EVALUATION OF CRACK DEPTH EVOLUTION BY OZONE DEGRADATION OF NATURAL RUBBER BEARING

Abstract

 Evolution of crack depth formed by ozone degradation is studied by laser microscopy that enables the simultaneous measurements of the depth, the number density and the length. The depth evolution depends on the ozone concentration of atmosphere CO₃ and the elongation rate of rubber α. Time dependency of the crack depth is well correlated by a parameter, t∙CO₃ / α², where t is the exposure time to ozone, except for the extreme small elongation rate. The depth can be evaluated from the crack length, that is easily measured at the surface, by a scaling law, while the length is under growing. Even after it stops, the depth is still developed.