The heat distortion temperature(HDT) of nylon-6(N6)/clay nanocomposites, including intercalated N6/Na-montmorillonite(Na-MMT) and exfoliated N6/organomontmorillonite(OMMT) composites, was investigated for both non-annealed and annealed test specimens in comparison with neat N6. As expected, the incorporation of MMT markedly improved HDT of the nanocomposites, with the highest HDT value obtained in the N6/OMMT system due to its exfoliated nanostructure. After an annealing treatment at 80C for 6 h, the HDT exhibited a significant increase for all the samples, particularly for the intercalated N6/Na-MMT nanocomposite that showed the highest increment of 34C. DSC, DMA and FTIR techniques were used to clarify the origin of the variation in HDT after annealing and the results suggested that the increases in the crystallinity, the Tg and the order of the degree of hydrogen bonding could account for the observed increases in the HDT of the nanocomposites after annealing. 44 refs.

The thermal properties of epoxy-clay nanocomposites synthesised by in-situ polymerisation of a prepolymer (DGEBA) crosslinked using methyl tetrahydrophthalic anhydride were studied. The inorganic phase was montmorillonite, exchanged with alkylammonium ions in order to give organophilic properties to the phyllosilicate. The morphology of epoxy-montmorillonite nanocomposites examined by X-ray diffraction and TEM showed that mixed delamination or intercalation or microdispersion could occur depending on type of organoclay. TGA showed that in nanocomposites the epoxy matrix was protected from the action of oxygen. Cone calorimeter tests showed that the rate of heat release in the nanocomposite combustion was markedly reduced. 48 refs.

Nanocomposites based on EVA (25 wt % vinyl acetate) and various organo-modified clays were prepared by melt blending and their morphology, tensile and thermal degradation properties were evaluated. Particular attention was paid to the influence of the nature and origin of the clay (montmorillonite or fluoromica) and to the effect of the nature of the ammonium cation organic modifier. It was shown that nanostructure and tensile properties were mainly dependent on the nature of the organic modifier, while the delay in thermal volatilisation of EVA during thermooxidation was mainly driven by the nature of the clay (particularly its aspect ratio), with no significant influence of the nanostructure on the nature of the organic modifier. 16 refs.

Screw design for the extrusion of thermoplastic composites is discussed with reference to polymer melt and screw geometry, pumping the polymer, barrel temperature override, screw wear and protection, and barrel wear. The fillers used in thermoplastics include talc, mica, calcium carbonate and nanoclay. Illustrations are given of the type of screw wear caused by fillers, of the way in which nitriding a screw can reduce wear, and of the use of tungsten carbide to improve barrel and screw lifetimes.

The melt mixing of functionalised polyolefins with a surface-modified layered silicate (montmorillonite) was investigated with the aim of preparing the corresponding micro/nanocomposites. The effect of the diethyl succinate groups, derived from the grafting of diethyl maleate(DEM) onto the polyolefins, on compatibility with an inorganic filler and the dispersion in a hydrophobic matrix was investigated. In order to avoid possible interference by polymer multiphase morphology, the amorphous poly(propylene-ran-ethylene)(EPM)(70/30 wt/wt), functionalised with DEM, was used in melt mixing with alkylammonium-salt-modified montmorillonite at different weight ratios by using a Brabender mixer. Materials with a nanoscale dispersion of the inorganic phase, as revealed by X-ray diffraction and TEM analyses, were obtained. Specific interactions, involving the carbonyl groups of the polyolefin functional groups and the polar sites on the filler surface, appeared to assist intercalation and/or exfoliation of the layered system. Similar results were obtained by starting with an unfunctionalised EPM and by performing the grafting reaction with DEM during melt mixing according to a one-step simplified procedure. 27 refs.

Sulphonated PETP ionomer/organically modified montmorillonite nanocomposites were prepared by melt extrusion. The random incorporation of ionic functionalities along the PETP backbone enhanced the interactions between the matrix polymer and montmorillonite clay, resulting in nanocomposites with a significantly exfoliated morphology. Incorporating the clay into the ionomers improved the mechanical properties and lowered the crystallisation rates. 29 refs.

Two model systems were studied in this paper. In the first system, the reinforcement by silica beads embedded in a soft polymeric matrix formed from nanolatex particles was investigated. The nanolatex was a core-shell latex of PMMA and polybutyl acrylate with a hydrophilic shell containing methacrylic acid. The aggregation of nanosilica beads was controlled by the solution pH before film formation. Lower pH yielded higher aggregation numbers. The dependence on the silica volume fraction was weaker than the pH dependence and higher volume fractions led to higher aggregation numbers. At identical volume fraction, the material with the highest aggregation numbers had the highest reinforcement factor. An analysis of the low-strain reinforcement was proposed. In the second system, silica beads were grafted with PS chains of controlled molecular weight. Some aggregation was always present in solution but it was low and it decreased during polymerisation. 31 refs.

