A positron annihilation lifetime study of isothermal structural relaxation in bisphenol‐A polycarbonate

Abstract
Positron annihilation lifetime spectroscopy has been used to study the isothermal relaxation response of compression molded bisphenol‐A polycarbonate at temperatures of 263, 273, and 303 K. The temperature dependence of both the lifetime and intensity of the ortho‐Positronium (o‐Ps) pickoff component is discussed in terms of ductile‐to‐brittle transition behavior and free volume theory. An additive exponential model and the Williams–Watt model were used to analyze the relaxation as a function of temperature and provided results consistent with the anticipated molecular mobility of polycarbonate at sub‐Tg temperatures.