared by crosslinking acrylamide with a host-guest macro-crosslinker assembled from poly(β-cyclodextrin) nanogel and azobenzeneacrylamide. The photoisomerizable azobenzene moiety can change its binding affinity with β-cyclodextrin, therefore the crosslinking density and rheology property of the hydrogel can be tuned with light stimulus. The hydrogel can repair its wound autonomously through the dynamic host-guest interaction. In addition, the wounded hydrogel will lose its ability of self-healing when exposed to ultraviolet light, and the self-healing behavior can be recovered upon the irradiation of visible light. The utilizing of host-guest macro-crosslinking approach manifests the as-prepared hydrogel reversible and light-switchable self-healing property, which would broaden the potential applications of self-healing polymers.

  18. Self reinforcing polymer composites

    SciTech Connect

    Kenig, S.

    1993-12-31

    In the advent of liquid crystalline polymers (LCPs), self reinforcing polymer composites comprising a polymer matrix and an LCP reinforcement, have become a reality. The so called self reinforcement is due to the LCPs orientability characteristics resulting from their rigid molecular backbone and anisotropy structure in the fluid state. Orientation development takes place during melt processing of the LCP composite blends where shear as well as elongational flows occur prior to consolidation to the solid state. By proper flow control anisotropy develops and in-situ composites are obtained. Polymer composites comprising self-reinforcement by LCPs during processing induced flow, were analyzed and studied with respect to their orientation development and resultant mechanical properties. The analysis commenced with the hydrodynamics of immiscible fluids in shear and elongational flows. Based on the analysis, orientation and morphology development in capillary extrusion was studied, using a variety of thermoplastic polymer matrices like amorphous and crystalline polyamides, polycarbonate and polyester in conjunction of a naphthalene based thermotropic LCP. Based on the flow-morphology relationship the amorphous polyamide/LCP composite was further investigated as it exhibited enhanced properties. Laminated composites based on LCP/amorphous polyamide were developed composed of unidirectional extruded and drawn sheets that were subsequently compression molded. Unidirectional, +45/{minus}45 and quasi-isotropic laminates were prepared and analyzed as to their microstructure and mechanical properties.

  19. Healable thermoset polymer composite embedded with stimuli-responsive fibres

    PubMed Central

    Li, Guoqiang; Meng, Harper; Hu, Jinlian

    2012-01-01

    Severe wounds in biological systems such as human skin cannot heal themselves, unless they are first stitched together. Healing of macroscopic damage in thermoset polymer composites faces a similar challenge. Stimuli-responsive shape-changing polymeric fibres with outstanding mechanical properties embedded in polymers may be able to close macro-cracks automatically upon stimulation such as heating. Here, a stimuli-responsive fibre (SRF) with outstanding mechanical properties and supercontraction capability was fabricated for the purpose of healing macroscopic damage. The SRFs and thermoplastic particles (TPs) were incorporated into regular thermosetting epoxy for repeatedly healing macroscopic damages. The system works by mimicking self-healing of biological systems such as human skin, close (stitch) then heal, i.e. close the macroscopic crack through the thermal-induced supercontraction of the SRFs, and bond the closed crack through melting and diffusing of TPs at the crack interface. The healing efficiency determined using tapered double-cantilever beam specimens was 94 per cent. The self-healing process was reasonably repeatable. PMID:22896563

  20. Healable thermoset polymer composite embedded with stimuli-responsive fibres.

    PubMed

    Li, Guoqiang; Meng, Harper; Hu, Jinlian

    2012-12-07

    Severe wounds in biological systems such as human skin cannot heal themselves, unless they are first stitched together. Healing of macroscopic damage in thermoset polymer composites faces a similar challenge. Stimuli-responsive shape-changing polymeric fibres with outstanding mechanical properties embedded in polymers may be able to close macro-cracks automatically upon stimulation such as heating. Here, a stimuli-responsive fibre (SRF) with outstanding mechanical properties and supercontraction capability was fabricated for the purpose of healing macroscopic damage. The SRFs and thermoplastic particles (TPs) were incorporated into regular thermosetting epoxy for repeatedly healing macroscopic damages. The system works by mimicking self-healing of biological systems such as human skin, close (stitch) then heal, i.e. close the macroscopic crack through the thermal-induced supercontraction of the SRFs, and bond the closed crack through melting and diffusing of TPs at the crack interface. The healing efficiency determined using tapered double-cantilever beam specimens was 94 per cent. The self-healing process was reasonably repeatable.

  1. Self-healing gelatin ionogels.

    PubMed

    Sharma, Anshu; Rawat, Kamla; Solanki, Pratima R; Bohidar, H B

    2017-02-01

    We demonstrate room temperature (20°C) self-healing, and substantial recovery (68-96%) of gel rigidity of gelatin, a polypeptide, ionogels (made in 1-ethyl-3-methylimidazolium chloride ionic liquid (IL) solutions via thermal treatment, IL≤5% (w/v)) after they were cut using a surgical blade. The recovery process did not require any stimuli, and the complete healing under ambient condition required about 10h.The self-healing owed its origin to the reformation of network structures via imidazolium ion mediated charge quenching of deprotonated residues, and hydrophobic interaction between neighbouring alkyl tails of IL molecules. The rate of healing determined from the growth of rigidity modulus was 20±5 mPa/s independent of ionic liquid content of the gel. This was true regardless of the fact that ionogels containing more IL had a lower gel modulus due to propensity of hydrophobic linkages, but these were agile enough to recover their network structures to a higher degree during the healing process. These features indicate that the gelatin ionogel being biocompatibile, and biodegradable holds great potential for applications in the field of biomedical engineering. Copyright © 2016 Elsevier B.V. All rights reserved.

  2. Bioinspired Self-Healing Materials

    NASA Astrophysics Data System (ADS)

    Aksay, Ilhan

    2005-03-01

    Synthetic materials are designed to satisfy only one or two functions, but biologically produced ones are multifunctional and have properties (e.g., self-replicating, self-healing) that have yet to be introduced into man-made materials. The objective of this lecture will be to provide an understanding of the important processes for controlling materials properties through nano- and microstructural design and processing with the goal of attaining multifunctionality. A case study will be on the possibility of producing structural materials with self-healing characteristics. In an effort to mimic self-repair functions of living systems, we have been working with self-assembling complex fluids that respond to fields generated by the defects and deposit materials at the site of the defect. Presently, the techniques are limited to certain materials systems as coatings or thin films. We partially mimic the process of blood clotting as a process of colloidal aggregation at a defect site. We show that under the influence of an electrical field, colloidal particles detect a defect and aggregate at the defect site to form a protective layer. The basis of this process is the electrohdrodynamic flow generated by the inhomogeneities. We then make this a permanent protective layer through the electrodeposition of a metal binder in the interstitials of the colloidal aggregate.

  3. Biomimetic, Self-Healing Nanocomposites for Aerospace Applications

    NASA Technical Reports Server (NTRS)

    Morse, Daniel E.

    2003-01-01

    This final report contains a summary of significant findings, and bibliographies of publications and patents resulting from the research. The findings are grouped as follows: A) Lustrin-Mimetic Self-Healing Polymer Networks; B) Nanostructure-Directing Catalysis of Synthesis of Electronically and Optoelectronically Active Metallo-oxanes and Organometallics; C) New Discovery that Molecular Stencils Control Directional Growth to Form Light-Weight Mineral Foams.

  4. Self-healing cable for extreme environments

    NASA Technical Reports Server (NTRS)

    Huston, Dryver R. (Inventor); Tolmie, Bernard R. (Inventor)

    2009-01-01

    Self-healing cable apparatus and methods disclosed. The self-healing cable has a central core surrounded by an adaptive cover that can extend over the entire length of the self-healing cable or just one or more portions of the self-healing cable. The adaptive cover includes an axially and/or radially compressible-expandable (C/E) foam layer that maintains its properties over a wide range of environmental conditions. A tape layer surrounds the C/E layer and is applied so that it surrounds and axially and/or radially compresses the C/E layer. When the self-healing cable is subjected to a damaging force that causes a breach in the outer jacket and the tape layer, the corresponding localized axially and/or radially compressed portion of the C/E foam layer expands into the breach to form a corresponding localized self-healed region. The self-healing cable is manufacturable with present-day commercial self-healing cable manufacturing tools.

  5. Lightweight polymer concrete composites

    SciTech Connect

    Fontana, J.J.; Steinberg, M.; Reams, W.

    1985-08-01

    Lightweight polymer concrete composites have been developed with excellent insulating properties. The composites consist of lightweight aggregates such as expanded perlites, multicellular glass nodules, or hollow alumina silicate microspheres bound together with unsaturated polyester or epoxy resins. These composites, known as Insulating Polymer Concrete (IPC), have thermal conductivites from 0.09 to 0.19 Btu/h-ft-/sup 0/F. Compressive strengths, dependent upon the aggregates used, range from 1000 to 6000 psi. These materials can be precast or cast-in-place on concrete substrates. Recently, it has been demonstrated that these materials can also be sprayed onto concrete and other substrates. An overlay application of IPC is currently under way as dike insulation at an LNG storage tank facility. The composites have numerous potentials in the construction industry such as insulating building blocks or prefabricated insulating wall panels.

  6. Tribology of polymer composites

    SciTech Connect

    Friedrich, K.

    1993-12-31

    Polymer composites are more and more used as structural components which are very often subjected to friction and wear loadings under use. This overview describes the following cases: (1) short fiber/thermoplastic matrix composites and their friction and wear properties as a function of both microstructural composition and external testing conditions. Special attention is focused on the effects of different polymer matrices, fiber reinforcements, and additional internal lubricants on the coefficient of friction and the specific wear rate of these materials when sliding against hard steel counterparts. Further effects on these tribological properties due to changes in testing temperature, sliding speed and contact pressure are outlined; (2) results of sliding wear experiments with continuous glass, carbon or aramid fiber/polymer matrix composites against steel counterparts. They were used to develop a hypothetical model composite with optimum wear resistance. This was achieved for hybrids with carbon fibers parallel and aramid fibers normal to the sliding direction of the counterpart; and (3) the friction and wear performance of thin layer composites strengthened with steel backeners to sustain very high pressure loadings during sliding wear.

  7. TiO2 nanotubes and mesoporous silica as containers in self-healing epoxy coatings

    PubMed Central

    Vijayan P., Poornima; Al-Maadeed, Mariam Ali S. A.

    2016-01-01

    The potential of inorganic nanomaterials as reservoirs for healing agents is presented here. Mesoporous silica (SBA-15) and TiO2 nanotubes (TNTs) were synthesized. Both epoxy-encapsulated TiO2 nanotubes and amine-immobilized mesoporous silica were incorporated into epoxy and subsequently coated on a carbon steel substrate. The encapsulated TiO2 nanotubes was quantitatively estimated using a ‘dead pore ratio’ calculation. The morphology of the composite coating was studied in detail using transmission electron microscopic (TEM) analysis. The self-healing ability of the coating was monitored using electrochemical impedance spectroscopy (EIS); the coating recovered 57% of its anticorrosive property in 5 days. The self-healing of the scratch on the coating was monitored using Scanning Electron Microscopy (SEM). The results confirmed that the epoxy pre-polymer was slowly released into the crack. The released epoxy pre-polymer came into contact with the amine immobilized in mesoporous silica and cross-linked to heal the scratch. PMID:27941829

  8. TiO2 nanotubes and mesoporous silica as containers in self-healing epoxy coatings

    NASA Astrophysics Data System (ADS)

    Vijayan P., Poornima; Al-Maadeed, Mariam Ali S. A.

    2016-12-01

    The potential of inorganic nanomaterials as reservoirs for healing agents is presented here. Mesoporous silica (SBA-15) and TiO2 nanotubes (TNTs) were synthesized. Both epoxy-encapsulated TiO2 nanotubes and amine-immobilized mesoporous silica were incorporated into epoxy and subsequently coated on a carbon steel substrate. The encapsulated TiO2 nanotubes was quantitatively estimated using a ‘dead pore ratio’ calculation. The morphology of the composite coating was studied in detail using transmission electron microscopic (TEM) analysis. The self-healing ability of the coating was monitored using electrochemical impedance spectroscopy (EIS); the coating recovered 57% of its anticorrosive property in 5 days. The self-healing of the scratch on the coating was monitored using Scanning Electron Microscopy (SEM). The results confirmed that the epoxy pre-polymer was slowly released into the crack. The released epoxy pre-polymer came into contact with the amine immobilized in mesoporous silica and cross-linked to heal the scratch.

  9. Precursor polymer compositions comprising polybenzimidazole

    DOEpatents

    Klaehn, John R.; Peterson, Eric S.; Orme, Christopher J.

    2015-07-14

    Stable, high performance polymer compositions including polybenzimidazole (PBI) and a melamine-formaldehyde polymer, such as methylated, poly(melamine-co-formaldehyde), for forming structures such as films, fibers and bulky structures. The polymer compositions may be formed by combining polybenzimidazole with the melamine-formaldehyde polymer to form a precursor. The polybenzimidazole may be reacted and/or intertwined with the melamine-formaldehyde polymer to form the polymer composition. For example, a stable, free-standing film having a thickness of, for example, between about 5 .mu.m and about 30 .mu.m may be formed from the polymer composition. Such films may be used as gas separation membranes and may be submerged into water for extended periods without crazing and cracking. The polymer composition may also be used as a coating on substrates, such as metal and ceramics, or may be used for spinning fibers. Precursors for forming such polymer compositions are also disclosed.

  10. Aerogel/polymer composite materials

    NASA Technical Reports Server (NTRS)

    Williams, Martha K. (Inventor); Smith, Trent M. (Inventor); Fesmire, James E. (Inventor); Roberson, Luke B. (Inventor); Clayton, LaNetra M. (Inventor)

    2010-01-01

    The invention provides new composite materials containing aerogels blended with thermoplastic polymer materials at a weight ratio of aerogel to thermoplastic polymer of less than 20:100. The composite materials have improved thermal insulation ability. The composite materials also have better flexibility and less brittleness at low temperatures than the parent thermoplastic polymer materials.

  11. Polymer/Carbon Nanotube Networks for Smart, Self-Repairing and Light-Weighted Nanocomposites

    DTIC Science & Technology

    2012-11-05

    was develop smart, strong, and light-weight polymer/carbon nanotube (CNT) composites which will sense tribologically induced damages and self-heal by...light-weight polymer/carbon nanotube (CNT) composites which will sense tribologically induced damages and self-heal by inhibiting such degradation...vol%). This might have been the reason, why we did not observe large difference in mechanical and tribological properties between virgin PS and PS/CNT

  12. Hydrogen-Bonding-Supported Self-Healing Antifogging Thin Films

    PubMed Central

    Zhang, Xiaojie; He, Junhui

    2015-01-01

    Inspired by the repair of DNA through efficient reformation of hydrogen bonds (H-bonds), herein we report a facile one-step approach to construction of self-healing antifogging thin films on the basis of partly cross-linked poly(vinyl alcohol)(PVA) and poly(acrylic acid)(PAA). By designing the molar ratio of hydroxyl groups to carboxyl groups, the cross-linked polymer thin films maintain abundant free hydroxyl groups to present excellent antifogging property, which is derived from the hydrophilicity and hygroscopicity of the thin films. The thin films showed smart intrinsic self-healing characteristics towards wounds caused by external forces, which is attributed to sufficient free hydroxyl groups at the scratched interfaces to reform H-bonds across the interfaces and a sufficient chain mobility that is indispensable for chain diffusion across the interfaces and hydroxyl groups association to form H-bonds. No synthetic surfaces reported so far possess all the unique characteristics of the polymer thin films: intrinsic self-healing, long-term antifogging, excellent mechanical property, high transmittance and large-scale feasibility. PMID:25784188

  13. Hydrogen-Bonding-Supported Self-Healing Antifogging Thin Films

    NASA Astrophysics Data System (ADS)

    Zhang, Xiaojie; He, Junhui

    2015-03-01

    Inspired by the repair of DNA through efficient reformation of hydrogen bonds (H-bonds), herein we report a facile one-step approach to construction of self-healing antifogging thin films on the basis of partly cross-linked poly(vinyl alcohol)(PVA) and poly(acrylic acid)(PAA). By designing the molar ratio of hydroxyl groups to carboxyl groups, the cross-linked polymer thin films maintain abundant free hydroxyl groups to present excellent antifogging property, which is derived from the hydrophilicity and hygroscopicity of the thin films. The thin films showed smart intrinsic self-healing characteristics towards wounds caused by external forces, which is attributed to sufficient free hydroxyl groups at the scratched interfaces to reform H-bonds across the interfaces and a sufficient chain mobility that is indispensable for chain diffusion across the interfaces and hydroxyl groups association to form H-bonds. No synthetic surfaces reported so far possess all the unique characteristics of the polymer thin films: intrinsic self-healing, long-term antifogging, excellent mechanical property, high transmittance and large-scale feasibility.

  14. Hydrogen-bonding-supported self-healing antifogging thin films.

    PubMed

    Zhang, Xiaojie; He, Junhui

    2015-03-18

    Inspired by the repair of DNA through efficient reformation of hydrogen bonds (H-bonds), herein we report a facile one-step approach to construction of self-healing antifogging thin films on the basis of partly cross-linked poly(vinyl alcohol)(PVA) and poly(acrylic acid)(PAA). By designing the molar ratio of hydroxyl groups to carboxyl groups, the cross-linked polymer thin films maintain abundant free hydroxyl groups to present excellent antifogging property, which is derived from the hydrophilicity and hygroscopicity of the thin films. The thin films showed smart intrinsic self-healing characteristics towards wounds caused by external forces, which is attributed to sufficient free hydroxyl groups at the scratched interfaces to reform H-bonds across the interfaces and a sufficient chain mobility that is indispensable for chain diffusion across the interfaces and hydroxyl groups association to form H-bonds. No synthetic surfaces reported so far possess all the unique characteristics of the polymer thin films: intrinsic self-healing, long-term antifogging, excellent mechanical property, high transmittance and large-scale feasibility.

  15. Self Healing in Concrete Materials

    NASA Astrophysics Data System (ADS)

    Li, Victor C.; Yang, En-Hua

    The phenomenon of self healing in concrete has been known for many years. It has been observed that some cracks in old concrete structures are lined with white crystalline material suggesting the ability of concrete to self-seal the cracks with chemical products by itself, perhaps with the aid of rainwater and carbon dioxide in air. Later, a number of researchers [1, 2] in the study of water flow through cracked concrete under a hydraulic gradient, noted a gradual reduction of permeability over time, again suggesting the ability of the cracked concrete to self-seal itself and slow the rate of water flow. The main cause of self-sealing was attributed to the formation of calcium carbonate, a result of reaction between unhydrated cement and carbon dioxide dissolved in water [1]. Thus, under limited conditions, the phenomenon of self-sealing in concrete is well established. Self-sealing is important to watertight structures and to prolonging service life of infrastructure.

  16. Self-healing at the nanoscale

    NASA Astrophysics Data System (ADS)

    Amendola, Vincenzo; Meneghetti, Moreno

    2009-09-01

    The design of self-healing materials is a very important but challenging topic in nanotechnology. Self-healing strategies, also inspired by natural processes, allow the fabrication of auto-repairing systems, and in recent years, materials engineering at the nanoscale has allowed further advances in this emerging field. In this mini review, we recall some interesting self-healing systems found in natural processes and others created by man-made activity with special emphasis on the role played in this field by nanostructures. Finally, the self-healing of gold nanoparticles during laser irradiation is considered in more detail since it is a rare example of a functional nanomaterial with self-repairing properties.

  17. Self-healing cable apparatus and methods

    NASA Technical Reports Server (NTRS)

    Huston, Dryver (Inventor); Esser, Brian (Inventor)

    2007-01-01

    Self-healing cable apparatus and methods are disclosed. The cable has a central core surrounded by an adaptive cover that can extend over the entire length of the cable or just one or more portions of the cable. The adaptive cover includes a protective layer having an initial damage resistance, and a reactive layer. When the cable is subjected to a localized damaging force, the reactive layer responds by creating a corresponding localized self-healed region. The self-healed region provides the cable with enhanced damage resistance as compared to the cable's initial damage resistance. Embodiments of the invention utilize conventional epoxies or foaming materials in the reactive layer that are released to form the self-healed region when the damaging force reaches the reactive layer.

  18. Self-healing catalysis in water.

    PubMed

    Costentin, Cyrille; Nocera, Daniel G

    2017-09-05

    Principles for designing self-healing water-splitting catalysts are presented together with a formal kinetics model to account for the key chemical steps needed for self-healing. Self-healing may be realized if the catalysts are able to self-assemble at applied potentials less than that needed for catalyst turnover. Solution pH provides a convenient handle for controlling the potential of these two processes, as demonstrated for the cobalt phosphate (CoPi) water-splitting catalyst. For Co(2+) ion that appears in solution due to leaching from the catalyst during turnover, a quantitative description for the kinetics of the redeposition of the ion during the self-healing process has been derived. The model reveals that OER activity of CoPi occurs with negligible film dissolution in neutral pH for typical cell geometries and buffer concentrations.

  19. Self-healing at the nanoscale.

    PubMed

    Amendola, Vincenzo; Meneghetti, Moreno

    2009-10-01

    The design of self-healing materials is a very important but challenging topic in nanotechnology. Self-healing strategies, also inspired by natural processes, allow the fabrication of auto-repairing systems, and in recent years, materials engineering at the nanoscale has allowed further advances in this emerging field. In this mini review, we recall some interesting self-healing systems found in natural processes and others created by man-made activity with special emphasis on the role played in this field by nanostructures. Finally, the self-healing of gold nanoparticles during laser irradiation is considered in more detail since it is a rare example of a functional nanomaterial with self-repairing properties.

  20. 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

  1. Polyfibroblast: A Self-Healing and Galvanic Protection Additive

    DTIC Science & Technology

    2011-09-27

    TESTING 8 3.5 ADHESION OF SPRAY COATINGS WITH MICROCAPSULES 8 3.6 CONTROLLING METAL COMPOSITION 9 3.7 SHEAR STRESS TESTING 9 Polyfibroblast...observed self-healing in real time using electrochemical impedance spectroscopy, we now show through this same technique the importance of the microcapsules ...OTS rich microcapsules have an improved shelf-life in comparison to polyurethane resin-filled microcapsules . Salt spray measurements, now completed

  2. A highly stretchable autonomous self-healing elastomer

    NASA Astrophysics Data System (ADS)

    Li, Cheng-Hui; Wang, Chao; Keplinger, Christoph; Zuo, Jing-Lin; Jin, Lihua; Sun, Yang; Zheng, Peng; Cao, Yi; Lissel, Franziska; Linder, Christian; You, Xiao-Zeng; Bao, Zhenan

    2016-06-01

    It is a challenge to synthesize materials that possess the properties of biological muscles—strong, elastic and capable of self-healing. Herein we report a network of poly(dimethylsiloxane) polymer chains crosslinked by coordination complexes that combines high stretchability, high dielectric strength, autonomous self-healing and mechanical actuation. The healing process can take place at a temperature as low as -20 °C and is not significantly affected by surface ageing and moisture. The crosslinking complexes used consist of 2,6-pyridinedicarboxamide ligands that coordinate to Fe(III) centres through three different interactions: a strong pyridyl-iron one, and two weaker carboxamido-iron ones through both the nitrogen and oxygen atoms of the carboxamide groups. As a result, the iron-ligand bonds can readily break and re-form while the iron centres still remain attached to the ligands through the stronger interaction with the pyridyl ring, which enables reversible unfolding and refolding of the chains. We hypothesize that this behaviour supports the high stretchability and self-healing capability of the material.

  3. A highly stretchable autonomous self-healing elastomer.

    PubMed

    Li, Cheng-Hui; Wang, Chao; Keplinger, Christoph; Zuo, Jing-Lin; Jin, Lihua; Sun, Yang; Zheng, Peng; Cao, Yi; Lissel, Franziska; Linder, Christian; You, Xiao-Zeng; Bao, Zhenan

    2016-06-01

    It is a challenge to synthesize materials that possess the properties of biological muscles-strong, elastic and capable of self-healing. Herein we report a network of poly(dimethylsiloxane) polymer chains crosslinked by coordination complexes that combines high stretchability, high dielectric strength, autonomous self-healing and mechanical actuation. The healing process can take place at a temperature as low as -20 °C and is not significantly affected by surface ageing and moisture. The crosslinking complexes used consist of 2,6-pyridinedicarboxamide ligands that coordinate to Fe(III) centres through three different interactions: a strong pyridyl-iron one, and two weaker carboxamido-iron ones through both the nitrogen and oxygen atoms of the carboxamide groups. As a result, the iron-ligand bonds can readily break and re-form while the iron centres still remain attached to the ligands through the stronger interaction with the pyridyl ring, which enables reversible unfolding and refolding of the chains. We hypothesize that this behaviour supports the high stretchability and self-healing capability of the material.

  4. Composite solid polymer electrolyte membranes

    DOEpatents

    Formato, Richard M.; Kovar, Robert F.; Osenar, Paul; Landrau, Nelson; Rubin, Leslie S.

    2006-05-30

    The present invention relates to composite solid polymer electrolyte membranes (SPEMs) which include a porous polymer substrate interpenetrated with an ion-conducting material. SPEMs of the present invention are useful in electrochemical applications, including fuel cells and electrodialysis.

  5. Composite solid polymer electrolyte membranes

    DOEpatents

    Formato, Richard M.; Kovar, Robert F.; Osenar, Paul; Landrau, Nelson; Rubin, Leslie S.

    2001-06-19

    The present invention relates to composite solid polymer electrolyte membranes (SPEMs) which include a porous polymer substrate interpenetrated with an ion-conducting material. SPEMs of the present invention are useful in electrochemical applications, including fuel cells and electrodialysis.

  6. Bio-Inspired Composite Interfaces: Controlling Hydrogel Mechanics via Polymer-Nanoparticle Coordination Bond Dynamics

    NASA Astrophysics Data System (ADS)

    Holten-Andersen, Niels

    2015-03-01

    In soft nanocomposite materials, the effective interaction between polymer molecules and inorganic nanoparticle surfaces plays a critical role in bulk mechanical properties. However, controlling these interfacial interactions remains a challenge. Inspired by the adhesive chemistry in mussel threads, we present a novel approach to control composite mechanics via polymer-particle interfacial dynamics; by incorporating iron oxide nanoparticles (Fe3O4 NPs) into a catechol-modified polymer network the resulting hydrogels are crosslinked via reversible coordination bonds at Fe3O4 NP surfaces thereby providing a dynamic gel network with robust self-healing properties. By studying the thermally activated composite network relaxation processes we have found that the polymer-NP binding energy can be controlled by engineering both the organic and inorganic side of the interface.

  7. Synthesis of a new hardener agent for self-healing epoxy resins

    NASA Astrophysics Data System (ADS)

    Raimondo, Marialuigia; Guadagno, Liberata; Naddeo, Carlo; Longo, Pasquale; Mariconda, Annaluisa; Agovino, Anna

    2014-05-01

    Actually, the development of smart composites capable of self-repair in aeronautical structures is still at the planning stage owing to complex issues to overcome. One of the critical points in the development of self-healing epoxy resin is related to the impossibility to employ primary amines as hardeners. In this paper, the synthesis of a new hardener for self-healing resins is shown together with applicability conditions/ranges.

  8. Self-Healing Nanocomposite Hydrogel with Well-Controlled Dynamic Mechanics

    NASA Astrophysics Data System (ADS)

    Li, Qiaochu; Mishra, Sumeet; Chen, Pangkuan; Tracy, Joseph; Holten-Andersen, Niels

    Network dynamics is a crucial factor that determines the macroscopic self-healing rate and efficiency in polymeric hydrogel materials, yet its controllability is seldom studied in most reported self-healing hydrogel systems. Inspired by mussel's adhesion chemistry, we developed a novel approach to assemble inorganic nanoparticles and catechol-decorated PEG polymer into a hydrogel network. When utilized as reversible polymer-particle crosslinks, catechol-metal coordination bonds yield a unique gel network with dynamic mechanics controlled directly by interfacial crosslink structure. Taking advantage of this structure-property relationship at polymer-particle interfaces, we next designed a hierarchically structured hybrid gel with two distinct relaxation timescales. By tuning the relative contribution of the two hierarchical relaxation modes, we are able to finely control the gel's dynamic mechanical behavior from a viscoelastic fluid to a stiff solid, yet preserving its fast self-healing property without the need for external stimuli.

  9. Enhancement of the self-healing ability in oxidation induced self-healing ceramic by modifying the healing agent

    NASA Astrophysics Data System (ADS)

    Nakao, Wataru; Abe, Shihomi

    2012-02-01

    The available temperature range of the self-healing induced by high temperature oxidation of SiC can be controlled by the particle size of the contained SiC particles. In this study, three types of alumina-SiC composites were prepared. The SiC particle sizes of the composites were 270, ˜30 nm, and less than 10 nm. The self-healing abilities were estimated by the strength recovery behavior at several temperatures. The use of nanometer-sized dispersed SiC particles as healing agent decreases the activation energy of the SiC oxidation obtained from the differential thermal analysis with several heating rates. This implies that smaller SiC particles can give rise to the oxidation at lower temperature. Moreover, the lowest temperature at which the cracked strength was completely recovered for 10 h was strongly affected by the SiC particle size. As the SiC particle size varied from 270 to ˜30 nm, the lowest temperature varied from 1300 to 950 °C. However, alumina composite containing SiC particles whose particle size is less than 10 nm cannot recover completely the cracked strength under every condition, because the space between crack walls cannot be filled with the formed oxide due to the small volume of SiC on the crack walls. Therefore, it was found that there is an optimal SiC particle size for endowing self-healing ability.

  10. Starch-filled polymer composites

    USDA-ARS?s Scientific Manuscript database

    This report describes the development of degradable polymer composites that can be made at room temperature without special equipments. The developed composites are made from ethyl cyanoacrylate and starch. The polymer composites produced by this procedure contain 60 wt% of starch with compressive s...

  11. Fire-safe polymers and polymer composites

    NASA Astrophysics Data System (ADS)

    Zhang, Huiqing

    The intrinsic relationships between polymer structure, composition and fire behavior have been explored to develop new fire-safe polymeric materials. Different experimental techniques, especially three milligram-scale methods---pyrolysis-combustion flow calorimetry (PCFC), simultaneous thermal analysis (STA) and pyrolysis GC/MS---have been combined to fully characterize the thermal decomposition and flammability of polymers and polymer composites. Thermal stability, mass loss rate, char yield and properties of decomposition volatiles were found to be the most important parameters in determining polymer flammability. Most polymers decompose by either an unzipping or a random chain scission mechanism with an endothermic decomposition of 100--900 J/g. Aromatic or heteroaromatic rings, conjugated double or triple bonds and heteroatoms such as halogens, N, O, S, P and Si are the basic structural units for fire-resistant polymers. The flammability of polymers can also be successfully estimated by combining pyrolysis GC/MS results or chemical structures with TGA results. The thermal decomposition and flammability of two groups of inherently fire-resistant polymers---poly(hydroxyamide) (PHA) and its derivatives, and bisphenol C (BPC II) polyarylates---have been systematically studied. PHA and most of its derivatives have extremely low heat release rates and very high char yields upon combustion. PHA and its halogen derivatives can completely cyclize into quasi-polybenzoxazole (PBO) structures at low temperatures. However, the methoxy and phosphate derivatives show a very different behavior during decomposition and combustion. Molecular modeling shows that the formation of an enol intermediate is the rate-determining step in the thermal cyclization of PHA. BPC II-polyarylate is another extremely flame-resistant polymer. It can be used as an efficient flame-retardant agent in copolymers and blends. From PCFC results, the total heat of combustion of these copolymers or blends

  12. Polymer Chemistry

    NASA Technical Reports Server (NTRS)

    Williams, Martha; Roberson, Luke; Caraccio, Anne

    2010-01-01

    This viewgraph presentation describes new technologies in polymer and material chemistry that benefits NASA programs and missions. The topics include: 1) What are Polymers?; 2) History of Polymer Chemistry; 3) Composites/Materials Development at KSC; 4) Why Wiring; 5) Next Generation Wiring Materials; 6) Wire System Materials and Integration; 7) Self-Healing Wire Repair; 8) Smart Wiring Summary; 9) Fire and Polymers; 10) Aerogel Technology; 11) Aerogel Composites; 12) Aerogels for Oil Remediation; 13) KSC's Solution; 14) Chemochromic Hydrogen Sensors; 15) STS-130 and 131 Operations; 16) HyperPigment; 17) Antimicrobial Materials; 18) Conductive Inks Formulations for Multiple Applications; and 19) Testing and Processing Equipment.

  13. Robust synthesis of epoxy resin-filled microcapsules for application to self-healing materials.

    PubMed

    Bolimowski, Patryk A; Bond, Ian P; Wass, Duncan F

    2016-02-28

    Mechanically and thermally robust microcapsules containing diglycidyl ether bisphenol A-based epoxy resin and a high-boiling-point organic solvent were synthesized in high yield using in situ polymerization of urea and formaldehyde in an oil-in-water emulsion. Microcapsules were characterized in terms of their size and size distribution, shell surface morphology and thermal resistance to the curing cycles of commercially used epoxy polymers. The size distribution of the capsules and characteristics such as shell thickness can be controlled by the specific parameters of microencapsulation, including concentrations of reagents, stirrer speed and sonication. Selected microcapsules, and separated core and shell materials, were analysed using thermogravimetric analysis and differential scanning calorimetry. It is demonstrated that capsules lose minimal 2.5 wt% at temperatures no higher than 120°C. These microcapsules can be applied to self-healing carbon fibre composite structural materials, with preliminary results showing promising performance.

  14. Electrostatic processing of polymers and polymer composites

    NASA Astrophysics Data System (ADS)

    Sanders, Elliot Howard

    2005-11-01

    Polymers are a broad class of molecules whose use in modern life is undeniable ranging from automobile parts to pharmaceuticals. One method applicable to polymer material production is known as electrostatic processing which includes electrospraying, used to produce films or microparticles, and electrospinning, which can be used to produce fibers or non-woven materials. Electrostatic processing typically results in products with droplet or fiber diameters on the micron or nanometer scale. We have sought to develop novel polymeric materials and composites using electrostatic processing. The end uses of these materials were diverse, and included controlled release of drugs, microencapsulation of proteins and enzymes, provision of molecular cues for directed cell growth, hydronium ion transport, and electrically conductive polymer and catalytically active composites. We have successfully demonstrated that electrostatic processing can be used to produce a wide variety of functionally active polymer based materials with significant commercial, medical, and scientific potential.

