Computer aided simulation of thermoplastic elastomer from poly (vinylidene fluoride)/hydrogenated nitrile rubber blend and its experimental verification

Theoretical understanding of thermoplastic elastomers (TPEs) from rubber-plastics blends is still obscure due to their complexities. Computer simulation would be a very promising method to understand miscibility, thermal transitions and polymer chain dynamics in these systems. As a representative example, novel TPEs prepared from poly (vinylidene fluoride) (PVDF) and hydrogenated nitrile rubber (HNBR) blends were investigated by atomistic and mesoscopic simulations and the results were compared with experiments. The specific volume of PVDF, HNBR and their blends was studied at various temperatures by atomistic simulation to estimate the glass-rubber transition. The estimated glass transition temperatures (T_g) showed good agreement with the experiments. In the blends, two T_gs were observed from both simulation and experiments, which in turn indicated immiscibility of the pristine polymers in the present compositions. Interaction parameter (χ) also suggested the immiscibility for both the blends. Dynamics of polymer chain indicated the lower relaxation rate of PVDF in the blends with respect to the pristine one, which is reflected in reduction of crystallization temperature for the blends. Radial distribution function revealed the separation of PVDF and agglomeration of HNBR chains in the blends owing to the formation of biphasic morphology. Morphology predicted by the Dissipative Particle Dynamics simulation was also in accord with the radial distribution analysis. This was further verified experimentally from microscopic analysis.