Abstract:

It has been found that the mechanical properties of solid propellants and plastic bonded explosives (PBX) depend heavily on the compatibility of the polymer binder and plasticizer used in their formulation. Two systems, one miscible and the other immiscible, were simulated by molecular dynamics (MD) simulations to test the usefulness of this molecular simulation technique. Density, cohesive energy density, and solubility parameters of hydroxyl-terminated polybutadiene (HTPB), dioctyl sebacate(DOS), nitroglycerine (NG), HTPB/DOS blend and HTPB/NG blend were calculated by MD simulations with the COMPASS force field for the prediction of polymer binder and plasticizer compatibility. Results show that HTPB/DOS is a miscible system but HTPB/NG is not miscible by comparing the difference in the solubility parameter value (△δ), pair correlation function and the change of density. The predictions agreed well with experimental observations. By calculating the pair correlation function the HTPB/plasticizer interaction was clarified. Therefore, the method used in this work is a useful tool to provide information on miscibility and other properties of a given polymer/plasticizer blend. In addition, it is a promising technique to help to design formulations for screening solid propellants and PBX before experimental tests.

Key words: Hydroxyl-terminated polybutadiene, Plasticizer, Compatibility, Molecular dynamics simulation, Pair correlation function