Showing papers on "Polymer nanocomposite published in 2003"

S2-Glass/Epoxy Polymer Nanocomposites: Manufacturing, Structures, Thermal and Mechanical Properties

Abstract: This paper is primarily focused in studying the effects of nanoclay particles such as montmorillonite on improving mechanical and thermal properties of fiber reinforced polymer matrix composite materials. Basic correlations between polymer morphology, strength, modulus, toughness, and thermal stability of thermoset nanocomposites were investigated as a function of layered silicate content. S2-glass/epoxy-clay nanocomposites were manufactured through an affordable vacuum assisted resin infusion method (VARIM). The nanocomposites are formed during polymerization when the adsorbing monomer separates the clay particles into nanometer scales. Transmission electron microscopy (TEM) and wide angle X-ray diffraction(WAXD) were used to characterize the morphology of the dispersed clay particles. The thermal properties such as onset of decomposition and glass transition temperatures were determined by Thermo Gravimetric Analysis (TGA) and Dynamic Modulus Analyzer (DMA). Mechanical properties such as interlaminar sh...

Polymer nanocomposites for aerospace applications: Properties

Abstract: Polymer nanocomposites may provide significantly increased modulus, gas barrier, thermal performance, atomic oxygen resistance, resistance to small molecule permeation and improved ablative performance when compared to typical traditional carbon-fiber-reinforced polymeric composites. This presentation gives a review on both theoretical and experimental investigations extracting valuable fundamental elements including field emission, thermal stability, and electrical, optical and mechanical properties of polymer nanocomposites for aerospace applicability.

Restricted Relaxation in Polymer Nanocomposites near the Glass Transition

Abstract: The relaxation behavior of organically modified layered silicate−epoxy nanocomposites was studied using a combination of standard and temperature-modulated differential scanning calorimetry. For such nanocomposites, the silicate layers were intercalated in the matrix resin and epoxy networks were grafted onto the silicate layer surfaces. Enthalpy recovery that occurred during physical aging was used as a probe to detect restricted relaxation behavior in the nanocomposites. Addition of the intercalated nanoparticles resulted in a slower overall relaxation rate and a wider distribution of relaxation times. The nanocomposites also showed a higher glass transition temperature compared to that of the unreinforced resin. To explain the observed results, a domain relaxation model was proposed that included three possible relaxation modes. On the basis of this model, the restricted relaxation arising from intercalated and exfoliated layered silicates can be understood.

Origin of Particle Clustering in a Simulated Polymer Nanocomposite and its Impact on Rheology

Abstract: Many nanoparticles have short-range interactions relative to their size, and these interactions tend to be “patchy” since the interatomic spacing is comparable to the nanoparticle size. For a dispersion of such particles, it is not a priori obvious what mechanism will control the clustering of the nanoparticles, and how the clustering will be affected by tuning various control parameters. To gain insight into these questions, we perform molecular dynamics simulations of polyhedral nanoparticles in a dense bead–spring polymer melt under both quiescent and steady shear conditions. We explore the mechanism that controls nanoparticle clustering and find that the crossover from dispersed to clustered states is consistent with the predictions for equilibrium particle association or equilibrium polymerization, and that the crossover does not appear to match the expectations for first-order phase separation typical for binary mixtures in the region of the phase diagram where we can equilibrate the system. At the ...

Mesoporous silica-reinforced polymer nanocomposites

Abstract: This research reports the use of organic-modified mesoporous silica particles as fillers to form organic/inorganic nanocomposites with improved thermal and mechanical properties. The particle fillers were synthesized by co-assembly of surfactant and silicate species prepared by hydrolysis and condensation reactions of tetraethoxysilane (TEOS) and (3-trimethoxysilyl)propyl methacrylate (TMSPMA) through an aerosol process. Selective surfactant removal resulted in mesoporous particles with high surface areas and with covalently bound propyl methacrylate ligands on the pore surface as indicated by XRD, TEM, N2 adsorption−desorption, FTIR, 13C NMR, 29Si NMR, and other techniques. Infiltration and subsequent in situ polymerization of (3-trimethoxysilyl)propyl methacrylate within and among the mesoporous silica particles result in nanocomposites with improved mechanical and thermal properties. Mechanical testing shows a significant increase in tensile strength, modulus, and toughness of the nanocomposites with l...

