A.A.S. Curvelo

Thermoplastic starch/natural rubber blends

Thermoplastic starch/natural rubber polymer blends were prepared using directly natural latex and cornstarch. The blends were prepared in an intensive batch mixer at 150 °C, with natural rubber content varying from 2.5 to 20%. The blends were characterised by mechanical analysis (stress-strain) and by scanning electron microscopy. The results revealed a reduction in the modulus and in tensile strength, becoming the blends less brittle than thermoplastic starch alone. Phase separation was observed in some compositions and was dependent on rubber and on plasticiser content (glycerol). Increasing plasticiser content made possible the addition of higher amounts of rubber. The addition of rubber was, however, limited by phase separation the appearance of which depended on the glycerol content. Scanning electron microscopy showed a good dispersion of the natural rubber in the continuos phase of thermoplastic starch matrix.

Wood pulp reinforced thermoplastic starch composites

Thermoplastic starch is potentially a low cost alternative biodegradable plastic that is readily available material, but owing to its poor mechanical properties and high susceptibility to water, its actual replacement of the polymers currently in use is limited. In this study we investigated the employment of wood pulp as fiber reinforcement for thermoplastic starch. The composites were prepared with regular cornstarch plasticized with glycerol in the presence of fiber. The matrix compositions were starch/glycerol 70/30, 80/20 and 90/10 (w/w). The wood pulp fiber content was varied from 5 to 15% by weight. The composites were characterized by mechanical tests, scanning electron microscope and water absorption experiments at 97% relative humidity. It was found that the addition of fiber led to a large increase in the elastic modulus and tensile strength and that these effects are very dependent on the glycerol content. The water absorbed by the composites was sharply reduced by the addition of pulp, and seems to be independent of the amount of glycerol and pulp content. Scanning electron microscopy of fracture surfaces revealed that fibers were well dispersed in the matrix and were strongly bonded to it.

DSC and solid state NMR characterization of hydroxyethylcellulose/polyether films

Thin solid films of hydroxyethylcellulose/oligoether were obtained by a grafting reaction of HEC with diisocyanates, and were then characterized by DSC, FTIR, NMR and complex impedance techniques. The transparency of these films in the visible range of the electromagnetic spectrum, the low T g , the good chain mobility and ionic conductivity of 8.8 x 10 -4 Scm -1 at 333 K, show that they can be used as solid electrolytes in electrochromic devices.

Polymer Electrolytes Derived from Hydroxiethylcellulose/Polyether Films

Abstract Polysaccharides, like cellulose and its derivatives, can be used in polymer electrolytes because of their aptitude to generate thin films. This paper reports the reaction of hydroxyethylcellulose with oligoether-based diisocyanates. The resulting networks were investigated by differential scanning calorimetry and infrared spectroscopy.