C-13 CP MAS NMR-STUDIES OF MORPHOLOGICAL-CHANGES IN POLYPROPYLENE .1.ANNEALING OF QUENCHED FILMS/

High-resolution C-13 cross-polarization/magic angle spinning (CP/MAS) spectra of the crystalline component of quench-cooled isotactic polypr opylene (iPP) were obtained by using a pulse sequence that incorporate s a delay period with a reduced spin locking field prior to cross-pola rization, thus exploiting the differences in H-1 T-1 rho relaxation ti mes between the various phases. The spectra of samples annealed at hig h temperature have resolved splitting, ranging between 0.2 and 1.1 ppm , for all carbon resonances. The methyl resonance is composed of three resolved peaks whose relative areas, as obtained through peak deconvo lution, depend on the anneal temperature. Large changes in these peak areas coincide with an exothermic transition observed by differential scanning calorimetry. The spectra of the interfacial and amorphous pha ses, obtained by subtraction, indicate a reduction in the amorphous co ntent at anneal temperatures >100 degrees C while the interfacial comp onent appears to increase owing to recrystallization and the formation of more amorphous/crystal interfaces.