Wu Yadan, Zhao Wenchen, Liu Yang, Liu Haitao, Yang Minglong, Sun Xun
Science and Technology on Advanced Ceramic Fibers and Composites Laboratory, College of Aerospace Science and Engineering, National University of Defense Technology, Changsha 410073, China.
Polymers (Basel). 2024 Sep 10;16(18):2552. doi: 10.3390/polym16182552.
The thermal stability and aging kinetics of polyimides have garnered significant research attention. As a newly developed class of high thermal stability polyimide, the thermal aging characteristics and degradation kinetics of phenylene-capped polyimide prepolymer (PMR350) have not yet been reported. In this article, the thermo-oxidative stability of PMR350 was investigated systematically. The thermal degradation kinetics of PMR350 resin under different atmospheres were also analyzed using the Flynn-Wall-Ozawa method, the Kissinger-Akahira-Sunose method, and the Friedman method. Thermogravimetric analysis (TGA) results revealed that the 5% thermal decomposition temperature (Td5%) of PMR350 in a nitrogen atmosphere was 29 °C higher than that in air, and the maximum thermal degradation rate was 0.0025%/°C, which is only one-seventh of that observed in air. Isothermal oxidative aging results indicated that the weight loss rate of PMR350 and the time-dependence relationship follow a first-order exponential growth function. PMR350 resin thermal decomposition reaction under air atmosphere includes one stage, with a degradation activation energy of approximately 57 kJ/mol. The reaction model g(α) fits the F model, and the integral form is given by g(α) = 1/(1 - α). In contrast, the thermal decomposition reaction under a nitrogen atmosphere consists of two stages, with degradation activation energies of 240 kJ/mol and 200 kJ/mol, respectively. The reaction models g(α) correspond to the A and D models, with the integral forms represented as g(α) = [-ln(1 - α)] and g(α) = [1 - (1 - α)] due to the oxygen accelerating thermal degradation from multiple perspectives. Moreover, PMR350 resin maintained high hardness and modulus even after thermal aging at 350 °C for 300 h. The results indicate that the resin exhibits excellent resistance to thermal and oxygen aging. This study represents the first systematic analysis of the thermal stability characteristics of PMR350 resin, offering essential theoretical insights and data support for understanding the mechanisms of thermal stability modification in PMR350 and its engineering applications.
聚酰亚胺的热稳定性和老化动力学已引起了大量的研究关注。作为新开发的一类具有高热稳定性的聚酰亚胺，亚苯基封端的聚酰亚胺预聚物（PMR350）的热老化特性和降解动力学尚未见报道。本文系统研究了PMR350的热氧化稳定性。还使用弗林-沃尔-小泽法、基辛格-赤平-ose法和弗里德曼法分析了PMR350树脂在不同气氛下的热降解动力学。热重分析（TGA）结果表明，PMR350在氮气气氛中的5%热分解温度（Td5%）比在空气中高29℃，最大热降解速率为0.0025%/℃，仅为在空气中观察到的速率的七分之一。等温氧化老化结果表明，PMR350的失重率与时间的依赖关系遵循一级指数增长函数。PMR350树脂在空气气氛下的热分解反应包括一个阶段，降解活化能约为57kJ/mol。反应模型g(α)符合F模型，其积分形式为g(α)=1/(1-α)。相比之下，在氮气气氛下的热分解反应由两个阶段组成，降解活化能分别为240kJ/mol和200kJ/mol。反应模型g(α)分别对应A和D模型，由于氧气从多个角度加速热降解，其积分形式表示为g(α)=[-ln(1-α)]和g(α)=[1-(1-α)]。此外，即使在350℃热老化300小时后，PMR350树脂仍保持高硬度和模量。结果表明该树脂表现出优异的抗热和抗氧老化性能。本研究首次对PMR350树脂的热稳定性特征进行了系统分析，为理解PMR350热稳定性改性机理及其工程应用提供了重要的理论见解和数据支持。
