Molecular Motions of Non-Crystalline BEK

Abstract

Relaxation behaviors of BEK, a new engineering plastic with high heat resistance (T g: 181° C, T m: 364° C), were investigated. Dielectric relaxation peaks were observed at -83° C and 51° C in 9.8 Hz, and their activation energies were 7 kcal/mol and 19 kcal/mol, respectively. The relaxation peaks were also observed in mechanical measurements. The `chemical structure-relaxation behavior' relationship in BEK and its related polymers suggests that the origins of the high temperature relaxation peak of BEK are crankshaft type chain motions while those of the low-temperature relaxation peak are wigglings of benzonitrile or phenyl groups.