Influence of semicrystalline morphology on the physical aging characteristics of poly(phenylene sulfide)

We report on the influence of semicrystalline morphology on the physical aging characteristics of poly(phenylene sulfide) or PPS. Specifically, the semierystalline morphology of PPS was described in terms of a three-phase system comprising a crystalline phase, a mobile-amorphous phase, and a rigid-amorphous phase. The physical aging kinetics were observed to depend on the relative amounts of the mobile-amorphous and rigid-amorphous phases, with accelerated aging rates measured in specimens with higher rigid-amorphous phase fraction. We suggest that the rigid-amorphous phase, which includes chain segments that are more tightly packed relative to the mobile-amorphous phase, is able to accelerate physical aging due to its relative proximity to a state of lower configurational entropy. It is also possible for localized cooperative relaxations within the rigid-amorphous phase to facilitate molecular rearrangements that accelerate the aging process. We also suggest that the configurational entropic state of the mobile- and the rigid-amorphous phases are perhaps more relevant to physical aging in semicrystalline polymers than the proximity of the aging temperature to the glass transition temperatures of the respective phases.