The relaxation behavior of amorphous PET in global chain orientation but nearly random segmental orientation (GOLR) state

Summary

In this report, the relaxation behavior of amorphous poly(ethylene terephthalate) (PET) in global chain orientation but nearly random segmental orientation (GOLR) state is studied by infrared dichroism, optical birefringence and hot shrinkage measurements at temperatures below or up PET's glass transition temperature, Tg. The results indicate that the difference in the relaxing rate between global chains and segments is at least in ∼ 10² times order above PET's Tg (∼ 84°C), with a rough approximation; while the sudden decrease of small Δn of the sample (∼ 10⁻⁴) upon being treated at about 85 ∼ 90°C, implies us that the small Δn is closely related with the orientation of global chains.