Investigation of the Effect of Strain Rate on Tensile Properties of Polyurethane Using Eyring Model

In the current research, samples of thermoset polyurethane were fabricated through the solution casting method. In order to investigate the effect of strain rate on the mechanical properties of polyurethane, a tensile test was done on standard samples, at ambient temperature and different strain rates (2×10-5 to 2×10-2); and activation enthalpy was obtained by using tensile test results and Eyring model equations. Chemical and thermal characterizations were done by fourier transform infrared spectroscopy, dynamical-mechanical analysis and thermogravimetry. Fracture surface of samples were also studied by scanning electron microscopy. Tensile test results showed that by increasing strain rate, tensile strength and elastic modulus were improved by 80 and 300% respectively, while fracture strain was reduced by more than 50%. It was also evident by investigation of SEM micrographs that the fracture surface of samples was changed to brittle fracture by increasing strain rate. Finally, the amount of activation enthalpy obtained was 45.49 kJ/mol, which is a new result for thermoset polyurethane.