Studies on thermally stimulated shape memory effect of segmented polyurethanes

✍ Scribed by Fengkui Li; Xian Zhang; Jianan Hou; Mao Xu; Xiaolie Luo; Dezhu Ma; Byung Kyu Kim

• Publisher: John Wiley and Sons
• Year: 1997
• Tongue: English
• Weight: 171 KB
• Volume: 64
• Category: Article
• ISSN: 0021-8995
• DOI: 10.1002/(sici)1097-4628(19970523)64:8<1511::aid-app8>3.0.co;2-k

✦ Synopsis

The shape memory behavior of a series of polycaprolactone/methane diisocyanate/ butanediol ( PCL /MDI /BDO) segmented polyurethanes of different composition was studied. The molecular weight of PCL diols was in the range of 1600 -7000, and the hard segment content varied from 7.8 to 27% by weight. Film specimens for shape memory measurements were prepared by drawing at temperatures above the melting temperature of the soft segment crystals and subsequent quick cooling to room temperature under constrained conditions. The shape memory process was observed and recorded in a heating process. Parameters describing the recovery temperature, ability, and speed were used to study the influence of structure and processing conditions on the shape memory behavior of the sample. It was found that the high crystallinity of the soft segment regions at room temperature and the formation of stable hard segment domains acting as physical crosslinks in the temperature range above the melting temperature of the soft segment crystals are the two necessary conditions for a segmented copolymer with shape memory behavior. The response temperature of shape memory is dependent on the melting temperature of the soft segment crystals. The final recovery rate and the recovery speed are mainly related to the stability of the hard segment domains under stretching and are dependent on the hard segment content of the copolymers.