Effect of Submicron Structures on the Mechanical Behavior of Polyethylene

Changes in submicron structures were found to affect the yielding behavior of polyethylene (PE) during tensile testing.The spatial inhomogeneity of the stress fields associated with density or crystallinity fluctuations on the submicron scaleenhanced the density fluctuation by a viscoelastic effect during stretching, resulting in the generation of voids. The amplitude of the spatial inhomogeneity of the submicron-scale stress field in linear low-density polyethylene (LLDPE) was smaller than that in high-density polyethylene (HDPE) due to the lower stability of the lamellar structures in the LLDPE under stretching. Thus, in the LLDPE case, the generation of voids and necking occurred after the enhancement started so that the LLDPE exhibited two yield points associated with the enhancement of the fluctuation and the generation and enhancement of voids on a stress-strain curve. On the other hand, the enhancement and generation and enhancement of voids occurred simultaneously in the HDPE, so the HDPE exhibited one yield point.