Showing papers on "Polymer nanocomposite published in 2004"
TL;DR: In this article, single-walled carbon nanotube (SWNT)/poly(methyl methacrylate) (PMMA) nanocomposites were prepared via coagulation method providing uniform dispersion of the nanotubes in the polymer matrix.
Abstract: Single-walled carbon nanotube (SWNT)/poly(methyl methacrylate) (PMMA) nanocomposites were prepared via our coagulation method providing uniform dispersion of the nanotubes in the polymer matrix. Optical microscopy, Raman imaging, and SEM were employed to determine the dispersion of nanotube at different length scales. The linear viscoelastic behavior and electrical conductivity of these nanocomposites were investigated. At low frequencies, G‘ becomes almost independent of the frequency as nanotube loading increases, suggesting an onset of solidlike behavior in these nanocomposites. By plotting G‘ vs nanotube loading and fitting with a power law function, the rheological threshold of these nanocomposites is ∼0.12 wt %. This rheological threshold is smaller than the percolation threshold of electrical conductivity, ∼0.39 wt %. This difference in the percolation threshold is understood in terms of the smaller nanotube−nanotube distance required for electrical conductivity as compared to that required to impe...
1,227 citations
TL;DR: This work demonstrates that the uniform dispersion of 1–5 vol.% of carbon nanotubes in a thermoplastic elastomer yields nanocomposites that can store and subsequently release, through remote means, up to 50% more recovery stress than the pristine resin.
Abstract: Stimuli-responsive (active) materials undergo large-scale shape or property changes in response to an external stimulus such as stress, temperature, light or pH1,2. Technological uses range from durable, shape-recovery eye-glass frames, to temperature-sensitive switches, to the generation of stress to induce mechanical motion3,4,5,6,7,8,9. Here, we demonstrate that the uniform dispersion of 1–5 vol.% of carbon nanotubes in a thermoplastic elastomer yields nanocomposites that can store and subsequently release, through remote means, up to 50% more recovery stress than the pristine resin. The anisotropic nanotubes increase the rubbery modulus by a factor of 2 to 5 (for 1–5 vol.%) and improve shape fixity by enhancing strain-induced crystallization. Non-radiative decay of infrared photons absorbed by the nanotubes raises the internal temperature, melting strain-induced polymer crystallites (which act as physical crosslinks that secure the deformed shape) and remotely trigger the release of the stored strain energy. Comparable effects occur for electrically induced actuation associated with Joule heating of the matrix when a current is passed through the conductive percolative network of the nanotubes within the resin. This unique combination of properties, directly arising from the nanocomposite morphology, demonstrates new opportunities for the design and fabrication of stimuli-responsive polymers, which are otherwise not available in one material system.
947 citations
TL;DR: In this article, the future of mesoscopic properties of nanocomposite polymers is discussed, and several interesting results to indicate the foreseeable future have been revealed, some of which are described on materials and processing, together with basic concepts and future direction.
Abstract: Polymer nanocomposites are defined as polymers in which small amounts of nanometer size fillers are homogeneously dispersed by only several weight percentages. Addition of just a few weight percent of the nanofillers has profound impact on the physical, chemical, mechanical and electrical properties of polymers. Such change is often favorable for engineering purpose. This nanocomposite technology has emerged from the field of engineering plastics, and potentially expanded its application to structural materials, coatings, and packaging to medical/biomedical products, and electronic and photonic devices. Recently these 'hi-tech' materials with excellent properties have begun to attract research people in the field of dielectrics and electrical insulation. Since new properties are brought about from the interactions of nanofillers with polymer matrices, mesoscopic properties are expected to come out, which would be interesting to both scientists and engineers. Improved characteristics are. expected as dielectrics and electrical insulation. Several interesting results to indicate the foreseeable future have been revealed, some of which are described on materials and processing in the paper together with basic concepts and future direction.
889 citations
TL;DR: In this article, a model describing the microstructure providing extremely strong and reversible tenso-resistive and piezo-resistant effects is proposed on the basis of atomic force microscopy of the conductive surface network of the composite.
