PHYSICAL AGING KINETICS OF SYNDIOTACTIC POLYSTYRENE AS DETERMINED FROM CREEP-BEHAVIOR

Creep experiments in uniaxial extension have been performed to explore the kinetics of the physical aging process in semicrystalline syndiot actic polystyrene (sPS) having two processing histories. Classical tim e-aging time superposition behavior was found for both materials at te mperatures from 70 to 95 degrees C, with the shift rate mu decreasing as temperature was increased. Virtually no aging was seen at 95 degree s C, the DSC determined glass transition, T-g. This behavior was atypi cal for a semicrystalline polymer and reminiscent of the behavior of g lassy amorphous thermoplastics. Some evidence for a separate crystalli ne aging mechanism > T-g, which manifests itself as only vertical shif ts without timescale shifts, is seen in experiments at T > 100 degrees C. Finally, the two different materials age differently, suggesting t hat some control of aging can be obtained by altering processing condi tions or morphology.