Segmental motions and associated dynamic mechanical thermal properties of a series of copolymers based on poly(hexamethylene terephthalate) and poly(1,4-cyclohexylenedimethylene terephthalate) (original) (raw)

The dynamic mechanical thermal properties of poly(hexamethylene terephthalate) (PHT), poly(1,4cyclohexylenedimethylene terephthalate) (PCT) and their P(HT-co-CT) random copolymers in the amorphous state were examined as a function of temperature and frequency. All the samples exhibited two main relaxation processes in the plot of tan δ versus temperature: the primary α-relaxation associated with the glass transition and the secondary β-relaxation attributed to the local segmental motions of mostly cyclohexylene rings for PCT and to cooperative motions of methylene, carboxyl, and phenylene groups for PHT. Both αand β-relaxation temperatures increased with increasing CT content. The activation energy of the α-relaxation increased with increasing CT content, whereas that of the β-relaxation decreased. The sub-glassy secondary β-relaxation processes of PCT and PHT were investigated in terms of the cooperativity of main-chain segmental motions.