Effect of Loading-Rate and Hydrolysis on Fracture Mechanism of Poly (L-lactide)

Abstract

Fracture toughness, K_<IC>, of poly (L-lactide) (PLLA) samples having different crystalline structures were evaluated at a quasi-static and impact loading-rate. Static K_<IC> tends to decrease as crystallinity increases, whereas dynamic K_<IC> tends to increase with increase of crystallinity. As a result, for amorphous sample, Static K_<IC> is greater than dynamic one; on the other hand, for highly crystallized sample, the relation is reversed. Effect of hydrolysis on K_<IC> was also examined by hydrolyzing the specimens in phosphate-buffered solution. For both amorphous and crystallized samples, K_<IC> decreases as hydrolysis time increase. SEM and optical micrography were performed to characterize fracture micromechanism. The results of micrographies were when correlated with fracture toughness test result.