Rate of Stress-activated Chain Scission

From a chemical viewpoint, bond scission under stress is a particular case of a un-imolecular dissociation reaction whose rate is enhanced by mechanical stress. As such, it could be treated with Eyring s transition-state theory [Eq. (37)], which permits one to bring the treatment of rate processes within the scope of thermodynamic arguments. By combining de Boer s thermodynamic formulation and the transition-state theory, Tobolsky and Eyring in 1943 developed the rate theory for thermally activated fracture of polymeric threads. When put into an Arrhenius- 

Several attempts to relate the rate for bond scission (kc) to the molecular stress have been reported over the years. The simplest and still the most popular is a linear relationship [Eq. (83)] between the decrease in activation energy and molecular stress [42]. 

The factor p has the dimension of volume and is identified as the activation volume for the reaction. 

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