Abstract: Electrically conductive polymer composites (ECPC) are shown as prospective large-size flexible pressure and stretch sensors for detecting of dangerous deformations and vibrations of vehicle parts. Reversible change of resistance dependent on stretch and pressure is obtained in electro-conductive polymer nanocomposites. At certain concentrations of carbon nano-particles a change of electrical resistance by more than four orders is observed at 40% relative stretch. The maximum sensitivity of nanocomposites is observed in the vicinity of the transition of electro-conductive percolation. Nanocomposites exhibit a very weak semiconductor-like temperature dependence of resistance. The tenso-resistive and piezo-resistive effects are found to be practically thermally stable in the region of 20–70 °C. A model description of the microstructure providing extremely strong and reversible tenso-resistive and piezo-resistive effects is proposed on the basis of atomic force microscopy of the conductive surface network of the composite. Reversibility of the effects is explained by higher mobility and stronger adhesion of carbon nano-particles to the polymer matrix compared to cohesion between them. The experimental data for tensile strain are in good agreement with theoretical equations derived from a model based on the change of particle separation under applied stress.
340 citations
TL;DR: In this article, the effect of the filler size, filler loading, and dispersion conditions of the nanofillers on the glass-transition temperature (Tg) have been studied.
Abstract: With advances in nanoscience and nanotechnology, there is increasing interest in polymer nanocomposites, both in scientific research and for engineering applications. Because of the small size of nanoparticles, the polymer–filler interface property becomes a dominant factor in determining the macroscopic material properties of the nanocomposites. The glass-transition behaviors of several epoxy nanocomposites have been investigated with modulated differential scanning calorimetry. The effect of the filler size, filler loading, and dispersion conditions of the nanofillers on the glass-transition temperature (Tg) have been studied. In comparison with their counterparts with micrometer-sized fillers, the nanocomposites show a Tg depression. For the determination of the reason for the Tg depression, the thermomechanical and dielectric relaxation processes of the silica nanocomposites have been investigated with dynamic mechanical analysis and dielectric analysis. The Tg depression is related to the enhanced polymer dynamics due to the extra free volume at the resin–filler interface. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 3849–3858, 2004
337 citations
TL;DR: In this article, the authors describe nanocomposite films of specially synthesized inorganic Prussian blue (PB) nanoparticles and linear poly(ethylene imine) (LPEI) that possess the unusual functional combination of high-performance electrochromism for displays and controllable dissolution for drug delivery.
Abstract: To maintain the momentum and impact of the field, assembled materials systems must increasingly incorporate broad functionality to meet real-world applications. Here we describe nanocomposite films of specially synthesized inorganic Prussian blue (PB) nanoparticles and linear poly(ethylene imine) (LPEI) that possess the unusual functional combination of high-performance electrochromism for displays and controllable dissolution for drug delivery. Fabrication using layer-by-layer (LBL) assembly was followed by spectroelectrochemical characterization, allowing a full composition determination rarely achieved for LBL films. The electrochromic performance of thick LPEI/PB nanocomposites most relevant to applications surpassed that of inorganic PB films with competitive switching speed and superior contrast. Oxidation beyond the primary electrochromic transition removes nanoparticle ionization and can controllably dissolve the films. Because PB is non-toxic we suggest this mechanism for controlled in-vivo drug delivery. The performance and multifunctional quality of these nanocomposites promise a strong impact on flexible displays, electrochromic windows, and even biomedical devices.
333 citations
TL;DR: In this article, the authors synthesized polymer nanocomposites of poly(methylmethacrylate) doped with varying concentrations of iron nanoparticles (∼20 nm in size).
