Efeitos da atapulgita no envelhecimento de compósitos à base de polipropileno moldados por injeção.

Abstract

This work deals with the influence of mixing procedure on the mechanical properties of polypropylene attapulgite composites having 0-40% filler content. Single and twin screw extrusion were employed. The influence of matrix thermal stabilization (Polibrasil's polypropylene HF-36) on the mechanical, thermal, physical and thermo-mechanical properties of injection moulded composites were also investigated. The results show that the best properties were obtained for thermally stabilised polypropylene/attapulgite composites obtained by twin-screw extrusion at 5% filler content, although good results were obtained up to 20% filler content. The composites at ideal formulation and mixing procedure were submitted to natural weathering, termal and accelerated ageing. It was also shown that attapulgite had a strong effect on the ageing characteristics of the optimized composites and that 1200 hours of natural weathering and 48 hours of thermal and accelerated ageing were enough to render the composite's mechanical properties unfit for service. This was attributed to impurities (iron) present in the filler which are capable to induce secondary photo-chemical reactions, thus accelerating polypropylene photo-oxidation.