高性能聚酰亚胺纤维纸层级结构建立与组分单元设计合成研究

High performance insulating paper and paper used for honeycomb structure materials have been dominated by aramid paper such as NOMEX paper for a long time. It is hard to improve the insulating and thermal properties of these papers due to their chemical structure and the electrical and thermal properties of the aramid fiber. Aiming to solve the above problems, this project proposed a new kind of high performance paper prepared by means of a wet papermaking process with polyimide materials as the basic raw materials. High toughness polyimide chopped fiber was used as the reinforcing material, polyimide pulp fabricated from high orientation degree polyimide fiber was used as the physical node, and precipitation fibers made from thermal plastic polyimide resin with lower dielectric permittivity were used as chemical bonding point. Furthermore, the chemical and spatial structure of the matrix, as well as the paper composition, microstructure, and interface situation, were optimized to decrease the dielectric permittivity and enhance insulation performance and heat resistance level. The relationship between chemical structure and the dielectric properties of the PI materials will be discussed. And the connection between chemical structure, orientation, and fibrillation of PI fibers will also be analyzed. Then, the hierarchical structure of the PI fiber paper will be established. Successful implementation of this project will play an important role in promoting high performance paper technology in our country and break the current situation wherein high performance paper is dependent on the import of foreign products.

长期以来，高性能绝缘纸和蜂窝结构用纸一直被以NOMEX纸为代表的芳纶纸所垄断，且由于芳纶的化学结构和电、热性能所限，该类特种纸的电绝缘性能和使用温度的提升空间越来越小。为解决以上问题，本研究提出利用聚酰亚胺(PI)材料为基本原材料，采用高韧性PI短切纤维作为增强材料，设计合成高取向度、高刚性PI纤维制备浆粕作为物理缠结点，设计合成热塑性、低介电、可溶型PI树脂制备沉析纤维作为化学粘结点，通过湿法抄纸技术制备一种全部由PI材料组成的纤维纸。通过各组分化学结构和空间结构的设计以及成纸组分、微观形貌和界面状态的调控，降低纤维纸的介电常数、提高绝缘性能和耐热等级，分析PI材料化学结构与介电性能之间的关系，理清PI纤维化学结构、取向结构与原纤化之间的规律，有效建立PI纤维纸的层级结构。本项目的成功实施对于提升我国在高性能特种纤维纸领域的技术水平，打破目前主要依靠进口国外产品的现状具有重要的作用。

高耐热特种纤维纸一方面可作为耐高温绝缘材料用于大功率电机和变压器绝缘，在高铁、风电等领域具有重要应用，另一方面还是蜂窝夹层支撑结构的关键原材料，在飞机、舰船等装备中可发挥重要作用。高性能聚酰亚胺（PI）纤维具有高强、高模、耐高温、耐老化、低吸湿和低介电、高绝缘等综合性能优势。采用PI纤维作为增强体，通过湿法抄纸工艺制备特种纤维纸，充分发挥PI纤维的综合性能优势，不仅可以有效解决传统芳纶纤维纸易吸湿影响介电、透波性能的不足，还可以进一步提高纤维纸的使用温度、绝缘性能和透波性能，在新一代飞机、舰船等装备中具有很好的应用前景。基于以上背景，本研究重点开展了PI沉析纤维化学结构设计合成研究、微支化交联结构对PI材料介电、力学、CTE等性能的影响研究、PI沉析纤维制备与影响因素研究、PI纤维纸组分配方和制备工艺研究等工作，获得了一种可用于制备沉析纤维的热塑性可溶型PI树脂，提出了一种通过构筑微支化交联结构实现PI材料介电常数和CTE值同步降低的设计思路，初步探索了PI纤维纸的组成结构与基本性能之间的关系，所制备的PI纤维纸抗张指数达到60Nm/g，热分解温度高于500℃。本项目的成功实施，对于促进高性能PI纤维纸发展，进一步提升高性能纤维纸的综合性能，进而带动相关装备升级发展具有重要意义。