PLASTIC-DEFORMATION OF ORIENTED LAMELLAE .2. HOT-ROLLING OF BETA-PHASE ISOTACTIC POLYPROPYLENE

Isotactic polypropylene was crystallized under temperature gradient and an oriented β-phase sample was obtained. The β-phase film was rolled in three orthogonal directions at 68, 96, 122, and 142°C. The deformation behavior was investigated by wide angle and small angle X-ray diffraction methods. Anisotropy in deformation was observed in each case, including the rotation of lamellae, interlamellar slip, longitudinal and transversal chain slip. At high temperatures, the deformation proceeded mainly by interlamellar slip whereas chain slip could hardly be observed. During the hot roll deformation, the original β-phase crystal was destroyed and then recrystallized into the c-axis-oriented α-phase crystal. The amount of the β→α phase transition increased with increasing rolling temperature and draw-ratio. The spacing of the newly appeared α-phase lamellae changed, depending only on the rolling temperature. The final c-axis-oriented texture was composed of α-phase crystals. From these results, it is considered that the deformation proceeds, not by incorporation of the original lamellar blocks, but through the melting or unfolding of the original β-phase lamellae and subsequent recrystallization into the c-axis-oriented α-phase lamellae. © 1979, The Society of Polymer Science, Japan. All rights reserved.