CHANGE OF DISTRIBUTION OF FREE-VOLUME HOLES DURING CRYSTALLIZATION OFPOLY(ETHYLENE-TEREPHTHALATE) REVEALED BY POSITRON-ANNIHILATION LIFETIME SPECTROSCOPY

Change of free volume holes during crystallization of amorphous poly(e thylene terephthalate) at 130 degrees C was investigated by positron a nnihilation lifetime technique together with the measurements of speci fic density and wide angle x-ray scattering (WAXS). The o-Ps intensity , I-3, decreased by 24.6% with the crystallization. This value agreed with the degree of crystallinity determined by the specific density an d WAXS, which indicates that o-Ps annihilation takes place in the amor phous part. The average o-Ps lifetime increased slightly by the crysta llization. Detailed analysis of the o-Ps lifetime by a continuous dist ribution model showed that the small size component of the distributio n disappeared due to the crystallization. The result is favorably comp ared with the recently proposed picture of crystallization which deals with the conformational change of ethylene group. (C) 1996 American I nstitute of Physics.