基于MD方法的增塑剂扩散行为的模拟研究

Molecular Dynamics Simulation of Plasticizer Diffusion

为克服实验手段的不足,用分子动力学方法模拟丁羟推进剂粘接体系中增塑剂癸二酸二辛酯(DOS)的扩散行为。利用分子模拟软件Materials Studio 4.3构建增塑剂和粘接体系的分子模型,选用COMPASS力场,对经几何优化后的混合体系进行分子动力学模拟,得到增塑剂在粘接体系中的均方位移,通过爱因斯坦方程得到其扩散系数。环境温度为273,298,310,323,348K时,DOS在丁羟推进剂粘接体系中的扩散系数分别为0.0010,0.0020,0.0025,0.0031,0.0043;DOS含量为23%,37.5%,47%,60%时,扩散系数分别为0.0025,0.0020,0.0018,0.0015(单位10-4cm2.s-1)。结果表明:随着温度的升高,扩散系数逐渐增大;随着增塑剂含量的增加,扩散系数依次略有下降。

To overcome the disadvantage of experimental methods, plasticizer diffusion in the bond system of hydroxyl terminated polybutadiene （HTPB） propellant was simulated by the molecular dynamies （MD） method. The molecular models of plastieizer and the bond system were constructed in the software of Materials Studio 4.3. The mixture system performed geometry optimization was simulated under the eondensed-phase optimized moleeular potentials for atomistie simulation studies （COMPASS） foree field. The mean square displaces of plasticizer in the bond system were obtained by statistical average. The plasticizer diffusion was obtained by Einstein equation. The diffusion coefficients （10^-4 em2 · s^-1） of dloetyl sebaeate （DOS） are respectively O. 0010,0. 0020, 0. 0025,0. 0031,0. 0043 at the temperature of 273,298,310,323,348 K; and are respeetively 0.0025,0. 0020,0.0018,0. 0015 at the content of 23%, 37.5% ,47%, 60%. The results show that the diffusion coefficients gradually increase with inereasing of environmental temperature and decrease a little with increasing of the DOS content.