Polymer Composites (polymer + composite)

Distribution by Scientific Domains
Distribution within Polymers and Materials Science

Kinds of Polymer Composites

  • conductive polymer composite


  • Selected Abstracts


    Actuating Single Wall Carbon Nanotube,Polymer Composites: Intrinsic Unimorphs,

    ADVANCED MATERIALS, Issue 11 2008
    Cheol Park
    A novel actuating single wall carbon nanotube (SWNT)/polymer composite is reported. It exhibits a large strain (2.6%) at a low driving voltage (<1 MV m,1) while possessing excellent mechanical and thermal properties. The strain energy density is at least an order of magnitude greater than any state-of-the-art polymeric materials reported. The actuating characteristic mainly originates from the electrostrictive contribution, presumably due to interfacial polarization. [source]


    Use of Enzymes for the Processing of Biomaterials

    INTERNATIONAL JOURNAL OF APPLIED CERAMIC TECHNOLOGY, Issue 1 2007
    Hidero Unuma
    Ceramic/polymer composites and hollow ceramic microspheres are receiving attention as biomaterials as a bone/tissue substitute and cancer remedy. This article describes the advantages of the use of enzymes as "controllable precipitant supplier" in the processing of such biomaterials. It has been demonstrated that hydroxyapatite (HA)/polymer composites and hollow microspheres of Y2O3, Fe3O4, and HA may be fabricated in a shorter time and using a simpler operation. [source]


    Functionalization of Shortened Single-Walled Carbon Nanotubes with Poly(p -dioxanone) by "Grafting-From" Approach

    MACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 9 2004
    Kuk Ro Yoon
    Abstract Summary: It has been a real challenge to form carbon nanotube (CNT)/polymer composites where CNTs are well-dispersed in the polymer matrix and the interactions between CNTs and polymers are effectively strong. In this paper, we applied surface-initiated, ring-opening polymerization (SI-ROP) of p -dioxanone (PDX) to shortened single-walled carbon nanotubes (s-SWCNTs) and successfully formed s-SWCNT/PPDX composites (see Figure). Due to intimate interactions between s-SWCNTs and PPDX, we observed dramatic changes in PPDX properties upon the formation of the composites: 10%-weight-loss-temperature of PPDX increased by 20,C (measured by thermogravimetric analysis) and the patterns of Tg and Tm were greatly altered. We did not observe any noticeable peaks from the composite up to 120,C in differential scanning calorimetry (DSC), while DSC data of PPDX itself showed Tg and Tm at ,13.4 and 103,C respectively. Schematic representation of the procedure for formation of s-SWCNT/PPDX composites. [source]


    Use of Enzymes for the Processing of Biomaterials

    INTERNATIONAL JOURNAL OF APPLIED CERAMIC TECHNOLOGY, Issue 1 2007
    Hidero Unuma
    Ceramic/polymer composites and hollow ceramic microspheres are receiving attention as biomaterials as a bone/tissue substitute and cancer remedy. This article describes the advantages of the use of enzymes as "controllable precipitant supplier" in the processing of such biomaterials. It has been demonstrated that hydroxyapatite (HA)/polymer composites and hollow microspheres of Y2O3, Fe3O4, and HA may be fabricated in a shorter time and using a simpler operation. [source]


    Effect of heat treatment on the electrical properties of lead zirconate titanate/poly (vinylidene fluoride) composites

    POLYMER INTERNATIONAL, Issue 6 2010
    Lijie Dong
    Abstract Ceramic/polymer composites are attracting increasing interest in materials research and practical applications due to the combination of excellent electric properties of piezoelectric ceramics and good flexibility of polymer matrices. In this case, the crystallization of the polymer has a significant effect on the electric properties of ceramic/polymer composites. Based on different heat treatment methods, the crystallization of poly(vinylidene fluoride) (PVDF) in composites of lead zirconate titanate (PZT) and PVDF can be controlled effectively. PZT/PVDF composites with various PVDF crystallizations exhibit distinctive dielectric and piezoelectric properties. When the crystallization of PVDF is 21%, the PZT/PVDF composites show a high dielectric constant (,) of 165 and a low dielectric loss (tan ,) of 0.03 at 103 Hz, and when the crystallization of PVDF reaches 34%, the piezoelectric coefficient (d33) of PZT/PVDF composites can be up to ca 100 pC N,1. By controlling the crystallization of PVDF, PZT/PVDF composites with excellent dielectric and piezoelectric properties were obtained, which can be employed as promising candidates in high-efficiency capacitors and as novel piezoelectric materials. Copyright 2010 Society of Chemical Industry [source]


    Highly Conductive Carbon Nanotube/Polymer Nanocomposites Achievable?

