Ozone Resistance

Ozone causes cracking in rubber. Test pieces are usually placed under a small degree of tension e.g. by bending round a mandril or stretching by 5%. The sample is exposed under static conditions to a controlled atmosphere containing ozone (typically 50 pphm).These cracks are graded by standard photographs, by measurements or by description, e.g. visible under "10 x magnification", "visible to the unaided eye" etc. Results may be recorded as the time taken to reach a particular grade of cracking, or by the grade of cracking apparent after a fixed period of time. See ASTM D1149