PP/silica nanocomposites with and without chemical linkage between the silica particles and the PP matrix were prepared by combining solid state modification (SSM) by grafting vinyl triethoxysilane (VTES) with a sol-gel method. VTES was grafted via SSM in porous PP particles. Bulk polymerisation under similar conditions to those of SSM resulted in homopolymerisation of VTES. However, size exclusion and NMR studies showed that VTES was grafted as a single monomeric unit in the amorphous phase of PP with the possibility of VTES-polymer grafting during SSM. Silica-like nanoparticles were synthesised in-situ by the sol-gel method. Spectroscopic results showed that the grafted VTES became part of the silica particles formed in-situ. No decrease in the molecular weight of PP was observed, indicating that chain scission was marginal compared with melt modification. The morphology of the nanocomposites showed a uniform dispersion of grafted VTES as well as in-situ formed silica. The silica particles formed in-situ were nearly spherical with sizes between 50 and 100 nm. 49 refs.

An in-situ, one step method for producing a uniform dispersion of lanthanum(III) oxide particles in a polyimide matrix during thermal curing was described. Small angle X-ray scattering (SAXS) results showed that the average radius of gyration of the newly formed nanoparticles was 2.4 nm and that the average interparticle distance was 9.7 nm. Both SAXS and dielectric measurements indicated that the particles were formed as the temperature increased from 150 to 300C during a 2 h ramp from 100 to 300C. The presence of 1% by volume of the nanoparticles in the polymer material relative to the neat polyimide indicated an increase of 3C in the glass transition temperature and the gas permeability showed a strong tortuosity effect. The gas permeability was reduced by a factor of 10 compared with the predicted reduction of the Maxwell model. The lanthanum ions existed in two different chemical environments in the nanoparticle. 57 refs.

Photoinitiated crosslinking polymerisation was used to prepare polyurethane acrylate, polyphenoxy acrylate, polyester acrylate and cycloaliphatic epoxide clay-based nanocomposites. The solvent-free resin containing 3 wt% of organophilic clay was cured within seconds on UV irradiation at ambient temperature. IR spectroscopy studies showed that the polymerisation reaction was rapid in thick samples (2 mm) because of the higher exotherm and the resulting rise in temperature. The organoclay did not slow down the photopolymerisation of either acrylate or epoxy resins. The presence of clay nanoparticles reduced the gloss of UV-cured coatings because of enhanced surface roughness. The viscoelastic and tensile properties of the nanocomposites were comparable to those of the neat UV-cured polymer but their moisture resistance was significantly increased. 35 refs.

Ionomer blends with cation/anion interactions were formed in-situ by mixing acidic rod-like sulphonated poly(para-phenylene) with alkyl side chains as the reinforcing component with poly(ethyl acrylate-co-4- vinylpyridine) or poly(styrene-co-4-vinylpyridine) as the flexible coiled matrix material. Acid-base interactions resulted in the molecular dispersion of the rod-like molecules in the matrix polymer. The mechanical properties of the ionomeric nanocomposites depended strongly on the degree of polymerisation of the rod-like component, the characteristics of the ionic interactions and the rod volume fraction. The multiple intermolecular ionic interactions resulted in a maximised filler-matrix interaction and hence in very high reinforcement. The mechanical behaviour of the blends depended on the aspect ratio of the filler polymer and could be qualitatively represented by applying the fuzzy cylinder model to describe the size and shape of the reinforcing molecules. 43 refs.

Cast PU thermosets were modified with randomly oriented exfoliated and intercalated montmorillonite clay using hydroxyl-terminated hyperbranched polyesters (HBP) as reactive additives to promote dispersion of the montmorillonite. The effect of the clay content on the stiffness of the nanocomposites was discussed in terms of micromechanical models which allowed correlations to be established between the properties of the final PU and the limiting high strain rate shear viscosity of the HBP or HBP/polyethylene glycol nanocomposite precursors. These models implied restrictions on the potential for mechanical reinforcement with unoriented platelets because of crowding effects. They also did not seem able to account simultaneously for the observed degrees of reinforcement in the glassy and rubbery states if currently accepted values for the stiffness of montmorillonite were assumed. Possible reasons for the observations were discussed. 43 refs.

Polyamide-6/clay nanocomposites with different clay loadings were prepared by melt compounding in a twin-screw extruder. In the melt state, the critical strain amplitude of the composites was sensitive to the strain amplitude response and decreased logarithmically with increasing clay loading. The elastic moduli of the composites were reversible under frequency loop sweeps. The strain amplitude response in the melt state showed strain thinning and in the solution state showed weak strain overshoot. It was suggested that strain thinning was caused by physical adsorption and entanglement of the polyamide-6 (PA) chains on the nanoclays and that weak strain overshoot was caused by weak bonds between the PA chains and the nanoclays. FTIR spectroscopy studies showed that the amide II band of the composites shifted towards higher wave numbers but the amide I band and N-H stretching were independent of clay loading. 28 refs.

