Relaxation phenomena and morphology in polymer blends based on polyurethanes investigated by various thermal analysis techniques

The thermal, thermomechanical and thermal-dielectric properties of polyuret hane blends based on branched polymer polyol (PUR) and styrene-acrylonitril e (SAN) copolymer were studied by differential scanning calorimetry (DSC), thermomechanical analysis (TMA), thermally stimulated depolarization curren ts (TSDC) techniques and dielectric relaxation spectroscopy (DRS). Several molecular mobility mechanisms associated with secondary local relaxations, primary (main) relaxations due to the dynamic glass transition and conducti vity effects were observed and studied in detail. The use of several molecu lar mobility techniques, characterized by various spatial and time scales, allowed for several intercomparisons, in particular with respect to the det ermination of glass transition temperatures and of the temperature dependen ce of relaxation times which indicate the advantages and the limits of each particular technique. The results by the different techniques suggests in agreement to each other, that on addition of SAN the microphase separation between hard segment (HS) microdomains and soft segment (SS) microphase of PUR is improved. (C) 2001 Elsevier Science B.V. All rights reserved.