Abstract: Magnetic nanoparticles embedded in polymer matrices have excellent potential for electromagnetic device applications like electromagnetic interference suppression. We have synthesized polymer nanocomposites of poly(methylmethacrylate) doped with varying concentrations of iron nanoparticles (∼20 nm in size). The iron nanoparticles were produced using a microwave plasma technique and have a natural oxide surface layer for passivation. These nanocomposites were processed using melt blending technique. The polymer processing conditions were optimized to achieve good uniform dispersion of the nanoparticles in the polymer matrix. The concentration and dispersion of nanoparticles were varied in a controlled way. Surface characterization with scanning electron microscopy indicates that, to a large extent, the iron nanoparticles are embedded in the bulk; the surface mainly showed features associated with the polymer surface. Static magnetic properties such as susceptibility and M–H loops were studied using a physi...
226 citations
TL;DR: In this article, the degree of intercalation spacing was determined by X-ray diffraction (XRD) and thermal degradation behavior was studied in thermogravimetry (TGA) and the chemical evolution in the solid residue was studied with an infrared microscope.
192 citations
TL;DR: In this article, a bottom-up approach to obtain polymer nanocomposites using cubic silsesquioxanes (POSS) nanoparticles as building blocks is reported, which is based on associative interaction between particles to form ordered nanostructure and limited crystal growth to render anisotropic shapes.
Abstract: A novel bottom-up approach to obtain polymer nanocomposites using cubic silsesquioxanes (POSS) nanoparticles as building blocks is reported. The design is based on associative interaction between particles to form ordered nanostructure and limited crystal growth to render anisotropic shapes. Specifically, the affinity between POSS units causes these particles to aggregate and closely pack into a crystalline lattice. The organic polymer, covalently connected to each POSS unit, limits the crystallization into a two-dimensional lattice as demonstrated in random copolymers of polybutadiene and cubic silsesquioxanes. The copolymers were synthesized by ring-opening metathesis copolymerization of cyclooctadiene and POSS bearing a polymerizable norbornene group. The polymers were characterized using NMR, DSC, TEM, WAXD, and SAXS. The data from TEM and X-ray diffraction clearly show the formation of two-dimensional lamellar-like nanostructures of assembled cubic silsesquioxanes.
183 citations
TL;DR: In this paper, the authors focus on polymer nanocomposites and their syntheses, properties and future applications, several of these application will be successful in the near future, and propose a new type of materials, based on smectite clays usually rendered hydrophobic through ionic exchange of the sodium interlayer cation with an onium cation.
Abstract: This paper focuses on polymer nanocomposites and their syntheses, properties and future applications, several of these application will be successful in the near future. This new type of materials, based on smectite clays usually rendered hydrophobic through ionic exchange of the sodium interlayer cation with an onium cation, may be prepared via various synthetic routes comprising exfoliation adsorption, in-situ intercalative polymerization and melt intercalation. The whole range of polymer matrices covered, i.e., thermoplastics, thermosets and elastomers. Small addition—typically less than 6 wt%—of these nanoscale inorganic fillers promote concurrently several properties of the polymer materials, including tensile characteristics, heat distortion temperature, scratch resistance, gas permeability resistance, and flame retardancy.
160 citations
TL;DR: In this article, a very low volume fraction of inorganic nanoparticles was used to improve the creep resistance of thermoplastic, and the results showed that the nanoparticles restricted the slippage, reorientation and motion of polymer chains.
TL;DR: In this paper, the chemical and physical properties of organobentonites were investigated, and epoxy nanocomposites were also studied, and the exchanged content of organo-surfactant, thermogravimetric was carried out and interlayer distance was measured by wide-angle X-ray diffractometer.
TL;DR: In this paper, transmission electron microscopy (TEM) and X-ray diffraction (XRD) were used to evaluate the dispersion and exfoliation of organo-clay.
