Shrinkage Behavior of Oriented Poly(ethylene terephthalate)

摘要

The kinetics of thermal shrinkage of poly(ethylene terephthalate) films have been characterized and related to various parameters of the stretching process. Amorphous orientation functions and levels of crystallinity have been found to be of major importance to the shrinkage process. As film extension ratios increase, shrinkage behavior passes through five different regions. Shrinkage first increases with extension ratio, decreases with further extension to reach a minimum, and then increases again as extension is continued to higher levels. A schematic model has been proposed o describe molecular changes in polymer chain structures, within each of the shrinkage regions. Activation energies of shrinkage have been determined in addition to equilibrium shrinkage and shrinkage rate constants.