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, beta w(p), regardless of the molecular weight, decreased upon annealing, and the energy required for cracking, w(e), did not change. On the basis of these results, it is suggested that annealing affects beta w(p) because the density fluctuation is amplified by annealing, and as a result, the strain in the plastic region is concentrated. Moreover, both beta w(p) and w(e) 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 (J(c)), we found that w(e) obtained from the EWF and J(c) was almost the same, indicating that w(e) 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.

Automated summary

The effects of annealing conditions and molecular weight on the energies required for cracking and plastic deformation were investigated. It was found that annealing reduced the energy required for plastic deformation, while the energy required for cracking remained the same. Additionally, increasing the molecular weight increased both the energy required for plastic deformation and cracking.