Probing the Amorphous Structure of Semicrystalline PET by Positron Annihilation Life Time Spectroscopy

摘要

Rigid amorphous fraction (RAF) in semicrystalline poly(ethylene terephthalate) is associated with very thin (20-40A) amorphous layers confined between the crystalline lamellas in the regions of lamella stacks.In comparison with mobile (regular) amorphous fraction (MAF),it is constrained and vitrifies at much higher than regular T_g temperature,presumably at crystallization temperature,T_c.The structure of semicrystalline PET was probed by positron annihilation lifetime spectroscopy (PALS).Systematic divergences in the o-PS annihilation lifetimes and intensities were observed,as a function of crystallinity.The results indicate that the fractional free volume of RAF as measured by the product of the hole number density and the average hole volume indeed showed a direct correlation with crystallization temperature.