Abstract: The dynamic mechanical properties of the segmented polyester polyurcthaneurea (PUU) elastomcrs based on 4,4'-diphenylmethane diisocyanate (MDI), ethylene diamine (ED) and polybutylene adipate (PBA) (mol. wt. of 1975 and 1228) have been studied. The results showed that PUU exhibited a two phase structure, and two major transitions corresponding to the soft and hard segments were observed. Several secondary relaxations were also observed. All the relaxations were affected by both the molecular weight of the soft segments and content of the hard segments. The degree of the phase segregation may be improved by increasing the hard segment content. There occured a multi-step rubbery platform in E～T curves. A model has been proposed for reasonable explanation for the existence of the multi-step platforms.

Key words: polyester polyurethaneurea, dynamic mechanical property, relaxation, phase segregation