In this paper some characteristics of the heterogeneous photodegradation of polypropylene (PP) and PP containing talc were analyzed. Samples produced by injection and compression moulding were exposed to ultraviolet radiation in the laboratory for periods of up to 48 weeks. Systematic procedures for exposure and sampling were adopted in an attempt to minimize the inherent variabilities of this type of study. The specimens were characterized by gel permeation chromatography, infrared spectroscopy, differential scanning calorimetry, X-ray diffraction, mechanical properties and light and electron microscopy. The heterogeneities in PP photodegradation can be related to three main aspects: (i) the semi-crystalline nature of PP; (ii) the depth-profile of degradation; (iii) the structural variations in different positions along the test bar. The consequences of these heterogeneities were discussed with emphasis on the effects on physical properties.
Photodegradation; polypropylene; ultraviolet radiation; heterogeneous degradation