  15. Tough Self-Healing Elastomers by Molecular Enforced Integration of Covalent and Reversible Networks.

    PubMed

    Wu, Jinrong; Cai, Li-Heng; Weitz, David A

    2017-10-01

    Self-healing polymers crosslinked by solely reversible bonds are intrinsically weaker than common covalently crosslinked networks. Introducing covalent crosslinks into a reversible network would improve mechanical strength. It is challenging, however, to apply this concept to "dry" elastomers, largely because reversible crosslinks such as hydrogen bonds are often polar motifs, whereas covalent crosslinks are nonpolar motifs. These two types of bonds are intrinsically immiscible without cosolvents. Here, we design and fabricate a hybrid polymer network by crosslinking randomly branched polymers carrying motifs that can form both reversible hydrogen bonds and permanent covalent crosslinks. The randomly branched polymer links such two types of bonds and forces them to mix on the molecular level without cosolvents. This enables a hybrid "dry" elastomer that is very tough with fracture energy 13500 Jm(-2) comparable to that of natural rubber. Moreover, the elastomer can self-heal at room temperature with a recovered tensile strength 4 MPa, which is 30% of its original value, yet comparable to the pristine strength of existing self-healing polymers. The concept of forcing covalent and reversible bonds to mix at molecular scale to create a homogenous network is quite general and should enable development of tough, self-healing polymers of practical usage. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  16. Self-Healing Networks: Redundancy and Structure

    PubMed Central

    Quattrociocchi, Walter; Caldarelli, Guido; Scala, Antonio

    2014-01-01

    We introduce the concept of self-healing in the field of complex networks modelling; in particular, self-healing capabilities are implemented through distributed communication protocols that exploit redundant links to recover the connectivity of the system. We then analyze the effect of the level of redundancy on the resilience to multiple failures; in particular, we measure the fraction of nodes still served for increasing levels of network damages. Finally, we study the effects of redundancy under different connectivity patterns—from planar grids, to small-world, up to scale-free networks—on healing performances. Small-world topologies show that introducing some long-range connections in planar grids greatly enhances the resilience to multiple failures with performances comparable to the case of the most resilient (and least realistic) scale-free structures. Obvious applications of self-healing are in the important field of infrastructural networks like gas, power, water, oil distribution systems. PMID:24533065

  17. Self-healing networks: redundancy and structure.

    PubMed

    Quattrociocchi, Walter; Caldarelli, Guido; Scala, Antonio

    2014-01-01

    We introduce the concept of self-healing in the field of complex networks modelling; in particular, self-healing capabilities are implemented through distributed communication protocols that exploit redundant links to recover the connectivity of the system. We then analyze the effect of the level of redundancy on the resilience to multiple failures; in particular, we measure the fraction of nodes still served for increasing levels of network damages. Finally, we study the effects of redundancy under different connectivity patterns-from planar grids, to small-world, up to scale-free networks-on healing performances. Small-world topologies show that introducing some long-range connections in planar grids greatly enhances the resilience to multiple failures with performances comparable to the case of the most resilient (and least realistic) scale-free structures. Obvious applications of self-healing are in the important field of infrastructural networks like gas, power, water, oil distribution systems.

  18. Vacuum flash evaporated polymer composites

    DOEpatents

    Affinito, J.D.; Gross, M.E.

    1997-10-28

    A method for fabrication of polymer composite layers in a vacuum is disclosed. More specifically, the method of dissolving salts in a monomer solution, vacuum flash evaporating the solution, condensing the flash evaporated solution as a liquid film, and forming the condensed liquid film into a polymer composite layer on a substrate is disclosed.

  19. Vacuum flash evaporated polymer composites

    DOEpatents

    Affinito, John D.; Gross, Mark E.

    1997-01-01

    A method for fabrication of polymer composite layers in a vacuum is disclosed. More specifically, the method of dissolving salts in a monomer solution, vacuum flash evaporating the solution, condensing the flash evaporated solution as a liquid film, and forming the condensed liquid film into a polymer composite layer on a substrate is disclosed.

  20. Self-Healing Behavior of Ethylene-Based Ionomers

    NASA Technical Reports Server (NTRS)

    Kalista, Stephen J., Jr.; Ward, Thomas C.; Oyetunji, Zainab

    2004-01-01

    The self-healing behavior of poly(ethylene-co-methacrylic acid) (EMAA)-based ionomers holds tremendous potential for use in a wide variety of unique applications. However, to effectively utilize this self-healing behavior and to design novel materials which possess this ability, the mechanism by which they heal must first be understood ionomers are a class of polymers that can be described as copolymers containing less than 15 mol% ionic content whereby the bulk properties are governed by ionic interactions within the polymer. These ionic groups aggregate into discrete regions known as multiplets which overlap forming clusters that act as physical cross-links profoundly influencing the bulk physical properties. These clusters possess an order-disorder transition (T(sub i)) where the clustered regions may rearrange themselves given time and stimuli. Recognizing the strong influence of these ionic regions on other well understood ionomer properties, their role in self-heating behavior will be assessed. The self-healing behavior is observed following projectile puncture. It has been suggested that during impact energy is passed to the ionomer material, heating it to the melt state. After penetration, it is proposed that the ionic regions maintain their attractions and flow together patching the hole. Thus, the importance of this ionic character and is unique interaction must be established. This will be accomplished through examination of materials with varying ionic content and through the analysis of the T(sub i). The specific ionomer systems examined include a number of ethylene-based materials. Materials of varying ionic content, including the non-ionic base copolymers, will be examined by peel tests, projectile impact and DSC analysis. The information will also be compared with some basic data on LDPE material.

  1. Self-Healing Behavior of Ethylene-Based Ionomers

    NASA Technical Reports Server (NTRS)

    Kalista, Stephen J., Jr.; Ward, Thomas C.; Oyetunji, Zainab

    2004-01-01

    The self-healing behavior of poly(ethylene-co-methacrylic acid) (EMAA)-based ionomers holds tremendous potential for use in a wide variety of unique applications. However, to effectively utilize this self-healing behavior and to design novel materials which possess this ability, the mechanism by which they heal must first be understood ionomers are a class of polymers that can be described as copolymers containing less than 15 mol% ionic content whereby the bulk properties are governed by ionic interactions within the polymer. These ionic groups aggregate into discrete regions known as multiplets which overlap forming clusters that act as physical cross-links profoundly influencing the bulk physical properties. These clusters possess an order-disorder transition (T(sub i)) where the clustered regions may rearrange themselves given time and stimuli. Recognizing the strong influence of these ionic regions on other well understood ionomer properties, their role in self-heating behavior will be assessed. The self-healing behavior is observed following projectile puncture. It has been suggested that during impact energy is passed to the ionomer material, heating it to the melt state. After penetration, it is proposed that the ionic regions maintain their attractions and flow together patching the hole. Thus, the importance of this ionic character and is unique interaction must be established. This will be accomplished through examination of materials with varying ionic content and through the analysis of the T(sub i). The specific ionomer systems examined include a number of ethylene-based materials. Materials of varying ionic content, including the non-ionic base copolymers, will be examined by peel tests, projectile impact and DSC analysis. The information will also be compared with some basic data on LDPE material.

  2. Self-healing and Resilient Critical Infrastructures

    NASA Astrophysics Data System (ADS)

    Gustavsson, Rune; Ståhl, Björn

    The paper describes methods and tools addressing self-healing and resilience of critical infrastructures, specifically power and information networks. Our case study is based on challenges addressed in the ongoing EU project INTEGRAL aiming at integrating DES/RES in cell-based virtual utilities. We propose two experimental environments, EXP II and INSPECT to support a structured approach in identifying, implementing and monitoring suitable self-healing mechanisms entailing an increasing system resilience in our systems. Our approach is based on own results from earlier EU projects and selected approaches from other international projects such as NSF GENI in the US and EU efforts such as SmartGrids and ARECI.

  3. Development of self-healing coatings for corrosion protection on metallic structures

    NASA Astrophysics Data System (ADS)

    Stankiewicz, Alicja; Barker, Michael B.

    2016-08-01

    Inspired by biological systems, artificial self-healing materials are designed for repairing local damage caused by external factors. The rapidly expanding field of self-healing systems contains, among others, materials with well-defined surface properties. Undoubtedly, enhancing surface functionalisation, by applying smart coatings, enjoys an extensive interest. The self-healing ability is particularly essential property for corrosion protection strategies, especially when the use of one of the most effective corrosion systems, based on chromium(VI) compounds, is now banned by the current registration, evaluation, authorisation and restriction of chemicals legislation. Self-healing protective coatings are produced using macromolecular compounds, ceramics, metals and composites. Considering the wide range of available materials, the number of potential combinations seems to be unlimited. The self-healing action of such coatings is activated by appropriate stimuli: temperature changes, radiation, pH changes, pressure changes and mechanical action. In this paper, the research and practical implications of the various approaches to achieving self-healing functionality of protective coatings, as well as potential developments in this area, are explored.

  4. Multilayer Electroactive Polymer Composite Material

    NASA Technical Reports Server (NTRS)

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

    2011-01-01

    An electroactive material comprises multiple layers of electroactive composite with each layer having unique dielectric, electrical and mechanical properties that define an electromechanical operation thereof when affected by an external stimulus. For example, each layer can be (i) a 2-phase composite made from a polymer with polarizable moieties and an effective amount of carbon nanotubes incorporated in the polymer for a predetermined electromechanical operation, or (ii) a 3-phase composite having the elements of the 2-phase composite and further including a third component of micro-sized to nano-sized particles of an electroactive ceramic incorporated in the polymer matrix.

  5. Damage healing ability of a shape-memory-polymer-based particulate composite with small thermoplastic contents

    NASA Astrophysics Data System (ADS)

    Nji, Jones; Li, Guoqiang

    2012-02-01

    The purpose of this study is to investigate the potential of a shape-memory-polymer (SMP)-based particulate composite to heal structural-length scale damage with small thermoplastic additive contents through a close-then-heal (CTH) self-healing scheme that was introduced in a previous study (Li and Uppu 2010 Comput. Sci. Technol. 70 1419-27). The idea is to achieve reasonable healing efficiencies with minimal sacrifice in structural load capacity. By first closing cracks, the gap between two crack surfaces is narrowed and a lesser amount of thermoplastic particles is required to achieve healing. The particulate composite was fabricated by dispersing copolyester thermoplastic particles in a shape memory polymer matrix. It is found that, for small thermoplastic contents of less than 10%, the CTH scheme followed in this study heals structural-length scale damage in the SMP particulate composite to a meaningful extent and with less sacrifice of structural capacity.

  6. Self-healing elastomer system

    NASA Technical Reports Server (NTRS)

    Keller, Michael W. (Inventor); Sottos, Nancy R. (Inventor); White, Scott R. (Inventor)

    2009-01-01

    A composite material includes an elastomer matrix, a set of first capsules containing a polymerizer, and a set of second capsules containing a corresponding activator for the polymerizer. The polymerizer may be a polymerizer for an elastomer. The composite material may be prepared by combining a first set of capsules containing a polymerizer, a second set of capsules containing a corresponding activator for the polymerizer, and a matrix precursor, and then solidifying the matrix precursor to form an elastomeric matrix.

  7. High temperature polymer concrete compositions

    SciTech Connect

    Fontana, J.J.; Reams, W.

    1985-02-19

    This invention is concerned with a polymer concrete composition, which is a two-component composition useful with many bases including metal. Component A, the aggregate composition, is broadly composed of silica, silica flour, portland cement, and acrylamide, whereas Component B, which is primarily vinyl and acrylyl reactive monomers is a liquid system.

  8. Layered plasma polymer composite membranes

    DOEpatents

    Babcock, W.C.

    1994-10-11

    Layered plasma polymer composite fluid separation membranes are disclosed, which comprise alternating selective and permeable layers for a total of at least 2n layers, where n is [>=]2 and is the number of selective layers. 2 figs.

  9. Morphing Metal and Elastomer Bicontinuous Foams for Reversible Stiffness, Shape Memory, and Self-Healing Soft Machines.

    PubMed

    Van Meerbeek, Ilse M; Mac Murray, Benjamin C; Kim, Jae Woo; Robinson, Sanlin S; Zou, Perry X; Silberstein, Meredith N; Shepherd, Robert F

    2016-04-13

    A metal-elastomer-foam composite that varies in stiffness, that can change shape and store shape memory, that self-heals, and that welds into monolithic structures from smaller components is presented.

  10. Reusable self-healing hydrogels realized via in situ polymerization.

    PubMed

    Vivek, Balachandran; Prasad, Edamana

    2015-04-09

    In this work, a self-healing hydrogel has been prepared using in situ polymerization of acrylic acid and acrylamide in the presence of glycogen. The hydrogel was characterized using NMR, SEM, FT-IR, rheology, and dynamic light scattering (DLS) studies. The developed hydrogel exhibits self-healing properties at neutral pH, high swelling ability, high elasticity, and excellent mechanical strength. The hydrogel exhibits modulus values (G', G″) as high as 10(6) Pa and shows an exceptionally high degree of swelling ratio (∼3.5 × 10(3)). Further, the polymer based hydrogel adsorbs toxic metal ions (Cd(2+), Pb(2+), and Hg(2+)) and organic dyes (methylene blue and methyl orange) from contaminated water with remarkable efficiency (90-98%). The mechanistic analysis indicated the presence of pseudo-second-order reaction kinetics. The reusability of the hydrogel has been demonstrated by repeating the adsorption-desorption process over five cycles with identical results in the adsorption efficiency.

  11. 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.

  12. A self-healing dielectric elastomer actuator

    NASA Astrophysics Data System (ADS)

    Hunt, Stacy; McKay, Thomas G.; Anderson, Iain A.

    2014-03-01

    Dielectric elastomer actuators that can provide muscle-like actuation are unable to self-heal like real muscle tissue. This severely limits dielectric elastomer reliability and robustness. This paper describes a way to instill self-healing into the DE by using a two-phase dielectric consisting of an open-cell silicone sponge saturated with silicone oil. When the dielectric is breached, the oil is able to flow back into any void, re-establishing the dielectric structure. The sponge holds the oil in place and provides dimensional stability, while the oil ensures the integrity of the dielectric layer. The operation of this has been demonstrated in a prototype DE actuator that continued to function despite being perforated multiple times with a sharp object.

  13. Dextran-based self-healing hydrogels formed by reversible diels-alder reaction under physiological conditions.

    PubMed

    Wei, Zhao; Yang, Jian Hai; Du, Xiao Jing; Xu, Feng; Zrinyi, Miklos; Osada, Yoshihito; Li, Fei; Chen, Yong Mei

    2013-09-01

    A dextran-based self-healing hydrogel is prepared by reversible Diels-Alder reaction under physiological conditions. Cytocompatible fulvene-modified dextran as main polymer chains and dichloromaleic-acid-modified poly(ethylene glycol) as cross-linkers are used. Both macro- and microscopic observation as well as the rheological recovery test confirm the self-healing property of the dextran-l-poly(ethylene glycol) hydrogels ("l" means "linked-by"). In addition, scanning electrochemical microscopy is used to qualitatively and quantitatively in situ track the self-healing process of the hydrogel for the first time. It is found that the longitudinal depth of scratch on hydrogel surface almost completely healed at 37 °C after 7 h. This work represents a facile approach for fabrication of polysaccharide self-healing hydrogel, which can be potentially used in several biomedical fields.

  14. Self-Healing, Inflatable, Rigidizable Shelter

    NASA Technical Reports Server (NTRS)

    Haight, Andrea; Gosau, Jan-Michael; Dixit, Anshu; Gleeson, Dan

    2012-01-01

    An inflatable, rigidizable shelter system was developed based on Rigi dization on Command (ROC) technology incorporating not only the requ ired low-stowage volume and lightweight character achieved from an i nflatable/rigidizable system, but also a self-healing foam system inc orporated between the rigidizable layers of the final structure to m inimize the damage caused by any punctures to the structure.

  15. Processing and performance of self-healing materials

    NASA Astrophysics Data System (ADS)

    Tan, P. S.; Zhang, M. Q.; Bhattacharyya, D.

    2009-08-01

    Two self-healing methods were implemented into composite materials with self-healing capabilities, using hollow glass fibres (HGF) and microencapsulated epoxy resin with mercaptan as the hardener. For the HGF approach, two perpendicular layers of HGF were put into an E-glass/epoxy composite, and were filled with coloured epoxy resin and hardener. The HGF samples had a novel ball indentation test method done on them. The samples were analysed using micro-CT scanning, confocal microscopy and penetrant dye. Micro-CT and confocal microscopy produced limited success, but their viability was established. Penetrant dye images showed resin obstructing flow of dye through damage regions, suggesting infiltration of resin into cracks. Three-point bend tests showed that overall performance could be affected by the flaws arising from embedding HGF in the material. For the microcapsule approach, samples were prepared for novel double-torsion tests used to generate large cracks. The samples were compared with pure resin samples by analysing them using photoelastic imaging and scanning electron microscope (SEM) on crack surfaces. Photoelastic imaging established the consolidation of cracks while SEM showed a wide spread of microcapsules with their distribution being affected by gravity. Further double-torsion testing showed that healing recovered approximately 24% of material strength.

  16. Carbon nanotube-polymer composite actuators

    DOEpatents

    Gennett, Thomas; Raffaelle, Ryne P.; Landi, Brian J.; Heben, Michael J.

    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.

  17. Polymer and composite polymer slot waveguides

    NASA Astrophysics Data System (ADS)

    Hiltunen, Marianne; Fegadolli, William S.; Lira, Hugo L. R.; Vahimaa, Pasi; Hiltunen, Jussi; Aikio, Sanna; Almeida, Vilson R.; Karioja, Pentti

    2014-05-01

    A fully polymer slot Young interferometer operating at 633 nm wavelength was fabricated by using nanoimprint molding method. The phase response of the interference pattern was measured with several concentrations of glucose-water solutions, utilizing both TE and TM polarization states. The sensor was experimentally found to detect a bulk refractive index change of 6.4×10-6 RIU. Temperature dependency of silicon slot waveguide has been demonstrated to be reduced with composite slot waveguide structure. The slot filled with thermally stable polymer having negative thermo-optic coefficient showed nearly an athermal operation of silicon slot waveguide. Experimental results show that the slot waveguide geometry covered with Ormocomp has thermo-optical coefficient of 6 pm/K.

  18. Self-Healing Supramolecular Self-Assembled Hydrogels Based on Poly(L-glutamic acid).

    PubMed

    Li, Guifei; Wu, Jie; Wang, Bo; Yan, Shifeng; Zhang, Kunxi; Ding, Jianxun; Yin, Jingbo

    2015-11-09

    Self-healing polymeric hydrogels have the capability to recover their structures and functionalities upon injury, which are extremely attractive in emerging biomedical applications. This research reports a new kind of self-healing polypeptide hydrogels based on self-assembly between cholesterol (Chol)-modified triblock poly(L-glutamic acid)-block-poly(ethylene glycol)-block-poly(L-glutamic acid) ((PLGA-b-PEG-b-PLGA)-g-Chol) and β-cyclodextrin (β-CD)-modified poly(L-glutamic acid) (PLGA-g-β-CD). The hydrogel formation relied on the host and guest linkage between β-CD and Chol. This study demonstrates the influences of polymer concentration and β-CD/Chol molar ratio on viscoelastic behavior of the hydrogels. The results showed that storage modulus was highest at polymer concentration of 15% w/v and β-CD/Chol molar ratio of 1:1. The effect of the PLGA molecular weight in (PLGA-b-PEG-b-PLGA)-g-Chol on viscoelastic behavior, mechanical properties and in vitro degradation of the supramolecular hydrogels was also studied. The hydrogels showed outstanding self-healing capability and good cytocompatibility. The multilayer structure was constructed using hydrogels with self-healing ability. The developed hydrogels provide a fascinating glimpse for the applications in tissue engineering.

  19. The self-healing potential of triazole-pyridine-based metallopolymers.

    PubMed

    Sandmann, Benedict; Happ, Bobby; Kupfer, Stephan; Schacher, Felix H; Hager, Martin D; Schubert, Ulrich S

    2015-04-01

    The development of artificial self-healing materials represents an emerging and challenging field in material science. Inspired by nature-for instance by the self-healing of mussel byssus threads-metallopolymers gain more and more attention as attractive self-healing materials. These compounds are able to combine the properties of both polymers and metal-ligand interactions. A novel metallopolymer is developed consisting of attached bidentate triazole-pyridine (TRZ-py) ligands and a low glass transition temperature (T g ) lauryl methacrylate backbone. The polymer is cross-linked with different Fe(II) and Co(II) salts. The resulting materials exhibit promising self-healing performance within time intervals of 5.5 to 26.5 h at moderate temperatures of 50 to 100 °C. The materials are characterized by X-ray scattering (SAXS), UV-Vis spectroscopy, and light microscopy. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  20. Sunlight-induced self-healing of a microcapsule-type protective coating.

    PubMed

    Song, Young-Kyu; Jo, Ye-Hyun; Lim, Ye-Ji; Cho, Sung-Youl; Yu, Hwan-Chul; Ryu, Byung-Cheol; Lee, Sang-In; Chung, Chan-Moon

    2013-02-01

    Photopolymerization behavior of a methacryloxypropyl-terminated polydimethylsiloxane (MAT-PDMS) healing agent was investigated in the presence of benzoin isobutyl ether (BIE) photoinitiator by Fourier transform infrared (FT-IR) spectroscopy. MAT-PDMS and BIE were microencapsulated with urea-formaldehyde polymer. The surface and shell morphology of the microcapsules was investigated by scanning electron microscopy (SEM). Mean diameter and size distribution of the microcapsules could be controlled by agitation rate. A coating matrix formulation was prepared by sol-gel reaction of tetraethyl orthosilicate (TEOS) in the presence of a polysiloxane and by subsequent addition of an adhesion promoter. The formulation and microcapsules were mixed to give a self-healing coating formulation, which was then sprayed to surface of cellulose-fiber-reinforced-cement (CRC) board or mortar. Contact angle measurements showed that both the polymerized MAT-PDMS and the prepared coating matrix are hydrophobic, and the coating matrix has good wettability with MAT-PDMS. It was confirmed by optical microscopy and SEM that, when the self-healing coating is damaged, the healing agent is released from ruptured microcapsules and fills the damaged region. The self-healing coating was evaluated as protective coating for mortar, and it was demonstrated by water permeability and chloride ion penetration tests that our system has sunlight-induced self-healing capability. Our self-healing coating is the first example of capsule-type photoinduced self-healing system, and offers the advantages of catalyst-free, environmentally friendly, inexpensive, practical healing.

  1. Intelligent, Biodegradable, and Self-Healing Hydrogels Utilizing DNA Quadruplexes.

    PubMed

    Tanaka, Shizuma; Wakabayashi, Kenta; Fukushima, Kazuki; Yukami, Shinsuke; Maezawa, Ryuki; Takeda, Yuhei; Tatsumi, Kohei; Ohya, Yuichi; Kuzuya, Akinori

    2017-09-19

    A new class of hydrogels utilizing DNA (DNA quadruplex gel) has been constructed by directly and symmetrically coupling deoxynucleotide phosphoramidite monomers to the ends of polyethylene glycols (PEGs) in liquid phase, and using the resulting DNA-PEG-DNA triblock copolymers as macromonomers. Elongation of merely four deoxyguanosine residues on PEG, which produces typically ≈10 grams of desired DNA-PEG conjugates in one synthesis, resulted in intelligent and biodegradable hydrogels utilizing DNA quadruplex formation, which are responsive to various input signals such as Na(+) , K(+) , and complementary DNA strand. Gelation of DNA quadruplex gels takes place within a few seconds upon the addition of a trigger, enabling free formation just like Ca(+) -alginate hydrogels or possible application as an injectable polymer (IP) gel. The obtained hydrogels show good thermal stability and rheological properties, and even display self-healing ability. © 2017 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA.

  2. Polymer - Ceramic Composites.

    DTIC Science & Technology

    1988-04-01

    characteristic properties of our composite films are then compared with those of Piezel, a commercially available composite, manufactured by the Daikin Industry...S obtained on PIEZEL (composite of PZT and PVDF copolymer, supplied by Daikin Industries Limited of Japan) are also presented. 1% % .... . ,,, ,,,,~m

  3. Properties and self-healing behavior of oil absorbent microspheres modified cement

    NASA Astrophysics Data System (ADS)

    Wang, Chunyu; Bu, Yuhuan; Zhao, Letian

    2017-09-01

    This paper concerns the properties and self-healing behavior of cement composites modified by oil absorbent microspheres with fumed silica shell. These microspheres, prepared by Pickering polymerization, possessed excellent properties, such as uniform particle size, good hydrophilicity and fine thermal stability. Furthermore, the effect of these microspheres on the properties of cement slurry was studied. The results showed that these microspheres had good compatibility with cement slurry, except for a slight effect on the consistency of cement slurry and the compressive strength of cement stone. At last, we derived the mathematical formulation of valid sealing for microcracks in self-healing cement, and measured sealing pressure under different filling conditions. The self-healing cement would guarantee the health, safety and high efficiency in the process of oil and gas production.

  4. Polymer composites for thermoelectric applications.

    PubMed

    McGrail, Brendan T; Sehirlioglu, Alp; Pentzer, Emily

    2015-02-02

    This review covers recently reported polymer composites that show a thermoelectric (TE) effect and thus have potential application as thermoelectric generators and Peltier coolers. The growing need for CO2-minimizing energy sources and thermal management systems makes the development of new TE materials a key challenge for researchers across many fields, particularly in light of the scarcity or toxicity of traditional inorganic TE materials based on Te and Pb. Recent reports of composites with inorganic and organic additives in conjugated and insulating polymer matrices are covered, as well as the techniques needed to fully characterize their TE properties. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  5. 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.

  6. High temperature polymer matrix composites

    NASA Technical Reports Server (NTRS)

    Serafini, Tito T. (Editor)

    1987-01-01

    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.

  7. Polymer compositions and methods

    SciTech Connect

    Allen, Scott D.; Willkomm, Wayne R.

    2016-09-27

    The present invention encompasses polyurethane compositions comprising aliphatic polycarbonate chains. In one aspect, the present invention encompasses polyurethane foams, thermoplastics and elastomers derived from aliphatic polycarbonate polyols and polyisocyanates wherein the polyol chains contain a primary repeating unit having a structure: ##STR00001## In another aspect, the invention provides articles comprising the inventive foam and elastomer compositions as well as methods of making such compositions.

  8. High temperature polymer matrix composites

    NASA Technical Reports Server (NTRS)

    Meador, Michael A.

    1987-01-01

    With the increased emphasis on high performance aircraft the need for lightweight, thermal/oxidatively stable materials is growing. Because of their ease of fabrication, high specific strength, and ability to be tailored chemically to produce a variety of mechanical and physical properties, polymers and polymer matrix composites present themselves as attractive materials for a number of aeropropulsion applications. In the early 1970s researchers at the NASA Lewis Research Center developed a highly processable, thermally stable (600 F) polyimide, PMR-15. Since that time, PMR-15 has become commercially available and has found use in military aircraft, in particular, the F-404 engine for the Navy's F/A-18 strike fighter. The NASA Lewis'contributions to high temperature polymer matrix composite research will be discussed as well as current and future directions.

  9. Can a fractured caprock self-heal?

    NASA Astrophysics Data System (ADS)

    Elkhoury, Jean E.; Detwiler, Russell L.; Ameli, Pasha

    2015-05-01

    The ability of geologic seals to prevent leakage of fluids injected into the deep subsurface is critical for mitigating risks associated with greenhouse-gas sequestration and natural-gas production. Fractures caused by tectonic or injection-induced stresses create potential leakage pathways that may be further enhanced by mineral dissolution. We present results from reactive-flow experiments in fractured caprock (dolomitic anhydrite), where additional dissolution occurs in the rock matrix adjacent to the fracture surfaces. Preferential dissolution of anhydrite left a compacted layer of dolomite in the fractures. At lower flow rate, rock-fluid reactions proceeded to near equilibrium within the fracture with preferential flow paths persisting over the 6-month duration of the experiment and a negligible change in permeability. At higher flow rate, permeability decreased by a dramatic two orders of magnitude. This laboratory-scale observation of self-healing argues against the likelihood of runaway permeability growth in fractured porous caprock composed of minerals with different solubilities and reaction kinetics. However, scaling arguments suggest that at larger length scales this self-healing process may be offset by the formation of dissolution channels. Our results have relevance beyond the greenhouse-gas sequestration problem. Chemical disequilibrium at waste injection sites and in hydrothermal reservoirs will lead to reactive flows that may also significantly alter formation permeability.

  10. Hybridized polymer matrix composite

    NASA Technical Reports Server (NTRS)

    Stern, B. A.; Visser, T.

    1981-01-01

    Under certain conditions of combined fire and impact, graphite fibers are released to the atmosphere by graphite fiber composites. The retention of graphite fibers in these situations is investigated. Hybrid combinations of graphite tape and cloth, glass cloth, and resin additives are studied with resin systems. Polyimide resins form the most resistant composites and resins based on simple novolac epoxies the least resistant of those tested. Great improvement in the containment of the fibers is obtained in using graphite/glass hybrids, and nearly complete prevention of individual fiber release is made possible by the use of resin additives.

  11. High-temperature polymer matrix composites

    NASA Technical Reports Server (NTRS)

    Meador, Michael A.

    1990-01-01

    Polymers research at the NASA Lewis Research Center has produced high-temperature, easily processable resin systems, such as PMR-15. In addition, the Polymers Branch has investigated ways to improve the mechanical properties of polymers and the microcracking resistance of polymer matrix composites in response to industry need for new and improved aeropropulsion materials. Current and future research in the Polymers Branch is aimed at advancing the upper use temperature of polymer matrix composites to 700 F and beyond by developing new resins, by examining the use of fiber reinforcements other than graphite, and by developing coatings for polymer matrix composites to increase their oxidation resistance.

  12. Duplicating Dynamic Strain-Stiffening Behavior and Nanomechanics of Biological Tissues in a Synthetic Self-Healing Flexible Network Hydrogel.

    PubMed

    Yan, Bin; Huang, Jun; Han, Linbo; Gong, Lu; Li, Lin; Israelachvili, Jacob N; Zeng, Hongbo

    2017-10-02

    Biological tissues can accurately differentiate external mechanical stresses and actively select suitable strategies (e.g., reversible strain-stiffening, self-healing) to sustain or restore their integrity and related functionalities as required. Synthetic materials that can imitate the characteristics of biological tissues have a wide range of engineering and bioengineering applications. However, no success has been demonstrated to realize such strain-stiffening behavior in synthetic networks, particularly using flexible polymers, which has remained a great challenge. Here, we present one such synthetic hydrogel material prepared from two flexible polymers (polyethylene glycol and branched polyethylenimine) that exhibits both strain-stiffening and self-healing capabilities. The developed synthetic hydrogel network not only mimics the main features of biological mechanically responsive systems but also autonomously self-heals after becoming damaged, thereby recovering its full capacity to perform its normal physiological functions.

  13. High temperature polymer concrete compositions

    DOEpatents

    Fontana, Jack J.; Reams, Walter

    1985-01-01

    This invention is concerned with a polymer concrete composition, which is a two-component composition useful with many bases including metal. Component A, the aggregate composition, is broadly composed of silica, silica flour, portland cement, and acrylamide, whereas Component B, which is primarily vinyl and acrylyl reactive monomers, is a liquid system. A preferred formulation emphasizing the major necessary components is as follows: ______________________________________ Component A: Silica sand 60-77 wt. % Silica flour 5-10 wt. % Portland cement 15-25 wt. % Acrylamide 1-5 wt. % Component B: Styrene 50-60 wt. % Trimethylolpropane 35-40 wt. % trimethacrylate ______________________________________ and necessary initiators, accelerators, and surfactants.

  14. Hybridized polymer matrix composites

    NASA Technical Reports Server (NTRS)

    London, A.

    1981-01-01

    Design approaches and materials are described from which are fabricated pyrostatic graphite/epoxy (Gr/Ep) laminates that show improved retention of graphite particulates when subjected to burning. Sixteen hybridized plus two standard Gr/Ep laminates were designed, fabricated, and tested in an effort to eliminate the release of carbon (graphite) fiber particles from burned/burning, mechanically disturbed samples. The term pyrostatic is defined as meaning mechanically intact in the presence of fire. Graphite particulate retentive laminates were constructed whose constituent materials, cost of fabrication, and physical and mechanical properties were not significantly different from existing Gr/Ep composites. All but one laminate (a Celion graphite/bis-maleimide polyimide) were based on an off-the-shelf Gr/Ep, the AS-1/3501-5A system. Of the 16 candidates studied, four thin (10-ply) and four thick (50-ply) hybridized composites are recommended.

  15. Polymer film composite transducer

    DOEpatents

    Owen, Thomas E.

    2005-09-20

    A composite piezoelectric transducer, whose piezoeletric element is a "ribbon wound" film of piezolectric material. As the film is excited, it expands and contracts, which results in expansion and contraction of the diameter of the entire ribbon winding. This is accompanied by expansion and contraction of the thickness of the ribbon winding, such that the sound radiating plate may be placed on the side of the winding.

  16. Novel self-healing dental resin with microcapsules of polymerizable triethylene glycol dimethacrylate and N,N-dihydroxyethyl-p-toluidine.

