Fracture Behavior of Polyurethane-Calcium Chloride Blends

Abstract

Two polyurethanes and their respective 1,5, and 10 wt.% CaCl2 blends were studied. The normalized strain energy (J-) was used to characterize the fracture susceptibility of films made from the polyurethane-calcium blends. The low normalized strain energy is correlated with ease of fracture. The normalized strain energy to failure for all the Biomer®-calcium chloride blends throughout the entire range of crack lengths was less than observed for the pure Biomer. The normalized strain energy values obtained for the Biomer-1 wt.% CaCl2 were comparatively lower than all other Biomer blends. At concentrations of 5 and 10 wt.%, there was some evidence that increase in the normalized strain energy to failure could be attributed to plasticization and crack arresting behavior of the calcium chloride dissolved in the matrix. The normalized strain energy values for calcium chloride blended with Pellethane® were different above and below the critical crack length. For initial crack lengths less than the critical length, the normalized strain energy for the Pellethane-calcium chloride blends were less than for pure Pellethane. At cracks larger than the critical length, the Pellethane-calcium blends displayed greater normalized strain energy to failure. The addition of a small amount of calcium chloride to Biomer and Pellethane leads to a reduction in the normalized strain energy which can be associated with lower fracture toughness. Pellethane appeared to be more susceptible than Biomer to the deterioration of its fracture properties.