Preparation and characterization of ZnS–polymer nanocomposite films with high refractive index

Abstract: Novel ZnS–poly(urethane-methacrylate macromer) (PUMM) nanocomposite films with high refractive index were prepared by incorporating thiophenol (PhSH)–4-thiomethyl styrene (TMSt)-capped ZnS nanoparticles into a urethane-methacrylate macromer (UMM), followed by spin-coating and ultraviolet radiation initiated free radical polymerization. PhSH–TMSt-capped colloidal ZnS solution was synthesized by reacting zinc acetate with H2S in N,N-dimethylformamide. UMM macromer was synthesized by reacting 2-hydroxyethyl methacrylate (HEMA) with isocyanate group terminated polythiourethane oligomer which was obtained from polyaddition of 2,2′-dimercaptoethyl sulfide (MES) with 2,4-tolylene diisocyanate (TDI). Thiol-capped ZnS nanoparticles were characterized and found to be 2.0–5.0 nm in diameter with a cubic phase structure. The chemical composition of these ZnS nanoparticles was determined to be Zn2+ ∶ S2− ∶ RS− = 1 ∶ 0.6 ∶ 0.6 using chemical analysis methods. The weight fraction of ZnS nanoparticles in the films was measured by TGA, and it accords well with that of theoretical calculation. FTIR and DSC studies show that ZnS nanoparticles were successfully immobilized into the polymer matrix and the resulting nanocomposite films have a good thermal stability. TEM images indicate that the ZnS nanoparticles were uniformly dispersed in the polymer matrix and the particles remained their original size (2–5 nm) before incorporation into the polymer matrix. The XPS depth profiling technique demonstrates that the ZnS nanoparticles were also dispersed homogeneously in the depth scales of the polymer matrix. The nanocomposite films show high optical transparency in the visible region (T > 95% at 550 nm) and high refractive index in the range of 1.645–1.796 at 632.8 nm as the content of thiol-capped ZnS nanoparticles linearly increased from 0 to 86 wt%.

Plasma coating of carbon nanofibers for enhanced dispersion and interfacial bonding in polymer composites

Abstract: Ultrathin films of polystyrene were deposited on the surfaces of carbon nanofibers using a plasma polymerization treatment. A small percent by weight of these surface-coated nanofibers were incorporated into polystyrene to form a polymer nanocomposite. The plasma coating greatly enhanced the dispersion of the nanofibers in the polymer matrix. High-resolution transmission-electron-microscopy (HRTEM) images revealed an extremely thin film of the polymer layer (∼3 nm) at the interface between the nanofiber and matrix. Tensile test results showed considerably increased strength in the coated nanofiber composite while an adverse effect was observed in the uncoated composites; the former exhibited shear yielding due to enhanced interfacial bonding while the latter fractured in a brittle fashion.

Helical Conformational Specificity of Enzymatically Synthesized Water-Soluble Conducting Polyaniline Nanocomposites

Abstract: A novel template guided enzymatic approach has been developed to synthesize optically active conducting polyaniline (PANI) nanocomposites in the presence of H2O2 as an oxidant, using (+) and (-) 10-camphorsulfonic acid (CSA) as a dopant and chiral inductor. The formation of chiral polyaniline in the nanocomposites was confirmed by circular dichroism (CD). Interestingly, the CD spectra of nanocomposites formed either with (+) or with (-) CSA show the enzyme itself plays a critical role in controlling the stereospecificity of the polyaniline (PANI) in the nanocomposite. The enzyme used for the polymerization of aniline in the nanocomposite was horseradish peroxidase (HRP). It was shown that this enzyme prefers a specific helical conformation, regardless of whether induced chirality in the complex CSA-aniline is from (+) or (-) CSA. UV-vis spectra show that the polyaniline is in the conducting form, and transmission electron micrographs (TEM) show that the nanocomposites are dispersed nicely with particle size dimensions in the range of 20-50 nm. Electron diffraction patterns of these chiral polymer nanocomposites suggest that these nanocomposites are in both crystalline and amorphous states.

Production and characterization of polymer nanocomposites with highly aligned single-walled carbon nanotubes.

Abstract: We report the production and characterization of polymer nanocomposites with single-walled carbon nanotubes having improved mechanical properties and exceptional nanotube alignment. High-pressure carbon monoxide nanotubes (HiPco) were efficiently distributed in polystyrene (PS) and polyethylene (PE) with a twin-screw compounder. Nanotube concentrations were 1, 5, 10, and 20 wt% in PE composites and 0.7 wt% in PS composites. PE composites were melt-spun into fibers to achieve highly aligned nanotubes. Polarized Raman spectroscopy shows that the degree of alignment increases with decreasing fiber diameter and decreases with increasing nanotube loading. The orientation distribution function of a 1 wt% HiPco/PE composite had a full width at half-maximum of approximately 5 degrees. The elastic modulus increases up to 450% relative to PE fibers for 20 wt% nanotube loading at an intermediate fiber diameter of 100 microns.

