Molecular dynamics and mesoscopic dynamics simulations for prediction of miscibility in polypropylene/polyamide-11 blends

The miscibility of polypropylene (PP)/polyamide-11 (PA11) blends were investigated by atomistic molecular dynamics (MD) and mesoscopic dynamics (MesoDyn) simulations. Five PP/PA11 blends (with the weight ratio at 90/10, 70/30, 50/50, 30/70 and 10/90) as well as pure PP and PA11 were examined. The Flory–Huggins interaction parameters, χ, which were computed for different blends and determined from the cohesive energy densities, were computed for different blends using atomistic simulations to predict blend miscibility. It was found that in the case of 90/10 PP/PA11 blend, miscibility was normally observed, but immiscibility was prevalent at higher compositions of PA11 component. The radial distribution functions g(r) of the inter-molecular carbon atomic pairs of PP–PA11, PP–PP and PA11–PA11 also indicate that 90/10 PP/PA11 is miscible, but at other compositions, these blends are immiscible. Kinetics of phase separation was examined by using density profiles calculated from the MesoDyn approach to examine miscibility/immiscibility aspects of the blends. All the simulations results are qualitatively consistent with the experimental results, and demonstrate that the modeling strategies in this study may provide a powerful tool for predicting miscibility and mesoscopic morphology of polymer blends.