    MACROMOLECULAR THEORY AND SIMULATIONS, Issue 3 2009
    Xinxin Sun
    Abstract Carbon nanotubes (NT) have attracted growing interest in recent years as a conducting filler in the development of conductive polymer composites. However, most of experimental results show that the conductivity of NT/polymer composites is significantly lower than expected. Can NTs be an effective conductive filler for improving the electrical conductivity of polymers? In order to answer this question, a continuum model was constructed by introducing effective tunneling conduction in a non-universal network for the prediction of electrical conductivity of NT/polymer composites. Based on this model, the effect of the microstructure of NT/polymer composites on conductivity was assessed particularly for NT/polyethylene, NT/polyimide, and NT/poly(vinyl alcohol) composites. NT contact resistance and tunneling resistance have significant influences on the conductivity. The effects of the potential barrier of polymer and the tortousity of single-walled NTs on the conductivity were also analyzed. NTs cannot be considered as a valuable conductive filler for the development of highly conductive polymer composites unless the contact and tunneling resistances are reduced significantly. [source]


    Processing Conditions and Aging Effect on the Morphology of PZT Electrospun Nanofibers, and Dielectric Properties of the Resulting 3,3 PZT/Polymer Composite

    JOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 11 2009
    Ebru Mensur Alkoy
    Lead zirconate titanate (PZT) nanofibers are obtained by electrospinning a sol,gel based solution and polyvinyl pyrrolidone (PVP) polymer, and by subsequent sintering of the electrospun precursor fibers. The average diameter of the precursor PZT/PVP green fibers has increased with the aging of the precursor solution along with an increase in the viscosity. Bead-free uniform green PZT/PVP fibers were collected at about an ,230 nm average fiber diameter using a 28 wt% PVP ratio solution with a viscosity of 290 mPa. Shrinkage of 40% was recorded on the fiber diameter after sintering. The X-ray diffraction pattern of the annealed PZT fibers exhibits no preferred orientation and a perovskite phase. Preparation of 3,3 nanocomposites by the infusion of polyvinylester into the nanofiber mat facilitates successful handling of the fragile mats and enables measurements of the dielectric properties. The dielectric constant of the PZT/polyvinylester nanocomposite of about 10% fiber volume fraction was found to be fairly stable and vary from 72 to 62 within the measurement range. The dielectric loss of the composite is below 0.08 at low frequencies and reaches a stable value of 0.04 for most of the measured frequencies. [source]


    Cement-Based 0-3 Piezoelectric Composites

    JOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 2 2002
    Zongjin Li
    To meet the requirements of development for smart or intelligent structures in civil engineering, new functional materials that have good compatibility with civil engineering structural materials are needed. In this study, for the first time in the field of piezoelectric materials, cement-based 0-3 piezoelectric (PZT) composites were fabricated by the normal mixing and spreading method. The new materials have very good compatibility with portland cement concrete. The cement-based 0-3 piezoelectric composites were shown to have a slightly higher piezoelectric factor and electromechanical coefficient than those of 0-3 PZT/polymer composites with a similar content of PZT particles; thus, they are adequate for sensor application. There is potential for the application of cement-based 0-3 PZT composites in civil engineering because of their better piezoelectric properties and good compatibility with portland cement concrete. [source]


    Nanotube,Polymer Composites for Ultrafast Photonics

    ADVANCED MATERIALS, Issue 38-39 2009
    Tawfique Hasan
    Abstract Polymer composites are one of the most attractive near-term means to exploit the unique properties of carbon nanotubes and graphene. This is particularly true for composites aimed at electronics and photonics, where a number of promising applications have already been demonstrated. One such example is nanotube-based saturable absorbers. These can be used as all-optical switches, optical amplifier noise suppressors, or mode-lockers to generate ultrashort laser pulses. Here, we review various aspects of fabrication, characterization, device implementation and operation of nanotube-polymer composites to be used in photonic applications. We also summarize recent results on graphene-based saturable absorbers for ultrafast lasers. [source]


