Plane-stress fracture Behavior of syndiotactic polypropylenes of various crystallinity as assessed by the essential work of fracture method

The fracture behavior of 1-mm-thick syndiotactic polypropylene (sPP) sheets of various crystallinity (owing the various stereo- and regioregularity) was studied by the essential work of fracture (EWF) concept. The specific work of fracture parameters were determined on tensile-loaded deeply double-edge notched (DDEN-T) specimens at various deformation rates (v = 1, 10 and 100 mm/min) at ambient temperature. As the DDEN-T specimens showed fun ligament yielding prior to subsequent necking, the energy partitioning method was adopted for data reduction. The specific essential work of fracture slightly increased as a function of crystallinity. Its yielding-related constituent increased with both crystallinity and deformation rate similarly to that of the yield strength and E-modulus. The specific plastic work parameters were less sensitive to crystallinity and deformation rate. The strain-induced crystalline phase transition from helical toward all-trans conformation was accompanied by voiding and crazing.