The Influence of Molecular Weight and Comonomer on the Shear Creep of Polyethylene

The occurrence of shear creep in polyethylene under applied stress results in deformation, which restricts the service life of the final product. However, the factors influencing shear creep and its underlying mechanisms remain unclear. This article investigates the effects of average molecular weight and comonomer on the shear creep behavior and underlying mechanisms of high-density polyethylene (HDPE). The materials chosen were HDPE with weight-average molecular weights (Mw) of 148,100, 191,800, 226,500, 252,700 and 325,100 g/mol, as well as copolymers incorporating propylene or octene as comonomers. The results indicate that creep deformation decreases with increasing Mw, and that polyethylene copolymers incorporating propylene and octene cause increased creep deformation compared to homopolymers. Dynamic mechanical analysis (DMA) and rheological testing were used to investigate the influence of Mw and comonomer on shear creep behavior. The experimental results demonstrate that increasing the weight-average molecular weight enhances molecular chain entanglement, thereby improving creep resistance. The incorporation of comonomers introduces branches into the polyethylene structure, reducing entanglement density and leading to diminished creep resistance. This study provides valuable insights and references for the development of polyethylene materials that resist shear creep.