Abstract: Organo-clay polymer nanocomposites offer improved material properties at very low filler loadings making them of immediate interest for application in body panels, claddings, and instrument panels. This improvement in properties requires that the organo-clay be well dispersed if not completely exfoliated. Conventionally, the dispersion and exfoliation of the organo-clay is evaluated using transmission electron microscopy (TEM) and X-ray diffraction (XRD). Although both TEM and XRD data were found to correlate with flexural modulus of thermoplastic olefin nanocomposite materials, only TEM proved successful in quantifying the dispersion of the organo-clay in all nanocomposite materials (exfoliated, tactoid, or agglomerated tactoid). XRD was found to be capable of detecting exfoliation and intercalation but is limited because of clay dilution, preferred orientation, mixed-layering, and other peak broadening factors. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 1110–1117, 2004
TL;DR: In this paper, a polymer nanocomposites of poly(3-hexylthiophene) (P3HT) with organically modified montmorillonite (om-MMT) clay have been prepared by the solvent casting method.
Abstract: Polymer nanocomposites (PNCs) of poly(3-hexylthiophene) (P3HT) with organically modified montmorillonite (om-MMT) clay have been prepared by the solvent casting method. WAXS and TEM studies indicate exfoliated clay structure for lower clay content, but at higher clay content (5%, w/w) intercalated structures appear. The interchain lamella of P3HT exists in the nanocomposite, and the P3HT crystals become more ordered, showing better X-ray diffraction peaks. The thermal stability of PNCs increases significantly, and 1% clay content PNC exhibits the maximum thermal stability. The glass transition temperature (Tg), β-transition temperature (Tβ), the melting point (Tm), and the enthalpy of fusion (ΔH) of the PNCs are increased as compared to those of pure P3HT. The storage modulus (G‘) of PNCs showed a dramatic increase from that of pure P3HT, and the increase is larger in the temperature range 20−50 °C. The FTIR study indicates a decrease in Si−O−Si and Si−O stretching frequency for the exfoliated clay struct...
TL;DR: In this article, a theoretical network model reproducing some significant features of the viscoelastic behavior of unentangled polymer melts reinforced with well dispersed non-agglomerated nanoparticles is presented.
TL;DR: The magnetic properties of the nanoparticles compressed into pellets and dispersed in the composites were both studied in this article, showing that when the particles were dispersed into the nanocomposite the coercivity was increased, suggesting a heightened anisotropy barrier.
TL;DR: In this article, a photo-initiated polymerization of a multifunctional acrylic resin containing organophilic clay was demonstrated by X-ray diffraction spectroscopy and by transmission electron microscopy.
TL;DR: In this article, the effect of the chemistry and shear on the dispersion of clay in polymer matrix via dynamic packing injection molding (DPIM) is investigated, in which the melt is firstly injected into the mold, then forced to move repeatedly in a chamber by two pistons that moved reversibly with the same frequency as the solidification progressively occurs from the mold wall to the molding core part.
TL;DR: In this article, a general approach to align organically modified layered silicates (OLS) parallel to the electric field-enhancing CTE, modulus and optical clarity in the reinforced direction is demonstrated.
Abstract: The next revolutionary leap forward for polymer nano-'composites' necessitates the development of tools to transform the currently random or ill-defined nanoscale morphologies into compositionally and spatially engineered hierarchal structures, paralleling that underpinning conventional continuous fiber reinforced composites and enabling experimental verification of morphology-mechanical property correlations. Here in, utilization of AC electric fields of modest strength (1-10 V/micron) is demonstrated as a general approach to align organically modified layered silicates (OLS) parallel to the electric field-enhancing CTE, modulus and optical clarity in the reinforced direction. Interfacial polarization arising from electrophoric motion of the organic-modifier on the layer surface induces a dipole parallel to the plane of the layer, which couples to the external field. Comparably, application of a static magnetic field (0.5-2 T) induces alignment of the layers parallel or perpendicular to the field, depending on the chemical composition of the OLS. The impact of field magnitude, field frequency, dielectric permittivity and magnetic permeability of the system is discussed to elucidate the molecular characteristics of induced dipole formation and establish the limits of the process.
TL;DR: In this paper, a novel process using ultrasonics to enhance the exfoliation and dispersion of clay platelets in polypropylene-based nanocomposites has been proposed and investigated.
