Morphology and mechanical behavior of polypropylene hot plate welds

Polypropylene tensile bars were hot plate welded and analyzed by microscopy and mechanical tests. The welding process caused significant modifications to the microstructure and shape of the bars at the weld zone. The weld morphology was affected by both the welding parameters and the thermal history of the components. Oriented textures, coarse spherulites, voids or sharp notches occurring at the beads are the key morphological factors that affect the weld quality. Weld performance is dependent upon the type of testing method used. A tensile impact test has been shown to be potentially useful for quality control, as the fracture behavior is affected by the overall morphoiogy.