Isotactic polypropylene sheets deformed by rolling to draw ratios between 6.6 and 15.8 were studied by wide-angle X-ray diffraction. Even order
c coefficients of the Legendre polynomial series describing the orientation distribution of the molecular chains were determined from measurements made on nine hkO and hkl crystal planes, for n up to 100. The correlation between the results obtained from these different X-ray reflections is excellent. All the coefficients were used to calculate the orientation distribution of the molecular chains, which cannot be measured directly since there are no reflections parallel to the c-axis for the monoclinic unit cell of isotactic polypropylene. The (P2(cos g)>c and (P4(cos Z)>c values are close to unity for the sheets rolled to 2 >/7.6, indicating that the polymer chains are already well oriented in the deformation direction at these draw ratios. However, the evolution of the crystal phase orientation beyond 2 = 8 can be characterized using the high-order (P,(cos Z)>c coefficients, which still increase up to the highest rolling ratio measured in this work
Посилання на статтю:
Characterization of the molecular orientation in highly oriented rolled polypropylene sheets by X-ray diffraction / Claude-Paul Lafrance and Robert E. Prud'homme // Polymer. – 1994. – Vol 35. – P. 3927-3935.