抄録
This paper deals with the estimation of thermal effect of weather on rubber and plastic sheets for roof membranes. Equations are first obtained which express the degradation of the sheets of monotonous property-changing, through thermal aging tests at constant temperatures, being based on the theory of chemical reaction rate. The equations have been proved to be valid to express the degradation of the sheets in the fields of varying temperature which are simplified conditions of the actual circumstance. Then, the authors try to express the degradation of the sheets exposed under the conditions of four kinds for three years at Tsukuba, northeast of Tokyo. The calculated and observed values of rubber sheets show a fairly good accordance each other. It may be concluded, therefore, that the rubber sheets are mainly degraded by the thermal effect of weather, and the degree of the degradation can be quantatively estimated by the equations. There exist some differences, however, between the calculated and observed values of the sheets of plasticized polyvinyl chloride. Therefore, the other elements of weather such as solar radiation and so on must be taken into account in order to estimate the degradation of these materials.