    PubMed

    Wu, Junling; Weir, Michael D; Zhang, Qiang; Zhou, Chuanjian; Melo, Mary Anne S; Xu, Hockin H K

    2016-02-01

    Bulk fracture is one of the primary reasons for resin-based dental restoration failures. To date, there has been no report on the use of polymerizable dental monomers with acceptable biocompatibility to develop a resin with substantial self-healing capability. The objectives of this study were to: (1) develop a self-healing resin containing microcapsules with triethylene glycol dimethacrylate (TEGDMA)-N,N-dihydroxyethyl-p-toluidine (DHEPT) healing liquid in poly(urea-formaldehyde) (PUF) shells for the first time, and (2) determine the physical and mechanical properties, self-healing efficiency, and fibroblast cytotoxicity. Microcapsules of polymerizable TEGDMA-DHEPT in PUF were prepared via an in situ polymerization method. Microcapsules were added into a BisGMA-TEGDMA resin at microcapsule mass fractions of 0%, 5%, 10%, 15% and 20%. A flexural test was used to measure composite strength and elastic modulus. A single edge V-notched beam method was used to measure fracture toughness KIC and self-healing efficiency. Flexural strength and elastic modulus (mean±sd; n=6) of resin containing 5-15% microcapsules were similar to control without microcapsules (p>0.1). Adding microcapsules into the resin increased the virgin KIC, which was about 40% higher at 15% microcapsules than that with 0% microcapsules (p<0.05). Specimens were fractured and healed, then fractured again to measure the healed KIC. A self-healing efficiency of about 65% in KIC recovery was obtained with 10-20% microcapsules. All specimens with 0-20% microcapsules had fibroblast viability similar to control without resin eluents (p>0.1). Self-healing dental resin containing microcapsules with polymerizable TEGDMA-DHEPT healing liquid in PUF shells were prepared for the first time with excellent self-healing capability. These microcapsules and self-healing resins containing them may be promising for dental restorations to heal cracks/damage and increase durability. Copyright © 2015 Academy of Dental

  17. Hybridized polymer matrix composites

    NASA Technical Reports Server (NTRS)

    House, E. E.; Hoggatt, J. T.; Symonds, W. A.

    1980-01-01

    The extent to which graphite fibers are released from resin matrix composites that are exposed to fire and impact conditions was determined. Laboratory simulations of those conditions that could exist in the event of an aircraft crash and burn situation were evaluated. The effectiveness of various hybridizing concepts in preventing this release of graphite fibers were also evaluated. The baseline (i.e., unhybridized) laminates examined were prepared from commercially available graphite/epoxy, graphite/polyimide, and graphite/phenolic materials. Hybridizing concepts investigated included resin fillers, laminate coatings, resin blending, and mechanical interlocking of the graphite reinforcement. The baseline and hybridized laminates' mechanical properties, before and after isothermal and humidity aging, were also compared. It was found that a small amount of graphite fiber was released from the graphite/epoxy laminates during the burn and impact conditions used in this program. However, the extent to which the fibers were released is not considered a severe enough problem to preclude the use of graphite reinforced composites in civil aircraft structure. It also was found that several hybrid concepts eliminated this fiber release. Isothermal and humidity aging did not appear to alter the fiber release tendencies.

  18. Stretchable Self-Healing Polymeric Dielectrics Cross-Linked Through Metal-Ligand Coordination.

    PubMed

    Rao, Ying-Li; Chortos, Alex; Pfattner, Raphael; Lissel, Franziska; Chiu, Yu-Cheng; Feig, Vivian; Xu, Jie; Kurosawa, Tadanori; Gu, Xiaodan; Wang, Chao; He, Mingqian; Chung, Jong Won; Bao, Zhenan

    2016-05-11

    A self-healing dielectric elastomer is achieved by the incorporation of metal-ligand coordination as cross-linking sites in nonpolar polydimethylsiloxane (PDMS) polymers. The ligand is 2,2'-bipyridine-5,5'-dicarboxylic amide, while the metal salts investigated here are Fe(2+) and Zn(2+) with various counteranions. The kinetically labile coordination between Zn(2+) and bipyridine endows the polymer fast self-healing ability at ambient condition. When integrated into organic field-effect transistors (OFETs) as gate dielectrics, transistors with FeCl2 and ZnCl2 salts cross-linked PDMS exhibited increased dielectric constants compared to PDMS and demonstrated hysteresis-free transfer characteristics, owing to the low ion conductivity in PDMS and the strong columbic interaction between metal cations and the small Cl(-) anions which can prevent mobile anions drifting under gate bias. Fully stretchable transistors with FeCl2-PDMS dielectrics were fabricated and exhibited ideal transfer characteristics. The gate leakage current remained low even after 1000 cycles at 100% strain. The mechanical robustness and stable electrical performance proved its suitability for applications in stretchable electronics. On the other hand, transistors with gate dielectrics containing large-sized anions (BF4(-), ClO4(-), CF3SO3(-)) displayed prominent hysteresis due to mobile anions drifting under gate bias voltage. This work provides insights on future design of self-healing stretchable dielectric materials based on metal-ligand cross-linked polymers.

  19. Hybridized polymer matrix composites

    NASA Technical Reports Server (NTRS)

    Henshaw, J.

    1983-01-01

    Methods of improving the fire resistance of graphite epoxy composite laminates were investigated with the objective of reducing the volume of loose graphite fibers disseminated into the airstream as the result of a high intensity aircraft fuel fire. Improvements were sought by modifying the standard graphite epoxy systems without significantly negating their structural effectiveness. The modifications consisted primarily of an addition of a third constituent material such as glass fibers, glass flakes, carbon black in a glassy resin. These additions were designed to encourage coalescense of the graphite fibers and thereby reduce their aerodynamic float characteristics. A total of 38 fire tests were conducted on thin (1.0 mm) and thick (6.0 mm) hybrid panels.

  20. Assisted self-healing in ripped graphene

    SciTech Connect

    Blaeckberg, L.; Sjoestrand, H.; Klintenberg, M.; Ringbom, A.

    2010-11-15

    A monolayer of sp{sup 2}-bonded carbon (graphene) is a material with great technological promise because of, for example, its transport, electrical, optical, and mechanical properties. In this work noble gas diffusion through ripped graphene sheets is explored. The motivation is improved detection systems used worldwide to verify compliance of the Comprehensive Nuclear-Test-Ban Treaty. It is demonstrated that even ripped graphene sheets and/or nonoverlapping graphene flakes inhibit noble gas diffusion. The latter has been shown for He and Xe where an infinitely long rip was constructed to have Stone-Wales edges. It is also shown that the ripped graphene layer self-heal in an alternating pentagon, hexagon, heptagon (5-6-7) and 7-6-5 pattern perpendicular to the rip. Moreover, the noble gas (He and Xe) assists in the healing process of wider rips.

  1. Segmented molecular design of self-healing proteinaceous materials

    PubMed Central

    Sariola, Veikko; Pena-Francesch, Abdon; Jung, Huihun; Çetinkaya, Murat; Pacheco, Carlos; Sitti, Metin; Demirel, Melik C.

    2015-01-01

    Hierarchical assembly of self-healing adhesive proteins creates strong and robust structural and interfacial materials, but understanding of the molecular design and structure–property relationships of structural proteins remains unclear. Elucidating this relationship would allow rational design of next generation genetically engineered self-healing structural proteins. Here we report a general self-healing and -assembly strategy based on a multiphase recombinant protein based material. Segmented structure of the protein shows soft glycine- and tyrosine-rich segments with self-healing capability and hard beta-sheet segments. The soft segments are strongly plasticized by water, lowering the self-healing temperature close to body temperature. The hard segments self-assemble into nanoconfined domains to reinforce the material. The healing strength scales sublinearly with contact time, which associates with diffusion and wetting of autohesion. The finding suggests that recombinant structural proteins from heterologous expression have potential as strong and repairable engineering materials. PMID:26323335

  2. Segmented molecular design of self-healing proteinaceous materials.

    PubMed

    Sariola, Veikko; Pena-Francesch, Abdon; Jung, Huihun; Çetinkaya, Murat; Pacheco, Carlos; Sitti, Metin; Demirel, Melik C

    2015-09-01

    Hierarchical assembly of self-healing adhesive proteins creates strong and robust structural and interfacial materials, but understanding of the molecular design and structure-property relationships of structural proteins remains unclear. Elucidating this relationship would allow rational design of next generation genetically engineered self-healing structural proteins. Here we report a general self-healing and -assembly strategy based on a multiphase recombinant protein based material. Segmented structure of the protein shows soft glycine- and tyrosine-rich segments with self-healing capability and hard beta-sheet segments. The soft segments are strongly plasticized by water, lowering the self-healing temperature close to body temperature. The hard segments self-assemble into nanoconfined domains to reinforce the material. The healing strength scales sublinearly with contact time, which associates with diffusion and wetting of autohesion. The finding suggests that recombinant structural proteins from heterologous expression have potential as strong and repairable engineering materials.

  3. Segmented molecular design of self-healing proteinaceous materials

    NASA Astrophysics Data System (ADS)

    Sariola, Veikko; Pena-Francesch, Abdon; Jung, Huihun; Çetinkaya, Murat; Pacheco, Carlos; Sitti, Metin; Demirel, Melik C.

    2015-09-01

    Hierarchical assembly of self-healing adhesive proteins creates strong and robust structural and interfacial materials, but understanding of the molecular design and structure-property relationships of structural proteins remains unclear. Elucidating this relationship would allow rational design of next generation genetically engineered self-healing structural proteins. Here we report a general self-healing and -assembly strategy based on a multiphase recombinant protein based material. Segmented structure of the protein shows soft glycine- and tyrosine-rich segments with self-healing capability and hard beta-sheet segments. The soft segments are strongly plasticized by water, lowering the self-healing temperature close to body temperature. The hard segments self-assemble into nanoconfined domains to reinforce the material. The healing strength scales sublinearly with contact time, which associates with diffusion and wetting of autohesion. The finding suggests that recombinant structural proteins from heterologous expression have potential as strong and repairable engineering materials.

  4. Active self-healing encapsulation of vaccine antigens in PLGA microspheres

    PubMed Central

    Desai, Kashappa-Goud H.; Schwendeman, Steven P.

    2013-01-01

    Herein, we describe the detailed development of a simple and effective method to microencapsulate vaccine antigens in poly(lactic-co-glycolic acid) (PLGA) by simple mixing of preformed active self-microencapsulating (SM) PLGA microspheres in a low concentration aqueous antigen solution at modest temperature (10-38 °C). Co-encapsulating protein-sorbing vaccine adjuvants and polymer plasticizers were used to “actively” load the protein in the polymer pores and facilitate polymer self-healing at temperature > hydrated polymer glass transition temperature, respectively. The microsphere formulation parameters and loading conditions to provide optimal active self-healing microencapsulation of vaccine antigen in PLGA was investigated. Active self-healing encapsulation of two vaccine antigens, ovalbumin and tetanus toxoid (TT), in PLGA microspheres was adjusted by preparing blank microspheres containing different vaccine adjuvant (aluminum hydroxide (Al(OH)3) or calcium phosphate). Active loading of vaccine antigen in Al(OH)3-PLGA microspheres was found to: a) increase proportionally with an increasing loading of Al(OH)3 (0.88-3 wt%) and addition of porosigen, b) decrease when the inner Al(OH)3/trehalose phase to 1 mL outer oil phase and size of microspheres was respectively > 0.2 mL and 63 μm, and c) change negligibly by PLGA concentration and initial incubation (loading) temperature. Encapsulation of protein sorbing Al(OH)3 in PLGA microspheres resulted in suppression of self-healing of PLGA pores, which was then overcome by improving polymer chain mobility, which in turn was accomplished by coincorporating hydrophobic plasticizers in PLGA. Active self-healing microencapsulation of manufacturing process-labile TT in PLGA was found to: a) obviate micronization- and organic solvent-induced TT degradation, b) improve antigen loading (1.4-1.8 wt% TT) and encapsulation efficiency (~ 97%), c) provide nearly homogeneous distribution and stabilization of antigen in polymer

  5. Effect of link oriented self-healing on resilience of networks

    NASA Astrophysics Data System (ADS)

    Shang, Yilun

    2016-08-01

    Many real, complex systems, such as the human brain and skin with their biological networks or intelligent material systems consisting of composite functional liquids, exhibit a noticeable capability of self-healing. Here, we study a network model with arbitrary degree distributions possessing natural link oriented recovery mechanisms, whereby a failed link can be recovered if its two end nodes maintain a sufficient proportion of functional links. These mechanisms are pertinent for many spontaneous healing and manual repair phenomena, interpolating smoothly between complete healing and no healing scenarios. We show that the self-healing strategies have profound impact on resilience of homogeneous and heterogeneous networks employing a percolation threshold, fraction of giant cluster, and link robustness index. The self-healing effect induces distinct resilience characteristics for scale-free networks under random failures and intentional attacks, and a resilience crossover has been observed at certain level of self-healing. Our work highlights the significance of understanding the competition between healing and collapsing in the resilience of complex networks.

  6. Self-healing dynamic bond-based rubbers: understanding the mechanisms in ionomeric elastomer model systems.

    PubMed

    Hohlbein, N; Shaaban, A; Bras, A R; Pyckhout-Hintzen, W; Schmidt, A M

    2015-08-28

    While it is traditionally accepted that the chain interactions responsible for the elastic response in an elastomeric network are ideally permanent and instantaneously active, the ongoing investigation of self-healing materials reveals that the introduction of self-healing properties into elastomers requires high mechanical integrity under dynamic load conditions, while on long timescales (or at extended temperatures), the chain and bond dynamics must allow for an intrinsic repair of micro cracks occurring during operation and aging. Based on an acrylate-based amorphous ionomer model system with pendant carboxylate groups allowing the systematic variation of the composition and the nature of the counter ion, we demonstrate the interrelation between the morphological, thermal, and mechanical properties, and identify the prerequisites and tools for property adjustment and optimization of self-healing efficiency. While the ion fraction is directly related to the effective network density and elastic performance, the crossover frequency between viscous and elastic behavior is influenced by the nature of the counter ion. In order to achieve reliable elastic response and optimal damage repair, the ion fraction in these systems should be in the range of 5 mol% and the chain dynamics should be appropriate to allow for excellent self-healing behavior at moderate healing temperatures.

  7. Self-Healing Glassy Thin Coating for High-Temperature Applications.

    PubMed

    Castanié, Sandra; Carlier, Thibault; Méar, François O; Saitzek, Sébastien; Blach, Jean-François; Podor, Renaud; Montagne, Lionel

    2016-02-17

    Glass thin films (with nanometer to micrometer thicknesses) are promising in numerous applications, both as passive coatings and as active components. Self-healing is a feature of many current technological developments as a means of increasing the lifetime of materials. In the context of these developments, we report on the elaboration of the first self-healing glassy thin-film coating developed specifically for high-temperature applications. This coating is obtained by pulsed laser deposition of alternating layers of vanadium boride (VB) and a multicomponent oxide glass. Self-healing is obtained through the oxidation of VB at the operating temperature. The investigation of the effect of elaboration parameters on the coating composition and morphology made it possible to obtain up to seven-layer coatings, with good homogeneity and perfect interfaces, and with a total thickness of less than 1 μm. The autonomic self-healing capacity of the coating has been demonstrated by an in situ experiment, which shows that a crack of nanometric dimension can be healed within a few minutes at 700 °C.

  8. Composites incorporated a conductive polymer nanofiber network

    DOEpatents

    Pozzo, Lilo Danielle; Newbloom, Gregory

    2017-04-11

    Methods of forming composites that incorporate networks of conductive polymer nanofibers are provided. Networks of less-than conductive polymers are first formed and then doped with a chemical dopant to provide networks of conductive polymers. The networks of conductive polymers are then incorporated into a matrix in order to improve the conductivity of the matrix. The formed composites are useful as conductive coatings for applications including electromagnetic energy management on exterior surfaces of vehicles.

  9. An attempt to prepare nonchromate, self-healing protective films containing molybdate on iron

    SciTech Connect

    Aramaki, K.

    1999-11-01

    Preparation of a nonchromate, self-healing protective film on an Fe surface was attempted. A protective film of 1,2-bis(triethoxysilyl)ethane ([C{sub 2}H{sub 5}O]{sub 3} Si[CH{sub 2}]{sub 2} Si[OC{sub 2}H{sub 5}]{sub 3}) polymer containing a fine powder of ammonium heptamolybdate tetrahydrate ([NH{sub 4}]{sub 6}Mo{sub 7}O{sub 24} {center{underscore}dot} 4H{sub 2}O) was prepared on a surface of Fe electrode passivated in aerated 0.1-M sodium molybdate (Na{sub 2}MoO{sub 4}). The protective ability of this film was examined on the covered electrode in an aerated 0.1-M sodium chloride (NaCl) solution at 30 C by polarization measurement. The protection efficiency (P) of the film was significantly high, 99.0%. After the electrode coated with the film was scratched with a knife edge, the self-healing ability of the film was estimated on the electrode in the NaCl solution by polarization measurement. The P value of the film on the scratched electrode was still high, 98.8%. The anodic process of Fe corrosion markedly was suppressed by the formation of a passive film at the scratched surface with molybdate ion (MoO{sub 4}{sup {minus}}) incorporated in the polymer film, resulting in a self-healing activity of the film.

  10. Thermosetting epoxy resin/thermoplastic system with combined shape memory and self-healing properties

    NASA Astrophysics Data System (ADS)

    Yao, Yongtao; Wang, Jingjie; Lu, Haibao; Xu, Ben; Fu, Yongqing; Liu, Yanju; Leng, Jinsong

    2016-01-01

    A novel and facile strategy was proposed to construct a thermosetting/thermoplastic system with both shape memory and self-healing properties based on commercial epoxy resin and poly(ɛ-caprolactone)-PCL. Thermoplastic material is capable of re-structuring and changing the stiffness/modulus when the temperature is above melting temperature. PCL microfiber was used as a plasticizer in epoxy resin-based blends, and served as a ‘hard segment’ to fix a temporary shape of the composites during shape memory cycles. In this study, the electrospun PCL membrane with a porous network structure enabled a homogenous PCL fibrous distribution and optimized interaction between fiber and epoxy resin. The self-healing capability is achieved by phase transition during curing of the composites. The mechanism of the shape memory effect of the thermosetting (rubber)/thermoplastic composite is attributed to the structural design of the thermoplastic network inside the thermosetting resin/rubber matrix.

  11. Self-healing encapsulation strategy for preparing highly stable, functionalized quantum-dot barcodes.

    PubMed

    Song, Tao; Liu, Junqing; Li, Wenbin; Li, Yunhong; Yang, Qiuhua; Gong, Xiaoqun; Xuan, Lixue; Chang, Jin

    2014-02-26

    Quantum dot (QD) barcodes are becoming an urgent requirement for researchers and clinicians to obtain high-density information in multiplexed suspension (bead-based) assay. However, how to improve the stability of quantum dot barcodes is a longstanding issue. Here, we present a new self-healing encapsulation strategy to generate functionalized uniform quantum dots barcodes with high physical and chemical stability. This efficient and facile strategy could make porous polymer microspheres self-heal to encapsulate QDs via the thermal motion and interaction of the molecular chains. Consequently, the new strategy solved especially the QDs leakage problem and improved the chemical stability under different pH physiological conditions as well as the longtime storage stability. In the meantime, the encoding capacity and the spatial distribution uniformity of quantum dots could be also improved. Furthermore, immunofluorescence assays for alpha fetoprotein (AFP) detections indicated that carboxyl groups on the surface of QD-encoded microspheres could facilitate efficient attachment of biomacromolecules.

  12. Development of a self-healing soft pneumatic actuator: a first concept.

    PubMed

    Terryn, Seppe; Mathijssen, Glenn; Brancart, Joost; Lefeber, Dirk; Assche, Guy Van; Vanderborght, Bram

    2015-07-07

    Inspired by the intrinsic softness and the corresponding embodied intelligence principles, soft pneumatic actuators (SPA) have been developed, which ensure safe interaction in unstructured, unknown environments. Due to their intrinsic softness, these actuators have the ability to resist large mechanical impacts. However, the soft materials used in these structures are in general susceptible to damage caused by sharp objects found in the unstructured environments. This paper proposes to integrate a self-healing (SH-) mechanism in SPAs, such that cuts, tears and perforations in the actuator can be self-healed. Diels-Alder (DA-) polymers, covalent polymer network systems based on the thermoreversible DA-reaction, were selected and their mechanical, as well as SH-properties, are described. To evaluate the feasibility of developing an SPA constructed out of SH-material, a single cell prototype, a SH-soft pneumatic cell (SH-SPC), was constructed entirely out of DA-polymers. Exploiting the SH-property of the DA-polymers, a completely new shaping process is presented in this paper, referred to as 'shaping through folding and self-healing'. 3D polygon structures, like the cubic SH-SPC, can be constructed by folding SH-polymer sheet. The sides of the structures can be sealed and made airtight using a SH-procedure at relatively low temperatures (<90 °C). Both the (thermo) mechanical and SH-properties of the SH-SPC prototype were experimentally validated and showed excellent performances. Macroscopic incisions in the prototype were completely healed using a SH-procedure (<70 °C). Starting from this single-cell prototype, it is straight-forward to develop a multi-cell prototype, the first SPA ever built completely out of SH-polymers.

  13. Electronically Conductive Composite Polymer Membranes.

    DTIC Science & Technology

    1985-09-20

    coats the individual fibers which make up the webs. Clearly, at this loading level ( 10 w/w S Nafion in the Gr), only a small fraction of the...NOO014-82K-0612 Task No. NR 627-838 cc TECHNICAL REPORT NO. 10 Mn Electronically Conductive Composite Polymer Membranes I- I by 0 Reginald M. Penner... 10 of Document Control Data - DO Form 1473. Copies of form available from cognizant contract administrator 85 IV, 03 O88 UNCLASSI FIED SECURITY

  14. Asphaltenes-based polymer nano-composites

    DOEpatents

    Bowen, III, Daniel E

    2013-12-17

    Inventive composite materials are provided. The composite is preferably a nano-composite, and comprises an asphaltene, or a mixture of asphaltenes, blended with a polymer. The polymer can be any polymer in need of altered properties, including those selected from the group consisting of epoxies, acrylics, urethanes, silicones, cyanoacrylates, vulcanized rubber, phenol-formaldehyde, melamine-formaldehyde, urea-formaldehyde, imides, esters, cyanate esters, allyl resins.

  15. Molecular self-healing mechanisms between C60-fullerene and anthracene unveiled by Raman and two-dimensional correlation spectroscopy.

    PubMed

    Geitner, R; Kötteritzsch, J; Siegmann, M; Fritzsch, R; Bocklitz, T W; Hager, M D; Schubert, U S; Gräfe, S; Dietzek, B; Schmitt, M; Popp, J

    2016-07-21

    The self-healing polymer P(LMA-co-MeAMMA) crosslinked with C60-fullerene has been studied by FT-Raman spectroscopy in combination with two-dimensional (2D) correlation analysis and density functional theory calculations. To unveil the molecular changes during the self-healing process mediated by the Diels-Alder equilibrium between 10-methyl-9-anthracenyl groups and C60-fullerene different anthracene-C60-fullerene adducts have been synthesized and characterized by time-, concentration- and temperature-dependent FT-Raman measurements. The self-healing process could be monitored via the C60-fullerene vibrations at 270, 432 and 1469 cm(-1). Furthermore, the detailed analysis of the concentration-dependent FT-Raman spectra point towards the formation of anthracene-C60-fullerene adducts with an unusual high amount of anthracene bound to C60-fullerene in the polymer film, while the 2D correlation analysis of the temperature-dependent Raman spectra suggests a stepwise dissociation of anthracene-C60-fullerene adducts, which are responsible for the self-healing of the polymer.

  16. Self-healing juvenile cutaneous mucinosis

    PubMed Central

    Kołodziejczyk, Beata; Gazda, Agnieszka; Hernik, Elżbieta; Szczygielska, Izabela; Koprowska, Marta Legatowicz

    2017-01-01

    Girl, aged 4 years old, began the disease with pain of the lower extremities, fever up to 38°C and signs of upper airway infection. Then the patient developed oedema and redness of the whole face, thickened skin, subcutaneous nodular foldings of the frontal, occipital, cervical and axillary regions, extensor areas of the joints; fine, hard whitish nodules in the frontal region and over interphalangeal joints of the hands, pruritus; oedemas of the ankles, knees and joints of the hands, cervical lymphadenopathy and hepatomegaly. Blood tests at the moment of the diagnosis revealed elevation of markers of inflammation as ESR and CRP, leukocytosis, thrombocytosis, hypoalbuminemia, and hyper-alfa-2-globulinemia. Histopathological examination of the skin biopsy specimen and subcutaneous tissue revealed myxoid subcutaneous tissue located under the dermis and a section consisting of myxoid mesenchymal tissue with inflammatory infiltration by histiocytic cells. The presence of acid mucopolysaccharides in fields of the myxoid tissue was also observed. The self-healing juvenile cutaneous mucinosis (SJCM) was diagnosed. PMID:28386144

  17. Self-healing juvenile cutaneous mucinosis.

    PubMed

    Kołodziejczyk, Beata; Gazda, Agnieszka; Hernik, Elżbieta; Szczygielska, Izabela; Rutkowska-Sak, Lidia; Koprowska, Marta Legatowicz

    2017-01-01

    Girl, aged 4 years old, began the disease with pain of the lower extremities, fever up to 38°C and signs of upper airway infection. Then the patient developed oedema and redness of the whole face, thickened skin, subcutaneous nodular foldings of the frontal, occipital, cervical and axillary regions, extensor areas of the joints; fine, hard whitish nodules in the frontal region and over interphalangeal joints of the hands, pruritus; oedemas of the ankles, knees and joints of the hands, cervical lymphadenopathy and hepatomegaly. Blood tests at the moment of the diagnosis revealed elevation of markers of inflammation as ESR and CRP, leukocytosis, thrombocytosis, hypoalbuminemia, and hyper-alfa-2-globulinemia. Histopathological examination of the skin biopsy specimen and subcutaneous tissue revealed myxoid subcutaneous tissue located under the dermis and a section consisting of myxoid mesenchymal tissue with inflammatory infiltration by histiocytic cells. The presence of acid mucopolysaccharides in fields of the myxoid tissue was also observed. The self-healing juvenile cutaneous mucinosis (SJCM) was diagnosed.

  18. Autonomic healing of polymer composites.

    PubMed

    White, S R; Sottos, N R; Geubelle, P H; Moore, J S; Kessler, M R; Sriram, S R; Brown, E N; Viswanathan, S

    2001-02-15

    Structural polymers are susceptible to damage in the form of cracks, which form deep within the structure where detection is difficult and repair is almost impossible. Cracking leads to mechanical degradation of fibre-reinforced polymer composites; in microelectronic polymeric components it can also lead to electrical failure. Microcracking induced by thermal and mechanical fatigue is also a long-standing problem in polymer adhesives. Regardless of the application, once cracks have formed within polymeric materials, the integrity of the structure is significantly compromised. Experiments exploring the concept of self-repair have been previously reported, but the only successful crack-healing methods that have been reported so far require some form of manual intervention. Here we report a structural polymeric material with the ability to autonomically heal cracks. The material incorporates a microencapsulated healing agent that is released upon crack intrusion. Polymerization of the healing agent is then triggered by contact with an embedded catalyst, bonding the crack faces. Our fracture experiments yield as much as 75% recovery in toughness, and we expect that our approach will be applicable to other brittle materials systems (including ceramics and glasses).

  19. Solvent sensitive polymer composite structures

    NASA Astrophysics Data System (ADS)

    Chiappini, A.; Armellini, C.; Carpentiero, A.; Minati, L.; Righini, G. C.; Ferrari, M.

    2013-11-01

    In this paper we describe a composite system based on polystyrene colloidal nanoparticles assembled and embedded in an elastomeric matrix (polymer colloidal crystal, PCC), in the specific we have designed a PCC structure which displays an iridescent green color that can be attributed to the photonic crystal effect. This effect has been exploited to create a chemical sensor, in fact optical measurements have evidenced that the composite structure presents a different optical response as a function of the solvent applied on the surface. In particular we have demonstrated that the PCC possess, for specific solvents: (i) high sensitivity, (ii) fast response (less than 1s), and (iii) reversibility of the signal change. Finally preliminary results on the PCC have shown that this system can be also used as optical writing substrate using a specific solvent as ink, moreover an erasing procedure is also reported and discussed.

  20. 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...

  1. All-printed magnetically self-healing electrochemical devices

    PubMed Central

    Bandodkar, Amay J.; López, Cristian S.; Vinu Mohan, Allibai Mohanan; Yin, Lu; Kumar, Rajan; Wang, Joseph

    2016-01-01

    The present work demonstrates the synthesis and application of permanent magnetic Nd2Fe14B microparticle (NMP)–loaded graphitic inks for realizing rapidly self-healing inexpensive printed electrochemical devices. The incorporation of NMPs into the printable ink imparts impressive self-healing ability to the printed conducting trace, with rapid (~50 ms) recovery of repeated large (3 mm) damages at the same or different locations without any user intervention or external trigger. The permanent and surrounding-insensitive magnetic properties of the NMPs thus result in long-lasting ability to repair extreme levels of damage, independent of ambient conditions. This remarkable self-healing capability has not been reported for existing man-made self-healing systems and offers distinct advantages over common capsule and intrinsically self-healing systems. The printed system has been characterized by leveraging crystallographic, magnetic hysteresis, microscopic imaging, electrical conductivity, and electrochemical techniques. The real-life applicability of the new self-healing concept is demonstrated for the autonomous repair of all-printed batteries, electrochemical sensors, and wearable textile-based electrical circuits, indicating considerable promise for widespread practical applications and long-lasting printed electronic devices. PMID:27847875

  2. All-printed magnetically self-healing electrochemical devices.

    PubMed

    Bandodkar, Amay J; López, Cristian S; Vinu Mohan, Allibai Mohanan; Yin, Lu; Kumar, Rajan; Wang, Joseph

    2016-11-01

    The present work demonstrates the synthesis and application of permanent magnetic Nd2Fe14B microparticle (NMP)-loaded graphitic inks for realizing rapidly self-healing inexpensive printed electrochemical devices. The incorporation of NMPs into the printable ink imparts impressive self-healing ability to the printed conducting trace, with rapid (~50 ms) recovery of repeated large (3 mm) damages at the same or different locations without any user intervention or external trigger. The permanent and surrounding-insensitive magnetic properties of the NMPs thus result in long-lasting ability to repair extreme levels of damage, independent of ambient conditions. This remarkable self-healing capability has not been reported for existing man-made self-healing systems and offers distinct advantages over common capsule and intrinsically self-healing systems. The printed system has been characterized by leveraging crystallographic, magnetic hysteresis, microscopic imaging, electrical conductivity, and electrochemical techniques. The real-life applicability of the new self-healing concept is demonstrated for the autonomous repair of all-printed batteries, electrochemical sensors, and wearable textile-based electrical circuits, indicating considerable promise for widespread practical applications and long-lasting printed electronic devices.

  3. Activation-deactivation of self-healing in supramolecular rubbers

    NASA Astrophysics Data System (ADS)

    Corte, Laurent; Maes, Florine; Montarnal, Damien; Cantournet, Sabine; Tournilhac, Francois; Leibler, Ludwik; Mines-Paristech Cnrs (Umr7633) Team; Espci-Paristech Cnrs (Umr7167) Team

    2011-03-01

    Self-healing materials have the ability to restore autonomously their structural integrity after damage. Such a remarkable property was obtained recently in supramolecular rubbers formed by a network of small molecules associated via hydrogen bonds. Here we explore this self-healing through an original tack experiment where two parts of supramolecular rubber are brought into contact and then separated. These experiments reveal that a strong self-healing ability is activated by damage even though the surfaces of a molded part are weakly self-adhesive. In our testing conditions, a five minute contact between crack faces is sufficient to recover most mechanical properties of the bulk while days are required to obtain such adhesion levels with melt-pressed surfaces. We show that the deactivation of this self-healing ability seems unexpectedly slow as compared to the predicted dynamics of supramolecular networks. Fracture faces stored apart at room temperature still self-heal after days but are fully deactivated within hours by annealing. Combining these results with microstructural observations gives us a deeper insight into the mechanisms involved in this self-healing process.

  4. Improved self-healing of polyethylene/carbon black nanocomposites by their shape memory effect.

    PubMed

    Wang, Xiaoyan; Zhao, Jun; Chen, Min; Ma, Lan; Zhao, Xiaodong; Dang, Zhi-Min; Wang, Zhenwen

    2013-02-07

    In this work, the improved self-healing of cross-linked polyethylene (PE) (cPE)/carbon black (CB) nanocomposites by their shape memory effect (SME) is investigated. CB nanoparticles are found to be homogeneously dispersed in the PE matrix and significantly increase the strength of the materials. Compared with the breaking of linear PE (lPE) at the melting temperature (T(m)), the cPE and cPE/CB nanocomposites still have high strength above T(m) due to the formation of networks. The cPE and cPE/CB nanocomposites show both high strain fixity ratio (R(f)) and high strain recovery ratio (R(r)). Crystallization-induced elongation is observed for all the prepared shape memory polymer (SMP) materials and the effect becomes less remarkable with increasing volume fraction of CB nanoparticles (v(CB)). The scratch self-healing tests show that the cross-linking of PE matrix, the addition of CB nanoparticles, and the previous stretching in the direction perpendicular to the scratch favor the closure of the scratch and its complete healing. This SME-aided self-healing could have potential applications in diverse fields such as coating and structure materials.

  5. State-of-the-art and prospect for self-healing asphalt concrete

    NASA Astrophysics Data System (ADS)

    Xiao, Dong

    2017-08-01

    In order to solve the problem of asphalt concrete pavement cracks, this paper summarizes the principle of self-healing asphalt concrete, and describes asphalt concrete self-healing technology in various countries. This paper also analyses the factors of influencing the self-healing ability of asphalt concrete and the evaluation index, and describes the prospect of asphalt concrete self-healing technology.

  6. Polymer/mesoporous metal oxide composites

    NASA Astrophysics Data System (ADS)

    Ver Meer, Melissa Ann

    Understanding the nature of the interfacial region between an organic polymer matrix and an inorganic filler component is essential in determining how this region impacts the overall bulk properties of the organic/inorganic hybrid composite material. In this work, polystyrene was used as the model polymer matrix coupled with silica-based filler materials to investigate the nature of structure-property relationships in polymer composites. Initial work was conducted on synthesis and characterization of colloidal and mesoporous silica particles melt blended into the polystyrene matrix. Modification of the interface was accomplished by chemically bonding the silica particles with the polystyrene chains through polymerization from the particle surface via atom transfer radical polymerization. High molecular weight polystyrene chains were formed and bulk test samples were evaluated with increased thermal stability of the grafted polymer composite system versus equivalent melt blended polymer composites. Polymer grafting was also conducted from the internal pores of mesoporous silica, further improving the thermal stability of the composite system without degrading dynamic mechanical properties. Characterization of the polymer composites was conducted with gel permeation chromatography, transmission electron microscopy, thermogravimetric analysis and dynamic mechanical analysis. It was also discovered during the polystyrene-silica composite studies that amorphous polystyrene can possess a less mobile phase, evident in a second peak of the loss tangent (tan delta). The long annealing times necessitated by the mesoporous silica composites were replicated in as received polystyrene. This new, less mobile phase is of particular interest in determining the mobility of polymer chains in the interfacial region.

