Microstructural Investigation of Deformation and Failure Mechanisms in Polypropylene

The automotive industry continues to expand its use of polymeric materials, which provide more cost effective, strength and durability than metals or ceramics. Thus, a better understanding of the mechanical behavior and microstructural characterization of polymers is essential to develop their improved strength and toughness. This paper describes the deformation and fracture study of commercially available semicrystalline polypropylene (PP). The specimen were subjected to tensile stress using a tensile testing machine and intentionally stopping at three different strain levels (10%, 20%, 35%). Samples were sectioned into different regions and then, using a scanning electron microscope (SEM), studied for microstructural changes, specifically characterization at each extension of the process of crack initiation and propagation. Other techniques, such as x-ray diffraction (XRD) were also employed to determine the crystallinity of the specimen, both on the surface and of the powder collected from the bulk.