Gross melt fracture of polyethylene. II: Effects of molecular structure

The effect of molecular structure (MW, MWD and LCB) on the critical tensile stress (σ_c) for the onset of gross melt fracture (OGMF), proposed in Part I (1) as a material‐dependent criterion for fracture, was determined for a group of polyethylenes varying in structure. These included linear low and high‐density polyethylenes and several materials produced using metallocene and constrained geometry catalysts. It was found that the critical stress is independent of M_W, for constant polydispersity but increases with increasing long chain branching and polydispersity. The addition of boron nitride particles had no effect on the σ_c up to a level of 0.5% by weight.