Plane‐stress fracture behavior of syndiotactic polypropylenes of various crystallinity as assessed by the essential work of fracture method

Abstract

Abstract 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 full 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.