Shi La, Ren Li, Li Yang, Fu Xiaolong, Meng Saiqin, Wang Jiangning
Xi'an Modern Chemistry Research Institute Xi'an 710065 China
RSC Adv. 2022 Jun 1;12(25):16319-16328. doi: 10.1039/d2ra02692a. eCollection 2022 May 23.
In this study, the crosslinking structures of nitrate ester plasticized polyether (NEPE) binders were constructed by a computational procedure. Based on the final crosslinking models, the glass transition temperatures, mechanical properties, and thermal expansion coefficients of polyethylene glycol400/multi-functional isocyanate (PEG400/N-100), polyethylene glycol400/toluene diisocyanate (PEG400/HDI), polyethylene glycol400/hexamethylene diisocyanate (PEG400/TDI) and polyethylene glycol400/isophorone diisocyanate (PEG400/IPDI) models were simulated by molecular dynamics, and could be confirmed by experiments. Then the bond-length distributions, conformation properties and cohesive energy densities were used to analyze in detail how the different cured structures influenced the mechanical and thermal properties. Furthermore, the radial distribution function, mean square radius of gyration, volume shrinkage and fraction free volume were calculated, which could directly explain the relationships between the intermolecular chains and macroscopical properties of the NEPE binders. Lastly, PEG400/N-100 and PEG400/HDI systems were chosen for the experiments. The dynamic mechanical analysis results explained that PEG400-HDI showed better flexibility and its value was 45 °C lower than that of PEG400-N100. The mechanical properties illustrated that the ultimate tensile strength and Young's modulus of PEG400/N-100 were both to an extent higher than that of PEG400/HDI in the temperature range of -40 °C to 50 °C, according to the results provided by a universal tensile test machine. The experimental results were in good agreement with the simulation analysis. This work can help us to have an efficient comprehension on the crosslinking structures and micro-property relationships of the NEPE binders and act as a guidance for designing applicable polyurethanes in propellant applications.
在本研究中，通过计算程序构建了硝酸酯增塑聚醚（NEPE）粘合剂的交联结构。基于最终的交联模型，采用分子动力学模拟了聚乙二醇400/多官能异氰酸酯（PEG400/N-100）、聚乙二醇400/甲苯二异氰酸酯（PEG400/HDI）、聚乙二醇400/六亚甲基二异氰酸酯（PEG400/TDI）和聚乙二醇400/异佛尔酮二异氰酸酯（PEG400/IPDI）模型的玻璃化转变温度、力学性能和热膨胀系数，并可通过实验进行验证。然后，利用键长分布、构象性质和内聚能密度详细分析了不同固化结构对力学和热性能的影响。此外，还计算了径向分布函数、均方回转半径、体积收缩率和自由体积分数，这些可以直接解释NEPE粘合剂分子间链与宏观性能之间的关系。最后，选择PEG400/N-100和PEG400/HDI体系进行实验。动态力学分析结果表明，PEG400-HDI表现出更好的柔韧性，其 值比PEG-400-N100低45℃。根据万能拉伸试验机提供的结果，力学性能表明，在-40℃至50℃的温度范围内，PEG400/N-100的极限拉伸强度和杨氏模量在一定程度上均高于PEG400/HDI。实验结果与模拟分析结果吻合良好。这项工作有助于我们有效地理解NEPE粘合剂的交联结构和微观性能关系，并为推进剂应用中适用聚氨酯的设计提供指导。
