新型加成固化型硼、硅协同分子级杂化酚醛树脂的设计、制备与性能研究

With rapid development of modern aerospace technology, new type spacecraft would run in aerobic environment for long time. Under this new kind of ablative environment, conventional phenolic resin can't meet the requirement of thermal protection system because of its low char-yielding property and poor thermo-oxidative stability. Therefore, it is imperative to develop novel anti-ablative resin with high performance. This project mainly focused on design, preparation and correlation study between structure and property of a novel addition-curable hybrid phenolic resin containing silicon and boron element with molecule level uniform distribution. Vinyl functional groups were introduced into phenolic structure by modification of hydroxyl groups to endow the hybrid resin with characteristics of addition cure. The silicon and boron element were connected into phenolic structure with chemical bonds and formed uniform distribution at molecule level, which imparts the hybrid resin excellent thermo-oxidative stability. A series of hybrid resin with different molecular structure and Si/B content were prepared by controlling reaction condition. After completing synthesis, characterization and property evaluation, in this project, further study was carried on cure mechanism, carbonization behavior and high temperature pyrolysis of the hybrid resin to reveal the correlation with its ablative property. Completion of the project would provide a practicable new approach to prepare high performance matrix for anti-ablative and high temperature resistant composites, showing a promising application propect of the hybrid resin in high technology fields.

现代宇航技术的飞速发展要求飞行器在有氧环境下、长时间飞行，传统酚醛树脂因残碳率低、不抗氧化等问题已难以满足其热防护的要求，迫切需要开发新型高性能的耐烧蚀树脂。本项目从分子结构设计的角度出发，通过调控反应条件，制备了硅、硼协同杂化的加成固化型酚醛树脂，并系统开展了其结构与性能关系研究。本项目通过酚羟基修饰的方法把乙烯基引入到树脂结构中，通过其热聚合实现了酚醛树脂的加成固化；以化学键的方式把硅和硼元素嫁接到树脂结构中，实现了该元素的分子级均匀分散，赋予了树脂优良的热氧稳定性。在完成树脂合成、表征及性能评价的基础上，本项目进一步开展了树脂的固化机理、碳化行为、高温裂解规律研究，阐述了其分子结构、固化物性能、碳化裂解规律与烧蚀性能的相关性。本项目的顺利完成为新型耐高温、耐烧蚀、抗氧化的高性能树脂的制备开辟一条可行的新途径，有望在我国的烧蚀防热等高技术领域获得应用。

针对传统酚醛树脂因残碳率低、抗氧化性能差，难以满足有氧、长时间烧蚀环境使用要求的问题，本项目设计并制备了硼、硅协同杂化酚醛树脂（BSPF）。完成了BSPF树脂的结构表征与合成工艺优化，系统地研究了该树脂的工艺性能、固化行为、热稳定性和抗氧化性能。研究结果表明，BSPF树脂具有优良的加工和固化工艺性能，通过乙烯基官能团的引入及其热聚合反应实现了树脂的加成固化，解决了传统酚醛树脂缩合反应导致的固化过程释放小分子的问题。BSPF分子结构中引入的分子级均匀分散的硼元素和硅元素及其协同作用，大幅提升了树脂的高温质量保留率和抗氧化性能。TGA的结果表明，BSPF氮气氛围下900℃下的质量保留率可达到87%，按比例计算较传统酚提高约45%；空气测试条件下，相对传统酚醛树脂，BSPF树脂的热分解行为明显向高温方向移动， 800℃下传统酚醛树脂已经分解完全，而BSPF的质量保留率仍高达约80%。SEM和XRD的结果表明，BSPF树脂在高温、有氧的条件下发生裂解时，树脂中的硼元素会形成低熔点的氧化硼组分，该组分的形成可以封堵因树脂有机组分分解而形成的微裂纹，进一步抑制氧气向树脂内部的扩散，从而对基体树脂的碳元素形成保护，更高的温度下树脂中的硅元素会形成合成碳化硅，硼和硅协同作用提升了树脂的抗氧化性能。高硅氧/BSPF树脂复合材料氧乙炔焰烧蚀试验评价的结果表明其线烧蚀率和质量烧蚀率分别为0.118mm/s和0.071g/s，明显低于传统酚醛树脂，说明BSPF树脂是一种新型高性能的耐烧蚀树脂，本项目为新型耐高温、耐烧蚀、抗氧化的高性能树脂的制备开辟一条可行的新途径，并有望在我国的烧蚀防热等高技术领域获得应用，实现了预期的研究目标。