Mt. Wang et al., DYNAMIC-MECHANICAL BEHAVIOR IN THE ETHYLENE TEREPHTHALATE ETHYLENE-OXIDE COPOLYMER WITH LONG SOFT SEGMENT AS A SHAPE-MEMORY MATERIAL, European Polymer Journal, 34(1), 1998, pp. 1-5
Several ethylene terephthalate-ethylene oxide segmented copolymers wit
h long soft segments, in which poly(ethylene oxide) (PEG) chains serve
as soft segments while poly(ethylene terephthalate) (PET) chains serv
e as hard segments, were investigated by dynamic mechanical analysis (
DMA). The PET-PEG copolymers show three distinguishable relaxation pro
cesses, alpha-, beta- and gamma-relaxation, within the examined concen
tration range of PET in the copolymers, and alpha-relaxation was assoc
iated with the glass transition of PEO segments in amorphous phase. Bo
th longer PEO segments and higher PET content would tend to decrease t
he alpha-relaxation temperature (T-alpha). The intensity of tan delta
for alpha-relaxation reduced with the increase of soft segment length,
and increased with PET content in the PET-PEG segmented copolymer. DM
A measurements were carried out on the samples containing 2000, 4000,
6000 and 10,000 FED segments, respectively. Relations between the inte
nsity of tan delta for alpha-relaxation and the maximum shape recovery
(R-f) were also: discussed. Experiments revealed that small energy di
ssipation and high physical crosslinking effects supplied by the PET c
omponent in the copolymer would be favorable for the material to show
a good shape recovery. (C) 1997 Elsevier Science Ltd.