Abstract
Rubber and plastic sheets installed on roofs are subjected to many elements of weathering, such as heat, radiation, moisture, gases and so on. The effect of heat was early recogninzed and discussed that the life of materials decrease according to increase the temperature of them. Many investigations have been reported on the method of estimating the life of electrical materials by thermal aging, based on the theory of chemical reaction rate. It is assumed in these investions that the materials obey a first order reaction rate. Almost the same method is often applied for estimating the degradation of organic building materials such as rubber and plastics in our country, in these days. The authors carried out the test of rubber and plastic sheets for roof covering, based on the theory of chemical reaction rate. Then, it has become clear that the materials do not always obey a first order reaction rate, and that a suitable reaction order for each materials must be determined to estimate the degradation of the material. In this report, the equations expressing the degree of degradation of rubber and plastic sheets foof covering have been developed, considering suitable reaction orders through thermal agins tests at four different temperatures, and calculated values by the equations/ obtained were compared with experimental values.