A universal method for the synthesis of metal and metal sulfide clusters embedded in polymer matrices

Abstract: Alkanethiolates of transition metals undergo thermolysis reactions at moderately low temperatures (120–200 °C), producing metal atoms or metal sulfide molecules and an organic by-product (disulfide or a thioether). Metal n-alkanethiolates (i.e., Mex(SCnH2n+1)y, with n = 12, 16 and 18) dissolve in polymers and the resulting solid solutions can be annealed to give polymer-embedded metal or metal sulfide clusters (i.e., metal/polymer nanocomposites). As an example, the preparation of silver, gold, cobalt and palladium clusters dispersed in polystyrene has been described, but the method is very general and a variety of metal/polymer and metal sulfide/polymer combinations can be obtained.

Influence of polymer matrix composition and architecture on polymer nanocomposite formation: Coarse-grained molecular dynamics simulation

Abstract: Coarse-grained molecular dynamics simulations of stacks of two-dimensional platelets immersed in a polymer melt were performed to investigate aspects of the polymer matrix that promote the formation of intercalated or exfoliated nanocomposite structures Such factors include temperature, copolymer architecture, and blend composition Increasing the polymer-sheet attractive interaction led to binding of the sheets, where individual beads simultaneously attract two neighboring sheets, thus kinetically blocking intercalation by occupying the perimeter of the affected gallery Polymers with a small polymer-sheet attraction, but having a strongly attractive chain end (end-functionalized polymers) minimized the bonding of adjacent sheets These systems exhibited some sheet sliding because a majority of the confined polymer beads only interacted weakly with adjacent sheets; however, the number density of intercalated polymer was low Mixtures of end-functionalized and nonfunctionalized polymers, however, yielded better intercalation efficiency For the mixed system, the reduced number of highly attractive beads provided sufficient interaction for intercalation to occur, enabling greater intercalation rates, less sheet-bridging, and incorporation of the nonfunctionalized polymers into the galleries © 2003 Wiley Periodicals, Inc J Polym Sci Part B: Polym Phys 41: 3272–3284, 2003

Optical polymer nanocomposites

Abstract: A composite material that includes a host matrix and a plurality of dispersed nanoparticles within the host matrix. Each of the plurality of nanoparticles may include a halogenated outer coating layer that seals the nanoparticle and prevents agglomeration of the nanoparticles within the host matrix. The invention also includes a process of forming the composite material. Depending on the nanoparticle material, the composite material may have various applications including, but not limited to, optical devices, windowpanes, mirrors, mirror panels, optical lenses, optical lens arrays, optical displays, liquid crystal displays, cathode ray tubes, optical filters, optical components, all these more generally referred to as components.

Effect of Chain Length of Amine and Nature and Loading of Clay on Styrene-Butadiene Rubber-Clay Nanocomposites

Abstract: Polymer nanocomposite is one of the highly discussed research topics in recent time. In this paper, we have reported the preparation and the properties of different nanoclays based on sodi...

Supercritical fluid applications in polymer nanocomposites

Abstract: Supercritical fluids have been used to synthesize and foam a variety of polymer nanocomposite materials. There have been significant advances in developing and characterizing nanoscale structures and using supercritical fluids to alter properties at the nanoscale. In this work we summarize these advances and discuss foam properties generated using supercritical carbon dioxide as well as relevant fundamental properties of the system.

Dispersion and distribution of organically modified montmorillonite in nylon‐66 matrix

Abstract: Nylon-66 nanocomposites were prepared by melt-compounding nylon-66 with an alkyl ammonium surfactant pretreated montmorillonite (MMT). The thermal stability of the organic MMT powders was measured by thermogravimetric analysis. The decomposition of the surfactant on the MMT occurred from 200 to 500 °C. The low onset decomposition temperature of the organic MMT is one shortcoming when it is used to prepare polymer nanocomposites at high melt-compounding temperatures. To provide greater property enhancement and better thermal stability of the polymer/MMT nanocomposites, it is necessary to develop MMT modified with more thermally stable surfactants. The dispersion and spatial distribution of the organic MMT layers in the nylon-66 matrix were characterized by X-ray diffraction. The organic MMT layers were exfoliated but not randomly dispersed in the nylon-66 matrix. A model was proposed to describe the spatial distribution of the organic MMT layers in an injection-molded rectangular bar of nylon-66/organic MMT nanocomposites. Most organic MMT layers were oriented in the injection-molding direction. Layers near the four surfaces of the bar were parallel to their corresponding surfaces; whereas those in the bulk differed from the near-surface layers and rotated themselves about the injection-molding direction. The influence of the spatial distribution of the organic MMT on crystallization of nylon-66 was also investigated. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 1234–1243, 2003

