Estimation of the Degree of Crystallinity of Partially Crystalline Polypropylenes Using 13C NMR |
| V. Hronský, M. Koval'aková, P. Vrábel, M. Uhrínová, D. Olčák
Department of Physics, Faculty of Electrical Engineering and Informatics, Technical University of Košice, Park Komenského 2, 042 00 Košice, Slovakia |
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| The paper deals with a method for the estimation of the degree of crystallinity for partially-crystalline isotactic-polypropylenes (i-PP) using high-resolution solid-state 13C NMR. For this purpose direct polarization 13C MAS NMR spectra were measured for i-PP samples with different degrees of crystallinity at 98°C. The areas beneath the resonance lines in these spectra correspond to the number of carbons in particular functional groups, while the widths and shapes of the lines reflect the degree of crystallinity, crystalline modifications, distribution of chain conformations and the chain mobility. The 13C MAS NMR spectra, measured using appropriate combination of delay time and high proton decoupling field, made it possible to detect only amorphous domains in the sample. This enabled identification of the lines associated with the amorphous domains in the complete 13C MAS NMR spectra and provided sufficient information for reliable estimation of the degree of crystallinity. The heteronuclear Overhauser enhancement of the 13C NMR signals due to short delay time was taken into account in our calculations. |
DOI: 10.12693/APhysPolA.126.409 PACS numbers: 61.41.+e, 76.60.-k, 81.05.Lg |