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.