    Conducting and transparent SWNT/polymer composites

    PHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 13 2006
    Urszula Dettlaff-Weglikowska
    Abstract Flexible, transparent and conducting poly(methyl methacrylate) (PMMA) composites films were prepared using SOCl2 functionalized SWNTs. Optical absorption spectra measured on composite films confirm that the composite preparation procedure preserves the electronic properties (position of the Fermi level) of the p-doped nanotubes in the polymer matrix. Due to the doping effect of SOCl2 the electrical conductivity of the composites is improved by a factor of 5. The light transmission of the composite films depends on the film thickness and on the nanotube concentration. The optical transmittance of visible light at 500 nm was found to be 92% for 0.1 wt% SWNT loading and 46% for 0.5 wt% SWNT loading. The thickness of the specimens was approximately 20 m. Conductivity measurement of the thin films performed with the four lead method revealed values 3.5 10,3 S/cm and 4.7 10,1 S/cm, respectively. ( 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]


    Piezoelectric Multilayer Ceramic/Polymer Composite Transducer with 2,2 Connectivity

    JOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 8 2006
    Chang-Bun Yoon
    A multilayer piezoelectric ceramic/polymer composite with 2,2 connectivity was fabricated by thermoplastic green machining after co-extrusion. The multilayer ceramic body was composed of piezoelectrically active lead zirconate titanate (PZN),lead zinc niobate (PZN)-lead zirconate titanate (PZT) layers and electrically conducting PZN,PZT/Ag layers. After co-extruding the thermoplastic body, which consisted of five piezoelectric layers interspersed with four conducting layers, it was computer numeric-controlled machined to create periodic channels within it. Following binder burnout and sintering, an 18 vol% array of 190 ,m thin PZT slabs with a channel size of 880 ,m was fabricated. The channels were filled with epoxy in order to fabricate a PZN,PZT/epoxy composite with 2,2 connectivity. The piezoelectric coefficient (effective d33) and hydrostatic figure of merit (dhgh) of the PZN,PZT/epoxy composite were 1200 pC/N and 20 130 10,15 m2/N, respectively. These excellent piezoelectric characteristics as well as the relatively simple fabrication procedure will contribute in widening the application range of the piezoelectric transducers. [source]


    Effect of heat treatment on the electrical properties of lead zirconate titanate/poly (vinylidene fluoride) composites

    POLYMER INTERNATIONAL, Issue 6 2010
    Lijie Dong
    Abstract Ceramic/polymer composites are attracting increasing interest in materials research and practical applications due to the combination of excellent electric properties of piezoelectric ceramics and good flexibility of polymer matrices. In this case, the crystallization of the polymer has a significant effect on the electric properties of ceramic/polymer composites. Based on different heat treatment methods, the crystallization of poly(vinylidene fluoride) (PVDF) in composites of lead zirconate titanate (PZT) and PVDF can be controlled effectively. PZT/PVDF composites with various PVDF crystallizations exhibit distinctive dielectric and piezoelectric properties. When the crystallization of PVDF is 21%, the PZT/PVDF composites show a high dielectric constant (,) of 165 and a low dielectric loss (tan ,) of 0.03 at 103 Hz, and when the crystallization of PVDF reaches 34%, the piezoelectric coefficient (d33) of PZT/PVDF composites can be up to ca 100 pC N,1. By controlling the crystallization of PVDF, PZT/PVDF composites with excellent dielectric and piezoelectric properties were obtained, which can be employed as promising candidates in high-efficiency capacitors and as novel piezoelectric materials. Copyright 2010 Society of Chemical Industry [source]


    Esterification effect of maleic anhydride on swelling properties of natural fiber/high density polyethylene composites

    JOURNAL OF APPLIED POLYMER SCIENCE, Issue 4 2007
    J. B. Naik
    Abstract The natural fibers (banana, hemp, and sisal) and high density polyethylene were taken for the preparation of natural fiber/polymer composites in different ratios of 40 : 60 and 45 : 55 (w/w). These fibers were esterified with maleic anhydride (MA) and the effect of esterification of MA was studied on swelling properties in terms of absorption of water, at ambient temperature, and steam. It was found that the steam penetrates more within lesserperiod of time than water at ambient temperature. Untreated fiber composites show more absorption of steam and water in comparison to MA-treated fiber composites. The more absorption of water was found in hemp fiber composites and less in sisal fiber composites. Steam absorption in MA-treated and untreated fiber composites are higher than the water absorption in respective fiber composites. The natural fiber/polymer composites containing low amount of fibers show less absorption of steam and water at ambient temperature than the composites containing more amount of fibers in respective fiber composites. 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007 [source]


