Phase separation in bimodal molecular weight high density polyethylene with differing branch contents by molecular dynamics and mesodyn simulation

The phase behavior of bimodal molecular weight high density polyethylene (BHDPE) in solid state was investigated. Hildebrand solubility parameters (δ) were calculated for the models of blends of higher molecular weight branch polyethylene (HBPE) with different branch contents and lower molecular weight linear polyethylene (LLPE), by using molecular dynamics (MD) simulations. These δ values were then used to calculate the corresponding Flory-Huggins interaction parameter (χ) between HBPE and LLPE models. In order to better understand the compatibility between LLPE and various HBPE, Mesodyn simulations were used to show the density profiles of the blends of LLPE with various HBPE at different compositions. The results indicated that the phase behavior of BHDPE was influenced by both the global branch content of the system and the local branch content, i.e., the branch content of HBPE.