Comparison of thermal/mechanical properties and shape memory effect of polyurethane block-copolymers with planar or bent shape of hard segment

A series of shape memory polyurethane copolymers synthesized from 1,4-phenyldiisocyanate (PDI) and poly(tetramethyleneglycol) (PTMG) plus 1,4-butanediol as chain extender were compared with similar ones from 4,4'-methylene-bis-phenyldiisocyanate (MDI) and PTMG in various shape memory tests at temperature ranges of +/- 20 degreesC around glass transition temperature (T-g). Similarity and some differences between two series were found in other characterization methods such as IR spectra, phase transition, and mechanical properties. Especially, T-g increased with the content of hard segment (PDI or MDI) and both copolymers generally showed similar T-g at the same content of hard segment. In addition, vibration and shock absorption ability was investigated by measuring both loss tan delta and storage modulus with dynamic mechanical analyzer. (C) 2003 Elsevier Science Ltd. All rights reserved.