STUDIES ON THERMAL-STABILITY AND BEHAVIOR OF POLYACETAL AND THERMOPLASTIC POLYURETHANE ELASTOMER BLENDS

The influence of thermoplastic polyurethane (TPU) elastomer on the rigidity of polyacetal (polyoxymethylene, POM) was studied by determining heat deflection temperature (HDT). The higher the content of TPU in the POM/TPU blend, the lower the HDT of the blend, as would be expected. A comparative study of the recycle capability of POM and the blends was carried out by measuring melt flow index (MFI) on each successive extrusion. Stress-strain behaviour of the virgin material and that obtained after fourth-time extrusion was analysed for POM and the blends. The effect of gamma-radiation on the mechanical behaviour of the blends was investigated. The kinetics of thermal degradation of POM, TPU and their blends was studied. The kinetic parameters, viz, activation energy and the order of reaction, were established. The values of the activation energy of the blends were found to be higher than those of the POM and TPU, indicating improved stability of the resultant blends.