    Electrically Controllable Omnidirectional Laser Emission from a Helical-Polymer Network Composite Film

    ADVANCED MATERIALS, Issue 7 2009
    Byoungchoo Park
    A liquid-crystal/polymer composite is used to produce a photonic bandgap system. Films of the composite show a large field-induced reversible color shift of the reflection band of over 150 nm. Intensity-controllable laser emission at relatively low lasing thresholds is generated from composite films doped with dye. Moreover, the laser exhibits omnidirectional emission propagation on application of an electric field. [source]


    A Novel Concept for Highly Oriented Carbon Nanotube Composite Tapes or Fibres with High Strength and Electrical Conductivity

    MACROMOLECULAR MATERIALS & ENGINEERING, Issue 11 2009
    Hua Deng
    Abstract A new concept is described for the creation of multifunctional polymer nanocomposite tapes (or fibres) that combines high stiffness and strength with good electrical properties and a low percolation threshold of carbon nanotubes (CNTs). The concept is based on a bicomponent tape (or fibre) construction consisting of a highly oriented polymer core and a conductive polymer composite (CPC) skin based on a polymer with a lower melting temperature than the core, enabling thermal annealing of these skins to improve conductivity through a dynamic percolation process while retaining the properties of the core and hence those of the tape (or fibre). The percolation threshold in the CPC skins of the highly drawn conductive bicomponent tapes could be decreased from 5.3 to 1.1,wt.-% after annealing. [source]


    Formation of in situ CB/PET Microfibers in CB/PET/PE Composites by Slit Die Extrusion and Hot Stretching

    MACROMOLECULAR MATERIALS & ENGINEERING, Issue 6 2004
    Xiang-Bin Xu
    Abstract Summary: In this present study, the in situ fabrication of a microfibrillar composite based on poly(ethylene terephthalate) (PET), polyethylene (PE), and carbon black (CB) is attempted. PET and CB were first melt mixed. The CB/PET compound and PE were subsequently melt extruded through a slit die and then hot stretched. The morphological observation of the as-stretched extrudate indicated that well-defined microfibers of CB/PET compound could be generated at appropriate CB contents and a fixed hot stretch ratio. In addition, CB was always selectively located in PET. The microfibrillar CB/PET/PE composite has the potential to be a new electrically conductive polymer composite. Morphology of the carbon black/poly(ethylene terephthalate)/polyethylene (PE) composite after additional mixing in the mixer at the processing temperature of PE. [source]


    Continuous surface modification process with ultraviolet/ozone for improving interfacial adhesion of poly(ethylene terephthalate)/epoxy composites

    POLYMER COMPOSITES, Issue 5 2006
    Paisan Khanchaitit
    This study proposed a continuous UV/ozone surface modification process for the production of polymeric fiber-reinforced polymer composite. A gas phase photoreactor using the conventional low-pressure mercury UV lamps and the economically made ozone generators were designed and constructed. Poly(ethylene terephthalate) (PET) fibers and epoxy resin were chosen as a reinforcement and a matrix, respectively. The synergistic effects of UV and various gas species (nitrogen, air, oxygen, air/ozone, and oxygen/ozone) exposure as well as the effects of exposure time, i.e., 2, 5, and 10 min, on the morphology and chemistry of PET-fiber surfaces were investigated by using a scanning electron microscope coupled with energy dispersive x-ray analysis (SEM/EDX). The tensile testing and analysis of fractography of the resulted composites were performed to evaluate the effectiveness of the process. The SEM/EDX results showed that the effects of the treatment were dependent on both the concentration of reactive species present in the gases and the exposure time. The PET fibers treated under UV/O2 + O3 exposure for 5 min yielded the resulting composite with the highest tensile strength value. Under this condition, the tensile strength of the composite can be increased up to 63% in comparison with that of the untreated PET fiber/epoxy composite. The results are of interest for application as an in-line surface modification for composite productions. POLYM. COMPOS., 27:484,490, 2006. 2006 Society of Plastics Engineers [source]


    Partially miscible poly(lactic acid)- blend -poly(propylene carbonate) filled with carbon black as conductive polymer composite

