Pulsed and CW NMR study of drawn polypropylene fibres

Pulsed and broad-line proton NMR was used in investigation of both the molecular motions and the relaxations in oriented partially crystalline polypropylene (PP) fibres. Proton NMR measurements were made of the spin-lattice and rotating-frame relaxation times (T1, T1r resp.), spectra unfolding into elementary components and the second moment of the spectra in the temperature range of 250-400 K for three kinds of drawn PP fibres. The fibres were made from isotactic PP marked as Tatren 430 produced by Slovnaft Bratislava. Relaxation time T1 was measured by a multiple-pulse saturation recovery method. Rotating-frame data T1r were obtained with radiofrequency field B1=1.7 mT using the spin-locking method. The results of the experiments show that the differences in nuclear relaxation behavior are closely related to the structural changes (crystallinity and orientation) caused by the drawing process at different temperatures. (Z.S.) 4 figs., 10 refs