Temperature dependence of crack-propagation parameters and crack morphology of the semicrystalline polyester poly(1,4-dimethylene-rans-cyclohexyl suberate)

Temperature-dependent crack propagation in the semicrystalline polymer poly(1,4-dimethylene-trans-cyclohexyl suberate) was studied as a function of forming temperature (spherulitic morphology) and molecular weight. All experiments were conducted between the glass transition temperature and the crystal melting point. Higher forming temperature (larger spherulitic size) produced lower energy to propagate (G_p). For a given morphology (single forming temperature), increasing the propagation temperature decreased the propagation energy. An equation relating G_p to the microscopic viscosity of the amorphous polymer fraction was derived. Experimental data were fitted to the equation, and Arrhenius activation energies for microscopic flow were obtained. The results show a decrease in activation energy with increased forming temperature and molecular weight, and are discussed in terms of lamellar tie-molecule population. Fracture morphology is related to thermal parameters and chain entanglements. The results indicate that much of G_p is due to plastic deformation.