Thermoplastic starch modified with microfibrillated cellulose and natural rubber latex: A broadband dielectric spectroscopy study.

Thermoplastic starch (TPS) biocomposites modified with cellulose microfibers and/or natural rubber were prepared via extrusion compounding. Glycerol and water served as plasticizers for starch. The dielectric properties of the TPS composites were examined via broadband dielectric spectroscopy in the temperature and frequency ranges of 30°C-65°C and 0.1Hz-10MHz, respectively. Each specimen was tested twice in order to study the effect of absorbed water. The hydrophobic/hydrophilic character of the modifiers governed the dielectric performance of the corresponding TPS biocomposites. Conducted analysis revealed two relaxation processes attributed to matrix-water-reinforcement interfacial polarization and glass to rubber transition of the TPS. Evaporation of water significantly affected the first process and only slightly the second one. Energy density, prior and after water evaporation, was also determined at constant field. By employing dielectric reinforcing function the contributions of water-assisted and constituents' originated interfacial phenomena could be separated.

Nanostructure in hybrid thermosets with interpenetrating networks and its effect on properties.

Hybrid resins composed of vinylester (VE) and aliphatic amine (Al-Am)-cured cycloaliphatic epoxy (Cal-EP) were produced and their morphology and properties (toughness, water uptake) determined. According to atomic force microscopy (AFM) results achieved on physically etched (ion eroded) specimens the hybrid resins possessed a nanoscaled interpenetrating network (IPN) structure, the characteristics of which depended on the VE/EP ratio. Characteristics of the IPN morphology, viz strand width and mean roughness data increase with increasing amount of the EP component. The fracture mechanical data (K(Q) and G(Q)) pass a maximum as a function of the VE/EP ratio, similar to that of the phase segregation term (alpha). The latter was deduced from dynamic-mechanical thermal analysis (DMTA) traces. The water sorption and diffusion behavior of the interpenetrated VE/EP hybrids were controlled by the relative amount of the EP (Cal-EP+Al-Am) used.