Chapter 57 - Polypropylene Copolymer

Abstract

This chapter reports that in polypropylene copolymer, tensile strength increases with increasing crystallinity and orientation, while impact strength decreases with increasing crystallinity and spherulite size. Spherulite types can also influence impact properties since the beta form has better impact properties than the alpha form. The crystallinity, morphology and orientation are dependent on the thermal history and manufacture of the sample and are influenced by subsequent processing, including welding. Morphological changes in polypropylene as a result of hot plate welding and vibration welding were studied. The chapter further informs that hot plate welds, which were made using standard (material manufacturer recommendations) and non-standard (to study the effect of increased plate removal time) conditions could be distinguished in terms of structural and morphological behavior, but not always on the basis of tensile strength. A table depicting welding details and tensile results for hot plate welded isotactic pipes made from polypropylene copolymerized with ethylene is also presented in the chapter.