  7. Heat transfer and fluid flow analysis of self-healing in metallic materials

    NASA Astrophysics Data System (ADS)

    Martínez Lucci, J.; Amano, R. S.; Rohatgi, P. K.

    2017-03-01

    This paper explores imparting self-healing characteristics to metal matrices similar to what are observed in biological systems and are being developed for polymeric materials. To impart self-healing properties to metal matrices, a liquid healing method was investigated; the met hod consists of a container filled with low melting alloy acting as a healing agent, embedded into a high melting metal matrix. When the matrix is cracked; self-healing is achieved by melting the healing agent allowing the liquid metal to flow into the crack. Upon cooling, solidification of the healing agent occurs and seals the crack. The objective of this research is to investigate the fluid flow and heat transfer to impart self-healing property to metal matrices. In this study, a dimensionless healing factor, which may help predict the possibility of healing is proposed. The healing factor is defined as the ratio of the viscous forces and the contact area of liquid metal and solid which prevent flow, and volume expansion, density, and velocity of the liquid metal, gravity, crack size and orientation which promote flow. The factor incorporates the parameters that control self-healing mechanism. It was observed that for lower values of the healing factor, the liquid flows, and for higher values of healing factor, the liquid remains in the container and healing does not occur. To validate and identify the critical range of the healing factor, experiments and simulations were performed for selected combinations of healing agents and metal matrices. The simulations were performed for three-dimensional models and a commercial software 3D Ansys-Fluent was used. Three experimental methods of synthesis of self-healing composites were used. The first method consisted of creating a hole in the matrices, and liquid healing agent was poured into the hole. The second method consisted of micro tubes containing the healing agent, and the third method consisted of incorporating micro balloons containing

  8. Recent development and biomedical applications of self-healing hydrogels.

    PubMed

    Wang, Yinan; Adokoh, Christian K; Narain, Ravin

    2017-08-23

    Hydrogels are of special importance, owing to their high-water content and various applications in biomedical and bio-engineering research. Self-healing properties is a common phenomenon in living organisms. Their endowed property of being able to self-repair after physical/chemical/mechanical damage to fully or partially its original properties demonstrates their prospective therapeutic applications. Due to complicated preparation and selection of suitable materials, the application of many host-guest supramolecular polymeric hydrogels are so limited. Thus, the design and construction of self-repairing material are highly desirable for effectively increase in the lifetime of a functional material. However, recent advances in the field of materials science and bioengineering and nanotechnology have led to the design of biologically relevant self-healing hydrogels for therapeutic applications. This review focuses on the recent development of self-healing hydrogels for biomedical application. Areas covered: The strategies of making self-healing hydrogels and their healing mechanisms are discussed. The significance of self-healing hydrogel for biomedical application is also highlighted in areas such as 3D/4D printing, cell/drug delivery, as well as soft actuators. Expert opinion: Materials that have the ability to self-repair damage and regain the desired mechanical properties, have been found to be excellent candidate materials for a range of biomedical uses especially if their unique characteristics are similar to that of soft-tissues. Self-healing hydrogels have been synthesized and shown to exhibit similar characteristics as human tissues, however, significant improvement is required in the fabrication process from inexpensive and nontoxic/non-hazardous materials and techniques, and, in addition, further fine-tuning of the self-healing properties are needed for specific biomedical uses.

  9. Damage, Self-Healing, and Hysteresis in Spider Silks

    PubMed Central

    De Tommasi, D.; Puglisi, G.; Saccomandi, G.

    2010-01-01

    Abstract In this article, we propose a microstructure-based continuum model to describe the material behavior of spider silks. We suppose that the material is composed of a soft fraction with entropic elasticity and a hard, damageable fraction. The hard fraction models the presence of stiffer, crystal-rich, oriented regions and accounts for the effect of softening induced by the breaking of hydrogen bonds. To describe the observed presence of crystals with different size, composition, and orientation, this hard fraction is modeled as a distribution of materials with variable properties. The soft fraction describes the remaining regions of amorphous material and is here modeled as a wormlike chain. During stretching, we consider the effect of bond-breaking as a transition from the hard- to the soft-material phase. As we demonstrate, a crucial effect of bond-breaking that accompanies the softening of the material is an increase in contour length associated with chains unraveling. The model describes also the self-healing properties of the material by assuming partial bond reconnection upon unloading. Despite its simplicity, the proposed mechanical system reproduces the main experimental effects observed in cyclic loading of spider silks. Moreover, our approach is amenable to two- or three-dimensional extensions and may prove to be a useful tool in the field of microstructure optimization for bioinspired materials. PMID:20441758

  10. Olefin metathesis for effective polymer healing via dynamic exchange of strong carbon-carbon bonds

    DOEpatents

    Guan, Zhibin; Lu, Yixuan

    2015-09-15

    A method of preparing a malleable and/or self-healing polymeric or composite material is provided. The method includes providing a polymeric or composite material comprising at least one alkene-containing polymer, combining the polymer with at least one homogeneous or heterogeneous transition metal olefin metathesis catalyst to form a polymeric or composite material, and performing an olefin metathesis reaction on the polymer so as to form reversible carbon-carbon double bonds in the polymer. Also provided is a method of healing a fractured surface of a polymeric material. The method includes bringing a fractured surface of a first polymeric material into contact with a second polymeric material, and performing an olefin metathesis reaction in the presence of a transition metal olefin metathesis catalyst such that the first polymeric material forms reversible carbon-carbon double bonds with the second polymeric material. Compositions comprising malleable and/or self-healing polymeric or composite material are also provided.

  11. Ultraviolet and thermally stable polymer compositions

    NASA Technical Reports Server (NTRS)

    Reinisch, R. F.; Gloria, H. R.; Goldsberry, R. E.; Adamson, M. J. (Inventor)

    1976-01-01

    A new class of polymers is provided, namely, poly (diarylsiloxy) arylazines. These novel polymers have a basic chemical composition which has the property of stabilizing the optical and physical properties of the polymer against the degradative effect of ultraviolet light and high temperatures. This stabilization occurs at wavelengths including those shorter than found on the surface of the earth and in the absence or presence of oxygen, making the polymers useful for high performance coating applications in extraterrestrial space as well as similar applications in terrestrial service. The invention also provides novel aromatic azines which are useful in the preparation of polymers such as those described.

  12. Ultraviolet and thermally stable polymer compositions

    NASA Technical Reports Server (NTRS)

    Reinisch, R. F.; Gloria, H. R.; Goldsberry, R. E.; Adamson, M. J. (Inventor)

    1974-01-01

    A class of polymers is provided, namely, poly(diarylsiloxy) arylazines. These polymers have a basic chemical composition which has the property of stabilizing the optical and physical properties of the polymer against the degradative effect of ultraviolet light and high temperatures. This stabilization occurs at wavelengths including those shorter than found on the surface of the earth and in the absence or presence of oxygen, making the polymers of the present invention useful for high performance coating applications in extraterrestrial space as well as similar applications in terrestrial service. The invention also provides aromatic azines which are useful in the preparation of polymers such as those of the present invention.

  13. Method of making molecularly doped composite polymer material

    DOEpatents

    Affinito, John D [Tucson, AZ; Martin, Peter M [Kennewick, WA; Graff, Gordon L [West Richland, WA; Burrows, Paul E [Kennewick, WA; Gross, Mark E. , Sapochak, Linda S.

    2005-06-21

    A method of making a composite polymer of a molecularly doped polymer. The method includes mixing a liquid polymer precursor with molecular dopant forming a molecularly doped polymer precursor mixture. The molecularly doped polymer precursor mixture is flash evaporated forming a composite vapor. The composite vapor is cryocondensed on a cool substrate forming a composite molecularly doped polymer precursor layer, and the cryocondensed composite molecularly doped polymer precursor layer is cross linked thereby forming a layer of the composite polymer layer of the molecularly doped polymer.

  14. Improved performance in polymer - inorganic composite photovoltaics

    NASA Astrophysics Data System (ADS)

    Breeze, Alison J.

    It has become increasingly clear over the past few decades that some form of alternative energy is needed to replace the traditional fossil fuels. I briefly discuss a few of the possible alternative sources, why solar energy is one of the more promising ones, give a short history of the development of the solar cell, and explain the motivations for research into polymer - inorganic composite solar cells. An introduction to conducting and semiconducting polymers, as well as the basics of polymer solar cell operation, is given. I present experimental results on the variation of several parameters such as polymer thickness, TiO2 and polymer morphology, and choice of electrodes for devices of the type ITO/TiO2/photoactive polymer/Au in order to probe the effects of charge transport, carrier mobility, light absorption and direction of the internal field on device efficiency. The results demonstrate that short exciton diffusion lengths, low carrier mobilities, and low absorption are the main factors limiting performance in plain polymer photovoltaics. Nanoparticle - polymer and polymer - polymer blend devices are explored as possible solutions for the first two deficiencies, with the polymer - polymer blend devices achieving the best results with an overall 0.6% power conversion efficiency. Many of the experimental results of polymer photovoltaics can be simulated using a simple model which includes terms for Schottky-like injection, ohmic current leakage, and collected photogenerated current. I discuss both the successes and failures of this model, as well as areas for future improvements.

  15. "Click"-Triggered Self-Healing Graphene Nanocomposites.

    PubMed

    Rana, Sravendra; Döhler, Diana; Nia, Ali Shaygan; Nasir, Mahmood; Beiner, Mario; Binder, Wolfgang H

    2016-11-01

    Strategies to compensate material fatigue are among the most challenging issues, being most prominently addressed by the use of nano- and microscaled fillers, or via new chemical concepts such as self-healing materials. A capsule-based self-healing material is reported, where the adverse effect of reduced tensile strength due to the embedded capsules is counterbalanced by a graphene-based filler, the latter additionally acting as a catalyst for the self-healing reaction. The concept is based on "click"-based chemistry, a universal methodology to efficiently link components at ambient reaction conditions, thus generating a "reactive glue" at the cracked site. A capsule-based healing system via a graphene-based Cu2 O (TRGO-Cu2 O-filler) is used, acting as both the catalytic species for crosslinking and the required reinforcement agent within the material, in turn compensating the reduction in tensile strength exerted by the embedded capsules. Room-temperature self-healing within 48 h is achieved, with the investigated specimen containing TRGO-Cu2 O demonstrating significantly faster self-healing compared to homogeneous (Cu(PPh3 )3 F, Cu(PPh3 )3 Br), and heterogeneous (Cu/C) copper(I) catalysts. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  16. Synergy between Galvanic Protection and Self-Healing Paints.

    PubMed

    Baird, Lance Michael; Patchan, Marcia W; Morris, Melanie; Maisano, Adam J; Phillips, Terry E; Benkoski, Jason J; Srinivasan, Rengaswamy

    2015-09-29

    Painting is a cost-effective technique to delay the onset of corrosion in metals. However, the protection is only temporary, as corrosion begins once the coating becomes scratched. Thus, an increasingly common practice is to add microencapsulated chemical agents to paint in order to confer self-healing capabilities. The additive's ability to protect the exposed surface from corrosion depends upon (i) how long the chemical agent takes to spread across the exposed metal; (ii) how long the agent takes to form an effective barrier layer; and (iii) what happens to the metal surface before the first two steps are complete. To understand this process, we first synthesized 23 ± 10 μm polyurea microcapsules filled with octadecyltrimethoxysilane (OTS), a liquid self-healing agent, and added them to a primer rich in zinc, a cathodic protection agent. In response to coating damage, the microcapsules release OTS into the scratch and initiate the self-healing process. By combining electrochemical impedance spectroscopy, chronoamperometry, and linear polarization techniques, we monitored the progress of self-healing. The results demonstrate how on-demand chemical passivation works synergistically with the cathodic protection: zinc preserves the surface long enough for self-healing by OTS to reach completion, and OTS prolongs the lifetime of cathodic protection.

  17. Self-healing phenomena of graphene: potential and applications

    NASA Astrophysics Data System (ADS)

    VijayaSekhar, K.; Acharyya, Swati Ghosh; Debroy, Sanghamitra; Miriyala, V. Pavan Kumar; Acharyya, Amit

    2016-01-01

    The present study investigates the self healing behavior of both pristine and defected single layer graphene using a molecular dynamic simulation. Single layer graphene containing various defects such as preexisting vacancies and differently oriented pre-existing cracks were subjected to uniaxial tensile loading till fracture occurred. Once the load was relaxed, the graphene was found to undergo self healing. It was observed that this self healing behaviour of cracks holds irrespective of the nature of pre-existing defects in the graphene sheet. Cracks of any length were found to heal provided the critical crack opening distance lies within 0.3-0.5 nm for a pristine sheet and also for a sheet with pre-existing defects. Detailed bond length analysis of the graphene sheet was done to understand the mechanism of self healing of graphene. The paper also discusses the immense potential of the self healing phenomena of graphene in the field of graphene based sub-nano sensors for crack sensing.

  18. Self-healing concrete by use of microencapsulated bacterial spores

    SciTech Connect

    Wang, J.Y.; Soens, H.; Verstraete, W.; De Belie, N.

    2014-02-15

    Microcapsules were applied to encapsulate bacterial spores for self-healing concrete. The viability of encapsulated spores and the influence of microcapsules on mortar specimens were investigated first. Breakage of the microcapsules upon cracking was verified by Scanning Electron Microscopy. Self-healing capacity was evaluated by crack healing ratio and the water permeability. The results indicated that the healing ratio in the specimens with bio-microcapsules was higher (48%–80%) than in those without bacteria (18%–50%). The maximum crack width healed in the specimens of the bacteria series was 970 μm, about 4 times that of the non-bacteria series (max 250 μm). The overall water permeability in the bacteria series was about 10 times lower than that in non-bacteria series. Wet–dry cycles were found to stimulate self-healing in mortar specimens with encapsulated bacteria. No self-healing was observed in all specimens stored at 95%RH, indicating that the presence of liquid water is an essential component for self-healing.

  19. Ultrasensitive Wearable Soft Strain Sensors of Conductive, Self-healing, and Elastic Hydrogels with Synergistic "Soft and Hard" Hybrid Networks.

    PubMed

    Liu, Yan-Jun; Cao, Wen-Tao; Ma, Ming-Guo; Wan, Pengbo

    2017-08-02

    Robust, stretchable, and strain-sensitive hydrogels have recently attracted immense research interest because of their potential application in wearable strain sensors. The integration of the synergistic characteristics of decent mechanical properties, reliable self-healing capability, and high sensing sensitivity for fabricating conductive, elastic, self-healing, and strain-sensitive hydrogels is still a great challenge. Inspired by the mechanically excellent and self-healing biological soft tissues with hierarchical network structures, herein, functional network hydrogels are fabricated by the interconnection between a "soft" homogeneous polymer network and a "hard" dynamic ferric (Fe(3+)) cross-linked cellulose nanocrystals (CNCs-Fe(3+)) network. Under stress, the dynamic CNCs-Fe(3+) coordination bonds act as sacrificial bonds to efficiently dissipate energy, while the homogeneous polymer network leads to a smooth stress-transfer, which enables the hydrogels to achieve unusual mechanical properties, such as excellent mechanical strength, robust toughness, and stretchability, as well as good self-recovery property. The hydrogels demonstrate autonomously self-healing capability in only 5 min without the need of any stimuli or healing agents, ascribing to the reorganization of CNCs and Fe(3+) via ionic coordination. Furthermore, the resulted hydrogels display tunable electromechanical behavior with sensitive, stable, and repeatable variations in resistance upon mechanical deformations. Based on the tunable electromechanical behavior, the hydrogels can act as a wearable strain sensor to monitor finger joint motions, breathing, and even the slight blood pulse. This strategy of building synergistic "soft and hard" structures is successful to integrate the decent mechanical properties, reliable self-healing capability, and high sensing sensitivity together for assembling a high-performance, flexible, and wearable strain sensor.

  20. Complex Multifunctional Polymer/Carbon-Nanotube Composites

    NASA Technical Reports Server (NTRS)

    Patel, Pritesh; Balasubramaniyam, Gobinath; Chen, Jian

    2009-01-01

    A methodology for developing complex multifunctional materials that consist of or contain polymer/carbon-nanotube composites has been conceived. As used here, "multifunctional" signifies having additional and/or enhanced physical properties that polymers or polymer-matrix composites would not ordinarily be expected to have. Such properties include useful amounts of electrical conductivity, increased thermal conductivity, and/or increased strength. In the present methodology, these properties are imparted to a given composite through the choice and processing of its polymeric and CNT constituents.

  1. Polymer Composites for Intelligent Food Packaging

    NASA Astrophysics Data System (ADS)

    He, Jiating; Yap, Ray Chin Chong; Wong, Siew Yee; Li, Xu

    2015-09-01

    Over the last 50 years, remarkable improvements in mechanical and barrier properties of polymer composites have been realized. Their improved properties have been widely studied and employed for food packaging to keep food fresh, clean and suitable for consumption over sufficiently long storage period. In this paper, the current progress of science and technology development of polymer composites for intelligent food packaging will be highlighted. Future directions and perspectives for exploring polymer composites for intelligent food packaging to reveal freshness and quality of food packaged will also be put forward.

  2. Innovative Self-Healing Seals for Solid Oxide Fuel Cells (SOFC)

    SciTech Connect

    Raj Singh

    2012-06-30

    Solid oxide fuel cell (SOFC) technology is critical to several national initiatives. Solid State Energy Conversion Alliance (SECA) addresses the technology needs through its comprehensive programs on SOFC. A reliable and cost-effective seal that works at high temperatures is essential to the long-term performance of the SOFC for 40,000 hours at 800°C. Consequently, seals remain an area of highest priority for the SECA program and its industry teams. An innovative concept based on self-healing glasses was advanced and successfully demonstrated through seal tests for 3000 hours and 300 thermal cycles to minimize internal stresses under both steady state and thermal transients for making reliable seals for the SECA program. The self-healing concept requires glasses with low viscosity at the SOFC operating temperature of 800°C but this requirement may lead to excessive flow of the glass in areas forming the seal. To address this challenge, a modification to glass properties by addition of particulate fillers is pursued in the project. The underlying idea is that a non-reactive ceramic particulate filler is expected to form glass-ceramic composite and increase the seal viscosity thereby increasing the creep resistance of the glass-composite seals under load. The objectives of the program are to select appropriate filler materials for making glass-composite, fabricate glass-composites, measure thermal expansion behaviors, and determine stability of the glass-composites in air and fuel environments of a SOFC. Self-healing glass-YSZ composites are further developed and tested over a longer time periods under conditions typical of the SOFCs to validate the long-term stability up to 2000 hours. The new concepts of glass-composite seals, developed and nurtured in this program, are expected to be cost-effective as these are based on conventional processing approaches and use of the inexpensive materials.

  3. Mechanics of biological polymer composites

    NASA Astrophysics Data System (ADS)

    Lomakin, Joseph

    2009-12-01

    Cartilage and cuticle are two natural materials capable of remarkable mechanical performance, especially considering the limitations on composition and processing conditions under which they are constructed. Their impressive properties are postulated to be a consequence of their complex multi-scale organization which has commonly been characterized by biochemical and microscopic methods. The objective of this dissertation is to overcome the limitations of such methods with mechanical analysis techniques generally reserved for the study of synthetic polymers. Methods for transient and dynamic mechanical analysis (DMA) of porcine TMJ disc sections and Tribolium castaneum and Tenebrio molitor elytral (modified forewing) cuticle were developed to characterize the mechanical performance of these biomaterials. The TMJ disc dynamic elastic modulus (E') was determined to be a strong function of disc orientation and pretension ranging from 700+/-240 kPa at (1g pretension) in the mediolateral direction to 73+/-8.5 MPa (150g preload) in the anteroposterior direction. Analogous mechanical testing was used to understand the relationship between composition and mechanical properties of beetle elytral cuticle at variable stages of maturation (tanning). Untanned elytra of both beetle species were ductile with a Young's modulus (E) of 44+/-8 MPa, but became brittle with an E of 2400+/-1100 MPa when fully tanned. Significantly, the E' of the TMJ disc and elytral cuticle exhibited a weak power law increase as a function of oscillation frequency. The exponent of the power law fit ( n) was determined to be a sensitive measure of molecular structure within these biomaterials. With increasing cuticular tanning, more so than with drying, the frequency dependence of cuticle E' diminished, suggesting cuticular cross-linking was an important component of tanning, as postulated by the quinone tanning hypothesis. The natural Black phenotype as well as TcADC iRNA suppressed Tribolium cuticle

  4. Impact of self-healing capability on network robustness

    NASA Astrophysics Data System (ADS)

    Shang, Yilun

    2015-04-01

    A wide spectrum of real-life systems ranging from neurons to botnets display spontaneous recovery ability. Using the generating function formalism applied to static uncorrelated random networks with arbitrary degree distributions, the microscopic mechanism underlying the depreciation-recovery process is characterized and the effect of varying self-healing capability on network robustness is revealed. It is found that the self-healing capability of nodes has a profound impact on the phase transition in the emergence of percolating clusters, and that salient difference exists in upholding network integrity under random failures and intentional attacks. The results provide a theoretical framework for quantitatively understanding the self-healing phenomenon in varied complex systems.

  5. Generation of self-healing and transverse accelerating optical vortices

    NASA Astrophysics Data System (ADS)

    Wei, Bing-Yan; Chen, Peng; Ge, Shi-Jun; Duan, Wei; Hu, Wei; Lu, Yan-Qing

    2016-09-01

    Self-healing and transverse accelerating optical vortices are generated via modulating Gaussian beams through subsequent liquid crystal q-plate and polarization Airy mask. We analyze the propagation dynamics of these vortex Airy beams, and find that they possess the features of both optical vortices and Airy beams. Topological charges and characteristics of nondiffraction, self-healing, and transverse acceleration are experimentally verified. In addition, vortex Airy beams with both topological charge and radial index are demonstrated and mode switch among Gaussian, vortex, vector, Airy beams and their combinations can be acquired easily. Our design provides a flexible and highly efficient way to generate unique optical vortices with self-healing and transverse acceleration properties, and facilitates prospective applications in optics and photonics.

  6. Targeted Self-Healing by Magnetically Guiding Microcapsules.

    PubMed

    Crall, Matthew D; Keller, Michael W

    2017-02-22

    Magnetically guided microcapsules are used to achieve self-healing with 1/10th of the healing components required using traditional self-healing approaches. Microcapsules are rendered responsive to magnetic fields by suspending magnetic nanoparticles in the core material. The nanoparticles are surface-modified to enable urea-formaldehyde encapsulation within a phenyl acetate core. Magnetic fields are used to guide the microcapsules to the expected fracture location in tapered double-cantilever beam (TDCB) epoxy specimens. This guiding method achieves an order of magnitude increase in local microcapsule concentration over controls, resulting in successful self-healing at microcapsule concentrations as low as 0.025 wt %. Additionally, the observed healing is both more consistent and significantly higher than that of control specimens, remaining relatively constant across all weight percentages tested.

  7. Anion-conducting polymer, composition, and membrane

    DOEpatents

    Pivovar, Bryan S [Los Alamos, NM; Thorn, David L [Los Alamos, NM

    2011-11-22

    Anion-conducing polymers and membranes with enhanced stability to aqueous alkali include a polymer backbone with attached sulfonium, phosphazenium, phosphazene, and guanidinium residues. Compositions also with enhanced stability to aqueous alkali include a support embedded with sulfonium, phosphazenium, and guanidinium salts.

  8. Anion-Conducting Polymer, Composition, and Membrane

    DOEpatents

    Pivovar, Bryan S.; Thorn, David L.

    2008-10-21

    Anion-conducing polymers and membranes with enhanced stability to aqueous alkali include a polymer backbone with attached sulfonium, phosphazenium, phosphazene, and guanidinium residues. Compositions also with enhanced stability to aqueous alkali include a support embedded with sulfonium, phosphazenium, and guanidinium salts.

  9. Anion-conducting polymer, composition, and membrane

    DOEpatents

    Pivovar, Bryan S.; Thorn, David L.

    2010-12-07

    Anion-conducing polymers and membranes with enhanced stability to aqueous alkali include a polymer backbone with attached sulfonium, phosphazenium, phosphazene, and guanidinium residues. Compositions also with enhanced stability to aqueous alkali include a support embedded with sulfonium, phosphazenium, and guanidinium salts.

  10. Anion-conducting polymer, composition, and membrane

    DOEpatents

    Pivovar, Bryan S.; Thorn, David L.

    2009-09-01

    Anion-conducing polymers and membranes with enhanced stability to aqueous alkali include a polymer backbone with attached sulfonium, phosphazenium, phosphazene, and guanidinium residues. Compositions also with enhanced stability to aqueous alkali include a support embedded with sulfonium, phosphazenium, and guanidinium salts.

  11. Thermally driven self-healing using copper nanofiber heater

    NASA Astrophysics Data System (ADS)

    Lee, Min Wook; Jo, Hong Seok; Yoon, Sam S.; Yarin, Alexander L.

    2017-07-01

    Nano-textured transparent heaters made of copper nanofibers (CuNFs) are used to facilitate accelerated self-healing of bromobutyl rubber (BIIR). The heater and BIIR layer are separately deposited on each side of a transparent flexible polyethylene terephthalate (PET) substrate. A pre-notched crack on the BIIR layer was bridged due to heating facilitated by CuNFs. In the corrosion test, a cracked BIIR layer covered a steel substrate. An accelerated self-healing of the crack due to the transparent copper nanofiber heater facilitated an anti-corrosion protective effect of the BIIR layer.

  12. Self-Healing in Mollusks, Lessons from Biology

    NASA Astrophysics Data System (ADS)

    Hinkley, Karen M.

    We will study major mechanisms of self-healing in Molluscan hard tissues taking lessons from biology. We are interested in mollusks because of the ease in monitoring the healing process using existing characterization techniques. The ability to self-heal their non-living hard tissues externally, make mollusks remarkable from both an evolutionary perspective and a materials perspective. Biological systems have evolved to repair their own hard tissues such as bone and dentin, but bone and tooth repair is accomplished with a specific blood supply for nutrient delivery at the cellular level. The Molluscan process of "self-healing" takes place in an aqueous environment where there are no direct supplies of nutrients. In fact the nutrients may be washed away from the injury site with the flow of water. This self-healing process is interesting to materials scientists as a possible model for synthesizing new Smart materials that do not need an in situ location for growth and gaining insight into biomineralization and its interaction with the organics regulating the process. This project will focus on two objectives firstly understanding the growth rates of shell deposition, growth and scar formation and secondly characterizing the biomineralization, microstructure, and mechanical properties of scar tissue as compared to normal tissue. By performing controlled injury experiments on two mollusk species, we can initiate the self-healing process and characterize all phases of its development. Using mechanical tests including micro-bend tests and atomic force microscopy with nanoindentation we can determine the hardness, micro-hardness, Young's modulus, strength and ductility of the self-healed tissue. In addition, scanning electron microscopy, transmission electron microscopy, atomic force microscopy, and x-ray crystallography will be used to determine the characteristics of the self-healed tissues. Molluscan self-healing is an excellent model for a self-assembly, highly

  13. Polymer Matrix Composite Material Oxygen Compatibility

    NASA Technical Reports Server (NTRS)

    Owens, Tom

    2001-01-01

    Carbon fiber/polymer matrix composite materials look promising as a material to construct liquid oxygen (LOX) tanks. Based on mechanical impact tests the risk will be greater than aluminum, however, the risk can probably be managed to an acceptable level. Proper tank design and operation can minimize risk. A risk assessment (hazard analysis) will be used to determine the overall acceptability for using polymer matrix composite materials.

  14. Microencapsulation of Self-healing Concrete Properties

    DTIC Science & Technology

    2012-08-01

    microencapsulation process itself. The objective of these steps is to streamline the process using different chemicals, techniques , and procedures... technique . The formation of a polymer at the interface between two liquid (Water and DCDP Interface) phases is known as interfacial polymerization...MICROCAPSULES Microcapsules can be evaluated and characterized using numerous techniques . These techniques include Transmission Electron Microscopy (TEM

  15. Conductor-polymer composite electrode materials

    DOEpatents

    Ginley, D.S.; Kurtz, S.R.; Smyrl, W.H.; Zeigler, J.M.

    1984-06-13

    A conductive composite material useful as an electrode, comprises a conductor and an organic polymer which is reversibly electrochemically dopable to change its electrical conductivity. Said polymer continuously surrounds the conductor in intimate electrical contact therewith and is prepared by electrochemical growth on said conductor or by reaction of its corresponding monomer(s) on said conductor which has been pre-impregnated or pre-coated with an activator for said polymerization. Amount of the conductor is sufficient to render the resultant composite electrically conductive even when the polymer is in an undoped insulating state.

  16. Self-healing of polymeric materials: The effect of the amount of DCPD confined within microcapsules

    NASA Astrophysics Data System (ADS)

    Chipara, Dorina M.; Perez, Alma; Lozano, Karen; Elamin, Ibrahim; Villarreal, Jahaziel; Salinas, Alfonso; Chipara, Mircea

    2013-03-01

    The self-healing SH) of polymers is based on the dispersion of a catalyst and of microcapsules filled with monomer within the polymeric matrix. Sufficiently large external stresses will rupture the microcapsule, releasing the monomer which will diffuse through the polymer and eventually will reach a catalyst particle igniting a polymerization reaction. The classical SH system includes first generation Grubbs catalyst and poly-urea formaldehyde microcapsules filled with DCPD. The polymerization reaction is a ring-opening metathesis. The size and the mechanical features of microcapsules are critical in controlling the SH process. Research was focused on the effect of DCPD on the size and thickness of microcapsules. Microscopy was used to determine the size of microcapsules (typically in the range of 10-4 m) and the thickness of the microcapsules (ranging between 10-6 to 10-8 m). Research revealed a thick disordered layer over a thin and more compact wall. Raman spectroscopy confirmed the confinement of DCPD, TGA measurements aimed to a better understanding of the degradation processes in inert atmosphere, and mechanical tests supported the ignition of self-healing properties. This research has been supported by National Science Foundation under DMR (PREM) grant 0934157.

  17. Mechanism of intramolecular photostabilization in self-healing cyanine fluorophores.

    PubMed

    van der Velde, Jasper H M; Ploetz, Evelyn; Hiermaier, Matthias; Oelerich, Jens; de Vries, Jan Willem; Roelfes, Gerard; Cordes, Thorben

    2013-12-16

    Organic fluorophores, which are popular labels for microscopy applications, intrinsically suffer from transient and irreversible excursions to dark-states. An alternative to adding photostabilizers at high concentrations to the imaging buffer relies on the direct linkage to the fluorophore. However, the working principles of this approach are not yet fully understood. In this contribution, we investigate the mechanism of intramolecular photostabilization in self-healing cyanines, in which photodamage is automatically repaired. Experimental evidence is provided to demonstrate that a single photostabilizer, that is, the vitamin E derivative Trolox, efficiently heals the cyanine fluorophore Cy5 in the absence of any photostabilizers in solution. A plausible mechanism is that Trolox interacts with the fluorophore through intramolecular quenching of triplet-related dark-states, which is a mechanism that appears to be common for both triplet-state quenchers (cyclooctatetraene) and redox-active compounds (Trolox, ascorbic acid, methylviologen). Additionally, the influence of solution-additives, such as cysteamine and procatechuic acid, on the self-healing process are studied. The results suggest the potential applicability of self-healing fluorophores in stochastic optical reconstruction microscopy (STORM) with optical super-resolution. The presented data contributes to an improved understanding of the mechanism involved in intramolecular photostabilization and has high relevance for the future development of self-healing fluorophores, including their applications in various research fields.

  18. Microencapsulation of Self Healing Agents for Corrosion Control Coatings

    NASA Technical Reports Server (NTRS)

    Jolley, S. T.; Li, W.; Buhrow, J. W.; Calle, L. M.

    2011-01-01

    Corrosion, the environmentally induced degradation of materials, is a very costly problem that has a major impact on the global economy. Results from a 2-year breakthrough study released in 2002 by the U.S. Federal Highway Administration (FHWA) showed that the total annual estimated direct cost associated with metallic corrosion in nearly every U.S. industry sector was a staggering $276 billion, approximately 3.1% of the nation's Gross Domestic Product (GOP). Corrosion protective coatings are widely used to protect metallic structures from the detrimental effects of corrosion but their effectiveness can be seriously compromised by mechanical damage, such as a scratch, that exposes the metallic substrate. The incorporation of a self healing mechanism into a corrosion control coating would have the potential to significantly increase its effectiveness and useful lifetime. This paper describes work performed to incorporate a number of microcapsule-based self healing systems into corrosion control coatings. The work includes the preparation and evaluation of self-healing systems based on curable epoxy, acrylate, and siloxane resins, as well as, microencapsulated systems based on passive, solvent born, healing agent delivery. The synthesis and optimization of microcapsule-based self healing systems for thin coating (less than 100 micron) will be presented.

  19. Self-Healing Hydrogel Pore-Filled Water Filtration Membranes.

    PubMed

    Getachew, Bezawit A; Kim, Sang-Ryoung; Kim, Jae-Hong

    2017-01-17

    Damages to water filtration membranes during installation and operation are known to cause detrimental loss of the product water quality. Membranes that have the ability to self-heal would recover their original rejection levels autonomously, bypassing the need for costly integrity monitoring and membrane replacement practices. Herein, we fabricated hydrogel pore-filled membranes via in situ graft polymerization of 2-acrylamido-2-methyl-1-propanesulfonic acid (AMPS) onto microporous poly(ether sulfone) (PES) substrates and successfully demonstrated their self-healing ability. Covalent attachment of the hydrogel to the substrate was essential for stable membrane performance. The membranes autonomously restore their particle rejection up to 99% from rejection levels as low as 30% after being physically damaged. We attribute the observed self-healing property to swelling of the pore-filling hydrogel into the damage site, strong hydrogen bonding, and molecular interdiffusion. The results of this study show that hydrogel pore-filled membranes are a promising new class of materials for fabricating self-healing membranes.

  20. Mechanically stiff, electrically conductive composites of polymers and carbon nanotubes

    SciTech Connect

    Worsley, Marcus A.; Kucheyev, Sergei O.; Baumann, Theodore F.; Kuntz, Joshua D.; Satcher, Jr., Joe H.; Hamza, Alex V.

