Abstract
The roofing membranes are often exposed outdoors under the condition of being stretched when they are applied on roof decks of less rigidity, for instance, the decks which are constructed with prefabricated roof panels, or which easily crack. It is said that these materials are deteriorated by weathering especially in case of being stretched. Therefore, it is important to make clear the weatherability of these materials under the condition of being stretched. The test were carried out from two different standpoints, one was wetherability of the materials themselves, and the other concearned the roof systems composed of them. Dumbbell specimens of the materials were exposed in Tokyo and Sapporo under tension, and specimens of roof systems were also exposed in both exposure sites, under the condition that joints in substrates of the roof systems were opened or sheared. The results obtained may be summarised as follows. Generally speaking, the lower the strain, the shorter the cracking and breaking times and the effect of outdoor exposure is severer in Tokyo than Sapporo. The same tendency can be seen in specimens of roof systems, the wider the joints, the shorter the cracking and breaking times in the same roof systems. Cracking has not been detected in some membrane which was flexibly bonded on substrate, though considerable cracking was detected in the same membrane rigidly bonded and in the streched dumbbells.