Nanocomposites based on multiblock polyester elastomers (PEE) and carbon nanotubes (CNT)

Abstract: Polymer nanocomposites including those containing carbon nanotubes appear to be of particular significance. Polymer nanocomposites based on thermoplastic poly(ether-ester) elastomer and carbon nanotubes have been prepared and investigated. The nanocomposites are obtained (in situ) by introducing the fillers into the reaction mixture and the synthesis of copolymer by polycondensation in the molten state. The nanotubes are dispersed in 1,4-butanediol by ultrasonication. Physical properties of the resulting nanocomposites are studied using the DSC, DMTA, SEM and mechanical tensile tests.

In Situ Synthesis of Polymer Nanocomposite Electrolytes Emitting a High Luminescence with a Tunable Wavelength

Abstract: Zinc oxide (ZnO) nanoparticle-based nanocomposite polymer electrolytes with a very high luminescence intensity were prepared by an in situ method, in which ZnO nanoparticle fillers were grown in the polymer matrix and ion carriers were inserted during the growth of the nanoparticles (contributed by a precursor). By using a high concentration of lithium hydroxide (LiOH) as the precursor, the remaining unreacted LiOH was distributed in the form of an amorphous complex around the produced ZnO nanoparticles, thus preventing the agglomeration of the nanoparticles. This resulted in a high number concentration of ZnO nanoparticles that serve as luminescent centers for inducing a high luminescence intensity. Compared to samples prepared using the usual concentration of LiOH (about 0.14 M), the luminescence intensity was enhanced by about 22 times for the ZnO nanopowder and 6 times for the nanocomposite polymer electrolytes (poly(ethylene glycol)/ZnO/Li+) when a LiOH concentration of 0.35 M was used.

Electrical and optical properties of ceramic–polymer nanocomposite coatings

Abstract: Transparent, conductive composite coatings were fabricated from suspensions of poly(vinyl acetate-acrylic) (PVAc-co-acrylic) copolymer latices (50–600 nm) and nanosized antimony-doped tin oxide (ATO) particles (∼15 nm). The suspensions were deposited as coatings onto poly(ethylene terephthalate) substrates and dried at 50 °C. Microstructure studies using field emission scanning electron microscopy and tapping-mode atomic force microscopy (TMAFM) indicated that the latex particles coalesced during drying and forced the ATO particles to segregate into the boundaries between the latex particles. Low phase contrast was observed with TMAFM; this result was consistent with the presence of PVAc-co-acrylic in the ATO-rich phase of the composite. The conductivity of the composite coatings followed a percolation power-law equation, with the percolation threshold between 0.05 and 0.075 volume fractions of ATO and the critical conductivity exponent ranging from 1.34 to 2.32. The highest direct-current conductivity of the composite coatings was around 10−2 S/cm. The optical transmittance and scattering behavior of the coatings were also investigated. Compared with the PVAc-co-acrylic coating, the composite coatings had lower transparency because of the Rayleigh scattering. The transparency of the composite coatings was improved by a reduction in the coating thickness. The best transparency for the coatings with a direct-current conductivity of approximately 10−2 S/cm was around 85% at a wavelength of 600 nm. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 1744–1761, 2003

Polymer nanocomposite implants with enhanced transparency and mechanical properties for administration within humans or animals

Abstract: Polymer nanocomposite implants with nanofillers and additives are described. The nanofillers described can be any composition with the preferred composition being those composing barium, bismuth, cerium, dysprosium, europium, gadolinium, hafnium, indium, lanthanum, neodymium, niobium, praseodymium, strontium, tantalum, tin, tungsten, ytterbium, yttrium, zinc, and zirconium. The additives can be of any composition with the preferred form being inorganic nanopowders comprising aluminum, calcium, gallium, iron, lithium, magnesium, silicon, sodium, strontium, titanium. Such nanocomposites are particularly useful as materials for biological use in applications such as drug delivery, biomed devices, bone or dental implants.

