Proton NMR determination of crystallinity in poly(ethylene terephthalate)

The results of proton NMR T1xz measurements on poly(ethylene terephthalate) (PET) films and fibers processed under various conditions are presented. Consistent with previous results, two domains are found in isotropic, amorphous PET. The NMR results provide an accurate measure of crystallinity in PET films and fibers, without requiring any assumptions about the semi‐crystalline morphology of the polymer. The NMR technique is particularly advantageous for PET fibers where orientation effects interfere with the more traditional density determination of crystallinity.