Abstract
Abstract : Positron annihilation lifetime spectroscopy (PALS) has been used to characterize as extruded and aged LEXAN polycarbonate. The long-lived component of the PALS analysis is attributed to orthoPositronium (oPs) pick off annihilations. The oPs pickoff component lifetime and intensity decrease as the result of the aging heat treatment, and this decrease is associated with a decrease in the free volume site size and concentration in glassy polycarbonate due to aging. Isothermal relaxation experiments performed over the range 12 C to 30 C performed on as-extruded and aged polycarbonate indicate that the relaxation kinetics are significantly different, and are consistent with a decrease in molecular mobility as the result of aging. An activation energy for structural relaxation of 8.2 kcal/mole for aged polycarbonate versus 3.0 kcal/ mole for unaged polycarbonate was determined. The relaxation kinetics observed using PALS is related to the structural state and molecular mobility of the polymer.
Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
