Department of Aircraft Engineering, Naval Aviation University, Yantai 264001, China.
School of Physics and Optoelectronic Engineering, Ludong University, Yantai 264001, China.
Molecules. 2023 Feb 14;28(4):1792. doi: 10.3390/molecules28041792.
Polyethylene glycols (PEG) and toluene diisocyanate (TDI) are often used as the main components of binders and curing agents in solid propellants, and their aging is an important issue in the storage and use of propellants. To study the aging behavior and aging mechanism of nitrate ester plasticized polyether propellant (NEPE) matrix during storage, the transition states of aging reactions of binder and curing agent were optimized at the (U)B3LYP/6-311G(d,p) level of theory, and the rate coefficients over the temperature range of 298-1000 K were calculated by CVT theory. The results showed that there were five kinds of aging reactions for binder, which included decomposition, nitration, H abstraction, oxidation, and crosslinking reactions. Among them, theenergy barriers of oxidation and H abstraction reactions were relatively low (79.3-91.2 kJ·mol) and the main reaction types of binder aging. The main aging reaction of curing agent was decomposition. Compared with the aging reactions of binder, the energy barriers of curing agent are higher (196.6-282.7 kJ·mol) and the reaction is more difficult to occur. By comparing the energy barriers and rate constants of different reactions, it is found that the aging of NEPE propellant matrix can be divided into two stages. In the first stage, the propellant matrix mainly undergoes H abstraction and oxidation reaction, and as the reaction proceeds, the products crosslink to form -O-O-, -C-C-, and -C-O-C- bonds. At this time, the long chain molecules of the propellant matrix crosslink, and the molecular weight increases. This stage corresponds to the rising stage of mechanical properties in the aging process of the propellant. In the second stage, the propellant matrix mainly undergoes decomposition and nitration, resulting in degradation, the reduction of molecular weights, and the appearance of holes and microcracks in the matrix. This stage corresponds to the decline of mechanical properties in the aging process of the propellant. The above simulation results are in good agreement with the aging experimental phenomena, revealing the microscopic mechanism of the changes in the macroscopic properties of NEPE propellant during the aging process, and providing a theoretical basis for the related research on the aging properties and anti-aging technology of NEPE propellant.
聚乙二醇（PEG）和甲苯二异氰酸酯（TDI）通常用作固体推进剂中粘合剂和固化剂的主要成分，它们的老化是推进剂储存和使用中的一个重要问题。为了研究硝酯增塑聚醚推进剂（NEPE）基体在储存过程中的老化行为和老化机理，在（U）B3LYP/6-311G（d，p）理论水平下优化了粘合剂和固化剂老化反应的过渡态，并通过 CVT 理论计算了在 298-1000 K 温度范围内的速率系数。结果表明，粘合剂有五种老化反应，包括分解、硝化、H 提取、氧化和交联反应。其中，氧化和 H 提取反应的能垒相对较低（79.3-91.2 kJ·mol），是粘合剂老化的主要反应类型。固化剂的主要老化反应是分解。与粘合剂的老化反应相比，固化剂的能垒较高（196.6-282.7 kJ·mol），反应更难发生。通过比较不同反应的能垒和速率常数，发现 NEPE 推进剂基体的老化可以分为两个阶段。在第一阶段，推进剂基体主要经历 H 提取和氧化反应，随着反应的进行，产物交联形成-O-O-、-C-C-和-C-O-C-键。此时，推进剂基体的长链分子交联，分子量增加。这一阶段对应于推进剂老化过程中力学性能的上升阶段。在第二阶段，推进剂基体主要经历分解和硝化，导致降解、分子量降低以及基体中出现孔和微裂纹。这一阶段对应于推进剂老化过程中力学性能的下降阶段。上述模拟结果与老化实验现象吻合较好，揭示了 NEPE 推进剂在老化过程中宏观性能变化的微观机理，为 NEPE 推进剂老化性能和抗老化技术的相关研究提供了理论依据。