    2015-07-21

    Using SWNT-CA as scaffolds to fabricate stiff, highly conductive polymer (PDMS) composites. The SWNT-CA is immersing in a polymer resin to produce a SWNT-CA infiltrated with a polymer resin. The SWNT-CA infiltrated with a polymer resin is cured to produce the stiff and electrically conductive composite of carbon nanotube aerogel and polymer.

  1. Aqueous vinylidene fluoride polymer coating composition

    NASA Technical Reports Server (NTRS)

    Bartoszek, Edward J. (Inventor); Christofas, Alkis (Inventor)

    1978-01-01

    A water-based coating composition which may be air dried to form durable, fire resistant coatings includes dispersed vinylidene fluoride polymer particles, emulsified liquid epoxy resin and a dissolved emulsifying agent for said epoxy resin which agent is also capable of rapidly curing the epoxy resin upon removal of the water from the composition.

  2. Fracture toughness testing of polymer matrix composites

    NASA Technical Reports Server (NTRS)

    Grady, Joseph E.

    1992-01-01

    The experimental techniques and associated data analysis methods used to measure the resistance to interlaminar fracture, or 'fracture toughness', of polymer matrix composite materials are described. A review in the use of energy techniques to characterize fracture behavior in elastic solids is given. An overview is presented of the types of approaches employed in the design of delamination-resistant composite materials.

  3. Development of nanoparticle stabilized polymer nanocontainers with high content of the encapsulated active agent and their application in water-borne anticorrosive coatings.

    PubMed

    Haase, Martin F; Grigoriev, Dmitry O; Möhwald, Helmuth; Shchukin, Dmitry G

    2012-05-08

    A novel method for the encapsulation of organic active agents in nanoparticle-armored polymer composite nanocontainers (analog of Pickering emulsions) is introduced. The multifunctionality of the constituents allows a fabrication path that does not require auxiliary materials. Embedding the composite nanocontainers into a water-based alkyd resin and subsequent film formation yields a homogeneous polymer film doped with highly disperse composite nanocontainers. The resistance and self-healing of such a film on aluminium is enhanced.

  4. Enhanced Access Polynomial Based Self-healing Key Distribution

    NASA Astrophysics Data System (ADS)

    Dutta, Ratna; Mukhopadhyay, Sourav; Dowling, Tom

    A fundamental concern of any secure group communication system is that of key management. Wireless environments create new key management problems and requirements to solve these problems. One such core requirement in these emerging networks is that of self-healing. In systems where users can be offline and miss updates self healing allows a user to recover lost keys and get back into the secure communication without putting extra burden on the group manager. Clearly self healing must be only available to authorized users and this creates more challenges in that we must ensure unauthorized or revoked users cannot, themselves or by means of collusion, avail of self healing. To this end we enhance the one-way key chain based self-healing key distribution of Dutta et al. by introducing a collusion resistance property between the revoked users and the newly joined users. Our scheme is based on the concept of access polynomials. These can be loosely thought of as white lists of authorized users as opposed to the more widely used revocation polynomials or black lists of revoked users. We also allow each user a pre-arranged life cycle distributed by the group manager. Our scheme provides better efficiency in terms of storage, and the communication and computation costs do not increase as the number of sessions grows as compared to most current schemes. We analyze our scheme in an appropriate security model and prove that the proposed scheme is computationally secure and not only achieving forward and backward secrecy, but also resisting collusion between the new joined users and the revoked users. Unlike most existing schemes the new scheme allows temporary revocation. Also unlike existing schemes, our construction does not collapse if the number of revoked users crosses a threshold value. This feature increases resilience against revocation based denial of service (DOS) attacks and thus improves availability of communication channel.

  5. Polymer Composites Corrosive Degradation: A Computational Simulation

    NASA Technical Reports Server (NTRS)

    Chamis, Christos C.; Minnetyan, Levon

    2007-01-01

    A computational simulation of polymer composites corrosive durability is presented. The corrosive environment is assumed to manage the polymer composite degradation on a ply-by-ply basis. The degradation is correlated with a measured pH factor and is represented by voids, temperature and moisture which vary parabolically for voids and linearly for temperature and moisture through the laminate thickness. The simulation is performed by a computational composite mechanics computer code which includes micro, macro, combined stress failure and laminate theories. This accounts for starting the simulation from constitutive material properties and up to the laminate scale which exposes the laminate to the corrosive environment. Results obtained for one laminate indicate that the ply-by-ply degradation degrades the laminate to the last one or the last several plies. Results also demonstrate that the simulation is applicable to other polymer composite systems as well.

  6. Glass/polymer composites and methods of making

    DOEpatents

    Samuels, W. D.; Exarhos, Gregory J.

    1995-01-01

    The present invention relates to new glass/polymer composites and methods for making them. More specifically, the invention is glass/polymer composites having phases that are at the molecular level and thereby practicably indistinguishable. The invention further discloses making molecular phase glass/polymer composites by mixing a glass and a polymer in a compatible solvent.

  7. Glass/polymer composites and methods of making

    DOEpatents

    Samuels, W.D.; Exarhos, G.J.

    1995-06-06

    The present invention relates to new glass/polymer composites and methods for making them. More specifically, the invention is glass/polymer composites having phases that are at the molecular level and thereby practicably indistinguishable. The invention further discloses making molecular phase glass/polymer composites by mixing a glass and a polymer in a compatible solvent.

  8. 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.

  9. Polymer hybrid nano/micro composites

    SciTech Connect

    Dzenis, Y.A.; Reneker, D.H.

    1994-12-31

    Nanocomposites based on ceramic and metal matrices attracted considerable attention during the past decade. Polymer based nanocomposites are much less well-known. Recently, a method of electrospinning of thin polymer fibers has been developed. Continuous, oriented fibers with diameters ranging from 50 nanometers to several microns have been prepared from over 30 different synthetic and natural polymers, including high temperature high modulus polyimide and polyaramid (Kevlar) fibers. The possible applications of these small fibers in hybrid polymer hierarchical composites are discussed. Micromechanics models of hybrid composites are developed based on the models for two component composites and on the principle of effective homogeneity. Effective thermoviscoelastic characteristics of nano and microfiber composite as well as nanofiber and microparticulate composites are calculated. ``Strong`` hybrid effects are observed in the dependence of effective moduli, loss factor, creep factor, and thermal expansion coefficient on fractional content of fibers of different diameters. The extrema are located at the higher fractions of larger reinforcing elements. Similarities of composite microstructures having synergistic ``extremal`` properties with some biological composites are noted.

  10. Nanoparticle-sulphur "inverse vulcanisation" polymer composites.

    PubMed

    Bear, Joseph C; Peveler, William J; McNaughter, Paul D; Parkin, Ivan P; O'Brien, Paul; Dunnill, Charles W

    2015-07-04

    Composites of sulphur polymers with nanoparticles such as PbS, with tunable optical properties are reported. A hydrothermal route incorporating pre-formed nanoparticles was used, and their physical and chemical properties evaluated by transmission and scanning electron microscopy, thermogravimetric and elemental analyses. These polymers are easily synthesised from an industrial waste material, elemental sulphur, can be cast into virtually any form and as such represent a new class of materials designed for a responsible energy future.

  11. Ionic conduction in polymer composite electrolytes

    NASA Astrophysics Data System (ADS)

    Dam, Tapabrata; Tripathy, Satya N.; Paluch, M.; Jena, S.; Pradhan, D. K.

    2016-05-01

    Conductivity and structural relaxation has been explored from modulus and dielectric loss formalisms respectively for a series of polymer composite electrolytes with zirconia as filler. The temperature dependence of conductivity followed Vogel-Tamman-Fulcher (VTF) behavior, which suggested a close correlation between conductivity and the segmental relaxation process in polymer electrolytes. Vogel temperature (T0) plays significant role in ion conduction process in these kind of materials.

  12. One-Pot Automated Synthesis of Quasi Triblock Copolymers for Self-Healing Physically Crosslinked Hydrogels.

    PubMed

    Voorhaar, Lenny; De Meyer, Bernhard; Du Prez, Filip; Hoogenboom, Richard

    2016-10-01

    The preparation of physically crosslinked hydrogels from quasi ABA-triblock copolymers with a water-soluble middle block and hydrophobic end groups is reported. The hydrophilic monomer N-acryloylmorpholine is copolymerized with hydrophobic isobornyl acrylate via a one-pot sequential monomer addition through reversible addition fragmentation chain-transfer (RAFT) polymerization in an automated parallel synthesizer, allowing systematic variation of polymer chain length and hydrophobic-hydrophilic ratio. Hydrophobic interactions between the outer blocks cause them to phase-separate into larger hydrophobic domains in water, forming physical crosslinks between the polymers. The resulting hydrogels are studied using rheology and their self-healing ability after large strain damage is shown. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  13. Highly Flexible, Tough, and Self-Healing Supramolecular Polymeric Materials Using Host-Guest Interaction.

    PubMed

    Nakahata, Masaki; Takashima, Yoshinori; Harada, Akira

    2015-09-23

    Flexible, tough, and self-healable polymeric materials are promising to be a solution to the energy problem by substituting for conventional heavy materials. A fusion of supramolecular chemistry and polymer chemistry is a powerful method to create such intelligent materials. Here, a supramolecular polymeric material using multipoint molecular recognition between cyclodextrin (CD) and hydrophobic guest molecules at polymer side chain is reported. A transparent, flexible, and tough hydrogel (host-guest gel) is formed by a simple preparation procedure. The host-guest gel shows self-healing property in both wet state and dry state due to reversible nature of host-guest interaction. The practical utility of the host-guest gel as a scratch curable coating is demonstrated.

  14. Hygrothermal modeling and testing of polymers and polymer matrix composites

    NASA Astrophysics Data System (ADS)

    Xu, Weiqun

    2000-10-01

    The dissertation, consisting of four papers, presents the results of the research investigation on environmental effects on polymers and polymer matrix composites. Hygrothermal models were developed that would allow characterization of non-Fickian diffusion coefficients from moisture weight gain data. Hygrothermal testing was also conducted to provide the necessary data for characterizing of model coefficients and model verification. In part 1, a methodology is proposed that would allow characterization of non-Fickian diffusion coefficients from moisture weight gain data for a polymer adhesive below its Tg. Subsequently, these diffusion coefficients are used for predicting moisture concentration profiles through the thickness of a polymer. In part 2, a modeling methodology based on irreversible thermodynamics applied within the framework of composite macro-mechanics is presented, that would allow characterization of non-Fickian diffusion coefficients from moisture weight gain data for laminated composites with distributed uniaxial damage. Comparisons with test data for a 5-harness satin textile composite with uniaxial micro-cracks are provided for model verifications. In part 3, the same modeling methodology based on irreversible thermodynamics is extended to the case of a bi-axially damaged laminate. The model allows characterization of nonFickian diffusion coefficients as well as moisture saturation level from moisture weight gain data for laminates with pre-existing damage. Comparisons with test data for a bi-axially damaged Graphite/Epoxy woven composite are provided for model verifications. Finally, in part 4, hygrothermal tests conducted on AS4/PR500 5HS textile composite laminates are summarized. The objectives of the hygrothermal tests are to determine the diffusivity and maximum moisture content of the laminate.

  15. Characterization and analysis of carbon fibre-reinforced polymer composite laminates with embedded circular vasculature

    PubMed Central

    Huang, C.-Y.; Trask, R. S.; Bond, I. P.

    2010-01-01

    A study of the influence of embedded circular hollow vascules on structural performance of a fibre-reinforced polymer (FRP) composite laminate is presented. Incorporating such vascules will lead to multi-functional composites by bestowing functions such as self-healing and active thermal management. However, the presence of off-axis vascules leads to localized disruption to the fibre architecture, i.e. resin-rich pockets, which are regarded as internal defects and may cause stress concentrations within the structure. Engineering approaches for creating these simple vascule geometries in conventional FRP laminates are proposed and demonstrated. This study includes development of a manufacturing method for forming vascules, microscopic characterization of their effect on the laminate, finite element (FE) analysis of crack initiation and failure under load, and validation of the FE results via mechanical testing observed using high-speed photography. The failure behaviour predicted by FE modelling is in good agreement with experimental results. The reduction in compressive strength owing to the embedding of circular vascules ranges from 13 to 70 per cent, which correlates with vascule dimension. PMID:20150337

  16. Characterization and analysis of carbon fibre-reinforced polymer composite laminates with embedded circular vasculature.

    PubMed

    Huang, C-Y; Trask, R S; Bond, I P

    2010-08-06

    A study of the influence of embedded circular hollow vascules on structural performance of a fibre-reinforced polymer (FRP) composite laminate is presented. Incorporating such vascules will lead to multi-functional composites by bestowing functions such as self-healing and active thermal management. However, the presence of off-axis vascules leads to localized disruption to the fibre architecture, i.e. resin-rich pockets, which are regarded as internal defects and may cause stress concentrations within the structure. Engineering approaches for creating these simple vascule geometries in conventional FRP laminates are proposed and demonstrated. This study includes development of a manufacturing method for forming vascules, microscopic characterization of their effect on the laminate, finite element (FE) analysis of crack initiation and failure under load, and validation of the FE results via mechanical testing observed using high-speed photography. The failure behaviour predicted by FE modelling is in good agreement with experimental results. The reduction in compressive strength owing to the embedding of circular vascules ranges from 13 to 70 per cent, which correlates with vascule dimension.

  17. FT-IR Investigation of Hoveyda-Grubbs'2{sup nd} Generation Catalyst in Self-Healing Epoxy Mixtures

    SciTech Connect

    Guadagno, Liberata; Naddeo, Carlo; Vittoria, Vittoria; Longo, Pasquale; Raimondo, Marialuigia; Mariconda, Annaluisa; Iannuzzo, Generoso; Russo, Salvatore

    2010-06-02

    The development of smart composites capable of self-repair on aeronautical structures is still at the planning stage owing to complex issues to overcome. A very important issue to solve concerns the components' stability of the proposed composites which are compromised at the cure temperatures necessary for good performance of the composite. In this work we analyzed the possibility to apply Hoveyda Grubbs' second generation catalyst (HG2) to develop self-healing systems. Our experimental results have shown critical issues in the use of epoxy precursors in conjunction with Hoveyda-Grubbs II metathesis catalyst. However, an appropriate curing cycle of the self-healing mixture permits to overcome the critical issues making possible high temperatures for the curing process without deactivating self-repair activity.

  18. Wear Characteristics of Polymer -Based Composites

    NASA Astrophysics Data System (ADS)

    Şahin, Y.; Mirzayev, H.

    2015-11-01

    The dry wear of polytetrafluoroethylene (PTFE)-based composites, including bronze-filled composites (B60), glass-filled composites (G15), and carbon-filled composites (C25), produced by the mold casting method were investigated under different sliding conditions. The Taguchi L27 method and the analysis of variance were used to identify the effect of process parameters on the wear of tested materials. Experimental results showed that the wear resistance of G15 polymer composites was better than those of C25 and B60 ones. The specific wear rate decreased with increasing sliding distance and load, but partly decreased with increasing tensile strength.

  19. A strong and stretchable self-healing film with self-activated pressure sensitivity for potential artificial skin applications

    PubMed Central

    Hou, Chengyi; Huang, Tao; Wang, Hongzhi; Yu, Hao; Zhang, Qinghong; Li, Yaogang

    2013-01-01

    Artificial skin, which mimics the functions of natural skin, will be very important in the future for robots used by humans in daily life. However, combining skin's pressure sensitivity and mechanical self-healing properties in a man-made material remains a challenging task. Here, we show that graphene and polymers can be integrated into a thin film which mimics both the mechanical self-healing and pressure sensitivity behavior of natural skin without any external power supply. Its ultimate strain and tensile strength are even two and ten times larger than the corresponding values of human skin, respectively. It also demonstrates highly stable sensitivity to a very light touch (0.02 kPa), even in bending or stretching states. PMID:24190511

  20. Electrophoretic deposition of chiral polymers and composites.

    PubMed

    Wang, Y; Pang, X; Zhitomirsky, I

    2011-10-15

    Electrophoretic deposition (EPD) method has been developed for the deposition of thin films of chiral polymers. EPD of poly-L-lysine (PLL) and poly-L-ornithine (PLO) films was performed for the first time on conductive substrates from aqueous and ethanol-water solutions. The deposition yield was monitored using a quartz crystal microbalance. The results demonstrated that the deposition yield can be varied by variation of the deposition time, voltage and polymer concentration in the solutions. It was shown that PLL and PLO provided stabilization and charging of hydroxyapatite (HA) nanoparticles in suspensions. Composite PLL-HA and PLO-HA films of controlled thickness were prepared by EPD. Electron microscopy investigations showed that the thickness of the PLL, PLO and composite films was varied in the range of 0-3 μm. The polymer and composite films can be used for biomedical applications.

  1. Polymer Matrix Composites for Propulsion Systems

    NASA Technical Reports Server (NTRS)

    Nettles, Alan T.

    2003-01-01

    The Access-to-Space study identified the requirement for lightweight structures to achieve orbit with a single-stage vehicle. Thus a task was undertaken to examine the use of polymer matrix composites for propulsion components. It was determined that the effort of this task would be to extend previous efforts with polymer matrix composite feedlines and demonstrate the feasibility of manufacturing large diameter feedlines with a complex shape and integral flanges, (i.e. all one piece with a 90 deg bend), and assess their performance under a cryogenic atmosphere.

  2. Ultrafast Self-Healing Nanocomposites via Infrared Laser and Their Application in Flexible Electronics.

    PubMed

    Wu, Shuwen; Li, Jinhui; Zhang, Guoping; Yao, Yimin; Li, Gang; Sun, Rong; Wong, Chingping

    2017-01-25

    The continuous evolution toward flexible electronics with mechanical robust property and restoring structure simultaneously places high demand on a set of polymeric material substrate. Herein, we describe a composite material composed of a polyurethane based on Diels-Alder chemistry (PU-DA) covalently linked with functionalized graphene nanosheets (FGNS), which shows mechanical robust and infrared (IR) laser self-healing properties at ambient conditions and is therefore suitable for flexible substrate applications. The mechanical strength can be tuned by varying the amount of FGNS and breaking strength can reach as high as 36 MPa with only 0.5 wt % FGNS loading. On rupture, the initial mechanical properties are restored with more than 96% healing efficiency after 1 min irradiation time by 980 nm IR laser. Especially, this is the highest value of healing efficiency reported in the self-healable materials based on DA chemistry systems until now, and the composite exhibits a high volume resistivity up to 5.6 × 10(11) Ω·cm even the loading of FGNS increased to 1.0 wt %. Moreover, the conductivity of the broken electric circuit which was fabricated by silver paste drop-cast on the healable composite substrate was completely recovered via IR laser irradiating bottom substrate mimicking human skin. These results demonstrate that the FGNS-PU-DA nanocomposite can be used as self-healing flexible substrate for the next generation of intelligent flexible electronics.

  3. Metal oxide-polymer composites

    NASA Technical Reports Server (NTRS)

    Wellinghoff, Stephen T. (Inventor)

    1994-01-01

    A method of making metal oxide clusters in a single stage by reacting a metal oxide with a substoichiometric amount of an acid in the presence of an oxide particle growth terminator and solubilizer. A method of making a ceramer is also disclosed in which the metal oxide clusters are reacted with a functionalized polymer. The resultant metal oxide clusters and ceramers are also disclosed.

  4. Metal oxide-polymer composites

    NASA Technical Reports Server (NTRS)

    Wellinghoff, Stephen T. (Inventor)

    1997-01-01

    A method of making metal oxide clusters in a single stage by reacting a metal oxide with a substoichiometric amount of an acid in the presence of an oxide particle growth terminator and solubilizer. A method of making a ceramer is also disclosed in which the metal oxide clusters are reacted with a functionalized polymer. The resultant metal oxide clusters and ceramers are also disclosed.

  5. Aging of Polymers and Composites.

    DTIC Science & Technology

    1981-07-21

    were cast according to the method described by Fanter. 12 A two-part silicone-rubber casting material ( RTV - 664 , General Electric) was poured into a...J. Wolf, Stress Mass Spectrometry of Nylon 66, Applications of Polymer Spectroscopy ( E . G . Brame, Jr., Ed.) (Academic Press, New York, NY, 1978) p...BEFORE COMPLETING FORM I. REPORT NUMBER 2. GOVT ACCESSION NO. 3. RECIPIENT’S CATALOG NUMBER MDC ( 0743 4. TITLE (and Subtitle) 5. TYPE OF REPORT & PERIOD

  6. Self Healing Concrete: A Biological Approach

    NASA Astrophysics Data System (ADS)

    Jonkers, Henk M.

    Concrete can be considered as a kind of artificial rock with properties more or less similar to certain natural rocks. As it is strong, durable, and relatively cheap, concrete is, since almost two centuries, the most used construction material worldwide, which can easily be recognized as it has changed the physiognomy of rural areas. However, due to the heterogeneity of the composition of its principle components, cement, water, and a variety of aggregates, the properties of the final product can widely vary. The structural designer therefore must previously establish which properties are important for a specific application and must choose the correct composition of the concrete ingredients in order to ensure that the final product applies to the previously set standards. Concrete is typically characterized by a high-compressive strength, but unfortunately also by a rather low-tensile strength. However, through the application of steel or other material reinforcements, the latter can be compensated for as such reinforcements can take over tensile forces.

  7. Polyfibroblast: A Self-Healing and Galvanic Protection Additive

    DTIC Science & Technology

    2013-03-22

    show failures with no clear cut differences between the control and the enhanced primers. Such adhesion issues are common when the surface has not...Resistivities of Control NCP and Enhanced NCP primers are 5xl06 and UxlO6 Ohm/sq respectively indicating we may be able to use simple enamel rater...instrumentation to evaluate self-healing. 1. Enamel rater evaluation underway. 2. 1 |im films of OTS prepared on Cold Rolled Steel and Blasted Steel panels

  8. Polyfibroblast: A Self-Healing and Galvanic Protection Additive

    DTIC Science & Technology

    2013-07-25

    OBIECTIVES 1 KEY ACCOMPLISHMENTS 3.1 ON SITE INSPECTION OF COATING HEALTH 2 3.2 MICROCAPSULE SHEAR STRENGTH 4 3.3 NEXT STEPS 5 1 Summary Initial...experiments with the handheld fluorescence microscope were successful in imaging Nile Red-loaded microcapsules within the self-healing paint. However...the microcapsule shells were brighter than the entrained fluid, making it difficult to assess the health of the coating. Shear strength

  9. Multiwalled Carbon nanotube - Strength to polymer composite

    NASA Astrophysics Data System (ADS)

    Pravin, Jagdale; Khan, Aamer. A.; Massimo, Rovere; Carlo, Rosso; Alberto, Tagliaferro

    2016-02-01

    Carbon nanotubes (CNTs), a rather fascinating material, are among the pillars of nanotechnology. CNTs exhibit unique electrical, mechanical, adsorption, and thermal properties with high aspect ratio, exceptional stiffness, excellent strength, and low density, which can be exploited in the manufacturing of revolutionary smart nano composite materials. The demand for lighter and stronger polymer composite material in various applications is increasing every day. Among all the possibilities to research and exploit the exceptional properties of CNTs in polymer composites we focused on the reinforcement of epoxy resin with different types of multiwalled carbon nano tubes (MWCNTs). We studied mechanical properties such as stress, strain, ultimate tensile strength, yield point, modulus and fracture toughness, and Young's modulus by plotting and calculating by means of the off-set method. The mechanical strength of epoxy composite is increased intensely with 1 and 3 wt.% of filler.

  10. A Multiple-Action Self-Healing Coating

    NASA Astrophysics Data System (ADS)

    Lutz, Alexander; van den Berg, Otto; Wielant, Jan; De Graeve, Iris; Terryn, Herman

    2015-12-01

    This paper describes a self-healing coating for corrosion protection of metals which combines two different types of self-healing mechanisms in one coating with multiple-healing functionality. 2-Mercaptobenzothiazole (MBT) was loaded into layered double hydroxide (LDH) carriers which were mixed into an acrylated polycaprolactone polyurethane based shape recovery coating and applied on Hot Dip Galvanized steel (HDG). The effect of triggered release of MBT on the protection of HDG became visible when samples with manually applied defects in the coating were immersed in 0.05 M NaCl solution (first, autonomous healing mechanism). The shape recovery (second, non-autonomous healing mechanism) was triggered by heating the samples for 2 minutes to 60°C. SEM-EDX and Raman Spectroscopy proved the presence of MBT in the LDH, in the MBT-loaded LDH in the coating and the released MBT on the HDG surface in the damaged area after being in contact with a solution containing corrosive ions. Electrochemical impedance spectroscopy (EIS) and scanning vibrating electrode technique (SVET) demonstrate the corrosion protection effect of MBT in the coating with a defect and the restoration of the barrier properties of the coating after defect closure. This way, the independent mechanisms of this multi-action self-healing coating could be demonstrated.

  11. Self-Healing in Cementitious Materials—A Review

    PubMed Central

    Van Tittelboom, Kim; De Belie, Nele

    2013-01-01

    Concrete is very sensitive to crack formation. As wide cracks endanger the durability, repair may be required. However, these repair works raise the life-cycle cost of concrete as they are labor intensive and because the structure becomes in disuse during repair. In 1994, C. Dry was the first who proposed the intentional introduction of self-healing properties in concrete. In the following years, several researchers started to investigate this topic. The goal of this review is to provide an in-depth comparison of the different self-healing approaches which are available today. Among these approaches, some are aimed at improving the natural mechanism of autogenous crack healing, while others are aimed at modifying concrete by embedding capsules with suitable healing agents so that cracks heal in a completely autonomous way after they appear. In this review, special attention is paid to the types of healing agents and capsules used. In addition, the various methodologies have been evaluated based on the trigger mechanism used and attention has been paid to the properties regained due to self-healing. PMID:28809268

  12. Self-Healing in Cementitious Materials-A Review.

    PubMed

    Van Tittelboom, Kim; De Belie, Nele

    2013-05-27

    Concrete is very sensitive to crack formation. As wide cracks endanger the durability, repair may be required. However, these repair works raise the life-cycle cost of concrete as they are labor intensive and because the structure becomes in disuse during repair. In 1994, C. Dry was the first who proposed the intentional introduction of self-healing properties in concrete. In the following years, several researchers started to investigate this topic. The goal of this review is to provide an in-depth comparison of the different self-healing approaches which are available today. Among these approaches, some are aimed at improving the natural mechanism of autogenous crack healing, while others are aimed at modifying concrete by embedding capsules with suitable healing agents so that cracks heal in a completely autonomous way after they appear. In this review, special attention is paid to the types of healing agents and capsules used. In addition, the various methodologies have been evaluated based on the trigger mechanism used and attention has been paid to the properties regained due to self-healing.

  13. Functionalized Agarose Self-Healing Ionogels Suitable for Supercapacitors.

    PubMed

    Trivedi, Tushar J; Bhattacharjya, Dhrubajyoti; Yu, Jong-Sung; Kumar, Arvind

    2015-10-12

    Agarose has been functionalized (acetylated/carbanilated) in an ionic liquid (IL) medium of 1-butyl-3-methylimidazolium acetate at ambient conditions. The acetylated agarose showed a highly hydrophobic nature, whereas the carbanilated agarose could be dissolved in water as well as in the IL medium. Thermoreversible ionogels were obtained by cooling the IL sols of carbanilated agarose at room temperature. The ionogel prepared from a protic-aprotic mixed-IL system (1-butyl-3-methylimidazolium chloride and N-(2-hydroxyethyl)ammonium formate) demonstrated a superior self-healing property, as confirmed from rheological measurements. The superior self-healing property of such an ionogel has been attributed to the unique inter-intra hydrogen-bonding network of functional groups inserted in the agarose. The ionogel was tested as a flexible solid electrolyte for an activated-carbon-based supercapacitor cell. The measured specific capacitance was found to be comparable with that of a liquid electrolyte system at room temperature and was maintained for up to 1000 charge-discharge cycles. Such novel functionalized-biopolymer self-healing ionogels with flexibility and good conductivity are desirable for energy-storage devices and electronic skins with superior lifespans and robustness.

  14. Gamma Irradiation of Active Self-healing PLGA Microspheres for Efficient Aqueous Encapsulation of Vaccine Antigens

    PubMed Central

    Desai, Kashappa-Goud H.; Kadous, Samer; Schwendeman, Steven P.

    2013-01-01

    Purpose To investigate the effect of γ-irradiation of poly(lactic-co-glycolic acid) (PLGA)/Al(OH)3/0 or 5 wt% diethyl phthalate (DEP) microspheres for active self-healing encapsulation of vaccine antigens. Methods Microspheres were irradiated with 60Co at 2.5 and 1.8 MRad and 0.37 and 0.20 MRad/h. Encapsulation of tetanus toxoid (TT) was achieved by mixing Al(OH)3-PLGA microspheres with TT solution at 10-38°C. Electron paramagnetic resonance (EPR) spectroscopy was used to examine free radical formation. Glass transition temperature (Tg) and molecular weight of PLGA was measured by differential scanning calorimetry and gel permeation chromatography, respectively. Loading and release of TT were examined by modified Bradford, amino acid analysis, and ELISA assays. Results EPR spectroscopy results indicated absence of free radicals in PLGA microspheres after γ-irradiation. Antigen-sorbing capacity, encapsulation efficiency, and Tg of the polymer were also not adversely affected. When DEP-loaded microspheres were irradiated at 0.2 MRad/h, some PLGA pores healed during irradiation and PLGA healing during encapsulation was suppressed. The molecular weight of PLGA was slightly reduced when DEP-loaded microspheres were irradiated at the same dose rate. These trends were not observed at 0.37 MRad/h. Gamma irradiation slightly increased TT initial burst release. Apart from the slightly higher polymer molecular weight decline caused by higher irradiation dose in case of DEP-loaded microspheres, the small increase in total irradiation dose from 1.8 to 2.5 MRad had insignificant effect on the polymer and microspheres properties analyzed. Conclusion Gamma irradiation is a plausible approach to provide a terminally sterilized, self-healing encapsulation PLGA excipient for vaccine delivery. PMID:23515830

  15. Method of making metal-polymer composite catalysts

    DOEpatents

    Zelena, Piotr [Los Alamos, NM; Bashyam, Rajesh [Los Alamos, NM

    2009-06-23

    A metal-polymer-carbon composite catalyst for use as a cathode electrocatalyst in fuel cells. The catalyst includes a heteroatomic polymer; a transition metal linked to the heteroatomic polymer by one of nitrogen, sulfur, and phosphorus, and a recast ionomer dispersed throughout the heteroatomic polymer-carbon composite. The method includes forming a heteroatomic polymer-carbon composite and loading the transition metal onto the composite. The invention also provides a method of making a membrane electrode assembly for a fuel cell that includes the metal-polymer-carbon composite catalyst.

  16. Acoustic emission monitoring of polymer composite materials

    NASA Technical Reports Server (NTRS)

    Bardenheier, R.

    1981-01-01

    The techniques of acoustic emission monitoring of polymer composite materials is described. It is highly sensitive, quasi-nondestructive testing method that indicates the origin and behavior of flaws in such materials when submitted to different load exposures. With the use of sophisticated signal analysis methods it is possible the distinguish between different types of failure mechanisms, such as fiber fracture delamination or fiber pull-out. Imperfections can be detected while monitoring complex composite structures by acoustic emission measurements.

  17. Self Healing in Coatings at High Temperatures

    NASA Astrophysics Data System (ADS)

    Sloof, Wim G.

    Alloys for high temperature applications in an oxidizing environment depend on the formation of a protective and slow growing oxide scale. The composition of these alloys is such that a continuous layer of a thermodynamically stable oxide is formed through selective oxidation of one of the constituting elements. Then, the oxide layer forms a barrier between the environment and the underlying alloy. The alloys for high temperature applications can be divided into alumina (Al2O3), silica (SiO2), or chromia (Cr2O3) formers, such as stainless steels, superalloys (Reed 2006), and intermetallics (MX, where M is Ti, Fe, Co or Ni, and X denotes Al, Si, or Cr). These materials are successfully applied in for example gas turbine engines (aero, marine, and industrial), heating equipment and automotive converters etc. In this chapter, the focus will be on alumina forming alloys encountered as coating material for blades and vanes in gas turbine engines. However, the principles addressed also apply to the other mentioned classes of high temperature alloys.

  18. Outdoor durability of wood-polymer composites

    Treesearch

    N. M. Stark; D. J. Gardner

    2008-01-01

    Wood-plastic composite (WPC) lumber is promoted as a low-maintenance, high-durability product (Clemons, 2002). However, after a decade of exterior use in the construction industry, questions have arisen regarding durability. These questions are based on documented evidence of failures in the field of WPC decking products due to such impacts as polymer degradation (...

  19. Aging Effects in Polymer Composites

    NASA Technical Reports Server (NTRS)

    Chamis, Chistos C.; McManus, Hugh L.

    1999-01-01

    Simulation of composites degradation due to aging are described. Laminate geometry, material properties, and matrix degradation states are specified as functions of position and time. Matrix shrinkage and property changes are modeled as functions of the degradation states. Aging effects at the laminate, ply, and micro levels are evaluated, to determine failure of any kind. The results obtained show substantial ply stress built up as a result of aging accompanied by comparable laminate strength degradation in matrix dominated composite strengths.

  20. Aging Effects in Polymer Composites

    NASA Technical Reports Server (NTRS)

    Chamis, Chistos C.; McManus, Hugh L.

    1999-01-01

    Simulation of composites degradation due to aging are described. Laminate geometry, material properties, and matrix degradation states are specified as functions of position and time. Matrix shrinkage and property changes are modeled as functions of the degradation states. Aging effects at the laminate, ply, and micro levels are evaluated, to determine failure of any kind. The results obtained show substantial ply stress built up as a result of aging accompanied by comparable laminate strength degradation in matrix dominated composite strengths.

  1. Self-lubricating polymer composites and polymer transfer film lubrication for space applications

    NASA Technical Reports Server (NTRS)

    Fusaro, Robert L.

    1990-01-01

    The use of self-lubricating polymers and polymer composites in space is somewhat limited today. In general, they are only used when other methods are inadequate. There is potential, however, for these materials to make a significant impact on future space missions if properly utilized. Some of the different polymers and fillers used to make self-lubricating composites are surveyed. The mechanisms of composite lubrication and wear, the theory behind transfer film lubricating mechanisms, and some factors which affect polymer composite wear and transfer are examined. In addition, some of the current space tribology application areas for self-lubricating polymer composites and polymer transfer are mentioned.

