Orientation and properties of sequentially drawn films of an isotactic polypropylene hydrogenated oligocyclopentadiene blend

Films of isotactic polypropylene (iPP) and a blend of iPP and hydrogenated oligocyclopentadiene (HOCP) oriented by one-way (uniaxial) and two-way (sequential biaxial) drawing were studied. The mechanical and thermal properties of the oriented iPP and iPP/HOCP blends as well as orientation behaviour were investigated by means of mechanical tests, d.s.c. and small- and wide-angle X-ray scattering including the pole figures technique. It was found that drawing of iPP/HOCP blends to a high strain leads to the formation of highly oriented films having mechanical properties greatly improved compared to plain iPP oriented under the same conditions. The studies revealed in one-way drawn samples the multicomponent texture with chain axis, c, oriented in the machine direction, MD, for all texture components. The lamellae are oriented with normals parallel to the c direction. Due to differences in the amorphous phase content the texture in the blend samples is less developed than in deformed plain iPP. The subsequent drawing along the transverse direction, TD, leads to the reorientation of the c axis towards the TD, the sharpening of texture and the destruction of the lamellar structure. It was found that the major deformation mechanisms active in iPP and iPP/HOCP blends are: the crystallographic slips systems of (010)[001], (100)[001], (110)[001] and {110} twinning modes. In addition the interlamellar sliding is active as the main deformation mechanism in the amorphous phase. The (010)[001] system is the easiest of the slip systems active and dominates the other mechanisms. (C) 1997 Elsevier Science Ltd.