Computer simulation of thermoplastic elastomers from rubber-plastic blends and comparison with experiments

Computer simulation could be a useful technique to scrutinize the properties of individual polymers as well as their blends. However, there is no work on computer simulation of thermoplastic elastomer from rubber-plastic blends. As representative example, binary compatibility of polyamide 6 (PA6) with fluoroelastomer (FKM) for a 40/60 composition of PA6/FKM thermoplastic elastomer was investigated by atomistic simulation and mesoscale dissipative particle dynamics simulation. The specific volume of PA6, FKM and their blend was studied at various temperatures to estimate the glass-rubber transition. The glass transition temperatures of pristine PA6 and FKM were found to be 336 K and 250 K respectively in line with the experimental values. The blend system displayed two distinct glass transition temperatures (348 K and 254 K for PA6 40FKM 60) as discerned from atomistic simulation. These values were also in agreement with the experimental findings. Two T_gs described immiscibility in the present composition. The Flory-Huggins interaction parameter χ, as determined from atomistic simulation, was estimated to be 0.25, also consistent with the experimental result. Among different potential energy contributions, van der Waals energy and torsion energy showed distinct inflection points for both the pristine polymers and their blend. These inflection points were near the glass transition temperature of the respective polymers. Polymer chain mobility depicted from the mean square displacement emphasized faster relaxation of PA6 over FKM in the blend. Dissipative particle dynamics (mesoscale) simulation suggested phase separation and dispersion of FKM in the PA6 matrix in line with the experimental results.