Abstract: A novel process using ultrasonics to enhance the exfoliation and dispersion of clay platelets in polypropylene-based nanocomposites has been proposed and investigated. The materials studied were isotactic polypropylene of various molecular weights reinforced with organophilic montmorillonite clay (nanoclay) at 4–6 wt% loadings. X-ray diffraction (XRD) and rheological measurements, on a model system of nanoclay in mineral oil, were first used to determine ultrasonic energy requirements. The effectiveness of the proposed ultrasonic processing technique on polypropylene nanocomposites was evaluated by XRD and transmission electron microscopy (TEM). The effects of added maleic anhydride–grafted polypropylene compatibilizer, polypropylene molecular weight, and pretreatment of the nanoclays on the nanocomposite exfoliation were also investigated. Results indicate that ultrasonic processing of polymer nanocomposites in the melt state is an effective method for improving exfoliation and dispersion of nanoclays. Issues regarding molecular weight degradation, optimization, mechanical properties, and continuous processing are beyond the scope of the present study and are currently being investigated in our laboratory. Polym. Eng. Sci. 44:1773–1782, 2004. © 2004 Society of Plastics Engineers.
TL;DR: In this article, magnetization studies on nanocrystalline nickel ferrite as powder particles and as diluted dispersion (10 ¼ ) in polymer matrix (polymer nanocomposites) are presented.
Abstract: The magnetization studies on nanocrystalline nickel ferrite as powder particles, and as diluted dispersion (10 wt.%) in polymer matrix (polymer nanocomposites) are presented. The two polymer-based nanocomposites were prepared via ball-milling and in situ polymerization, respectively. The magnetization measurements provide strong evidence of surface effects to magnetization, which explains the non-saturation of magnetization at high fields. The differences in the magnetization behavior of nickel ferrite as powder particles and in the ball-milled nanocomposite and the nanocomposite prepared via in situ polymerization are attributed to the different extent of interparticle interactions between the particles and the preparation route. The magnetization versus applied field behavior of the three ferrite systems show a similar jump in the initial part of the magnetization curve in all the cases which implies the existence of a core-shell like morphology of the particles over a large temperature range and its dominance over the interparticle interaction effects between the particles.
TL;DR: In this article, high molecular weight poly(methyl methacrylate) PMMA-clay nanocomposite, ethylene carbonate (EC)/propylene carbonates (PC) as plasticizer, and LiClO 4 electrolyte are reported.
TL;DR: In this paper, the first attempt to fill polymers with hollow solid lubricant nanoparticles was made and it was found that application of the fullerene-like (IF) WS 2 or MoS 2 solid lubricants led to a considerable improvements in the tribological behavior of the nanocomposites.
Abstract: Recent experiments showed that the addition of inorganic fullerene-like (IF) WS 2 or MoS 2 solid lubricant nanoparticles in oil, grease or impregnated into porous matrix provides remarkable lubricating properties of friction pairs in a wide range of operating conditions. Inorganic nanoparticles filled polymer composites show low friction and high wear resistance. This work reports the first attempt to fill polymers with hollow solid lubricant nanoparticles. It was found that application of the IF solid lubricant nanoparticles leads to a considerable improvements in the tribological behavior of the nanocomposites. The morphology of the surface layers and the mechanism of the friction reduction by the IF nanoparticles are discussed.
15 Sep 2004-Materials Science and Engineering A-structural Materials Properties Microstructure and Processing
TL;DR: In this article, the main results obtained within a project on mechanical properties of polymer-based nanocomposites are presented, together with original experimental results and micro-mechanical modeling.