High throughput methods for polymer nanocomposites research: Extrusion, NMR characterization and flammability property screening

Abstract: A large number of parameters influence polymer-nanocomposite performance and developing a detailed understanding of these materials involves investigation of a large volume of the associated multi-dimensional property space. This multi-dimensional parameter space for polymer-nanocomposites consists of the obvious list of different material types under consideration, such as “polymer” and “nano-additive,” but also includes interphase surface chemistry, and processing conditions. This article presents combinatorial library design and high-throughput screening methods for polymer nanocomposites intended as flame-resistant materials. Here, we present the results of using a twin-screwn extruder to create composition-gradient library strips of polymer nanocomposites that are screened with a solid-state NMR method to rapidly evaluate the optimal processing conditions for achieving nanocomposite dispersion. In addition, we present a comparison of a new rapid Cone calorimetry method to conventional Cone calorimetry and to the gradient heat-flux flame spread method.

Electrical properties of polymer nanocomposites based upon organophilic layered silicates

Abstract: An investigation on space charge and conduction properties of electrical-insulating polymer nanocomposites is presented. Space charge, conduction current and electric strength measurements were performed. Different poling field were considered, in order to derive the space charge accumulation characteristics and infer the mechanisms for conduction and trapping of charge carriers. Two families of insulating materials were considered, that is, isotactic polypropylene, PP, and a copolymer ethylene-vinylacetate, EVA, both filled by organophilic layered silicates as nanomaterials. The comparison among unfilled and nanofilled materials, with different filler concentrations, shows that space charge accumulation phenomena are considerably affected by the presence of nanofillers: space charge accumulation threshold, but also the density of trapped charge at high fields, decrease, in fact, as nanofiller content increases. Likewise, conduction current increases for nanofilled materials. Electric strength can be also positively affected by nanofillers.

Polymer nanocomposite containing CdS-ZnS core-shell particles: Optical properties and morphology

Abstract: Composites of nanosized CdS–ZnS core–shell particles well dispersed in polycetyl- p-vinylbenzyldimethylammonium chloride (PCVDAC) were fabricated and their optical properties and morphology were studied. The core-shell particles of less than 10 nm in size were prepared with the reverse micellar solutions formed by a polymerizable anionic surfactant, CVDAC, and a direct thermal radical polymerization of the micellar solution led to the nanocomposite containing well-dispersed core–shell particles. The shell was inferred from small angle x-ray scattering to be around a monolayer thick. This monolayer coating, however, was enough to produce an appreciable enhancement in photoluminescence for the ZnS-coated CdS system (wider band gap material on narrower band gap material), and a degradation in photoluminescence for the CdS-coated ZnS system. However, a complete coverage of the CdS core with ZnS was required to realize the photoluminescence enhancement for the ZnS-coated CdS system. The polymer domains in the composite were found to be composed of lamellar stacks due to the comb-like structure of PCVDAC. The interlamellar distance was 3.9 nm with smectic liquid crystalline texture observed under polarized optical microscope. The core–shell particles were believed to locate at the grain boundary of the liquid crystalline domains.

Viscoelasticity and relaxation characteristics of polystyrene/clay nanocomposite

Abstract: Polymer nanocomposites based on an organophilically modified montmorillonite (OMMT) and polystyrene (PS) are prepared via a solvent casting method using chloroform as a cosolvent to examine their dynamic viscoelastic and relaxation properties, in which the increased basal spacings of the OMMT determined by X-ray diffraction indicated the intercalation of PS chains into OMMT interlayer. From the measured viscoelastic properties originated from the nanocomposite interaction between polymer and OMMT, we were able to determine the characteristic behavior of PS/OMMT nanocomposites. Storage and loss moduli are found to give the transition from liquid-like to solid-like behavior as the clay content increases, especially in the low frequency region. Stress relaxation behavior was also enhanced by showing more solid-like characteristics with increasing OMMT.

Polymer Nanocomposites and Their Applications

Abstract: Recent developments ofpolymer nanocomposites were reviewed in terms Offobrlcotlon, mechonlcal ond barrier properties, thermal stobiiity, flame retardoncy and otherfundionol properties. PolymerlC/oy nonocomposltes can befabricated through In situ polymerlsatlon, solution blending, and melt compounding. The high asped rotio and huge surface area of clay layers are responsible for the enhanced properties at low clay loading. These nanacomposltes are being used in automotive ond packoglng applications. Other polymer nanocomposltes with electrical, magnetic or optical properties were also discussed briefly. Their applications include eledrochemical display devices, eledrical and magnetiC shields, wave absorption, eledronic packaging, PTC resistors, photonic devices, etc.