自增韧增强可降解自交联超支化环氧树脂的制备、性能及自交联和降解机理

Design of self-crosslinkable single component epoxy resins with high performance and degradation properties are the key challenge to the development of environmentally-friendly epoxy resins. Based mainly on aromatic amine and isocyanate, single component hyperbranched epoxy resins (DHEP) bearing carbamate and hexahydrotriazine groups, which possess multifunctional properties, including self-toughening and reinforcing, self-crosslinking and degradability, will be prepared. Diamine degraded directly from carbamate will be used to crosslink the epoxy resin, and hexahydrotriazine group can be degraded by using acid as catalyst and reused as curing agent. We will study the effect of micro-structure (component, molecular weight and epoxy value) on the stability and self-crosslinking property, as well as the mechanical and degradable performance of cured DHEP, and will study the curing-driven phase separation and self-toughening and reinforcing mechanism. Degradation mechanism and self-crosslinking mechanism of the DHEP will be elucidated by studying factors including breaking energy, degradation temperature and crosslinking reaction heat of carbamate structure. The degradation and recycling mechanism of the cured DHEP will also be explored by studying factors such as breaking energy, degradation temperature, recyclates component of the hexahydrotriazine structure, and recycling efficiency of the recyclates for the curing of epoxy resins. Through the above research, a novel approach for preparing DHEP with degradable and self-crosslinkable properties will be obtained, and the effect of the micro-structures of DHEP on the degradation-driven self-crosslinking curing reaction of carbamate group of DHEP, and degradation behavior of hexahydrotriazine group, as well as their mechanism, in cured DHEP and recycling efficiency will also be elucidated. This work may serve as an important recognition and fundamental theoretical guidance for the design and preparation of self-crosslinking single-component degradable epoxy resins and recycling.

自交联单组分高性能环氧树脂的设计制备和降解循环利用是其环境友好发展的关键科学问题。本项目拟以芳香胺、异氰酸酯为主要原料制备含氨基甲酸酯和环三嗪结构的自增韧增强、可降解自交联的单组分超支化环氧树脂（DHEP），氨基甲酸酯基热解产生二元胺交联固化环氧树脂，环三嗪基酸性降解实现其循环利用。研究微观结构（组成、分子量和环氧值）对DHEP的稳定性、自交联行为及其固化后的机械和降解性能的影响规律，分析自交联固化诱导微观相分离过程和自增韧增强机理；研究氨基甲酸酯基团的断裂能、热解温度、自交联反应热的影响规律，探索热解机理和自交联机理；研究环三嗪基的断裂能、降解温度、降解产物组成及再固化环氧树脂的循环利用效率及影响规律，探索降解机理。将获得DHEP的制备工艺，明确DHEP的微观结构对其热解自交联和降解反应及循环利用效率的影响规律和机理，对自交联单组分环氧树脂的设计、降解循环利用提供规律性认识和理论。

自交联单组分高性能环氧树脂的设计制备和降解循环利用是环氧树脂环境友好发展的关键科学难题。针对这些挑战，本项目以芳香胺、异氰酸酯为主要原料制备了微观结构（支化度和环氧值）可控的自增韧增强、可降解自交联的单组分超支化环氧树脂（DHEP），研究并获得了环氧树脂的微观结构对DHEP流变性能和机械性能的影响规律，发现了支化度和环氧值中等的环氧树脂综合性能最好。在此基础上，为深入研究环氧树脂降解和循环利用的影响因素和规律，合成和详细表征了不同化学结构（聚酯、柠檬酸生物基、六氢均三嗪基和异氰酸酯基）的自交联可降解超支化环氧树脂，详细研究了不同结构对其自交联固化体系自增韧增强机理、降解机理及循环利用效率的影响规律。获得了以下规律和认识：几种超支化环氧树脂对双酚A型环氧树脂均有明显的增强增韧功能，超支化的拓扑结构能显著提高双酚A型环氧树脂的降解性能和流变性能；异氰酸酯基的引入可实现环氧树脂的自固化特性；聚酯和柠檬酸生物基结构的引入，可使超支化环氧树脂固化物能在较温和的条件（90℃/2h）完全降解；六氢均三嗪结构的引入可获得耐磨性、铅笔硬度、附着力和热性能优异的超支化环氧树脂，且其固化物能够在相对环境友好的条件（磷酸溶液）完全降解，降解的产物经分离提纯能高效回收和循环利用。本项目的研究为设计合成综合性能优异的环氧树脂提供了思路，为环氧树脂及其复合材料的降解和循环利用提供了重要的实验数据、规律性认识和理论基础，有助于环氧树脂产业和行业的健康发展。