Natural and accelerated weathering of stabilized copolymer ethylene-propylene (low ethylene content)

The photo stability of ethylene-propylene copolymers (low ethylene content) containing different stabilizing systems is investigated. Infrared spectro scopy and elongation at break techniques are used to follow the degradation process under natural and accelerated UV exposure. It is found that the co mbination of antiacid calcium stearate and phenolic antioxidant acts as a p rooxidant. The addition of HALS, particularly the one with low molecular we ight, remarkably improves its performance by in creasing the induction peri od. Subsequent combinations with inorganic filler prove that it is not bene ficial to add CaCO3 and Talc to the stabilizing systems tested herein; both drastically reduce the induction period that is opposite to what was obser ved when TiO2 was added. Contrary, these compounds have apparently no effec t on retention of mechanical properties that change in a very complex manne r. For practical purposes, natural and accelerated weatherings were compared i n 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 polypr opylene sample from measurements in accelerated conditions is related to th e nature of its stabilization system.