An organically modified montmorillonite was compounded with ethylene vinyl acetate copolymer (EVA), low density polyethylene (LDPE), and high density polyethylene (HDPE) in a twin‐screw extruder. The resulting organoclay‐polyethylene nanocomposites were then blown into films. Tensile properties and oxygen permeability of these nanocomposite films were investigated to understand the effects of organoclay on different types of polyethylene. It was found that the clay enhancing effects are function of the matrix. The mechanical and oxygen barrier properties of clay/EVA systems increased with clay loading. Both the tensile modulus and oxygen barrier of EVA doubled at 5 wt% clay. Maleic anhydride grafted polyethylene (MAPE) usually is used as a compatibilizer for LDPE and HDPE‐based nanocomposites. However, the MAPEs were found to weaken the oxygen barrier of the PEs, especially for HDPE. This is believed to be a result of less compactness caused by the large side groups and the increase in polarity of the MAPEs. Incorporating 5 wt% clay improves the oxygen barrier by 30% and the tensile modulus by 37% for the LDPE/MAPE system. Incorporation of clay does not enhance the properties of the HDPE‐based systems, likely due to large domain structure and poor bonding. Halpin–Tsai equation and the tortuous path equation were used to model the tensile modulus and oxygen permeability of the clay/EVA nanocomposite films. POLYM. ENG. SCI., 47:1101–1107, 2007. © 2007 Society of Plastics Engineers

Despite many advantages of wood–polyethylene composites, the shortcomings of this kind of composite include relatively low modulus, low notched impact resistance, relatively large thermal expansion, as well as substantial creep. In this article, in addition to using maleic anhydride grafted polyethylene as compatibilizer, organoclay was introduced into the polyethylene matrix so as to further enhance the thermal and mechanical performance. First, the influence of maleic anhydride grafted polyethylene type and loading on the morphology and properties of wood/HDPE composites was studied. Then, the effects of organoclay loading and of the compounding procedure on the wood/HDPE composites were investigated. The compatibilization was found to result in better polymer impregnation on the wood, reduced linear thermal expansion coefficients, and significantly improved mechanical properties. Incorporation of organoclay further reduced the thermal expansion and elevated the heat deflection temperature. More compatibilizer is needed to maintain the mechanical properties with the presence of clay. POLYM. ENG. SCI., 47:797–803, 2007. © 2007 Society of Plastics Engineers

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Poly(lactic acid) (PLA)/clay/wood nanocomposites were prepared by melt extrusion of PLA, nanoclay, and wood flour (WF). The clay particles exhibit an intercalated structure in the PLA matrix and the addition of WF slightly increases the spacing in the galleries of the intercalated structure. The intercalated clay particles and WF in the PLA matrix restrict the motion of the PLA molecules and crystals. The tensile and flexural moduli of PLA/clay/wood nanocomposites with 30 wt% WF, respectively, increase from 3.75 to 7.08 GPa and from 3.83 to 6.01 GPa compared to neat PLA by adding up to 5 wt% nanoclay. Voids around clay particles, observed via scanning electron microscopy are associated with the negative effect of the clay particles on the interfacial adhesion between the WF and the PLA matrix. Clay particles improve the thermal decomposition temperature (T d) of PLA/clay/wood nanocomposites by about 10°C compared to that of PLA/wood composites. The effects of clay particles on other thermal properties such as glass transition temperature (Tg), melting temperature (Tm), and linear thermal expansion are also discussed in this article.

Two-dimensional arborols are bolaform amphiphiles in which a central, hydrophobic spacer separates twin hydrophilic ends. Under appropriate conditions, these relatively small molecules assemble into very long fibers; subsequently, the system gels if the arborol concentration is sufficiently high. The diffusion of linear or slightly branched dextran probes in 3 and 6% arborol gels, as determined by fluorescence photobleaching recovery, resembles that of dextrans in water, suggesting a highly open network structure. Melting the gels produces almost no change in diffusion of the dextran probes. Small-angle X-ray scattering (SAXS) of wet arborol gels at different concentrations and temperatures reveals the diameter of the repeating unit of the fibers to be 8.26+/-0.68 nm. This dimension, which is independent of concentration and temperature, exceeds the length of a single arborol molecule by about a factor of 3. Rheological investigation identifies the linear response regime of the gels and permits an examination of the weak correlation between dextran probe diffusion and gel viscoelasticity.

The dependence of Young’s modulus on temperature and clay content of polyethylene/clay nanocomposites (PCN) and wood/polymer/clay nanocomposites (WPCN) is investigated. It is found that the moduli of PCN and WPCN vary linearly with temperature within 25 and 80°C. The addition of nanoclay in the presence of a maleic anhydride grafted polyethylene (MAPE) compatibilizer blend results in an increase of the modulus and strength of the composites. The Young’s moduli of the PCN and WPCN decrease linearly with increase in temperature.

The effects of compatibiliser molecular weight, temperature of the first mixing zone of the extruder and nanoclay loading on the mechanical and thermal properties of polymer–clay nanocomposites (PCNs) were investigated. It was found that the molecular weight of the compatibiliser, the temperature of the first mixing zone of the extruder and the nanoclay content have significant effects on the mechanical and thermal properties of the polyethylene–clay nanocomposites. The blending of the high and low molecular weight compatibilisers allowed a more efficient interface between the nanoclay and the polymer matrix. Coupling a more efficient bonding with the high shear in the first mixing zone of the extruder at a low temperature produced an intercalated/exfoliated nanoclay filler resulting in enhanced mechanical properties of the PCNs.

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