Effects of Iron Oxide Pigments on Degree of Photodegradation of Polyvinyl Chloride Film on Aluminum Plate

Abstract

As the results of the tests for photodegradation of plasticized polyvinyl chloride on aluminum plate containing several kinds of iron oxide pigments, it was found by electron microscopy and chemical analysis that the remarkable accelerating factors for the photodegradation included impurities such as copper in the oxides in addition to the shapes of oxide particles. Though the shapes, diameters, and manufacturing process of iron oxide particles had no effects on the photodegradation, it was clearly shown that the coagulation of pigment particles was more active in polyvinyl chloride film which had been more photodegraded referring to the relation between the change in shapes of pigment particles and degree of photodegradation of polyvinyl chloride film before and after the outdoor exposure test; and the plasticized polyvinyl chloride containing oxide of greater secondary coagulation characteristics showed a stronger tendency to accelerate the photodegradation. It was also observed by electron microscopy that the photodegradation of polyvinyl chloride film pigmented by iron oxide gradually developed from the irradiated surface to the interior of the film specimen and the degree of degradation was greater when the above developing speed was higher.