  2. Joining of polymer composite materials

    SciTech Connect

    Magness, F.H.

    1990-11-01

    Under ideal conditions load bearing structures would be designed without joints, thus eliminating a source of added weight, complexity and weakness. In reality the need for accessibility, repair, and inspectability, added to the size limitations imposed by the manufacturing process and transportation/assembly requirements mean that some minimum number of joints will be required in most structures. The designer generally has two methods for joining fiber composite materials, adhesive bonding and mechanical fastening. As the use of thermoplastic materials increases, a third joining technique -- welding -- will become more common. It is the purpose of this document to provide a review of the available sources pertinent to the design of joints in fiber composites. The primary emphasis is given to adhesive bonding and mechanical fastening with information coming from documentary sources as old as 1961 and as recent as 1989. A third, shorter section on composite welding is included in order to provide a relatively comprehensive treatment of the subject.

  3. Piezoelectric Nanoparticle-Polymer Composite Materials

    NASA Astrophysics Data System (ADS)

    McCall, William Ray

    Herein we demonstrate that efficient piezoelectric nanoparticle-polymer composite materials can be synthesized and fabricated into complex microstructures using sugar-templating methods or optical printing techniques. Stretchable foams with excellent tunable piezoelectric properties are created by incorporating sugar grains directly into polydimethylsiloxane (PDMS) mixtures containing barium titanate (BaTiO3 -- BTO) nanoparticles and carbon nanotubes (CNTs), followed by removal of the sugar after polymer curing. Porosities and elasticity are tuned by simply adjusting the sugar/polymer mass ratio and the electrical performance of the foams showed a direct relationship between porosity and the piezoelectric outputs. User defined 2D and 3D optically printed piezoelectric microstructures are also fabricated by incorporating BTO nanoparticles into photoliable polymer solutions such as polyethylene glycol diacrylate (PEGDA) and exposing to digital optical masks that can be dynamically altered. Mechanical-to-electrical conversion efficiency of the optically printed composite is enhanced by chemically altering the surface of the BTO nanoparticles with acrylate groups which form direct covalent linkages with the polymer matrix under light exposure. Both of these novel materials should find exciting uses in a variety of applications including energy scavenging platforms, nano- and microelectromechanical systems (NEMS/MEMS), sensors, and acoustic actuators.

  4. Characterizing SWCNT Dispersion in Polymer Composites

    NASA Technical Reports Server (NTRS)

    Lillehei, Peter T.; Kim, Jae-Woo; Gibbons, Luke; Park, Cheol

    2007-01-01

    The new wave of single wall carbon nanotube (SWCNT) infused composites will yield structurally sound multifunctional nanomaterials. The SWCNT network requires thorough dispersion within the polymer matrix in order to maximize the benefits of the nanomaterial. However, before any nanomaterials can be used in aerospace applications a means of quality assurance and quality control must be certified. Quality control certification requires a means of quantification, however, the measurement protocol mandates a method of seeing the dispersion first. We describe here the new tools that we have developed and implemented to first be able to see carbon nanotubes in polymers and second to measure or quantify the dispersion of the nanotubes.

  5. Nano polypeptide particles reinforced polymer composite fibers.

    PubMed

    Li, Jiashen; Li, Yi; Zhang, Jing; Li, Gang; Liu, Xuan; Li, Zhi; Liu, Xuqing; Han, Yanxia; Zhao, Zheng

    2015-02-25

    Because of the intensified competition of land resources for growing food and natural textile fibers, there is an urgent need to reuse and recycle the consumed/wasted natural fibers as regenerated green materials. Although polypeptide was extracted from wool by alkaline hydrolysis, the size of the polypeptide fragments could be reduced to nanoscale. The wool polypeptide particles were fragile and could be crushed down to nano size again and dispersed evenly among polymer matrix under melt extrusion condition. The nano polypeptide particles could reinforce antiultraviolet capability, moisture regain, and mechanical properties of the polymer-polypeptide composite fibers.

  6. Polymer compositions, polymer films and methods and precursors for forming same

    DOEpatents

    Klaehn, John R; Peterson, Eric S; Orme, Christopher J

    2013-09-24

    Stable, high performance polymer compositions including polybenzimidazole (PBI) and a melamine-formaldehyde polymer, such as methylated, poly(melamine-co-formaldehyde), for forming structures such as films, fibers and bulky structures. The polymer compositions may be formed by combining polybenzimidazole with the melamine-formaldehyde polymer to form a precursor. The polybenzimidazole may be reacted and/or intertwined with the melamine-formaldehyde polymer to form the polymer composition. For example, a stable, free-standing film having a thickness of, for example, between about 5 .mu.m and about 30 .mu.m may be formed from the polymer composition. Such films may be used as gas separation membranes and may be submerged into water for extended periods without crazing and cracking. The polymer composition may also be used as a coating on substrates, such as metal and ceramics, or may be used for spinning fibers. Precursors for forming such polymer compositions are also disclosed.

  7. Self-healing in segmented metallized film capacitors: Experimental and theoretical investigations for engineering design

    NASA Astrophysics Data System (ADS)

    Belko, V. O.; Emelyanov, O. A.

    2016-01-01

    A significant increase in the efficiency of modern metallized film capacitors has been achieved by the application of special segmented nanometer-thick electrodes. The proper design of the electrode segmentation guarantees the best efficiency of the capacitor's self-healing (SH) ability. Meanwhile, the reported theoretical and experimental results have not led to the commonly accepted model of the SH process, since the experimental SH dissipated energy value is several times higher than the calculated one. In this paper, we show that the difference is caused by the heat outflow into polymer film. Based on this, a mathematical model of the metallized electrode destruction is developed. These insights in turn are leading to a better understanding of the SH development. The adequacy of the model is confirmed by both the experiments and the numerical calculations. A procedure of optimal segmented electrode design is offered.

  8. Piezoelectric Polymer/Ceramic Composite

    DTIC Science & Technology

    1989-05-02

    significant. The current in ?iEZEL samole was cbserved to reach steady state level in the region cf -i05 sec whereas in t-he prepared composites the tine talen ... technology is not a’ silable for prodccinc s;ch materials in tOe areas and thicknesses required for commecrcial applications in c:apacitolrs. Y~i5.h~4 ’~ x

  9. Thermal conductivity and multiferroics of electroactive polymers and polymer composites

    NASA Astrophysics Data System (ADS)

    Jin, Jiezhu

    Electronically conducting polymers and electromechanical polymers are the two important branches of the cutting-edge electroactive polymers. They have shown significant impact on many modern technologies such as flat panel display, energy transport, energy conversion, sensors and actuators. To utilize conducting polymers in microelectronics, optoelectronics and thermoelectrics, it is necessary to have a comprehensive study of their thermal conductivity since thermal conductivity is a fundamental materials property that is particularly important and sometimes a determining factor of the device performance. For electromechanical polymers, larger piezoelectric effect will contribute to the improvement of magnetoelectric (ME) coupling efficiency in their multiferroic composites. This dissertation is devoted to characterizing electronically conducting polymers for their electrical and thermal conductivity, and developing new classes of electromechanical polymers and strain-mediated electromechanical polymer-based multiferroic ME composites. Conducting polymers opened up new possibilities for devices combining novel electrical and thermal properties, but there has been limited understanding of the length-scale effect of the electrical and thermal conductivity, and the mechanism underlying the electricity and heat transport behavior. In this dissertation, the analytical model and experimental technique are presented to measure the in-plane thermal conductivity of polyaniline thin films. For camphorsulfonic acid doped polyaniline patterned on silicon oxide/silicon substrate using photolithography and reactive ion etching, the thermal conductivity of the film with thickness of 20 nm is measured to be 0.0406 W/m˙K, which significantly deviates from their bulk (> 0.26 W/m˙K). The size effect on thermal conductivity at this scale is attributed to the significant phonon boundary scattering. When the film goes up to 130 nm thick, the thermal conductivity increases to 0.166 W

  10. Mechanical Properties of Polymer Nano-composites

    NASA Astrophysics Data System (ADS)

    Srivastava, Iti

    Thermoset polymer composites are increasingly important in high-performance engineering industries due to their light-weight and high specific strength, finding cutting-edge applications such as aircraft fuselage material and automobile parts. Epoxy is the most widely employed thermoset polymer, but is brittle due to extensive cross-linking and notch sensitivity, necessitating mechanical property studies especially fracture toughness and fatigue resistance, to ameliorate the low crack resistance. Towards this end, various nano and micro fillers have been used with epoxy to form composite materials. Particularly for nano-fillers, the 1-100 nm scale dimensions lead to fascinating mechanical properties, oftentimes proving superior to the epoxy matrix. The chemical nature, topology, mechanical properties and geometry of the nano-fillers have a profound influence on nano-composite behavior and hence are studied in the context of enhancing properties and understanding reinforcement mechanisms in polymer matrix nano-composites. Using carbon nanotubes (CNTs) as polymer filler, uniquely results in both increased stiffness as well as toughness, leading to extensive research on their applications. Though CNTs-polymer nano-composites offer better mechanical properties, at high stress amplitude their fatigue resistance is lost. In this work covalent functionalization of CNTs has been found to have a profound impact on mechanical properties of the CNT-epoxy nano-composite. Amine treated CNTs were found to give rise to effective fatigue resistance throughout the whole range of stress intensity factor, in addition to significantly enhancing fracture toughness, ductility, Young's modulus and average hardness of the nano-composite by factors of 57%, 60%, 30% and 45% respectively over the matrix as a result of diminished localized cross-linking. Graphene, a one-atom-thick sheet of atoms is a carbon allotrope, which has garnered significant attention of the scientific community and is

  11. Setup of Extruded Cementitious Hollow Tubes as Containing/Releasing Devices in Self-Healing Systems

    PubMed Central

    Formia, Alessandra; Terranova, Salvatore; Antonaci, Paola; Pugno, Nicola Maria; Tulliani, Jean Marc

    2015-01-01

    The aim of this research is to produce self-healing cementitious composites based on the use of cylindrical capsules containing a repairing agent. Cementitious hollow tubes (CHT) having two different internal diameters (of 2 mm and 7.5 mm) were produced by extrusion and used as containers and releasing devices for cement paste/mortar healing agents. Based on the results of preliminary mechanical tests, sodium silicate was selected as the healing agent. The morphological features of several mix designs used to manufacture the extruded hollow tubes, as well as the coatings applied to increase the durability of both core and shell materials are discussed. Three-point bending tests were performed on samples produced with the addition of the above-mentioned cementitious hollow tubes to verify the self-healing effectiveness of the proposed solution. Promising results were achieved, in particular when tubes with a bigger diameter were used. In this case, a substantial strength and stiffness recovery was observed, even in specimens presenting large cracks (>1 mm). The method is inexpensive and simple to scale up; however, further research is needed in view of a final optimization. PMID:28788038

  12. Electrosprayed Multi-Core Alginate Microcapsules as Novel Self-Healing Containers

    NASA Astrophysics Data System (ADS)

    Hia, Iee Lee; Pasbakhsh, Pooria; Chan, Eng-Seng; Chai, Siang-Piao

    2016-10-01

    Alginate microcapsules containing epoxy resin were developed through electrospraying method and embedded into epoxy matrix to produce a capsule-based self-healing composite system. These formaldehyde free alginate/epoxy microcapsules were characterized via light microscope, field emission scanning electron microscope, fourier transform infrared spectroscopy and thermogravimetric analysis. Results showed that epoxy resin was successfully encapsulated within alginate matrix to form porous (multi-core) microcapsules with pore size ranged from 5-100 μm. The microcapsules had an average size of 320 ± 20 μm with decomposition temperature at 220 °C. The loading capacity of these capsules was estimated to be 79%. Under in situ healing test, impact specimens showed healing efficiency as high as 86% and the ability to heal up to 3 times due to the multi-core capsule structure and the high impact energy test that triggered the released of epoxy especially in the second and third healings. TDCB specimens showed one-time healing only with the highest healing efficiency of 76%. The single healing event was attributed by the constant crack propagation rate of TDCB fracture test. For the first time, a cost effective, environmentally benign and sustainable capsule-based self-healing system with multiple healing capabilities and high healing performance was developed.

  13. Setup of Extruded Cementitious Hollow Tubes as Containing/Releasing Devices in Self-Healing Systems.

    PubMed

    Formia, Alessandra; Terranova, Salvatore; Antonaci, Paola; Pugno, Nicola Maria; Tulliani, Jean Marc

    2015-04-21

    The aim of this research is to produce self-healing cementitious composites based on the use of cylindrical capsules containing a repairing agent. Cementitious hollow tubes (CHT) having two different internal diameters (of 2 mm and 7.5 mm) were produced by extrusion and used as containers and releasing devices for cement paste/mortar healing agents. Based on the results of preliminary mechanical tests, sodium silicate was selected as the healing agent. The morphological features of several mix designs used to manufacture the extruded hollow tubes, as well as the coatings applied to increase the durability of both core and shell materials are discussed. Three-point bending tests were performed on samples produced with the addition of the above-mentioned cementitious hollow tubes to verify the self-healing effectiveness of the proposed solution. Promising results were achieved, in particular when tubes with a bigger diameter were used. In this case, a substantial strength and stiffness recovery was observed, even in specimens presenting large cracks (>1 mm). The method is inexpensive and simple to scale up; however, further research is needed in view of a final optimization.

  14. Electrosprayed Multi-Core Alginate Microcapsules as Novel Self-Healing Containers.

    PubMed

    Hia, Iee Lee; Pasbakhsh, Pooria; Chan, Eng-Seng; Chai, Siang-Piao

    2016-10-03

    Alginate microcapsules containing epoxy resin were developed through electrospraying method and embedded into epoxy matrix to produce a capsule-based self-healing composite system. These formaldehyde free alginate/epoxy microcapsules were characterized via light microscope, field emission scanning electron microscope, fourier transform infrared spectroscopy and thermogravimetric analysis. Results showed that epoxy resin was successfully encapsulated within alginate matrix to form porous (multi-core) microcapsules with pore size ranged from 5-100 μm. The microcapsules had an average size of 320 ± 20 μm with decomposition temperature at 220 °C. The loading capacity of these capsules was estimated to be 79%. Under in situ healing test, impact specimens showed healing efficiency as high as 86% and the ability to heal up to 3 times due to the multi-core capsule structure and the high impact energy test that triggered the released of epoxy especially in the second and third healings. TDCB specimens showed one-time healing only with the highest healing efficiency of 76%. The single healing event was attributed by the constant crack propagation rate of TDCB fracture test. For the first time, a cost effective, environmentally benign and sustainable capsule-based self-healing system with multiple healing capabilities and high healing performance was developed.

  15. Electrosprayed Multi-Core Alginate Microcapsules as Novel Self-Healing Containers

    PubMed Central

    Hia, Iee Lee; Pasbakhsh, Pooria; Chan, Eng-Seng; Chai, Siang-Piao

    2016-01-01

    Alginate microcapsules containing epoxy resin were developed through electrospraying method and embedded into epoxy matrix to produce a capsule-based self-healing composite system. These formaldehyde free alginate/epoxy microcapsules were characterized via light microscope, field emission scanning electron microscope, fourier transform infrared spectroscopy and thermogravimetric analysis. Results showed that epoxy resin was successfully encapsulated within alginate matrix to form porous (multi-core) microcapsules with pore size ranged from 5–100 μm. The microcapsules had an average size of 320 ± 20 μm with decomposition temperature at 220 °C. The loading capacity of these capsules was estimated to be 79%. Under in situ healing test, impact specimens showed healing efficiency as high as 86% and the ability to heal up to 3 times due to the multi-core capsule structure and the high impact energy test that triggered the released of epoxy especially in the second and third healings. TDCB specimens showed one-time healing only with the highest healing efficiency of 76%. The single healing event was attributed by the constant crack propagation rate of TDCB fracture test. For the first time, a cost effective, environmentally benign and sustainable capsule-based self-healing system with multiple healing capabilities and high healing performance was developed. PMID:27694922

  16. Active photo-thermal self-healing of shape memory polyurethanes

    NASA Astrophysics Data System (ADS)

    Kazemi-Lari, Mohammad A.; Malakooti, Mohammad H.; Sodano, Henry A.

    2017-05-01

    Structural health monitoring (SHM) has received significant interest over the past decade and has led to the development of a wide variety of sensors and signal processing techniques to determine the presence of changes or damage in a structural system. The topic has attracted significant attention due to the safety and performance enhancing benefits as well as the potential lifesaving capabilities offered by the technology. While the resulting systems are capable of sensing their surrounding structural and environmental conditions, few methods exist for using the information to autonomously react and repair or protect the system. One of the major challenges in the future implementation of SHM systems is their coupling with materials that can react to the damage to heal themselves and return to normal function. The coupling of self-healing materials with SHM has the potential to significantly prolong the lifetime of structural systems and extend the required inspection intervals. In the present study, an optical fiber based self-healing system composed of mendable polyurethanes based on the thermally reversible Diels-Alder (DA) reaction is developed. Inspired by health monitoring techniques, active photo-thermal sensing and actuation is achieved using infrared laser light passing through an optical fiber and a thermal power sensor to detect the presence of cracking in the structure. Healing is triggered as the crack propagates through the polymer and fractures the embedded optical fiber. Through a feedback loop, the detected power drop by the sensor is utilized as a signal to heat the cracked area and stimulate the shape memory effect of the polyurethane and the retro-DA reaction. The healing performance results indicate that this novel integrated system can be effectively employed to monitor the incidence of damage and actively heal a crack in the polymer.

  17. Piezoelectric nanoparticle-polymer composite foams.

    PubMed

    McCall, William R; Kim, Kanguk; Heath, Cory; La Pierre, Gina; Sirbuly, Donald J

    2014-11-26

    Piezoelectric polymer composite foams are synthesized using different sugar-templating strategies. By incorporating sugar grains directly into polydimethylsiloxane mixtures containing barium titanate nanoparticles and carbon nanotubes, followed by removal of the sugar after polymer curing, highly compliant materials with excellent piezoelectric properties can be fabricated. Porosities and elasticity are tuned by simply adjusting the sugar/polymer mass ratio which gave an upper bound on the porosity of 73% and a lower bound on the elastic coefficient of 32 kPa. The electrical performance of the foams showed a direct relationship between porosity and the piezoelectric outputs, giving piezoelectric coefficient values of ∼112 pC/N and a power output of ∼18 mW/cm3 under a load of 10 N for the highest porosity samples. These novel materials should find exciting use in a variety of applications including energy scavenging platforms, biosensors, and acoustic actuators.

  18. Polymer light harvesting composites for optoelectronic applications

    NASA Astrophysics Data System (ADS)

    Sun, Sam-Shajing; Wang, Dan

    2015-09-01

    Polymer based optoelectronic composites and thin film devices exhibit great potential in space applications due to their lightweight, flexible shape, high photon absorption coefficients, and robust radiation tolerance in space environment. Polymer/dye composites appear promising for optoelectronics applications due to potential enhancements in both light harvesting and charge separation. In this study, the optoelectronic properties of a series of molecular dyes paired with a conjugated polymer Poly(3-hexylthiophene-2,5-diyl) (P3HT) were investigated. Specifically, the solution PL quenching coefficients (Ksv) of dye/polymer follows a descending order from dyes of Chloro(protoporphyrinato)iron(III) (Hemin), Protoporphyrin, to meso-Tetra(4-carboxyphenyl)porphine (TCPP). In optoelectronic devices made of the P3HT/dye/PCBM composites, the short circuit current densities Jsc as well as the overall power conversion efficiencies (PCE) also follow a descending order from Hemin, Protoporphyrin, to TCPP, despite Hemin exhibits the intermediate polymer/dye LUMO (lowest unoccupied molecular orbital) offset and lowest absorption coefficient as compared to the other two dyes, i.e., the cell optoelectronic efficiency did not follow the LUMO offsets which are the key driving forces for the photo induced charge separations. This study reveals that too large LUMO offset or electron transfer driving force may result in smaller PL quenching and optoelectronic conversion efficiency, this could be another experimental evidence for the Marcus electron transfer model, particularly for the Marcus `inverted region'. It appears an optimum electron transfer driving force or strong PL quenching appears more critical than absorption coefficient for optoelectronic conversion devices.

  19. Multi-Ferroic Polymer Nanoparticle Composites for Next Generation Metamaterials

    DTIC Science & Technology

    2016-05-23

    AFRL-AFOSR-JP-TR-2016-0056 Multi-Ferroic Polymer Nanoparticle Composites for Next Generation Metamaterials Yuanzhe Piao SEOUL NATIONAL UNIVERSITY...Mar 2015 4. TITLE AND SUBTITLE Multi-Ferroic Polymer Nanoparticle Composites for Next Generation Metamaterials 5a.  CONTRACT NUMBER 5b.  GRANT NUMBER... polymer composites consisting of magnetic nanoparticles that possess high , and low tan and polymer matrix with high dielectric constant and

  20. Development of Carbon-Nanotube/Polymer Composites

    NASA Technical Reports Server (NTRS)

    Reynolds, Thomas A.

    2005-01-01

    A report presents a short discussion of one company's effort to develop composites of carbon nanotubes in epoxy and other polymer matrices. The focus of the discussion is on the desirability of chemically modifying carbon nanotubes to overcome their inherent chemical nonreactivity and thereby enable the formation of strong chemical bonds between nanotubes and epoxies (or other polymeric matrix materials or their monomeric precursors). The chemical modification is effected in a process in which discrete functional groups are covalently attached to the nanotube surfaces. The functionalization process was proposed by the company and demonstrated in practice for the first time during this development effort. The covalently attached functional groups are capable of reacting with the epoxy or other matrix resin to form covalent bonds. Furthermore, the company uses this process to chemically modify the nanotube surfaces, affording tunable adhesion to polymers and solubility in select solvents. Flat-sheet composites containing functionalized nanotubes demonstrate significantly improved mechanical, thermal, and electrical properties.

  1. Interface characteristics of nanorope reinforced polymer composites

    NASA Astrophysics Data System (ADS)

    Ahmed, Khondaker S.; Keng, Ang K.

    2013-09-01

    A shear-lag model is proposed to obtain interface characteristics of nanorope reinforced polymer composites using representative volume element (RVE) concept. In the axisymmetric RVE, the nanorope is modelled as a closed-packed cylindrical lattice consisting seven single-walled carbon nanotubes. In the model, rope is considered to be perfectly bonded with the polymer resin where the nanotubes are assumed to be chemically non-bonded with each other in the rope system. Since, nanotubes are considered to be non-bonded in the nanorope there must exist a van der Waals interaction in terms of Lennard-Jones potential. A separate model is also proposed to determine the cohesive stress caused by this interaction. Closed form analytical solutions are derived for stress components of rope, resin and individual carbon nanotubes in the rope system. Parametric study has also been conducted to investigate the influences of key composite factors involved at both perfectly bonded and non-bonded interfaces.

  2. Durability of polymer composite materials

    NASA Astrophysics Data System (ADS)

    Liu, Liu

    The purpose of this research is to examine structural durability of advanced composite materials under critical loading conditions, e.g., combined thermal and mechanical loading and shear fatigue loading. A thermal buckling model of a burnt column, either axially restrained or under an axial applied force was developed. It was predicted that for a column exposed to the high heat flux under simultaneous constant compressive load, the response of the column is the same as that of an imperfection column; the instability of the burnt column happens. Based on the simplified theoretical prediction, the post-fire compressive behavior of fiberglass reinforced vinyl-ester composite columns, which have been exposed to high heat flux for a certain time was investigated experimentally, the post-fire compressive strength, modulus and failure mode were determined. The integrity of the same column under constant compressive mechanical loading combined with heat flux exposure was examined using a specially designed mechanical loading fixture that mounted directly below a cone calorimeter. All specimens in the experiments exhibited compressive instability. The experimental results show a thermal bending moment exists and has a significant influence on the structural behavior, which verified the thermal buckling model. The trend of response between the deflection of the column and exposure time is similar to that predicted by the model. A new apparatus was developed to study the monotonic shear and cyclic-shear behavior of sandwich structures. Proof-of-concept experiments were performed using PVC foam core polymeric sandwich materials. Shear failure occurred by the extension of cracks parallel to the face-sheet/core interface, the shear modulus degraded with the growth of fatigue damage. Finite element analysis was conducted to determine stress distribution in the proposed specimen geometry used in the new technique. Details for a novel apparatus used for the fatigue testing of thin

  3. Electrowetting without electrolysis on self-healing dielectrics.

    PubMed

    Dhindsa, Manjeet; Heikenfeld, Jason; Weekamp, Wim; Kuiper, Stein

    2011-05-03

    An electrowetting system with protection against dielectric breakdown is presented. It comprises an electrolyte and a Parylene-C film deposited on an aluminum electrode. The system demonstrates virtually instantaneous self-healing (within 100 ms) after dielectric breakdown under both DC and certain AC electrowetting conditions. DC current response during electrowetting on intentionally damaged Parylene-C is presented. Also presented is a characterization of DC offset voltages and duty cycle percentages required for electrolysis free AC electrowetting between 10 Hz and 4 kHz.

  4. Silicon-Containing Polymers and Composites

    DTIC Science & Technology

    2012-03-28

    superhydrophobic . FluoroPOSS polymer composite surfaces can be superhydrophobic and superoleophobic. Superhydrophilic and superoleophobic surfaces...Silicone-Modified Materials ACS N ti l M ti a ona ee ng 28 March 2012 Joseph M. Mabry Air Force Research Laboratory Propulsion Materials & Applications j...Superhydrophilic Hydrophilic Hydrophobic Superhydrophobic θ ~ 0° 0°< θ < 90° θ > 90° θ* > 150° 3DISTRIBUTION A. Approved for public release; distribution

  5. Self-healing hybrid nanocomposites consisting of bisphosphonated hyaluronan and calcium phosphate nanoparticles.

    PubMed

    Nejadnik, M Reza; Yang, Xia; Bongio, Matilde; Alghamdi, Hamdan S; van den Beucken, Jeroen J J P; Huysmans, Marie C; Jansen, John A; Hilborn, Jöns; Ossipov, Dmitri; Leeuwenburgh, Sander C G

    2014-08-01

    Non-covalent interactions are often regarded as insufficient to construct macroscopic materials of substantial integrity and cohesion. However, the low binding energy of such reversible interactions can be compensated by increasing their number to work in concert to create strong materials. Here we present the successful development of an injectable, cohesive nanocomposite hydrogel based on reversible bonds between calcium phosphate nanoparticles and bisphosphonate-functionalized hyaluronic acid. These nanocomposites display a capacity for self-healing as well as adhesiveness to mineral surfaces such as enamel and hydroxyapatite. Most importantly, these non-covalently cross-linked composites are surprisingly robust yet biodegradable upon extensive in vitro and in vivo testing and show bone interactive capacity evidenced by bone ingrowth into material remnants. The herein presented method provides a new methodology for constructing nanoscale composites for biomedical applications, which owe their integrity to reversible bonds.

  6. Constitutive Modeling of Piezoelectric Polymer Composites

    NASA Technical Reports Server (NTRS)

    Odegard, Gregory M.; Gates, Tom (Technical Monitor)

    2003-01-01

    A new modeling approach is proposed for predicting the bulk electromechanical properties of piezoelectric composites. The proposed model offers the same level of convenience as the well-known Mori-Tanaka method. In addition, it is shown to yield predicted properties that are, in most cases, more accurate or equally as accurate as the Mori-Tanaka scheme. In particular, the proposed method is used to determine the electromechanical properties of four piezoelectric polymer composite materials as a function of inclusion volume fraction. The predicted properties are compared to those calculated using the Mori-Tanaka and finite element methods.

  7. Radiation-Shielding Polymer/Soil Composites

    NASA Technical Reports Server (NTRS)

    Sen, Subhayu

    2007-01-01

    It has been proposed to fabricate polymer/ soil composites primarily from extraterrestrial resources, using relatively low-energy processes, with the original intended application being that habitat structures constructed from such composites would have sufficient structural integrity and also provide adequate radiation shielding for humans and sensitive electronic equipment against the radiation environment on the Moon and Mars. The proposal is a response to the fact that it would be much less expensive to fabricate such structures in situ as opposed to transporting them from Earth.

  8. The life times of polymer composites in construction

    NASA Astrophysics Data System (ADS)

    Meier, Urs

    2016-05-01

    This paper discusses examples that prove the long-term reliability of Fiber Reinforced Polymers (FRP) under extreme loading conditions and outdoor weathering. Results of polymer/steel-composite anchorage systems, Glass Fiber Reinforced Polymer (GFRP) plates and shells, GFRP box girders, Carbon Fiber Reinforced Polymer (CFRP) post-tensioning tendons and CFRP stays are going to be presented.

  9. Methods of Making and Using Shape Memory Polymer Composite Patches

    NASA Technical Reports Server (NTRS)

    Hood, Patrick J.

    2011-01-01

    A method of repairing a composite component having a damaged area including: laying a composite patch over the damaged area: activating the shape memory polymer resin to easily and quickly mold said patch to said damaged area; deactivating said shape memory polymer so that said composite patch retains the molded shape; and bonding said composite patch to said damaged part.

  10. Solid particle erosion of polymers and composites

    NASA Astrophysics Data System (ADS)

    Friedrich, K.; Almajid, A. A.

    2014-05-01

    After a general introduction to the subject of solid particle erosion of polymers and composites, the presentation focusses more specifically on the behavior of unidirectional carbon fiber (CF) reinforced polyetheretherketone (PEEK) composites under such loadings, using different impact conditions and erodents. The data were analyzed on the basis of a newly defined specific erosive wear rate, allowing a better comparison of erosion data achieved under various testing conditions. Characteristic wear mechanisms of the CF/PEEK composites consisted of fiber fracture, matrix cutting and plastic matrix deformation, the relative contribution of which depended on the impingement angles and the CF orientation. The highest wear rates were measured for impingement angles between 45 and 60°. Using abrasion resistant neat polymer films (in this case PEEK or thermoplastic polyurethane (TPU) ones) on the surface of a harder substrate (e.g. a CF/PEEK composite plate) resulted in much lower specific erosive wear rates. The use of such polymeric films can be considered as a possible method to protect composite surfaces from damage caused by minor impacts and erosion. In fact, they are nowadays already successfully applied as protections for wind energy rotor blades.

  11. Conjugated polymer composite nanoparticles by rapid mixing.

    PubMed

    Jung, Christoph; de Roo, Tjaard; Mecking, Stefan

    2014-12-01

    Composite nanoparticles from poly[(9,9-di-n-octylfluoren-2,7-diyl)-alt-(benzo[2,1,3]thiadiazol-4,8-diyl)] (F8BT) and poly(9,9-di-n-hexylfluoren-2,7-diyl) (PF) with embedded inorganic nanoparticles (TiO2 , CdSe, and CdSe/CdS) are prepared through kinetic trapping by rapid turbulent mixing in a multi-inlet vortex mixer without the need for polymer functionalization. High contents of inorganic materials up to 50-60 wt% are realized for all composites. The influence of flow ratios, sodium dodecyl sulfate (SDS) concentration, and absolute flow rates on the particle size and morphology is studied. High water-to-THF ratios and high total flow rates around 2 m s(-1) yield particle sizes below 50 nm. By adjusting these parameters, controlled particle sizes between 30 to several hundred nanometers are obtained. Composite particles from CdSe/CdS and F8BT or PF show a strong quenching of the polymer emission and near exclusive emission from the inorganic nanocrystal, which indicates an efficient energy transfer with fluorescence quantum yields of 23% for the F8BT/CdSe/CdS composites and 21% for the PF/CdSe/CdS composites. The dispersions are colloidally stable for several months.

  12. SLPMC- Self Lubricating Polymer Matrix Composites

    NASA Astrophysics Data System (ADS)

    Macho, C.; Merstallinger, A.; Brodowski-Hanemann, G.; Palladino, M.; Pambaguian, L.

    2013-09-01

    The paper is surveying the current state of knowledge and results of the ESA-project "SLPMC" on a polymer composite based on PTFE. The two targets of this project are to investigate lubrication mechanisms in PTFE-based composites under tribological conditions relevant to space applications (air, nitrogen, vacuum). Secondly, to develop a new composite to fulfill future needs by space applications. Hence, in the frame of this project several new composites based on PTFE and hard fillers were defined, procured and tested on material level. Results are compared to reference materials being currently use.This paper focuses on tribological results derived by pin-on-disc tests. (Later on testing on ball bearing and plain bearing are foreseen.) The influences of parameters like load, speed, atmosphere and temperature are discussed and compared to other already known materials.

  13. Puncture-Healing Thermoplastic Resin Carbon-Fiber-Reinforced Composites

    NASA Technical Reports Server (NTRS)

    Gordon, Keith L. (Inventor); Siochi, Emilie J. (Inventor); Grimsley, Brian W. (Inventor); Cano, Roberto J. (Inventor); Czabaj, Michael W. (Inventor)

    2015-01-01

    A composite comprising a combination of a self-healing polymer matrix and a carbon fiber reinforcement is described. In one embodiment, the matrix is a polybutadiene graft copolymer matrix, such as polybutadiene graft copolymer comprising poly(butadiene)-graft-poly(methyl acrylate-co-acrylonitrile). A method of fabricating the composite is also described, comprising the steps of manufacturing a pre-impregnated unidirectional carbon fiber preform by wetting a plurality of carbon fibers with a solution, the solution comprising a self-healing polymer and a solvent, and curing the preform. A method of repairing a structure made from the composite of the invention is described. A novel prepreg material used to manufacture the composite of the invention is described.

  14. Self-healing Characteristics of Collagen Coatings with Respect to Surface Abrasion

    NASA Astrophysics Data System (ADS)

    Kim, Chang-Lae; Kim, Dae-Eun

    2016-03-01

    A coating based on collagen with self-healing properties was developed for applications in mechanical components that are prone to abrasion due to contact with a counter surface. The inherent swelling behavior of collagen in water was exploited as the fundamental mechanism behind self-healing of a wear scar formed on the surface. The effects of freeze-drying process and water treatment of the collagen coatings on their mechanical and self-healing properties were analyzed. Water was also used as the medium to trigger the self-healing effect of the collagen coatings after the wear test. It was found that collagen coatings without freeze-drying did not demonstrate any self-healing effect whereas the coatings treated by freeze-drying process showed remarkable self-healing effect. Overall, collagen coatings that were freeze-dried and water treated showed the best friction and self-healing properties. Repeated self-healing ability of these coatings with respect to wear scar was also demonstrated. It was also confirmed that the self-healing property of the collagen coating was effective over a relatively wide range of temperature.

