PHYSICAL AGING OF POLY(CHLOROTRIFLUOROETHYLENE) - A POSITRON-ANNIHILATION STUDY

Isothermal annealing of poly(chlorotrifluoroethylene) (PCTFE) was carr ied out at a temperature of 70 degrees C (slightly above T-g) using th e positron annihilation lifetime (PAL) technique. Both the o-Ps lifeti me and intensity shows systematic variation with ageing time, and its intensity can be represented by two additive decay exponentials. The f ree volume which is estimated using the Nakanishi et al. equation deve loped from Tao's model, exhibits Doolittle type free volume relaxation . Physical ageing seems to yield close packing of polymer chains witho ut crystallization. The relaxation time, and the nonexponentiality par ameter, were estimated using a Kolrausch-Williams-Watt (KWW) function. (C) 1997 Elsevier Science Ltd.