The strain dependence of the reaction rate of rubbery materials with ozone was discussed on the basis of the activation energy and the strain energy. The stretched molecular chains of rubbery materials can acquire the strain energy to be excited to the higher energy level than that of unstretched molecular chains, which results in the temporary reduction of the activation energy of the degradation reaction. Our theory predicts the spinodal-like transition will occur for the evaluation behavior of the ozone cracks at the higher strain energy. We observed such transition phenomena on the rubbery materials for laminated rubber bearings. The ozone resistance of the rubber material can be predicted by our theory and the experiment in different strain conditions.
