Effect of Annealing on Free-Volume Properties of Poly(ethylene Terephthalate) Studied by Positron Annihilation

The effect of annealing on free-volume properties of poly( ethylene terephthalate) was studied using a set of samples annealed for two hours in air at eight temperatures between 80ºC and 220ºC. The fractional free-volume in the samples was estimated from ortho-positronium lifetime and its relative intensity. The variations of fractional free-volume and of the macroscopic specific volume with annealing temperature were compared. The variation of the pore volume probability density functions with the annealing temperature was found. The interdependence between S- and W-parameters was also discussed.