Evaluation of the Service Life of Galvanized Steel Sheet Coated with Polyvinyl Chloride Resin

抄録

This paper report about the evaluation of the service life of a galvanized steel sheet coated with thermoplastic polyvinyl chloride resin and intended for an exterior building material. It can be summarized as follows:
(1) A dew cycle weathering test is the best method as an accelerated weathering test because it gives a high acceleration to deterioration and reveals the similar deteriorated condition to outdoor weathering testing.
(2) It can be safely said that the polyvinyl chloride resin is oxidized and the double bond is formed because of the dechloridization of the polyvinyl chloride resin in the film surface layer.
(3) Of all the deterioration factors, ultraviolet rays and heat are most significant.
(4) Appearance change, physical change, and decrease in adhesion strength between film and steel sheet are caused by the chemical change of the resin.
(5) Although the film surface of polyvinyl chloride resin on a galvanized steel sheet deteriorates, the bulk material does not deteriorate. Accordingly, the evidence accounts for the high corrosion resistance of the film.