Theoretical simulations on the glass transition temperatures and mechanical properties of modified glycidyl azide polymer

Abstract Molecular dynamics (MD) simulations were carried out to study the glass transition temperature and mechanical properties of glycidyl azide polymer (GAP) most widely used in propellants and explosives as an energetic binder. Other three polymers derived from GAP with different side groups were designed and simulated under the COMPASS force field, with the ensembles of constant particle number, volume, temperature (NVT) and constant particle number, pressure, temperature (NPT). It was found that the densities and free volumes of polymers changed regularly along with the decrease of temperature and the transition occurred at the turning point. Thus the glass transition temperatures ( T g ) were predicted in two methods based on density and free volume theory. The simulation results showed that the introduction of –NO 2 made important contribution on reducing the T g of polymers, and the probable mechanism was discussed. Moreover, several mechanical properties of four pure polymer systems such as Young’s modulus, Shear modulus, Bulk modulus and Poisson’s ratio, etc, were calculated. The calculated results revealed that the single introduction of –NO 2 increased the mechanical properties parameters more obviously than other two polymers. Overall, a new method was used for GAP modification in order to improve its mechanical properties at low temperatures, and provides some guidance to the GAP modification via changing substituent groups of side chain.