HTPB推进剂中增塑剂扩散系数计算

针对丁羟推进剂/衬层界面增塑剂的迁移问题,研究增塑剂的扩散特性。采用分子动力学方法模拟增塑剂在丁羟粘合剂体系中的运动,再通过爱因斯坦关系式求得扩散系数;采用对衬层加厚的粘接试件进行加速老化实验方法,再通过费克第二定律计算得到增塑剂的扩散系数;考察不同环境温度和不同增塑剂含量条件下癸二酸二辛酯的扩散系数的变化。分析认为,增塑剂在丁羟粘合体系高分子链段运动产生的间隙中,以"跳跃"方式发生空间位置迁移。结果表明,扩散系数模拟值和实验值基本一致,数量级为10-12m2/s;温度升高,增塑剂运动活性加强,有效活动空间增大,扩散系数增大;粘合体系与增塑剂的共容限量使得增塑剂含量大于3%时,模拟得到的扩散系数依次略有下降。分子动力学方法计算增塑剂扩散系数更具优势。

Measurement of diffusion coefficient of plasticizer in HTPB propellant

Aiming at the plasticizer migration in the interface between HTPB propellant and liner,the diffusibility of plasticizer was studied.The diffusion coefficients were obtained by two methods.Firstly,plasticizer diffusivity in the bond system of HTPB propellant was simulated by the molecular dynamics method and the diffusion coefficient was obtained by Einstein equation.Secondly,taking the bonding interface of propellant and thickening liner as the object,the accelerated migration test of plasticizer was performed and the diffusion coefficient was obtained by the second law(Fick).The diffusion coefficients of dioctyl sebacate were discussed under different temperatures and at different contents of plasticizer.It was analyzed that plasticizer migrated by jump on the space situation which were produced when macromolecule chain moved in the HTPB bond system.The results indicated that the magnitude order of DOS diffusion coefficient was 10-12 m2/s.The diffusion coefficients gradually increased with increasing of environmental temperature because of more intense activity and larger active space of plasticizer.Yet the diffusion coefficients decreased a little with the increasing of DOS content when content was more than 3%.It is more advantageous to measure diffusion coefficient of plasticizer by molecule dynamics.