    POLYMER INTERNATIONAL, Issue 9 2008
    Wang Ning
    Abstract BACKGROUND: Conductive polymer composites (CPCs) can be obtained by filling polymer matrices with electrically conductive particles, and have a wide variety of potential applications. In the work reported, the biodegradable polymer poly(lactic acid) (PLA) as a partially miscible blend with poly(propylene carbonate) (PPC) was used as a polymer matrix. Carbon black (CB) was used as the conducting filler. RESULTS: Fourier transform infrared spectroscopy revealed interactions between matrix and CB filler; this interaction was stronger in PPC- blend -CB than in PLA- blend -CB composites. A rheology study showed that low-viscosity PPC could improve the fluidity of the CPCs, but decrease that of CB. With increasing CB content, the enforcement effect, storage modulus and glass transition temperature increased, but the elongation at break decreased. CPCs exhibited the lowest electrical percolation thresholds of 1.39 vol.% CB when the content of PPC in PLA- blend -PPC was 40 wt%. The conductivity of CPCs containing 5.33 vol.% CB and 40 wt% PPC reached 1.57 S cm,1. Scanning electron microscopy revealed that CB exhibits a preference for dispersion in the low-viscosity phase (PPC) of the multiphase matrix. CONCLUSION: In the presence of CB, partially miscible PLA- blend -PPC could form multi-percolation CPCs. Moreover, the combination of PLA and PPC with CB broadens novel application of both renewable polymers and CPCs. Copyright 2008 Society of Chemical Industry [source]


    Fracture behaviour of cracked carbon nanotube-based polymer composites: Experiments and finite element simulations

    FATIGUE & FRACTURE OF ENGINEERING MATERIALS AND STRUCTURES, Issue 2 2010
    Y. KURONUMA
    ABSTRACT This paper studies the fracture behaviour of cracked carbon nanotube (CNT)-based polymer composites by a combined numerical,experimental approach. Tensile tests were conducted on single-edge cracked plate specimens of CNT/polycarbonate composites at room temperature and liquid nitrogen temperature (77 K), and the critical loads for fracture instabilities were determined. Elastic,plastic finite element simulations of the tests were then performed to evaluate the,J -integrals corresponding to the experimentally determined critical loads. Scanning electron microscopy examinations were also made on the specimen fracture surfaces, and the fracture mechanisms of the CNT-based composites were discussed. [source]


    Conjugated Polymers: Enhanced Charge Transportation in Semiconducting Polymer/Insulating Polymer Composites: The Role of an Interpenetrating Bulk Interface (Adv. Funct.

    ADVANCED FUNCTIONAL MATERIALS, Issue 11 2010
    Mater.
    By taking advantage of two-phase interface engineering in three dimensions, X. Yang and co-workers demonstrate on page 1714 the substantially improved (instead of decreased) electrical properties of conjugated polymer/insulating polymer composites. This novel approach paves the way for preparing high-performance semiconducting polymer composites with reduced cost, improved mechanical properties, and environmental stability. [source]


    Enhanced Charge Transportation in Semiconducting Polymer/Insulating Polymer Composites: The Role of an Interpenetrating Bulk Interface

    ADVANCED FUNCTIONAL MATERIALS, Issue 11 2010
    Guanghao Lu
    Abstract The charge transportation in poly(3-butylthiophene) (P3BT)/insulating polymer composites is studied both microscopically and macroscopically. The increased mobility of free charge carriers, in particular hole mobility, contributes to the enhanced electrical conductivity of this semiconductor/insulator composite. The conductivity origin of the composite, as revealed by conductive-atomic force microscopy (C-AFM), comes mainly from the P3BT network, whose carrier mobility has been improved as a result of reduced activation energy for charge transportation upon forming an interface with the insulating matrix. Both the huge interfacial area and interconnected conductive component are morphologically required for the enhanced electrical property of the composite. An increased size of the P3BT domains, which correspondingly reduces the interfacial area between the two components, ruins the enhancement. This study clarifies the mechanism of the higher electrical properties achieved in a semiconducting polymer upon blending with an insulating polymer, which will further promote the development of these low-cost, easily processable, and environmentally stable composites. [source]


    Structural Fabrication and Functional Modulation of Nanoparticle,Polymer Composites

