C-13 NMR-SPECTRA OF ISOTACTIC POLYPROPYLENE FILM DURING STRETCHING AND SHRINKAGE

The line-shape of C-13-NMR spectra of highly crystalline isotatic polypropylene film during stretching and subsequent shrinkage was investigated. Well-resolved splittings of the resonance peaks of methylene and methyl carbons before stretching disappear with increasing stretching ratio (lambda- > 10) and recover, although incompletely, by the subsequent shrinkage. Structural properties such as crystallinity and d-spacings of (110) and (040) planes were also measured during stretching and shrinkage. The crystallinity decreases with increasing stretching ratio. When the sample of lambda- = 10 was shrunk, ca 60% of delta-X(c) was recovered, where delta-X(c) is the difference between the crystallinity before and after stretching. The d-spacing of (110) and (040) planes slightly change during stretching and recover almost to the initial values as a result of the shrinkage.