  15. Self-healing Characteristics of Collagen Coatings with Respect to Surface Abrasion.

    PubMed

    Kim, Chang-Lae; Kim, Dae-Eun

    2016-03-24

    A coating based on collagen with self-healing properties was developed for applications in mechanical components that are prone to abrasion due to contact with a counter surface. The inherent swelling behavior of collagen in water was exploited as the fundamental mechanism behind self-healing of a wear scar formed on the surface. The effects of freeze-drying process and water treatment of the collagen coatings on their mechanical and self-healing properties were analyzed. Water was also used as the medium to trigger the self-healing effect of the collagen coatings after the wear test. It was found that collagen coatings without freeze-drying did not demonstrate any self-healing effect whereas the coatings treated by freeze-drying process showed remarkable self-healing effect. Overall, collagen coatings that were freeze-dried and water treated showed the best friction and self-healing properties. Repeated self-healing ability of these coatings with respect to wear scar was also demonstrated. It was also confirmed that the self-healing property of the collagen coating was effective over a relatively wide range of temperature.

  16. Self-healing Characteristics of Collagen Coatings with Respect to Surface Abrasion

    PubMed Central

    Kim, Chang-Lae; Kim, Dae-Eun

    2016-01-01

    A coating based on collagen with self-healing properties was developed for applications in mechanical components that are prone to abrasion due to contact with a counter surface. The inherent swelling behavior of collagen in water was exploited as the fundamental mechanism behind self-healing of a wear scar formed on the surface. The effects of freeze-drying process and water treatment of the collagen coatings on their mechanical and self-healing properties were analyzed. Water was also used as the medium to trigger the self-healing effect of the collagen coatings after the wear test. It was found that collagen coatings without freeze-drying did not demonstrate any self-healing effect whereas the coatings treated by freeze-drying process showed remarkable self-healing effect. Overall, collagen coatings that were freeze-dried and water treated showed the best friction and self-healing properties. Repeated self-healing ability of these coatings with respect to wear scar was also demonstrated. It was also confirmed that the self-healing property of the collagen coating was effective over a relatively wide range of temperature. PMID:27010967

  17. Hierarchical Self-healing Key Distribution for Heterogeneous Wireless Sensor Networks

    NASA Astrophysics Data System (ADS)

    Yang, Yanjiang; Zhou, Jianying; Deng, Robert H.; Bao, Feng

    Self-healing group key distribution aims to achieve robust key distribution over lossy channels in wireless sensor networks (WSNs). However, all existing self-healing group key distribution schemes in the literature consider homogenous WSNs which are known to be unscalable. Heterogeneous WSNs have better scalability and performance than homogenous ones. We are thus motivated to study hierarchial self-healing group key distribution, tailored to the heterogeneous WSN architecture. In particular, we revisit and adapt Dutta et al.’s model to the setting of hierarchical self-healing group key distribution, and propose a concrete scheme that achieves computational security and high efficiency.

  18. Durable polymer-aerogel based superhydrophobic coatings, a composite material

    DOEpatents

    Kissel, David J; Brinker, Charles Jeffrey

    2014-03-04

    Provided are polymer-aerogel composite coatings, devices and articles including polymer-aerogel composite coatings, and methods for preparing the polymer-aerogel composite. The exemplary article can include a surface, wherein the surface includes at least one region and a polymer-aerogel composite coating disposed over the at least one region, wherein the polymer-aerogel composite coating has a water contact angle of at least about 140.degree. and a contact angle hysteresis of less than about 1.degree.. The polymer-aerogel composite coating can include a polymer and an ultra high water content catalyzed polysilicate aerogel, the polysilicate aerogel including a three dimensional network of silica particles having surface functional groups derivatized with a silylating agent and a plurality of pores.

  19. Durable polymer-aerogel based superhydrophobic coatings: a composite material

    DOEpatents

    Kissel, David J.; Brinker, Charles Jeffrey

    2016-02-02

    Provided are polymer-aerogel composite coatings, devices and articles including polymer-aerogel composite coatings, and methods for preparing the polymer-aerogel composite. The exemplary article can include a surface, wherein the surface includes at least one region and a polymer-aerogel composite coating disposed over the at least one region, wherein the polymer-aerogel composite coating has a water contact angle of at least about 140.degree. and a contact angle hysteresis of less than about 1.degree.. The polymer-aerogel composite coating can include a polymer and an ultra high water content catalyzed polysilicate aerogel, the polysilicate aerogel including a three dimensional network of silica particles having surface functional groups derivatized with a silylating agent and a plurality of pores.

  20. Molecular composites and polymer blends containing ionic polymers

    NASA Astrophysics Data System (ADS)

    Tsou, Li-Chun

    1997-11-01

    Polymer blends are generally immiscible due to the unfavorable thermodynamics of mixing. By the introduction of ion-dipole interaction, mechanical properties of the PPTA anion/polar polymers (such as PVP, PEO and PPrO) molecular composites have been investigated in relation to their miscibility and microstructural morphology. Optical clarity observed in the glassy PPTA anion/PVP system suggest the presence of miscibility, since the refractive indices between the two components are quite different, nsb{PVP} = 1.509 and nsb{PPTA} = 1.644. In general, the difference greater than 0.01 is sufficient to make blends opaque. DSC measurements, showing a composition dependent Tsb{g} and a melting temperature depression, also indicate the miscibility achieved at the molecular level, about 50-100 A. By using the Hoffman-Weeks plot, a negative Flory-Huggins interaction parameter, chi = -1.10, is obtained for the PPTA anion/PEO molecular composites. An irregular spherulitic pattern and a reduced crystal size suggest that PPTA anion is intimately mixed with the amorphous PEO, both inter- and intra-spherulitically. Molecular composites exhibit not only an enhanced tensile strength and modulus, but also a greater fracture toughness, Ksb{IC}, e.g., an 80% increase at a 2 wt% PPTA anion addition. An enhanced tensile strength associated with a reduced crystallinity suggests that PPTA anion is the major contributor to the superior tensile properties instead of the crystalline phase. Upon addition of PPTA anion to PPrO, a slower relaxation rate and a better thermal stability are observed. Significant enhancement is found when the monovalent K salt is replaced with a divalent Ca salt. The molecular reinforcement achieved via ion-dipole interactions is more effective than the rigid filler effect obtained in the non-ionic PPTA/PPrO blend: e.g., a modulus enhancement of 814% vs. 286%, as compared with the value for PPrO. Two phase systems with microphase separation are developed since many

  1. Networked Microgrids for Self-healing Power Systems

    SciTech Connect

    Wang, Zhaoyu; Chen, Bokan; Wang, Jianhui; Chen, Chen

    2015-06-17

    This paper proposes a transformative architecture for the normal operation and self-healing of networked microgrids (MGs). MGs can support and interchange electricity with each other in the proposed infrastructure. The networked MGs are connected by a physical common bus and a designed two-layer cyber communication network. The lower layer is within each MG where the energy management system (EMS) schedules the MG operation; the upper layer links a number of EMSs for global optimization and communication. In the normal operation mode, the objective is to schedule dispatchable distributed generators (DGs), energy storage systems (ESs) and controllable loads to minimize the operation costs and maximize the supply adequacy of each MG. When a generation deficiency or fault happens in a MG, the model switches to the self-healing mode and the local generation capacities of other MGs can be used to support the on-emergency portion of the system. A consensus algorithm is used to distribute portions of the desired power support to each individual MG in a decentralized way. The allocated portion corresponds to each MG’s local power exchange target which is used by its EMS to perform the optimal schedule. The resultant aggregated power output of networked MGs will be used to provide the requested power support. Test cases demonstrate the effectiveness of the proposed methodology.

  2. Performance characteristics of a self-sealing/self-healing barrier

    SciTech Connect

    McGregor, R.G. |; Stegemann, J.A.

    1997-12-31

    Environment Canada and the Netherlands Energy Research Foundation are co-developers of a patented Self-Sealing/Self-Healing (SS/SH) Barrier system for containment of wastes which is licensed to Water Technology International Corporation. The SS/SH Barrier is intended for use as either a liner or cover for landfills, contaminated sites, secondary containment areas, etc., in the industrial, chemical, mining and municipal sectors, and also as a barrier to hydraulic flow for the transportation and construction industry. The SS/SH Barrier`s most significant feature is its capability for self-repair in the event of a breach. By contrast, conventional barrier systems, such as clay, geomembrane, or geosynthetic clay liners can not be repaired without laborious excavation and reconstruction. Laboratory investigations have shown that the SS/SH Barrier concept will function with a variety of reactive materials. Self-Sealing/Self-Healing Barriers are cost competitive and consistently exhibit hydraulic conductivities ranging from 10{sup -9} to 10{sup -13} m/s, which decrease with time. These measurements meet or exceed the recommended hydraulic conductivity required by EPA for clay liners (<1x10{sup -9} m/s) used in landfills and hazardous waste sites. Results of mineralogical examination of the seal, diffusion testing, hydraulic conductivity measurement, and durability testing, including wet/dry, freeze/thaw cycling and leachate compatibility are also presented.

  3. "Click chemistry" in tailor-made polymethacrylates bearing reactive furfuryl functionality: a new class of self-healing polymeric material.

    PubMed

    Kavitha, A Amalin; Singha, Nikhil K

    2009-07-01

    This investigation reports the effective use of the Diels-Alder (DA) reaction, a "click reaction" in the preparation of thermally amendable and self-healing polymeric materials having reactive furfuryl functionality. In this case, the DA and retro-DA (rDA) reactions were carried out between the tailor-made homo- and copolymer of furfuryl methacrylate prepared by atom-transfer radical polymerization and a bismaleimide (BM). The kinetic studies of DA and rDA reactions were carried out using Fourier transform infrared spectroscopy. The DA polymers were insoluble in toluene at room temperature. When the DA polymers were heated at 100 degrees C in toluene, it was soluble. This is because of the cleavage between furfuryl functionality and BM. The chemical cross-link density was determined by the Flory-Rehner equation. The cross-linked polymer showed much greater adhesive strength at room temperature, but the adhesive strength was quite low at higher temperature. The self-healing capability was studied by using scanning electron microscopy analysis. The thermal and dynamic mechanical properties of the thermally amendable cross-linked materials were investigated by thermogravimetric analysis and dynamic mechanical analysis.

  4. Dynamic gold nanoparticle, polymer-based composites

    NASA Astrophysics Data System (ADS)

    Firestone, Millicent; Junghans, Ann; Hayden, Steven; Majeski, Jaroslaw; CINT, Lujan Team

    2014-03-01

    Artificial polymer-based biomembranes may serve as a foundational architecture for the integration and spatial organization of metal nanoparticles forming functional nanocomposites. Nonionic triblock copolymer (PEO-PPO-PEO), lipid-based gels, containing Au nanoparticles (NPs) can be prepared by either external doping of the preformed nanoparticles or by in-situ reduction of Au 3+. Neutron reflectivity on quartz supported thin films of the Au NP -doped polymer-based biomembranes was used to determine the location of the Au. The nanoparticles were found to preferentially reside within the ethylene oxide chains located at the interface of the bulk water channels and the amphiphile bilayers. The embedded Au nanoparticles can act as localized heat sinks, inducing changes in the polymer conformation. The collective, thermally-triggered expansion and contraction of the EO chains modulate the mesophase structure of the gels. Synchrotron X-ray scattering (SAXS) was used to monitor mesophase structure as a function of both temperature and photo-irradiation. These studies represent a first step towards designingexternally-responsive polymer-nanoparticle composites.

  5. Silica/Polymer and Silica/Polymer/Fiber Composite Aerogels

    NASA Technical Reports Server (NTRS)

    Ou, Danny; Stepanian, Christopher J.; Hu, Xiangjun

    2010-01-01

    Aerogels that consist, variously, of neat silica/polymer alloys and silica/polymer alloy matrices reinforced with fibers have been developed as materials for flexible thermal-insulation blankets. In comparison with prior aerogel blankets, these aerogel blankets are more durable and less dusty. These blankets are also better able to resist and recover from compression . an important advantage in that maintenance of thickness is essential to maintenance of high thermal-insulation performance. These blankets are especially suitable as core materials for vacuum- insulated panels and vacuum-insulated boxes of advanced, nearly seamless design. (Inasmuch as heat leakage at seams is much greater than heat leakage elsewhere through such structures, advanced designs for high insulation performance should provide for minimization of the sizes and numbers of seams.) A silica/polymer aerogel of the present type could be characterized, somewhat more precisely, as consisting of multiply bonded, linear polymer reinforcements within a silica aerogel matrix. Thus far, several different polymethacrylates (PMAs) have been incorporated into aerogel networks to increase resistance to crushing and to improve other mechanical properties while minimally affecting thermal conductivity and density. The polymethacrylate phases are strongly linked into the silica aerogel networks in these materials. Unlike in other organic/inorganic blended aerogels, the inorganic and organic phases are chemically bonded to each other, by both covalent and hydrogen bonds. In the process for making a silica/polymer alloy aerogel, the covalent bonds are introduced by prepolymerization of the methacrylate monomer with trimethoxysilylpropylmethacrylate, which serves as a phase cross-linker in that it contains both organic and inorganic monomer functional groups and hence acts as a connector between the organic and inorganic phases. Hydrogen bonds are formed between the silanol groups of the inorganic phase and the

  6. The analysis of thermoplastic characteristics of special polymer sulfur composite

    NASA Astrophysics Data System (ADS)

    Książek, Mariusz

    2017-01-01

    Specific chemical environments step out in the industry objects. Portland cement composites (concrete and mortar) were impregnated by using the special polymerized sulfur and technical soot as a filler (polymer sulfur composite). Sulfur and technical soot was applied as the industrial waste. Portland cement composites were made of the same aggregate, cement and water. The process of special polymer sulfur composite applied as the industrial waste is a thermal treatment process in the temperature of about 150-155°C. The result of such treatment is special polymer sulfur composite in a liquid state. This paper presents the plastic constants and coefficients of thermal expansion of special polymer sulfur composites, with isotropic porous matrix, reinforced by disoriented ellipsoidal inclusions with orthotropic symmetry of the thermoplastic properties. The investigations are based on the stochastic differential equations of solid mechanics. A model and algorithm for calculating the effective characteristics of special polymer sulfur composites are suggested. The effective thermoplastic characteristics of special polymer sulfur composites, with disoriented ellipsoidal inclusions, are calculated in two stages: First, the properties of materials with oriented inclusions are determined, and then effective constants of a composite with disoriented inclusions are determined on the basis of the Voigt or Rice scheme. A brief summary of new products related to special polymer sulfur composites is given as follows: Impregnation, repair, overlays and precast polymer concrete will be presented. Special polymer sulfur as polymer coating impregnation, which has received little attention in recent years, currently has some very interesting applications.

  7. Phase stability and dynamics of entangled polymer-nanoparticle composites.

    PubMed

    Mangal, Rahul; Srivastava, Samanvaya; Archer, Lynden A

    2015-06-05

    Nanoparticle-polymer composites, or polymer-nanoparticle composites (PNCs), exhibit unusual mechanical and dynamical features when the particle size approaches the random coil dimensions of the host polymer. Here, we harness favourable enthalpic interactions between particle-tethered and free, host polymer chains to create model PNCs, in which spherical nanoparticles are uniformly dispersed in high molecular weight entangled polymers. Investigation of the mechanical properties of these model PNCs reveals that the nanoparticles have profound effects on the host polymer motions on all timescales. On short timescales, nanoparticles slow-down local dynamics of the host polymer segments and lower the glass transition temperature. On intermediate timescales, where polymer chain motion is typically constrained by entanglements with surrounding molecules, nanoparticles provide additional constraints, which lead to an early onset of entangled polymer dynamics. Finally, on long timescales, nanoparticles produce an apparent speeding up of relaxation of their polymer host.

  8. Modified glass fibre reinforced polymer composites

    NASA Astrophysics Data System (ADS)

    Cao, Yumei

    A high ratio of strength to density and relatively low-cost are some of the significant features of glass fibre reinforced polymer composites (GFRPCs) that made them one of the most rapidly developed materials in recent years. They are widely used as the material of construction in the areas of aerospace, marine and everyday life, such as airplane, helicopter, boat, canoe, fishing rod, racket, etc. Traditionally, researchers tried to raise the mechanical properties and keep a high strength/weight ratio using all or some of the following methods: increasing the volume fraction of the fibre; using different polymeric matrix material; or changing the curing conditions. In recent years, some new techniques and processing methods were developed to further improve the mechanical properties of glass fibre (GF) reinforced polymer composite. For example, by modifying the surface condition of the GF, both the interface strength between the GF and the polymer matrix and the shear strength of the final composite can be significantly increased. Also, by prestressing the fibre during the curing process of the composite, the tensile, flexural and the impact properties of the composite can be greatly improved. In this research project, a new method of preparing GFRPCs, which combined several traditional and modern techniques together, was developed. This new method includes modification of the surface of the GF with silica particles, application of different levels of prestressing on the GF during the curing process, and the change of the fibre volume fraction and curing conditions in different sets of experiments. The results of the new processing were tested by the three-point bend test, the short beam shear test and the impact test to determine the new set of properties so formed in the composite material. Scanning electronic microscopy (SEM) was used to study the fracture surface of the new materials after the mechanical tests were performed. By taking advantages of the

  9. Polymer-fullerene composite solar cells.

    PubMed

    Thompson, Barry C; Fréchet, Jean M J

    2008-01-01

    Fossil fuel alternatives, such as solar energy, are moving to the forefront in a variety of research fields. Polymer-based organic photovoltaic systems hold the promise for a cost-effective, lightweight solar energy conversion platform, which could benefit from simple solution processing of the active layer. The function of such excitonic solar cells is based on photoinduced electron transfer from a donor to an acceptor. Fullerenes have become the ubiquitous acceptors because of their high electron affinity and ability to transport charge effectively. The most effective solar cells have been made from bicontinuous polymer-fullerene composites, or so-called bulk heterojunctions. The best solar cells currently achieve an efficiency of about 5%, thus significant advances in the fundamental understanding of the complex interplay between the active layer morphology and electronic properties are required if this technology is to find viable application.

  10. Photomechanical actuation in polymer-nanotube composites.

    PubMed

    Ahir, Samit V; Terentjev, Eugene M

    2005-06-01

    For some systems, energy from an external source can trigger changes in the internal state of the structure, leading to a mechanical response much larger than the initial input. The ability to unlock this internal work in a solid-state structure is of key importance for many potential applications. We report a novel phenomenon of photo-induced mechanical actuation observed in a polymer-nanotube composite when exposed to infrared radiation. At small strains the sample tends to expand, when stimulated by photons, by an amount that is orders of magnitude greater than the pristine polymer. Conversely, at larger applied pre-strain, it will contract under identical infrared excitation. The behaviour is modelled as a function of orientational ordering of nanotubes induced by the uniaxial extension. It is thought that no other materials can display this continuously reversible response of so large a magnitude, making rubber nanocomposites important for actuator applications.

  11. Creep of plain weave polymer matrix composites

    NASA Astrophysics Data System (ADS)

    Gupta, Abhishek

    Polymer matrix composites are increasingly used in various industrial sectors to reduce structural weight and improve performance. Woven (also known as textile) composites are one class of polymer matrix composites with increasing market share mostly due to their lightweight, their flexibility to form into desired shape, their mechanical properties and toughness. Due to the viscoelasticity of the polymer matrix, time-dependent degradation in modulus (creep) and strength (creep rupture) are two of the major mechanical properties required by engineers to design a structure reliably when using these materials. Unfortunately, creep and creep rupture of woven composites have received little attention by the research community and thus, there is a dire need to generate additional knowledge and prediction models, given the increasing market share of woven composites in load bearing structural applications. Currently, available creep models are limited in scope and have not been validated for any loading orientation and time period beyond the experimental time window. In this thesis, an analytical creep model, namely the Modified Equivalent Laminate Model (MELM), was developed to predict tensile creep of plain weave composites for any orientation of the load with respect to the orientation of the fill and warp fibers, using creep of unidirectional composites. The ability of the model to predict creep for any orientation of the load is a "first" in this area. The model was validated using an extensive experimental involving the tensile creep of plain weave composites under varying loading orientation and service conditions. Plain weave epoxy (F263)/ carbon fiber (T300) composite, currently used in aerospace applications, was procured as fabrics from Hexcel Corporation. Creep tests were conducted under two loading conditions: on-axis loading (0°) and off-axis loading (45°). Constant load creep, in the temperature range of 80-240°C and stress range of 1-70% UTS of the

  12. 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

  13. Charge dynamics in ionic polymer metal composites

    NASA Astrophysics Data System (ADS)

    Porfiri, Maurizio

    2008-11-01

    In this paper, we study the charge dynamics in ionic polymer metal composites (IPMCs) in response to a voltage difference applied across their electrodes. We use the Poisson-Nernst-Planck equations to model the time evolution of the electric potential and the concentration of mobile counterions. We present an analytical solution of the nonlinear initial-boundary value problem by using matched asymptotic expansions. We determine the charge and electric potential distributions as functions of time in the whole IPMC region. We show that in the bulk polymer region the IPMC is approximately electroneutral; in contrast, charge distribution boundary layers arise at the polymer-electrode interfaces. Prominent charge depletion and enrichment at the polymer-electrode interface are present even at moderately low input-voltage levels. We use the proposed analytical solution to derive a physics-based circuit model of IPMCs. The equivalent circuit comprises a linear resistor in series connection with a nonlinear capacitor. We derive closed-form expressions for the resistance and the capacitance by conducting a qualitative phase-plane analysis of the inner approximation of the asymptotic expansion. The circuit conductivity is independent of the IPMC dielectric constant and is proportional to the ion diffusivity; whereas, the capacitance is proportional to the square root of the dielectric constant and is independent of the diffusivity. The conductivity depends on the polymer thickness, while the capacitance is independent of it. The capacitance nonlinearity is extremely pronounced, and dramatic capacitance reduction is observed for moderately low voltage levels. We validate the proposed analytical solution along with the derived circuit model through extensive comparisons with finite element results available in the technical literature.

  14. Fabrication of self-healing super-hydrophobic surfaces on aluminium alloy substrates

    SciTech Connect

    Wang, Yang; Wei Liu, Xiao; Zhang, Hai Feng Zhou, Zhi Ping

    2015-04-15

    We present a method to fabricate a super-hydrophobic surface with a self-healing ability on an aluminium alloy substrate. The coatings are obtained by combining a two-step process (first, the substrate is immersed in a solution of HCl, HF and H{sub 2}O, and then in boiling water) and succeeding surface fluorination with a solution of poly(vinylidene-fluoride-co-hexafluoropropylene) and a fluoroalkyl silane. The morphological features and chemical composition were studied by scanning electron micrometry and energy-dispersive X-ray spectroscopy. The prepared super-hydrophobic aluminium surfaces showed hierarchical structures forming pores, petals and particles with a contact angle of 161° and a sliding angle of 3°.

  15. Polymer: bioceramic composites optimization by tetracycline addition.

    PubMed

    Pataro, André L; Oliveira, Michele F; Teixeira, Karina I R; Turchetti-Maia, Regina M M; Lopes, Miriam T P; Wykrota, Francisco H L; Sinisterra, Rubén D; Cortés, Maria E

    2007-05-04

    The aim of this study was to evaluate the biocompatibility of composites of poly-lactic acid polymer (PLA) and copolymer of lactic and glycolic acid (PLGA), dispersed in a bioceramic matrix, Osteosynt (BC), to which tetracycline (TC) was added. The in vitro test used direct contact test (ASTM F-813) and elution test (USP-XXIII, ISO 10993-5), and in vivo evaluation was performed after subcutaneous implantation in outbread Swiss mice. The 0.01% (w/w) TC addition did not affect composite cytotoxicity in vitro. The macroscopic and histologic evaluation in vivo after 1, 7, 13, 21, 28 and 56 days showed an initial intense infiltrate of inflammatory cells for most of the groups. The tissue showed normal pattern after 21 days for all the groups. TC addition exhibited significantly larger reduction of inflammation signs (Mann-Whitney test, p<0.05) in the critical period of the resolution of the inflammatory process. Angiogenesis, cellular adsorption and fibrous deposit were observed on SEM evaluation. In conclusion, TC addition optimized composites polymer/bioceramic biocompatibility, contributing to anti-inflammatory response during the early phases of the wound healing process.

  16. Polymer-composite materials for radiation protection.

    PubMed

    Nambiar, Shruti; Yeow, John T W

    2012-11-01

    Unwanted exposures to high-energy or ionizing radiation can be hazardous to health. Prolonged or accumulated radiation dosage from either particle-emissions such as alpha/beta, proton, electron, neutron emissions, or high-energy electromagnetic waves such as X-rays/γ rays, may result in carcinogenesis, cell mutations, organ failure, etc. To avoid occupational hazards from these kinds of exposures, researchers have traditionally used heavy metals or their composites to attenuate the radiation. However, protective gear made of heavy metals are not only cumbersome but also are capable of producing more penetrative secondary radiations which requires additional shielding, increasing the cost and the weight factor. Consequently, significant research efforts have been focused toward designing efficient, lightweight, cost-effective, and flexible shielding materials for protection against radiation encountered in various industries (aerospace, hospitals, and nuclear reactors). In this regard, polymer composites have become attractive candidates for developing materials that can be designed to effectively attenuate photon or particle radiation. In this paper, we review the state-of-the-art of polymer composites reinforced with micro/nanomaterials, for their use as radiation shields.

  17. Modeling Carbon-Black/Polymer Composite Sensors

    PubMed Central

    Lei, Hua; Pitt, William G.; McGrath, Lucas K.; Ho, Clifford K.

    2012-01-01

    Conductive polymer composite sensors have shown great potential in identifying gaseous analytes. To more thoroughly understand the physical and chemical mechanisms of this type of sensor, a mathematical model was developed by combining two sub-models: a conductivity model and a thermodynamic model, which gives a relationship between the vapor concentration of analyte(s) and the change of the sensor signals. In this work, 64 chemiresistors representing eight different carbon concentrations (8–60 vol% carbon) were constructed by depositing thin films of a carbon-black/polyisobutylene composite onto concentric spiral platinum electrodes on a silicon chip. The responses of the sensors were measured in dry air and at various vapor pressures of toluene and trichloroethylene. Three parameters in the conductivity model were determined by fitting the experimental data. It was shown that by applying this model, the sensor responses can be adequately predicted for given vapor pressures; furthermore the analyte vapor concentrations can be estimated based on the sensor responses. This model will guide the improvement of the design and fabrication of conductive polymer composite sensors for detecting and identifying mixtures of organic vapors. PMID:22518071

  18. Multi-Ferroic Polymer Nanoparticle Composites for Next Generation Metamaterials

    DTIC Science & Technology

    2016-06-15

    AFRL-AFOSR-JP-TR-2016-0061 Multi-Ferroic Polymer Nanoparticle Composites for Next Generation Metamaterials Sylvie Begin-Colin UNIVERSITE DE...TITLE AND SUBTITLE Multi-Ferroic Polymer Nanoparticle Composites for Next Generation Metamaterials 5a.  CONTRACT NUMBER 5b.  GRANT NUMBER FA2386-12-1...Multi-Ferroic Polymer Nanoparticle Composites for Next Generation Metamaterials AOARD 124014 Final Report – S. Begin – IPCMS Strasbourg France

  19. Phase stability and dynamics of entangled polymer-nanoparticle composites

    SciTech Connect

    Mangal, Rahul; Srivastava, Samanvaya; Archer, Lynden A.

    2015-06-10

    Nanoparticle–polymer composites, or polymer–nanoparticle composites (PNCs), exhibit unusual mechanical and dynamical features when the particle size approaches the random coil dimensions of the host polymer. Here, we harness favourable enthalpic interactions between particle-tethered and free, host polymer chains to create model PNCs, in which spherical nanoparticles are uniformly dispersed in high molecular weight entangled polymers. Investigation of the mechanical properties of these model PNCs reveals that the nanoparticles have profound effects on the host polymer motions on all timescales. On short timescales, nanoparticles slow-down local dynamics of the host polymer segments and lower the glass transition temperature. On intermediate timescales, where polymer chain motion is typically constrained by entanglements with surrounding molecules, nanoparticles provide additional constraints, which lead to an early onset of entangled polymer dynamics. Finally, on long timescales, nanoparticles produce an apparent speeding up of relaxation of their polymer host.

  20. Phosphazene polymer containing composites and method for making phosphazene polymer containing composites

    SciTech Connect

    Allen, C.A.; Grey, A.E.; McCaffrey, R.R.; Simpson, B.M.; Stone, M.L.

    1990-12-31

    The object of the invention is to provide a composite material comprised of phosphazene polymer. A feature of phosphazene-containing composites is their superior stiffness, thermal stability, and hardness which is lacking in more typical composite constituents. An advantage of using phosphazene composites is a wider range of applications, including uses in harsh environments. Another object of the present invention provides a method for producing phosphazene-containing composite materials through a pultrusion process. In brief, these and other objects are achieved by a composite produced by first coating a reinforcing material with an inorganic phosphazene compound and then polymerizing the phosphazene compound so as to confer superior thermal, physical and chemical resistance qualities to the composite. 2 figs., 6 tabs.

  1. Effect of blast furnace slag on self-healing of microcracks in cementitious materials

    SciTech Connect

    Huang, Haoliang; Ye, Guang; Damidot, Denis

    2014-06-01

    The physico-chemical process of self-healing in blast furnace slag cement paste was investigated in this paper. With a high slag content i.e., 66% in cement paste and saturated Ca(OH)₂ solution as activator, it was found that the reaction products formed in cracks are composed of C-S-H, ettringite, hydrogarnet and OH–hydrotalcite. The fraction of C-S-H in the reaction products is much larger than the other minerals. Large amount of ettringite formed in cracks indicates the leaching of SO₄⁻² ions from the bulk paste and consequently the recrystallization. Self-healing proceeds fast within 50 h and then slows down. According to thermodynamic modeling, when the newly formed reaction products are carbonated, the filling fraction of crack increases first and then decreases. Low soluble minerals such as silica gel, gibbsite and calcite are formed. Compared to Portland cement paste, the potential of self-healing in slag cement paste is higher when the percentage of slag is high. Highlights: • Self-healing reaction products in slag cement paste were characterized. • Self-healing reaction products formed in time were quantified with image analysis. • Self-healing in slag cement paste was simulated with a reactive transport model. • Effect of carbonation on self-healing was investigated by thermodynamic modeling. • Effect of slag on self-healing was discussed based on experiments and simulation.

  2. Pressurized vascular systems for self-healing materials

    PubMed Central

    Hamilton, A. R.; Sottos, N. R.; White, S. R.

    2012-01-01

    An emerging strategy for creating self-healing materials relies on embedded vascular networks of microchannels to transport reactive fluids to regions of damage. Here we investigate the use of active pumping for the pressurized delivery of a two-part healing system, allowing a small vascular system to deliver large volumes of healing agent. Different pumping strategies are explored to improve the mixing and subsequent polymerization of healing agents in the damage zone. Significant improvements in the number of healing cycles and in the overall healing efficiency are achieved compared with prior passive schemes that use only capillary forces for the delivery of healing agents. At the same time, the volume of the vascular system required to achieve this superior healing performance is significantly reduced. In the best case, nearly full recovery of fracture toughness is attained throughout 15 cycles of damage and healing, with a vascular network constituting just 0.1 vol% of the specimen. PMID:21957119

  3. Self-healing patterns in ferromagnetic-superconducting hybrids

    SciTech Connect

    Vlasko-Vlasov, V. K.; Palacious, E.; Rosenmann, D.; Pearson, J.; Jia, Y.; Wang, Y. L.; Welp, U.; Kwok, W-K

    2015-01-28

    We study magnetic flux dynamic effects in a superconducting bridge with thin soft magnetic stripes placed either on top or under the bridge. Voltage-current (VI) measurements reveal that the edges of magnetic stripes oriented transvers or along the bridge introduce channels or barriers for vortex motion, resulting in the decrease or increase of the critical current, respectively. We demonstrate a remarkable self-healing effect whereby the magnetic pinning strength for the longitudinal stripes increases with current. The self-field of the current polarizes the magnetic stripes along their width, which enhances the stray fields at their edges and creates a dynamic vortex pinning landscape to impede vortex flow. Our results highlight new strategies to engineer adaptive pinning topologies in superconducting-ferromagnetic hybrids.

  4. Injectable Self-Healing Hydrogel with Antimicrobial and Antifouling Properties.

    PubMed

    Li, Lin; Yan, Bin; Yang, Jingqi; Huang, Weijuan; Chen, Lingyun; Zeng, Hongbo

    2017-03-22

    Microbial adhesion, biofilm formation and associated microbial infection are common challenges faced by implanted biomaterials (e.g., hydrogels) in bioengineering applications. In this work, an injectable self-healing hydrogel with antimicrobial and antifouling properties was prepared through self-assembly of an ABA triblock copolymer employing catechol functionalized polyethylene glycol (PEG) as A block and poly{[2-(methacryloyloxy)-ethyl] trimethylammonium iodide}(PMETA) as B block. This hydrogel exhibits excellent thermosensitivity, and can effectively inhibit the growth of E. coli (>99.8% killing efficiency) and prevent cell attachment. It can also heal autonomously from repeated damage, through mussel-inspired catechol-mediated hydrogen bonding and aromatic interactions, exhibiting great potential in bioengineering applications.

  5. Rheo-mechanical model for self-healing asphalt pavement

    NASA Astrophysics Data System (ADS)

    Gömze, A. L.; Gömze, L. N.

    2017-01-01

    Examining the rheological properties of different asphalt mixtures at different temperatures, pressures and deformation conditions on the combined rheo-tribometers the authors have found that the generally used Burgers-model doesn’t explain the deformation properties of asphalt mixtures and pavements under loading forces and loading pressures. To understand better the rheological and deformation properties of such complex materials like asphalt mixtures and pavements the authors used Malvern Mastersizer X laser granulometer, Bruker D8 Advance X-ray diffractometer, Hitachi TM 1000 Scanning Elektronmicroscope, Tristar 3000 specific surface tester and the combined rheo-tribometer developed and patented by the authors. After the complex investigation of different asphalt mixtures the authors have found a new, more complex rheological model for the asphalts including self-healing asphalt pavements.