    ADVANCED FUNCTIONAL MATERIALS, Issue 10 2010
    Hao Zhang
    Abstract This review article summarizes recent progress in the fabrication methodologies and functional modulations of nanoparticle (NP),polymer composites. On the basis of the techniques of NP synthesis and surface modification, the fabrication methods of nanocomposites are highlighted; these include surface-initiated polymerization on NPs, in situ formation of NPs in polymer media, and the incorporation through covalent linkages and supramolecular assemblies. In these examples, polymers are foremost hypothesized as inert hosts that stabilize and integrate the functionalities of NPs, thus improving the macroscopic performance of NPs. Furthermore, due to the unique physicochemical properties of polymers, polymer chains are also dynamic under heating, swelling, and stretching. This creates an opportunity for modulating NP functionalities within the preformed nanocomposites, which will undoubtedly promote the developments of optoelectronic devices, optical materials, and intelligent materials. [source]


    Preparation of High-Performance Conductive Polymer Fibers through Morphological Control of Networks Formed by Nanofillers

    ADVANCED FUNCTIONAL MATERIALS, Issue 9 2010
    Hua Deng
    Abstract A general method is described to prepare high-performance conductive polymer fibers or tapes. In this method, bicomponent tapes/fibers containing two layers of conductive polymer composites (CPCs) filled with multiwall carbon nanotubes (MWNT) or carbon black (CB) based on a lower-melting-temperature polymer and an unfilled polymer core with higher melting temperature are fabricated by a melt-based process. Morphological control of the conductive network formed by nanofillers is realized by solid-state drawing and annealing. Information on the morphological and electrical change of the highly oriented conductive nanofiller network in CPC bicomponent tapes during relaxation, melting, and crystallization of the polymer matrix is reported for the first time. The conductivity of these polypropylene tapes can be as high as 275,S,m,1 with tensile strengths of around 500,MPa. To the best of the authors' knowledge, it is the most conductive, high-strength polymer fiber produced by melt-processing reported in literature, despite the fact that only ,5,wt.% of MWNTs are used in the outer layers of the tape and the overall MWNT content in the bicomponent tape can be much lower (typically ,0.5,wt.%). Their applications could include sensing, smart textiles, electrodes for flexible solar cells, and electromagnetic interference (EMI) shielding. Furthermore, a modeling approach was used to study the relaxation process of highly oriented conductive networks formed by carbon nanofillers. [source]


    Cone calorimeter testing of S2 glass reinforced polymer composites

    FIRE AND MATERIALS, Issue 7 2009
    Alexander B. Morgan
    Abstract With the ever increasing demand for fuel savings on vehicles, there is a strong push to replace metal with polymeric + fiber (carbon/glass) composites. However, the replacement of metal with polymeric composites can lead to additional fire risk. Our study focused on glass fiber reinforced polymer composites meant for vehicular structural applications, and flammability performance of these composites was studied by cone calorimetery. The effects of fiberglass loading, nanocomposite use (clay, carbon nanofiber) and polymer type (epoxy, phenolic) were studied under a heat flux of 50kW/m2 to better understand the potential effects that these variables would have on material flammability. It was found that as fiberglass loading increased, flammability decreased, but at a cost to structural integrity of the residual polymer + fiber char. The use of nanocomposites has little effect on reducing flammability in this set of samples, but the use of phenolic resins in comparison with epoxy resins was found to yield the greatest improvements in flammability performance. Further, the phenolic system yielded a higher level of structural integrity to the final polymer + fiberglass char when compared with the other polymer systems of low heat release. Copyright 2009 John Wiley & Sons, Ltd. [source]


    Enhanced Photorefractivity of Poly(N -vinylcarbazole)-Based Composites through Electric-Field Treatments and Ionic Liquid Doping

    ADVANCED FUNCTIONAL MATERIALS, Issue 3 2009
    Jos A. Quintana
    Abstract It is shown that the photorefractive (PR) performance of polymer composites based on poly(N -vinylcarbazole) can be improved when samples are subjected to an electric field for a certain time, i.e. conditioned, previous to the PR characterization. It is also found that for conditioned samples the addition of an organic ionic liquid to the PR composition allows to obtain PR effect without the need of using a sensitizer. The typical electric field treatment time at room temperature and at a field of 20,V m,1 is 20,min. This procedure leads to a decrease of dark conductivity and an increase of photoconductivity, and consequently an increase of conductivity contrast. This results in higher PR two-beam-coupling gain coefficients and shorter response times, particularly at low fields. Dependencies of the process dynamics on impurities, applied field strength, temperature and the presence of an organic ionic liquid are examined in detail. It is remarkable the significant increase of the PR gain coefficients, and more drastically of the net gain coefficients, observed at low fields (<55,V m,1), when an ionic organic liquid such as benzalkonium chloride is added to unsensitized conditioned PR composites. These findings open a new route to improve the PR performance, not only of PVK-based composites, but also of other types of organic materials, the main advantage being that no sensitizer is needed. [source]


