Differential scanning calorimetry analysis of silicon-containing and phosphorus-containing segmented polyurethane. II Annealing effect

The effect of thermal annealing on the multiple endothermic behavior and mo rphological changes in the silicon-containing and phosphorus-containing seg mented polyurethane (Si-PU and P-PU) has been studied by differential scann ing calorimetry (DSC). In the amorphous hard segments of the Si-PU and P-PU polymers that were annealed below T2, both the T1 temperature, and magnitu de of T1 endotherm increased linearly as a function of the logarithmic anne aling time (log t(alpha)). This result demonstrated that the endothermic be havior (T1 endotherm) is typical of enthalpy relaxation resulting from the physical aging of the amorphous hard segment. Furthermore, the P-PU polymer was unstable than the Si-PU polymer due to the fact that the phosphorus-co ntaining hard segment produce aged more easily. Dissociation of domains and enthalpy relaxation of hard segments for the Si-PU polymer was associated with T2 endothermic behavior. However, the enthalpy relaxations of the T2 e ndothermic behavior for P-PU polymer was absent, which could be attribute t o the behavior of degradation in the temperature range of T2 endotherm. (C) 2001 John Wiley & Sons, Inc.