Within the injection molding process the molten polymer is forced to extend as it flows through the nozzle and gates. Binding's analytical method was used to quantify an amorphous and semi-crystalline material's resistance to the extensional deformation at the high rate typically experienced in these regions. Conducting these experiments over various temperatures we are able to provide a temperature dependent extensional viscosity for the materials. Using the extensional model developed we are able to provide an improved simulation of the injection molding process.