The weathering test of polypropylene composites

Commercial Malen P polypropylenes (i) pure, (ii) filled (20%) with chalk or talc, and (iii) UV-stabilized with 0.2 or 0.4% of a hindered amine Light stabilizer, Tinuvin 791, were studied in laboratory weathering tests. The samples were exposed to UV-irradiation at doses of 0-950 MJ/m(2) with moisture cycles and programmed temperature and relative humidity in the test chamber. Progress in composites photodegradation was studied by measuring M and MWD determined by gel permeation chromatography and mechanical properties like elongation, tensile stress and notched impact strength. For white composites resistance to yellowing under irradiation was studied. Chalk was found to be the better filler than tale; it stabilized mechanical properties and enhanced color resistance. Additional application of a UV-stabilizer increased the light stability of tested samples, presumably by forming a protective coat on a filler surface that prevented the adverse effect of metals contained in the filler.