This study aimed to establish a quantitative evaluation method for the evaluation of ozone cracks in accordance with JIS K 6259-1. Natural and chloroprene rubber without antiozonants were exposed to ozone, and crack length, width, and depth were analyzed three-dimensionally using a laser microscope. Distinct differences in crack morphology were observed between the two rubbers. Crack propagation occurred in two stages: a proportional “single stage” of depth and length and a “linkage stage” where length increased rapidly. Crack depth shape changes were related to condition rank: higher ranks showed more pot-bottom-like and asymmetrical shapes. These results suggest that the JIS method, based only on crack number and length, may not sufficiently reflect crack severity.
