Supramolecular mechanisms of shear deformation upon reorientation of flexible-chain semicrystalline polymers

For LDPE and PA-6, the supramolecular mechanisms of reorientation at sufficiently high angles relative to the direction of primary orientation (70°-75°) and at a marked difference between the temperature of primary thermal treatment T 1 (85 and 200°C, respectively) and the temperature of reorientation T 2 ∼ 20°C were studied. The above polymers are characterized by different values of critical shear angles and easiest slip systems of crystallites. In this case, one may also observe quite different X-ray patterns related to the development of a new phase as induced by plastic deformation because, after the melting of initial crystallites, the recrystallization of PE takes place, whereas PA-6 becomes, to a marked extent, amorphous. In PA-6, the crystallites that are located favorably for their shearing along the planes containing H bonds are the first to experience the deformation. In the region of elastic deformation, the fibrils are shown to be rotated as a whole due to interlamellar slippage inside fibrils. Within the crystallites, shear deformation may either involve the rotation of macromolecules or proceed without their rotation.