The Aging Process in Polymers, Positron Annihilation Lifetime Studies

Abstract : Our research effort on this project investigated the capability of positron annihilation lifetime (PAL) spectroscopy to characterize quantitatively the molecular-level structural disorder in the amorphous phase of polymer materials and to enhance our understanding of the relationships between molecular disorder and the functional properties of such materials. A particular interest was to characterize the change in free volume during isothermal annealing, which is the origin of the well-known physical aging effect in mechanical properties of polymeric glasses such as embrittlement.