Fotodegradação do poliestireno de alto impacto contendo linhas de solda.

Abstract

The presence of weld lines, formed during processing, is very common in polymer products, causing premature failure during service. In injection moulded samples, for example, weld lines are generated in cavities with more than one injection gate, causing a mechanical discontinuity when flow fronts are joined. Although this phenomenon is extensively studied in relation to processing conditions and mechanical properties, very little work was done in the investigation of degradation effects. This article shows a study on the influence of weld line on high-impact polystyrene (HIPS) photodegradation. Tensile bars prepared by single and double-gated injection moulding were exposed under two different exposure conditions for periods of up to 150 days. The results showed that weld lines caused a reduction in tensile strength and maximum elongation of unexposed samples but they do not cause further deterioration in comparison to the single-gated bars. Analyses by infrared spectroscopy revealed a high level of chemical degradation.