Abstract: This work presents the main results obtained within a project on mechanical properties of polymer based nanocomposites. The specific point was how to analyze and model the filler–filler interactions in the description of the viscoelastic behavior of these materials. This paper aims at presenting the general strategy used by the different partners to address this question, together with original experimental results and micro-mechanical modeling. Different nanocomposite materials were fabricated using the latex route, leading to random dispersions of rigid submicronic particles (PS = polystyrene, silica) in a flexible polybutylacrylate matrix at various volume fractions. In addition, encapsulated silica particles in a styrene–acrylate copolymer were produced, leading, after film formation, to a limited number of contacts between silica fillers. The processing route of these encapsulated particles was optimized and the resulting morphology was analyzed by TEM experiments. In the case of random mixtures, a strong effect of reinforcement appears in the rubbery field of the soft phase when the filler content is above a critical fraction (percolation threshold). The reinforcement in the rubbery plateau can be still exacerbated in the case of the PS particles if the material undergoes a heat treatment above the main relaxation of the PS phase. These experimental results illustrate the difference between geometrical percolation (when particles are just in contact) and mechanical percolation (with strong interactions between the fillers). The comparison of the results for PS and silica fillers shows once more that the strength of the interactions plays an important role. To account for the whole set of experimental data, two ways of modeling were explored: (i) homogenization methods based on generalized self-consistent schemes and (ii) a discrete model of spheres assembly which explicitly describes the ability of the contacts to transmit efforts.
TL;DR: In this paper, it was demonstrated that nanocomposites, consisting of an electrically insulating oxide core and PMMA coating, exhibit strong luminescence, connected to the interface, where PMMA is bond via a carboxylate bonding to the surface.
Abstract: It is demonstrated that nanocomposites, consisting of an electrically insulating oxide core and PMMA coating exhibit strong luminescence. This luminescence is connected to the interface, where PMMA is bond via a carboxylate bonding to the surface. In this case, luminescence is originated at the carbonyl group of the coating polymer. With decreasing particle size, this emission shows a blue shift, following a law inversely the ones found for quantum confinement systems. For semi-conducting oxides, such as ZnO, this interface related emission is found additionally to quantum confinement phenomena.
TL;DR: Yang et al. as mentioned in this paper developed a polymer composite material with high dielectric constant based on the mechanism of interfacial polarization, although they need precision filler concentration control to achieve high reliability and low processing temperature.
Abstract: Metal nanoparticles exhibit a number of interesting characteristics, including unique physical, chemical, optical, magnetic, and electric properties. Numerous investigations have exploited their properties in a readily usable form by incorporating them into polymers. The current focus of interest is the behavior of such polymer nanocomposites near the percolation loading levels of the metal nanoparticles. This material is particularly suitable for the new integral passive technology. Discrete capacitors are used in many applications, such as noise suppression, filtering, tuning, decoupling, bypassing, termination, and frequency determination, and they occupy a substantial amount of surface area on a substrate. Thus there are limitations in the number of capacitors that can be placed around the chip. Integral passive components are gradually replacing discrete components because of the inherent advantages of improved electrical performance, increased real estate on the printed wiring board, miniaturization of interconnect distance, reduced processing costs, and efficient electronics packaging. For integral capacitors, polymer composite material has emerged as a potential candidate because it meets the requirements of low processing temperature and reasonably high dielectric constant. Yang and Wong, whose patent was filed in 2001, demonstrated novel integral passive component materials with extraordinarily high dielectric constants (K > 1000) and high reliability performance. These materials are characterized by high dielectric constant based on the mechanism of interfacial polarization, although they need precision filler concentration control. The current study overcomes this drawback and produces the composite through an in situ reduction in an epoxy matrix. Material characterization was done through TEM, SEM, X-ray analysis, and energy-dispersive analysis for X rays. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 1531–1538, 2004
TL;DR: In this article, the fabrication of nanotubes polymer/nanocomposites tailored to fit aerospace needs has been discussed and further insight is given on developments in nanofibers and nanotube production for good load transfer on the composite systems.
Abstract: Nanocomposite polymers have tremendous potential to enhance the performance of macromolecular materials used for composite matrices. Effective utilization of carbon nanotubes in composite applications depends strongly on the ability to homogeneously disperse them throughout the matrix without destroying their integrity. This work looks at the fabrication for montmorillonite, fullerenes and nanotubes polymer/nanocomposites tailored to fit aerospace needs. Further insight is also given on developments in nanofibers and nanotubes production for good load transfer on the composite systems.
