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Abstract
The photo stability of ethylene-propylene copolymers (low ethylene content) containing different stabilizing systems is investigated. Infrared spectroscopy and elongation at break techniques are used to follow the degradation process under natural and accelerated UV exposure. It is found that the combination of antiacid calcium stearate and phenolic antioxidant acts as a pro-oxidant. The addition of HALS, particularly the one with low molecular weight, remarkably improves its performance by in creasing the induction period. Subsequent combinations with inorganic filler prove that it is not beneficial to add CaCO3 and Talc to the stabilizing systems tested herein; both drastically reduce the induction period that is opposite to what was observed when TiO2 was added. Contrary, these compounds have apparently no effect on retention of mechanical properties that change in a very complex manner.
For practical purposes, natural and accelerated weatherings were compared in the determination of the accelerated factor of the UV exposure device. It varies in a wide range (from 4 to more than 25) depending on the nature of the additive system. Then the prediction of the natural lifetime of polypropylene sample from measurements in accelerated conditions is related to the nature of its stabilization system.