Effects of molding temperatures on aqueous fatigue behavior of polycarbonate

Fatigue behavior of polycarbonate was investigated to evaluate its potenitial as a material for prosthetic heart valves. Smooth and notched small cantilever specimens were injection molded using various combinations of cylinder and mold temperates. Fatigue testing was conducted in a machine specifically designed to accommodate multipe specimens inliquid environments. Results presented herein are for water immersion. The fatigue lives fell on Weibull distributions with nonzero minimum-life parameters. S-N equations were fitted at constant probabilities of failure; most of these had nonzero fatigue-limit parameters. Polycarbonate fatigue strengths, of notched spcimens particularly, were greatly influenced by cylinder and mold temperatures. Notch sensitivities varied from very low to quite high. These effects were attributed to molecular orientation and residual stresses.