Phase Behavior and Molecular Mobility in Polyurethane/Styrene-Acrylonitrile Blends

摘要

Differential scanning calorimetry (DSC), thermally stimulated depolariza- tion currents (TSDC)techniques, dielectric relaxation spectroscopy (DRS), and dynamic mechanical thermal analysis (DMTA), covering together a wide range oftemperdtures and frequencies, were employed to investigate molecular mobility and microphase separation in blends of crosslinked polyurethane (PUR) and styrene-acrylonitrile (SAN) copolymer, prepared by reactive blending with polymerpolyols. The results by each technique indicate that the degree of microphase separation of PUR into hard- segment (HS) microdomains and soft-segment (88) niicrophase increases on addition of SAN .The various techniques were critically compared to each other, with respect to their characteristic time and length scales,on the basis of activation diagrams (Arrhe- nius plots). The results show that for the dynamic glass transition of the PUR 88 niicrophase the characteristic time scales at the same temperature are similar for DMTA, DSC, and TSDC and shorter forDRS.1ntermsoffra~lity, the PUR/SAN blends are classified as fr~le systems.