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Tensile stresses accelerate the rate of oxidation by ozone of films of polyolefins, high‐density and low‐density polyethylene, and isotactic polypropylene. Experiments have been performed on thin (up to 20 μm) uniaxially oriented films under constant stress σ, under conditions where the chemical kinetics rather than diffusion dominates. It is found that the oxidation rate is proportional to exp(γ′σ/RT) where γ′ is an empirical constant. The effects of unimolecular chain scission and the change of molecular polymer parameters under stress on this dependence are negligible. An analogy with the kinetics of oxidation of stressed cycloparaffins by ozone is noted. A mechanism is suggested to explain the accelerating effect of tensile deformations on chemical processes involving rehybridization of carbon atoms in the main chain from the sp3 to the sp2 state. An ESR study with a stable nitroxyl radical probe revealed a change in the segmental mobility of polymer chains in the course of loading.

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