  6. Pressurized vascular systems for self-healing materials.

    PubMed

    Hamilton, A R; Sottos, N R; White, S R

    2012-05-07

    An emerging strategy for creating self-healing materials relies on embedded vascular networks of microchannels to transport reactive fluids to regions of damage. Here we investigate the use of active pumping for the pressurized delivery of a two-part healing system, allowing a small vascular system to deliver large volumes of healing agent. Different pumping strategies are explored to improve the mixing and subsequent polymerization of healing agents in the damage zone. Significant improvements in the number of healing cycles and in the overall healing efficiency are achieved compared with prior passive schemes that use only capillary forces for the delivery of healing agents. At the same time, the volume of the vascular system required to achieve this superior healing performance is significantly reduced. In the best case, nearly full recovery of fracture toughness is attained throughout 15 cycles of damage and healing, with a vascular network constituting just 0.1 vol% of the specimen.

  7. Comparison of self-healing ionomer to aluminium-alloy bumpers for protecting spacecraft equipment from space debris impacts

    NASA Astrophysics Data System (ADS)

    Francesconi, A.; Giacomuzzo, C.; Grande, A. M.; Mudric, T.; Zaccariotto, M.; Etemadi, E.; Di Landro, L.; Galvanetto, U.

    2013-03-01

    This paper discusses the impact behavior of a self-healing ionomeric polymer and compares its protection capability against space debris impacts to that of simple aluminium-alloy bumpers. To this end, 14 impact experiments on both ionomer and Al-7075-T6 thin plates with similar surface density were made with 1.5 mm aluminium spheres at velocity between 1 and 4 km/s.First, the perforation extent in both materials was evaluated vis-à-vis the prediction of well known hole-size equations; then, attention was given to the damage potential of the cloud of fragments ejected from the rear side of the target by analysing the craters pattern and the momentum transferred to witness plates mounted on a ballistic pendulum behind the bumpers.Self-healing was completely successful in all but one ionomer samples and the primary damage on ionomeric polymers was found to be significantly lower than that on aluminium. On the other hand, aluminium plates exhibited slightly better debris fragmentation abilities, even though the protecting performance of ionomers seemed to improve at increasing impact speed.

  8. Solid state self-healing system: Effects of using PDGEBA, PVC and PVA as linear healing agents

    NASA Astrophysics Data System (ADS)

    Muhamad, Noor Nabilah; Jamil, Mohd. Suzeren Md.; Abdullah, Shahrum

    2014-09-01

    The solid state self-healing system was obtained by employing a thermosetting epoxy resin, into which a thermoplastic is dissolved. In this study, the effect of healing efficiency was investigated by using different thermoplastic polymers which are poly(bisphenol-A-co-epichlorohydrin), polyvinyl chloride and polyvinyl alcohol as healing agents. Healing was achieved by heating the fractured resins to a specific temperature i.e. above their glass transition temperature (Tg) which obtained from dynamic mechanical analysis (DMA) to mobilize the polymeric chains of the healing agent. The curing reaction in the epoxy resins were characterized by means of Fourier transform infrared spectroscopy (FTIR). Izod impact test was been performed to demonstrate self-healing of the different specimens. Under test, it was found that healable resin with PDGEBA has highest healing efficiency followed by PVC and PVA, with 63%, 35% and 18% of average percentage healing efficiencies respectively. These results are due to the different solubility parameters of the thermoset/network and thermoplastic polymer which led to the phase separation. Morphological studies prove the fracture-healing process and morphological properties of the resins.

  9. Accelerated Aging of Polymer Composite Bridge Materials

    SciTech Connect

    Carlson, Nancy Margaret; Blackwood, Larry Gene; Torres, Lucinda Laine; Rodriguez, Julio Gallardo; Yoder, Timothy Scott

    1999-03-01

    Accelerated aging research on samples of composite material and candidate ultraviolet (UV) protective coatings is determining the effects of six environmental factors on material durability. Candidate fastener materials are being evaluated to determine corrosion rates and crevice corrosion effects at load-bearing joints. This work supports field testing of a 30-ft long, 18-ft wide polymer matrix composite (PMC) bridge at the Idaho National Engineering and Environmental Laboratory (INEEL). Durability results and sensor data from tests with live loads provide information required for determining the cost/benefit measures to use in life-cycle planning, determining a maintenance strategy, establishing applicable inspection techniques, and establishing guidelines, standards, and acceptance criteria for PMC bridges for use in the transportation infrastructure.

  10. Polymer precursors for ceramic matrix composites

    NASA Technical Reports Server (NTRS)

    Litt, M. H.; Kumar, K.

    1986-01-01

    The synthesis and characterization of a polycyclohexasilane is reported. Because of its cyclic structure, it is anticipated that this polymer might serve as a precursor to SIC having a high char yield with little rearrangement to form small, volatile cyclic silanes, and, as such, would be of interest as a precursor to SiC composite matrices and fibers, or as a binder in ceramic processing. Several approaches to the synthesis of a bifunctional cyclic monomer were attempted; the most successful of these was metal coupling of PhMeSiCl2 and Me2SiCl2. The procedure gives six-membered ring compounds with all degrees of phenyl substitution, from none to hexaphenyl. The compounds with from 0-2 groups were isolated and characterized. The fraction with degree of phenyl substitution equal to 2, a mixture of cis and trans 1,2-; 1,3-; and 1,4 isomers, was isolated in 32 percent yield. Pure 1,4 diphenyldecamethylcyclohexasilane was isolated from the mixed diphenyl compounds and characterized. Diphenyldecamethylcyclohexasilanes were dephenylated to dichlorodecamethylcyclohexasilanes by treating with H2SO4.NH4Cl in benzene. The latter were purified and polymerized by reacting with sodium in toluene. The polymers were characterized by HPGPC, elemental analysis, proton NMR, and IR. Thermogravimetric analyses were carried out on the polymers. As the yield of residual SiC was low, polymers were heat treated to increase the residual char yield. As high as 51.52 percent residual char yield was obtained in one case.

  11. Inorganic-organic composite solid polymer electrolytes

    SciTech Connect

    Abraham, K.M.; Koch, V.R.; Blakley, T.J.

    2000-04-01

    Inorganic-organic composite solid polymer electrolytes (CSPEs) have been prepared from the poly(ethylene oxide) (PEO)-like electrolytes of the general formula polyvinylidene fluoride-hexafluoropropylene (PVdF-HFP)-PEO{sub n}-LiX and Li{sup +}-conducting ceramic powders. In the PEO-like electrolytes, PVdF-HFP is the copolymer of PVdF and HFP, PEO{sub n} is a nonvolatile oligomeric polyethylene oxide of {approximately}400 g/mol molecular weight, and LiX is lithium bis(trifluoroethylsulfonyl)imide. Two types of inorganic oxide ceramic powders were used: a highly Li{sup +}-conducting material of the composition 14 mol % Li{sub 2}O-9Al{sub 2}O{sub 3}-38TiO{sub 2}-39P{sub 2}O{sub 5}, and the poorly Li{sup +}-conducting Li-silicates Li{sub 4{minus}x}M{sub x}SiO{sub 4} where M is Ca or Mg and x is 0 or 0.05. The composite electrolytes can be prepared as thin membranes in which the Li{sup +} conductivity and good mechanical strength of the Li{sup +}-conducting inorganic ceramics are complemented by the structural flexibility and high conductivity of organic polymer electrolytes. Excellent electrochemical and thermal stabilities have been demonstrated for the electrolyte films. Li//composite electrolyte//LiCoO{sub 2} rechargeable cells have been fabricated and cycled at room temperature and 50 C.

  12. Composite layers for barrier coatings on polymers

    NASA Astrophysics Data System (ADS)

    Brochhagen, Markus; Vorkoetter, Christoph; Boeke, Marc; Benedikt, Jan

    2016-09-01

    Amorphous hydrogenated carbon (a-C:H), amorphous hydrogenated silicon (a-Si:H), and SiO2 thin films are of high interest because they can serve as a gas barrier on polymers. To understand how the coating changes the overall barrier properties of the thin film-polymer system, optical, mechanical, and barrier properties have to be studied. One of the important characteristic of such coatings is their compressive stress, which has beneficial as well as unwanted effects. The stress can cause deformation of the bulk material or de-lamination of the film. The mechanical stability can be improved and it is possible to reduce cracking due to elongation, as the compressive stress can compensate externally applied tensile strain. Stress and mechanical properties of composite layers can be manipulated directly by embedding nanoparticles in an amorphous matrix film. Therefore nanoparticles and amorphous layers are investigated before they can be assembled in a composite layer. Growth rates as well as optical and mechanical properties are explored in this work. An inductively coupled plasma source was used for all amorphous layers and the silicon nanoparticles with diameter around 5 nm were produced in a capacitively coupled plasma reactor. This work is supported by DFG within SFB-TR87.

  13. Multifunctional Nanofibers Comprised of Conducting and Ferroelectric Polymer Composites

    DTIC Science & Technology

    2015-08-04

    SECURITY CLASSIFICATION OF: Work on this proposal concentrated on studying the following polymers : poly(vinylidene fluoride-trifluoroethylene) (PVDF...prepare thin films and electrospinning to prepare fine fibers of these polymers . The goal was to make devices and sensors. Using an atomic force...2014 Approved for Public Release; Distribution Unlimited Multifunctional nanofibers comprised of conducting and ferroelectric polymer composites The

  14. Demonstrating the self-healing behaviour of some selected ceramics under combustion chamber conditions

    NASA Astrophysics Data System (ADS)

    Farle, A.; Boatemaa, L.; Shen, L.; Gövert, S.; Kok, J. B. W.; Bosch, M.; Yoshioka, S.; van der Zwaag, S.; Sloof, W. G.

    2016-08-01

    Closure of surface cracks by self-healing of conventional and MAX phase ceramics under realistic turbulent combustion chamber conditions is presented. Three ceramics namely; Al2O3, Ti2AlC and Cr2AlC are investigated. Healing was achieved in Al2O3 by even dispersion of TiC particles throughout the matrix as the MAX phases, Ti2AlC and Cr2AlC exhibit intrinsic self-healing. Fully dense samples (>95%) were sintered by spark plasma sintering and damage was introduced by indentation, quenching and low perpendicular velocity impact methods. The samples were exposed to the oxidizing atmosphere in the post flame zone of a turbulent flame in a combustion chamber to heal at temperatures of approx. 1000 °C at low pO2 levels for 4 h. Full crack-gap closure was observed for cracks up to 20 mm in length and more than 10 μm in width. The reaction products (healing agents) were analysed by scanning electron microscope, x-ray microanalysis and XRD. A semi-quantification of the healing showed that cracks in Al2O3/TiC composite (width 1 μm and length 100 μm) were fully filled with TiO2. In Ti2AlC large cracks were fully filled with a mixture of TiO2 and Al2O3. And in the Cr2AlC, cracks of up to 1.0 μm in width and more than 100 μm in length were also completely filled with Al2O3.

  15. Integrated Modeling of Polymer Composites Under High Energy Laser Irradiation

    DTIC Science & Technology

    2015-10-30

    the SThM measurements deviates from standard procedures for neat resin and prepreg composites . Individual carbon fibers are suspended or draped across...AFRL-RX-WP-TR-2016-0071 INTEGRATED MODELING OF POLYMER COMPOSITES UNDER HIGH ENERGY LASER IRRADIATION Brent Volk, Gregory Ehlert...DAVIS, Chief Composite Materials and Processing Section Composite Materials and Processing Section Composite Branch

  16. Mechanical Evaluation of Polymer Composite Hip Protectors

    PubMed Central

    Melo, Jose Daniel Diniz; Barbosa, Ayrles S. Gonçalves; Guerra, Ricardo Oliveira

    2010-01-01

    Hip fractures often result in serious health implications, particularly in the geriatric population, and have been related to long-term morbidity and death. In most cases, these fractures are caused by impact loads in the area of the greater trochanter, which are produced in a fall. This work is aimed at developing hip protectors using composite materials and evaluating their effectiveness in preventing hip fractures under high impact energy (120 J). The hip protectors were developed with an inner layer of energy absorbing soft material and an outer rigid shell of fiberglass-reinforced polymer composite. According to the experimental results, all tested configurations proved to be effective at reducing the impact load to below the average fracture threshold of proximal femur. Furthermore, an addition of Ethylene Vinyl Acetate (EVA) to the impacted area of the composite shell proved to be beneficial to increase impact strength of the hip protectors. Thus, composite hip protectors proved to be a viable alternative for a mechanically efficient and cost-effective solution to prevent hip fractures. PMID:20871841

  17. Methods of making composite optical devices employing polymer liquid crystal

    DOEpatents

    Jacobs, Stephen D.; Marshall, Kenneth L.; Cerqua, Kathleen A.

    1991-01-01

    Composite optical devices using polymer liquid crystal materials both as optical and adhesive elements. The devices are made by assembling a heated polymer liquid crystal compound, while in a low viscosity form between optically transparent substrates. The molecules of the polymer are oriented, while in the liquid crystalline state and while above the glass transition temperature (T.sub.g) of the polymer, to provide the desired optical effects, such as polarization, and selective reflection. The liquid crystal polymer cements the substrates together to form an assembly providing the composite optical device.

  18. Methods of making composite optical devices employing polymer liquid crystal

    DOEpatents

    Jacobs, S.D.; Marshall, K.L.; Cerqua, K.A.

    1991-10-08

    Composite optical devices are disclosed using polymer liquid crystal materials both as optical and adhesive elements. The devices are made by assembling a heated polymer liquid crystal compound, while in a low viscosity form between optically transparent substrates. The molecules of the polymer are oriented, while in the liquid crystalline state and while above the glass transition temperature (T[sub g]) of the polymer, to provide the desired optical effects, such as polarization, and selective reflection. The liquid crystal polymer cements the substrates together to form an assembly providing the composite optical device. 7 figures.

  19. On the use of crystalline admixtures in cement based construction materials: from porosity reducers to promoters of self healing

    NASA Astrophysics Data System (ADS)

    Ferrara, Liberato; Krelani, Visar; Moretti, Fabio

    2016-08-01

    The project detailed in this paper aims at a thorough characterization of the effects of crystalline admixtures, currently employed as porosity reducing admixtures, on the self-healing capacity of the cementitious composites, i.e. their capacity to completely or partially re-seal cracks and, in case, also exhibit recovery of mechanical properties. The problem has been investigated with reference to both a normal strength concrete (NSC) and a high performance fibre reinforced cementitious composite (HPFRCC). In the latter case, the influence of flow-induced fibre alignment has also been considered in the experimental investigation. With reference to either 3-point (for NSC) or 4-point (for HPFRCC) bending tests performed up to controlled crack opening and up to failure, respectively before and after exposure/conditioning recovery of stiffness and stress bearing capacity has been evaluated to assess the self-healing capacity. In a durability-based design framework, self-healing indices to quantify the recovery of mechanical properties will also be defined. In NSC, crystalline admixtures are able to promote up to 60% of crack sealing even under exposure to open air. In the case of HPFRCCs, which would already feature autogenous healing capacity because of their peculiar mix compositions, the synergy between the dispersed fibre reinforcement and the action of the crystalline admixture has resulted in a likely ‘chemical pre-stressing’ of the same reinforcement, from which the recovery of mechanical performance of the material has greatly benefited, up to levels even higher than the performance of the virgin un-cracked material.

  20. Metal-polymer composites comprising nanostructures and applications thereof

    DOEpatents

    Wang, Hsing-Lin [Los Alamos, NM; Jeon, Sea Ho [Dracut, MA; Mack, Nathan H [Los Alamos, NM

    2012-04-03

    Metal-polymer composites, and methods of making and use thereof, said composites comprising a thermally-cured dense polyaniline substrate; an acid dopant; and, metal nanostructure deposits wherein the deposits have a morphology dependent upon the acid dopant.

  1. Metal-polymer composites comprising nanostructures and applications thereof

    DOEpatents

    Wang, Hsing-Lin [Los Alamos, NM; Jeon, Sea Ho [Dracut, MA; Mack, Nathan H [Los Alamos, NM

    2011-08-02

    Metal-polymer composites, and methods of making and use thereof, said composites comprising a thermally-cured dense polyaniline substrate; an acid dopant; and, metal nanostructure deposits wherein the deposits have a morphology dependent upon the acid dopant.

  2. Preparation of pinewood/polymer/composites using gamma irradiation

    NASA Astrophysics Data System (ADS)

    Ajji, Zaki

    2006-09-01

    Wood/polymer composites (WPC) have been prepared from pinewood with different compounds using gamma irradiation: butyl acrylate, butyl methacrylate, styrene, acrylamide, acrylonitrile, and unsaturated polyester styrene resin. The polymer loading was determined with respect to the compound concentration and the irradiation dose. The polymer loading increases generally with increase in the monomer or polymer concentration. Tensile and compression strength have been improved in the four cases, but no improvement was observed using unsaturated polyester styrene resin or acrylamide.

  3. Affordable, Lightweight, Highly Conductive Polymer Composite Electronic Packaging Structures

    DTIC Science & Technology

    1996-06-01

    matrix composite materials and how various material designs can be utilized in various structural/thermal configurations to produce electronic housings and...conductive polymer composite electronic packaging (i.e., electronic housings and heat sinks). The research will center on predominately polymer

  4. Polymer Composite Containing Carbon Nanotubes and Their Applications.

    PubMed

    Park, Sung-Hoon; Bae, Joonwon

    2016-10-27

    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 nano-material 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

  5. Adhesion and Long-Term Barrier Restoration of Intrinsic Self-Healing Hybrid Sol-Gel Coatings.

    PubMed

    Abdolah Zadeh, Mina; van der Zwaag, Sybrand; Garcia, Santiago J

    2016-02-17

    Self-healing polymeric coatings aiming at smart and on-demand protection of metallic substrates have lately attracted considerable attention. In the present paper, the potential application of a dual network hybrid sol-gel polymer containing reversible tetrasulfide groups as a protective coating for the AA2024-T3 substrate is presented. Depending on the constituent ratio, the developed polymer exhibited a hydrophobic surface, high adhesion strength, and an effective long-term corrosion protection in 0.5 M NaCl solution. Upon thermal treatment, the healable hybrid sol-gel coating demonstrated full restoration of the barrier properties as well as recovery of the coating adhesion and surface properties (e.g., hydrophobicity and surface topology) necessary for lifetime extension of corrosion protective coatings. Excellent long-term barrier restoration of the coating was only obtained if the scratch width was less than the coating thickness.

  6. Shock wave profiles in polymer matrix composite

    NASA Astrophysics Data System (ADS)

    Boteler, J. Michael; Rajendran, A. M.; Grove, David

    2000-04-01

    The promise of lightweight armor which is also structurally robust is of particular importance to the Army for future combat vehicles. Fiber reinforced organic matrix composites such as Polymer Matrix Composite (PMC) are being considered for this purpose due to their lower density and promising dynamic response. The work discussed here extends the prior work of Boteler who studied the delamination strength of PMC and Dandekar and Beaulieu who investigated the compressive and tensile strengths of PMC. In a series of shock wave experiments, the wave profile was examined as a function of propagation distance in PMC. Uniaxial strain was achieved by symmetric plate impact in the ARL 102 mm bore single-stage light gas gun. Embedded polyvinylidene flouride (PVDF) stress-rate gauges provided a stress history at three unique locations in the PMC and particle velocity history was recorded with VISAR. All stress data was compared to a Lagrangian hydrocode (EPIC) employing a model to describe the viscoelastic response of the composite material in one-dimension. The experimental stress histories displayed attenuation and loading properties in good agreement with model predictions. However, the unloading was observed to be markedly different than the hydrocode simulations. These results are discussed.

  7. Repetitive Biomimetic Self-healing of Ca2+-Induced Nanocomposite Protein Hydrogels

    PubMed Central

    Chen, Jun; Dong, Qiuchen; Ma, Xiaoyu; Fan, Tai-Hsi; Lei, Yu

    2016-01-01

    Self-healing is a capacity observed in most biological systems in which the healing processes are autonomously triggered after the damage. Inspired by this natural behavior, researchers believed that a synthetic material possessing similar self-recovery capability could also be developed. Albeit various intrinsic self-healing systems have been developed over the past few decades, restriction on the biocompatibility due to the required synthetic conditions under extreme pH and with poisonous cross-linker significantly limits their application in biomedical field. In this study, a highly biocompatible nanocomposite protein hydrogel with excellent biomimetic self-healing property is presented. The self-healing protein gel is made by inducing calcium ions into the mixture of heat-induced BSA nano-aggregates and pristine BSA molecules at room temperature and under physiological pH due to the ion-mediated protein-protein association and the bridging effect of divalent Ca2+ ions. The as-prepared protein hydrogel shows excellent repetitive self-healing properties without using any external stimuli at ambient condition. Such outstanding self-recovery performance was quantitatively evaluated/validated by both dynamic and oscillatory rheological analysis. Moreover, with the presence of calcium ions, the self-healing behavior can be significantly facilitated/enhanced. Finally, the superior biocompatibility demonstrated by in vitro cytotoxicity analysis suggests that it is a promising self-healing material well-suited for biomedical applications. PMID:27545280

  8. Repetitive Biomimetic Self-healing of Ca(2+)-Induced Nanocomposite Protein Hydrogels.

    PubMed

    Chen, Jun; Dong, Qiuchen; Ma, Xiaoyu; Fan, Tai-Hsi; Lei, Yu

    2016-08-22

    Self-healing is a capacity observed in most biological systems in which the healing processes are autonomously triggered after the damage. Inspired by this natural behavior, researchers believed that a synthetic material possessing similar self-recovery capability could also be developed. Albeit various intrinsic self-healing systems have been developed over the past few decades, restriction on the biocompatibility due to the required synthetic conditions under extreme pH and with poisonous cross-linker significantly limits their application in biomedical field. In this study, a highly biocompatible nanocomposite protein hydrogel with excellent biomimetic self-healing property is presented. The self-healing protein gel is made by inducing calcium ions into the mixture of heat-induced BSA nano-aggregates and pristine BSA molecules at room temperature and under physiological pH due to the ion-mediated protein-protein association and the bridging effect of divalent Ca(2+) ions. The as-prepared protein hydrogel shows excellent repetitive self-healing properties without using any external stimuli at ambient condition. Such outstanding self-recovery performance was quantitatively evaluated/validated by both dynamic and oscillatory rheological analysis. Moreover, with the presence of calcium ions, the self-healing behavior can be significantly facilitated/enhanced. Finally, the superior biocompatibility demonstrated by in vitro cytotoxicity analysis suggests that it is a promising self-healing material well-suited for biomedical applications.

  9. Repetitive Biomimetic Self-healing of Ca2+-Induced Nanocomposite Protein Hydrogels

    NASA Astrophysics Data System (ADS)

    Chen, Jun; Dong, Qiuchen; Ma, Xiaoyu; Fan, Tai-Hsi; Lei, Yu

    2016-08-01

    Self-healing is a capacity observed in most biological systems in which the healing processes are autonomously triggered after the damage. Inspired by this natural behavior, researchers believed that a synthetic material possessing similar self-recovery capability could also be developed. Albeit various intrinsic self-healing systems have been developed over the past few decades, restriction on the biocompatibility due to the required synthetic conditions under extreme pH and with poisonous cross-linker significantly limits their application in biomedical field. In this study, a highly biocompatible nanocomposite protein hydrogel with excellent biomimetic self-healing property is presented. The self-healing protein gel is made by inducing calcium ions into the mixture of heat-induced BSA nano-aggregates and pristine BSA molecules at room temperature and under physiological pH due to the ion-mediated protein-protein association and the bridging effect of divalent Ca2+ ions. The as-prepared protein hydrogel shows excellent repetitive self-healing properties without using any external stimuli at ambient condition. Such outstanding self-recovery performance was quantitatively evaluated/validated by both dynamic and oscillatory rheological analysis. Moreover, with the presence of calcium ions, the self-healing behavior can be significantly facilitated/enhanced. Finally, the superior biocompatibility demonstrated by in vitro cytotoxicity analysis suggests that it is a promising self-healing material well-suited for biomedical applications.

  10. Principles and Applications of Ultrasonic-Based Nondestructive Methods for Self-Healing in Cementitious Materials

    PubMed Central

    Ahn, Eunjong; Kim, Hyunjun; Sim, Sung-Han; Shin, Sung Woo; Shin, Myoungsu

    2017-01-01

    Recently, self-healing technologies have emerged as a promising approach to extend the service life of social infrastructure in the field of concrete construction. However, current evaluations of the self-healing technologies developed for cementitious materials are mostly limited to lab-scale experiments to inspect changes in surface crack width (by optical microscopy) and permeability. Furthermore, there is a universal lack of unified test methods to assess the effectiveness of self-healing technologies. Particularly, with respect to the self-healing of concrete applied in actual construction, nondestructive test methods are required to avoid interrupting the use of the structures under evaluation. This paper presents a review of all existing research on the principles of ultrasonic test methods and case studies pertaining to self-healing concrete. The main objective of the study is to examine the applicability and limitation of various ultrasonic test methods in assessing the self-healing performance. Finally, future directions on the development of reliable assessment methods for self-healing cementitious materials are suggested. PMID:28772640

  11. Principles and Applications of Ultrasonic-Based Nondestructive Methods for Self-Healing in Cementitious Materials.

    PubMed

    Ahn, Eunjong; Kim, Hyunjun; Sim, Sung-Han; Shin, Sung Woo; Shin, Myoungsu

    2017-03-10

    Recently, self-healing technologies have emerged as a promising approach to extend the service life of social infrastructure in the field of concrete construction. However, current evaluations of the self-healing technologies developed for cementitious materials are mostly limited to lab-scale experiments to inspect changes in surface crack width (by optical microscopy) and permeability. Furthermore, there is a universal lack of unified test methods to assess the effectiveness of self-healing technologies. Particularly, with respect to the self-healing of concrete applied in actual construction, nondestructive test methods are required to avoid interrupting the use of the structures under evaluation. This paper presents a review of all existing research on the principles of ultrasonic test methods and case studies pertaining to self-healing concrete. The main objective of the study is to examine the applicability and limitation of various ultrasonic test methods in assessing the self-healing performance. Finally, future directions on the development of reliable assessment methods for self-healing cementitious materials are suggested.

  12. Computer-aided design of polymers and composites

    NASA Technical Reports Server (NTRS)

    Kaelble, D. H.

    1985-01-01

    This book on computer-aided design of polymers and composites introduces and discusses the subject from the viewpoint of atomic and molecular models. Thus, the origins of stiffness, strength, extensibility, and fracture toughness in composite materials can be analyzed directly in terms of chemical composition and molecular structure. Aspects of polymer composite reliability are considered along with characterization techniques for composite reliability, relations between atomic and molecular properties, computer aided design and manufacture, polymer CAD/CAM models, and composite CAD/CAM models. Attention is given to multiphase structural adhesives, fibrous composite reliability, metal joint reliability, polymer physical states and transitions, chemical quality assurance, processability testing, cure monitoring and management, nondestructive evaluation (NDE), surface NDE, elementary properties, ionic-covalent bonding, molecular analysis, acid-base interactions, the manufacturing science, and peel mechanics.

  13. Developing polymer composite materials: carbon nanotubes or graphene?

    PubMed

    Sun, Xuemei; Sun, Hao; Li, Houpu; Peng, Huisheng

    2013-10-04

    The formation of composite materials represents an efficient route to improve the performances of polymers and expand their application scopes. Due to the unique structure and remarkable mechanical, electrical, thermal, optical and catalytic properties, carbon nanotube and graphene have been mostly studied as a second phase to produce high performance polymer composites. Although carbon nanotube and graphene share some advantages in both structure and property, they are also different in many aspects including synthesis of composite material, control in composite structure and interaction with polymer molecule. The resulting composite materials are distinguished in property to meet different applications. This review article mainly describes the preparation, structure, property and application of the two families of composite materials with an emphasis on the difference between them. Some general and effective strategies are summarized for the development of polymer composite materials based on carbon nanotube and graphene. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  14. Computer-aided design of polymers and composites

    NASA Technical Reports Server (NTRS)

    Kaelble, D. H.

    1985-01-01

    This book on computer-aided design of polymers and composites introduces and discusses the subject from the viewpoint of atomic and molecular models. Thus, the origins of stiffness, strength, extensibility, and fracture toughness in composite materials can be analyzed directly in terms of chemical composition and molecular structure. Aspects of polymer composite reliability are considered along with characterization techniques for composite reliability, relations between atomic and molecular properties, computer aided design and manufacture, polymer CAD/CAM models, and composite CAD/CAM models. Attention is given to multiphase structural adhesives, fibrous composite reliability, metal joint reliability, polymer physical states and transitions, chemical quality assurance, processability testing, cure monitoring and management, nondestructive evaluation (NDE), surface NDE, elementary properties, ionic-covalent bonding, molecular analysis, acid-base interactions, the manufacturing science, and peel mechanics.

  15. Inorganic-organic composite polymers and methods of making

    DOEpatents

    Josowicz, M.A.; Exarhos, G.J.

    1996-10-29

    The invention is a composition of an inorganic-organic polymer composite and a method of making it. The inorganic portion of the fundamental polymer composite polymer repeat is a speciated inorganic heterocyclic compound, and the organic portion of the polymer repeat is a cyclic organic radical anion compound having at least two charged sites. The composition of the present invention is made by combining a cyclic organic radical anion compound with a speciated inorganic heterocyclic compound by a nucleophilic substitution thereby forming a polymer of an inorganic-organic composite. The cyclic organic radical anion compound is preferably generated electrochemically. The nucleophilic substitution is alternately carried out chemically or electrochemically. A preferred embodiment of the present invention includes performing the nucleophilic substitution at the cathode of an electrochemical cell. 2 figs.

  16. Inorganic-organic composite polymers and methods of making

    DOEpatents

    Josowicz, Mira A.; Exarhos, Gregory J.

    1996-01-01

    The invention is a composition of an inorganic-organic polymer composite and a method of making it. The inorganic portion of the fundamental polymer composite polymer repeat is a speciated inorganic heterocyclic compound, and the organic portion of the polymer repeat is a cyclic organic radical anion compound having at least two charged sites. The composition of the present invention is made by combining a cyclic organic radical anion compound with a speciated inorganic heterocyclic compound by a nucleophilic substitution thereby forming a polymer of an inorganic-organic composite. The cyclic organic radical anion compound is preferably generated electrochemically. The nucleophilic substitution is alternately carried out chemically or electrochemically. A preferred embodiment of the present invention includes performing the nucleophilic substitution at the cathode of an electrochemical cell.

  17. Advanced composite polymer electrolyte fuel cell membranes

    SciTech Connect

    Wilson, M.S.; Zawodzinski, T.A.; Gottesfeld, S.; Kolde, J.A.; Bahar, B.

    1995-09-01

    A new type of reinforced composite perfluorinated polymer electrolyte membrane, GORE-SELECT{trademark} (W.L. Gore & Assoc.), is characterized and tested for fuel cell applications. Very thin membranes (5-20 {mu}m thick) are available. The combination of reinforcement and thinness provides high membrane, conductances (80 S/cm{sup 2} for a 12 {mu}m thick membrane at 25{degrees}C) and improved water distribution in the operating fuel cell without sacrificing longevity or durability. In contrast to nonreinforced perfluorinated membranes, the x-y dimensions of the GORE-SELECT membranes are relatively unaffected by the hydration state. This feature may be important from the viewpoints of membrane/electrode interface stability and fuel cell manufacturability.

  18. Fracture toughness testing of polymer matrix composites

    NASA Technical Reports Server (NTRS)

    Grady, Joseph E.

    1992-01-01

    A review of the interlaminar fracture indicates that a standard specimen geometry is needed to obtain consistent fracture toughness measurements in polymer matrix composites. In general, the variability of measured toughness values increases as the toughness of the material increases. This variability could be caused by incorrect sizing of test specimens and/or inconsistent data reduction procedures. A standard data reduction procedure is therefore needed as well, particularly for the tougher materials. Little work has been reported on the effects of fiber orientation, fiber architecture, fiber surface treatment or interlaminar fracture toughness, and the mechanisms by which the fibers increase fracture toughness are not well understood. The little data that is available indicates that woven fiber reinforcement and fiber sizings can significantly increase interlaminar fracture toughness.

  19. Polymer Matrix Composites: A Perspective for a Special Issue of Polymer Reviews

    SciTech Connect

    Kessler, Michael R.

    2012-09-04

    Polymer matrix composites, with their high specific strength and stiffness, are used in a wide range of applications from large wind turbine blades to microelectronics. This perspective article provides a brief primer on polymer matrix composites, discusses some of their advantages and limitations, and describes a number of emerging trends in the field. In addition, it introduces four review articles on the topics of recent developments in carbon fibers, natural fiber reinforced composites, evaluation of the interface between the fiber reinforcement and polymer matrix, and carbon nanotube reinforced polymers.

  20. Effects of reprocessing on nanoalumina polymer composites

    NASA Astrophysics Data System (ADS)

    Huang, Chunchia

    The life cycle of reprocessed polymer nanocomposites is a critical factor associated with their growing use, but the limited work on reprocessing of nanocomposites has focused solely on the effects of organoclays. This research investigated of the structure and property changes during reprocessing of polypropylene (PP) and polycarbonate (PC) nanocomposites with 3 wt. % nanoalumina. Neat PP and PC were used as controls. Reprocessing of the neat polymers and nanocomposites produced no indication of oxidation (in FTIR), no changes in the glass transition temperature of PC and the melting temperatures of PP, and no changes in thermal stability (as measured using thermogravimetric analysis). Significant decreases, however, occurred in the melt viscosity of the materials. The introduction of nanoalumina during twin screw extrusion also produced a significant decrease in the viscosity and a 10°C decrease in the glass transition temperature of the PC nanocomposite. Color changes did not correspond to the chain scission in PP and PC; neat PP and PP composite yellowed, neat PC turned brown, and the PC nanocomposite did not change color. Dispersion of the nanoalumina in both PP and PC improved with repeated reprocessing, the crystallinity in the PP/nanoalumina composites remained constant. The Young's moduli of both the PP and PP/A12O3 nanocomposite were similar, whereas the Young's modulus values of the PC/A1 2O3 nanocomposite was slighted lower than that of the neat PC. In contrast, the elongations at break of the PP/A12O3 and PC/A12O3 nanocomposites were, respectively, 50% and 16% of the values measured for the neat resins. All modulus and elongation at break values, however, remained constant over five reprocessing cycles. This behavior suggests that the major degradation mechanism during reprocessing of neat PP and PP nanocomposites was thermal-mechanical polymer chain scission and that the nanoalumina enhanced this degradation in the PC/nanoalumina. This additional