    A Versatile, Molecular Engineering Approach to Simultaneously Enhanced, Multifunctional Carbon-Nanotube, Polymer Composites,

    ADVANCED FUNCTIONAL MATERIALS, Issue 1 2006
    J. Chen
    Abstract Single-walled carbon nanotubes (SWNTs) are recognized as the ultimate carbon fibers for high-performance, multifunctional composites. The remarkable multifunctional properties of pristine SWNTs have proven, however, difficult to harness simultaneously in polymer composites, a problem that arises largely because of the smooth surface of the carbon nanotubes (i.e., sidewalls), which is incompatible with most solvents and polymers, and leads to a poor dispersion of SWNTs in polymer matrices, and weak SWNT,polymer adhesion. Although covalently functionalized carbon nanotubes are excellent reinforcements for mechanically strong composites, they are usually less attractive fillers for multifunctional composites, because the covalent functionalization of nanotube sidewalls can considerably alter, or even destroy, the nanotubes' desirable intrinsic properties. We report for the first time that the molecular engineering of the interface between non-covalently functionalized SWNTs and the surrounding polymer matrix is crucial for achieving the dramatic and simultaneous enhancement in mechanical and electrical properties of SWNT,polymer composites. We demonstrate that the molecularly designed interface of SWNT,matrix polymer leads to multifunctional SWNT,polymer composite films stronger than pure aluminum, but with only half the density of aluminum, while concurrently providing electroconductivity and room-temperature solution processability. [source]


    Driving High-Performance n- and p-type Organic Transistors with Carbon Nanotube/Conjugated Polymer Composite Electrodes Patterned Directly from Solution

    ADVANCED MATERIALS, Issue 37 2010
    Sondra L. Hellstrom
    We report patterned deposition of carbon nanotube/conjugated polymer composites from solution with high nanotube densities and excellent feature resolution. Such composites are suited for use as electrodes in high-performance transistors of pentacene and C60, with bottom-contact mobilities of > 0.5 and > 1 cm2 V,1 s,1, respectively. This represents a clear step towards development of inexpensive, high-performance all-organic circuits. [source]


    Inkjet-Printed Quantum Dot,Polymer Composites for Full-Color AC-Driven Displays

    ADVANCED MATERIALS, Issue 21 2009
    Vanessa Wood
    Colloidal quantum dot,polymer composites are used for inkjet-print deposition of high-resolution, patterned, multicolored thin films in the fabrication of robust, bright, full-color AC-driven displays. The left panel shows a photograph of a complete device on a flexible substrate under UV illumination, while the right panel shows photographs of the electroluminescence of red, green, and blue 80 mm2 pixels. [source]


    Ceramic,Polymer Ba0.6Sr0.4TiO3/Poly(Methyl Methacrylate) Composites with Different Type Composite Structures for Electronic Technology

    INTERNATIONAL JOURNAL OF APPLIED CERAMIC TECHNOLOGY, Issue 4 2010
    Hong Wang
    Ba0.6Sr0.4TiO3 (BST)/poly(methyl methacrylate) (PMMA) composites with 0,3, 1,3, and 2,2 type structures were prepared and studied. The effect of composite type on the dielectric properties of BST/PMMA composites was comprehensively investigated by both theoretical and experimental methods. The 1,3 type composite shows the highest permittivity and dielectric tunability, while the 2,2 and 0,3 type composites show lower permittivity as well as lower dielectric tunabilities. The experimentally measured dielectric properties are in agreement with the theoretically calculated values. The results help in understanding and tailoring the dielectric properties of ceramic,polymer composites by choosing a suitable composite structure. [source]


    Fabrication and Nanocompression Testing of Aligned Carbon-Nanotube,Polymer Nanocomposites,

    ADVANCED MATERIALS, Issue 16 2007
    J. Garca
    The reinforcement of fiber,polymer composites with arrays of aligned carbon nanotubes (CNTs) is reported. Nanocomposite features containing vertically aligned CNTs and a commercially available polymer are fabricated and mechanically characterized with a direct nanocompression method using a flat punch mounted on a nanoindenter (see figure). The results show a reinforcement of 220,% at a CNT volume fraction of 2,%. [source]