TL;DR: The structural transformation and catalytic properties of metal/polymer nanocomposites derived from hypercross-linked polystyrene (HPS) exhibiting both microporosity and macroporeosity, and filled with Pt nanoparticles, are investigated in the direct oxidation of L-sorbose to 2-keto-L-gulonic acid as mentioned in this paper.
Abstract: The structural transformation and catalytic properties of metal/polymer nanocomposites derived from hypercross-linked polystyrene (HPS) exhibiting both microporosity and macroporosity, and filled with Pt nanoparticles, are investigated in the direct oxidation of L-sorbose to 2-keto-L-gulonic acid. Transmission electron microscopy, X-ray photoelectron spectroscopy, X-ray diffraction, anomalous small-angle X-ray scattering, and catalytic studies suggest that the catalytically active species, nanoparticles of mixed composition with a mean diameter of 1.6 nm, develop after the initial induction period. At the highest selectivity (96.8%) at 100% L-sorbose conversion, the catalytic activity is measured to be 2.5 10 -3 mol/mol Pt-s, which corresponds to a 4.6-fold increase in activity relative to the Pt-modified microporous HPS previously reported. This substantial increase in catalytic activity is attributed to the presence of macropores, which facilitate mass transport and, consequently, accessibility of the nanoparticle surface for reactants.
TL;DR: In this paper, wide angle X-ray scattering (WAXS) was used to ascertain the degree of layer swelling and extensional flow properties of EVA nanocomposites.
Abstract: Shear and extensional rheological measurements were conducted in conjunction with laser light scattering (LLS) on ethylene-vinyl acetate copolymer (EVA) nanocomposites. The materials were prepared by melt-mixing EVA and commercially acquired layered silicates. Wide Angle X-Ray Scattering (WAXS) was used to ascertain the degree of layer swelling. This could be attributed to the intercalation of polymer chains into the interlayer of the silicates. The nanocomposites prepared were determined to be predominantly intercalated in nature. In shear rheological tests, the nanocomposites exhibited an increase in viscoelastic properties compared to the pure EVA. The extent of this property enhancement was not as pronounced as had been reported in many instances with respect to other polymer nanocomposites. This could be attributed to the absence of a network structure normally observed in an exfoliated system. The extensional rheological tests showed an increase in extensional flow properties. This was confirmed by the LLS, which indicated that the filled systems had higher deformability than the unfilled one. Polym. Eng. Sci. 44:1220–1230, 2004. © 2004 Society of Plastics Engineers.
TL;DR: In this article, the authors show the temperate induced structural rearrangements of nanocomposites based on poly[ethylene-co-(vinyl acetate)] (EVA) interacalated-organomodified clay (at 3-30 wt.-% silicate addition) which occur in the range between 75 and 350°C.
Abstract: The success of the use of layered silicates in polymer nanocomposites, to improve physical and chemical properties is strickly related to a deeper knowledge of the mechanistic aspects on which the final features are grounded. This work shows the temperate induced structural rearrangements of nanocomposites based on poly[ethylene-co-(vinyl acetate)] (EVA) interacalated-organomodified clay (at 3-30 wt.-% silicate addition) which occur in the range between 75 and 350°C. In situ high temperature X-ray diffraction (HT-XRD) studies have been performed of the nanocomposite structure at increasing temperatures under inert/oxidative atmosphere. Heating between 75 and 225°C, under nitrogen or air, causes the layered silicate to migrate towards the nanocomposite surface and to increase its interlayer distance. The degradation of both the clay organomodifier and the VA units of the EVA polymer seems to play a key role in driving the evolution of the silicate phase in the low temperature range. The structural modifications of the nanocomposites in the high temperature range (250-350°C), dependent on the atmosphere, either inert or oxidizing, in which the samples were heated. Heating under nitrogen led to deintercalation and thus a decrease of the silicate interlayer space, whereas exfoliation was the main process under air leading to an increase of the silicate interlayer space.