The mechanical properties of nylon-6/clay nanocomposites with different clay aspect ratios and orientation were studied. Unidirectional reinforcement and higher aspect ratios could significantly improve the modulus, strength and heat distortion temperature of the nanocomposites with a marginal loss in ductility. The experimental results for the effect of filler orientation on the modulus enhancement of the nanocomposites agreed reasonably well with the predictions of the Mori-Tanaka model. 61 refs.

The role of multi-walled carbon nanotubes and clay in the fire retardancy of ethylene-vinyl acetate (EVA) copolymer nanocomposites was studied. The nanotubes played an important part in the reduction of the peak heat release rate of the composites by forming low permeability graphitic carbon in the char. Adding clay to the carbon nanotube/EVA composite tended to enhance the formation of graphitic carbon and the clay enhanced nanocomposites appeared to have a better resistance to char oxidation. 15 refs. 15 refs.

PP-grafted maleic anhydride (PPgMA)/montmorillonite clay nanocomposites were prepared by extrusion and by injection moulding. The thermal degradation and fire retardant behaviour of the nanocomposites were improved compared with those of pure PPgMA and this improvement was greater for injection moulded specimens than for extruded specimens. These properties deteriorated in UV-irradiated nanocomposites. However, UV-irradiated pure PPgMA showed an outstanding improvement in fire retardant properties. Reasons for these observations were discussed. 18 refs.

Nanocomposites based on isotactic PP and organically modified bentonite clay were prepared by melt intercalation. Thermooxidation of compression moulded films of the nanocomposites was carried out at 110C for up to 165 h. IR spectroscopy results showed that the PP compounds based on the modified clay had a higher thermal stability in the solid state than those with the natural clay which may have been due to a higher dispersion of clay particles reducing oxygen diffusion through the samples. However, the thermal degradation of PP with the modified clay was higher than the pure polymer. This may have resulted from the acidic nature of the clay, interaction between the clay and PP stabilisers and decomposition of the organic salt during processing. 36 refs.

Siloxane-polyoxypropylene nanocomposites were doped with varying amounts of lithium perchlorate and the viscoelastic properties and structure of the nanocomposites during gelation investigated as a function of doping. The results obtained were analysed using the linear aggregate growth, mass fractal growth and scalar percolation models. The growth rate constant of aggregates during gelation was determined by quasi-elastic light scattering and correlated with the evolution of rheological properties. Lithium 7 NMR spectroscopy and FTIR spectroscopy were utilised to study the evolution of the fraction of lithium ions coordinated in different sites during gelation and the role of polymer molec.wt. in doping was examined. 32 refs.

Hybrid biopolymer nanocomposites obtained by the intercalation of high molec.wt. biopolymers into layered solids, such as clay, layered doubled hydroxides, phosphates and vanadium pentoxide xerogels, are reviewed. Sections are included on hybrids based on biopolymers and inorganic solids, intercalation of neutral biopolymers, intercalation of positively and negatively charged biopolymers and trends in functional bionanocomposites. 134 refs.

A comprehensive review is presented on the general strategies for the design of functional hybrids, including sol-gel methods, bridged precursor route and hydrothermal synthesis, and applications of hybrids, such as organic-inorganic composites, sol-gel derived hybrid materials, bio-inspired hybrid materials, Ormocers, hybrid nanocomposites based on functional nanoclusters and nanoparticles, intercalated hybrids and hybrid nanocomposites based on clays. Applications covered include protective and decorative coatings, barrier materials, dental applications, microelectronic applications, micro-optics, batteries, photovoltaic cells and proton exchange membrane fuel cells. 326 refs.

Nanocomposites were prepared by stirring organically-modified montmorillonite in low viscosity epoxy resin followed by sonication. Samples were also prepared by adding a toluene suspension of the clay to epoxy resin. Diethylenetriamine was used as the curing agent, samples being cured at 80 C and subjected to post-curing heat treatment at 140 C. Direct preparation gave predominantly intercalated nanocomposites with strong interfacial bonding, which increased strength and brittleness. The use of a solvent enhanced clay exfoliation and plasticised the resin. The curing kinetics were influenced both by the clay organic modifier and the solvent, whilst the extent of curing was approximately the same for both pure epoxy and the nanocomposites. The clay additions also significantly enhanced the thermal stability, particularly at concentrations above the critical volume fraction, as determined by the change in slope of the storage modulus plotted as a function of clay concentration, and attributed to flocculation. 31 refs.