On deformation mechanisms of β-polypropylene 2.: Changes of lamellar structure caused by tensile load

Several beta-polypropylene (beta-PP) samples were stretched to various strains at room temperature. The morphologies of the deformed specimens were studied by scanning electron microscopy and transmission electron microscopy. The deformation was highly inhomogeneous in the beta-PP specimens. In the early stage of deformation, horizontal lamellae were stretched to separation and deformation bands were formed within a spherulite in some regions. The: deformation bands coalesced as strain increased. Near the yield point, some deformation bands developed into crazes across the spherulite boundaries. Meanwhile, melting spots and shear bands were found in the yielded sample. However, the main cause of failure was cracking across the specimen. (C) 1999 Elsevier Science Ltd. All rights reserved.