Effects of molecular weight and annealing conditions on the essential work of fracture of polycarbonate.

The effects of annealing conditions and molecular weight on the energies required for cracking and plastic deformation were investigated by the essential work of fracture (EWF) method. We found that the energy required for plastic deformation, βwp, regardless of the molecular weight, decreased upon annealing, and the energy required for cracking, we, did not change. On the basis of these results, it is suggested that annealing affects βwp because the density fluctuation is amplified by annealing, and as a result, the strain in the plastic region is concentrated. Moreover, both βwp and we increased with the molecular weight because the increase of molecular weight increases the number of entanglements formed by a molecular chain. In addition, comparing the values of the J‐integral (Jc), we found that we obtained from the EWF and Jc was almost the same, indicating that we obtained from the EWF also involves the energy required for plastic deformation when the deformation around the notch changes from biaxial stretching to uniaxial stretching. [ABSTRACT FROM AUTHOR]