Dielectric investigations of microphase separation in polyurethane - styrene/acrylonitrile blends

摘要

This work deals with dielectric studies of microphase separation in blends of thermoplastic polyurethanes (TPUs) and styrene/acrylonitrile (SAN) copolymers.The dielectric techniques used include broadband ac dielectric relaxation spectroscopy (ORS) - in frequency range of 10{sup}2 to 10{sup}6 Hz and temperature range of 200 to 450 K and thermally stimulated depolarization currents (TSDC) techniques.TSDC tecnhiques were mainly employed to investigate the sub - glass local relaxations in TPU, SAN and their blends. ORS allowed to follow the dynamics of the glass transition in the pure components and their blends. The a - relaxation due totheglass-rubber transition of the TPU phase becomes faster with increasing SAN content. On the other hand, the a - relaxation due to the glass-rubber transition in SAN becomes slower with increasing TPU content. These results are in agreement with glass transition measurements by calorimetry (DSC). The shape of dielectric loss peak for the primary a - relaxation of SAN does not change significantly with temperature and blend composition.