桐油衍生物固化环氧大豆油过程的交联网络结构演变与固化行为研究

生物基环氧树脂固化过程伴随复杂的交联反应与热物理行为，交联网络结构的演变直接影响热固树脂的理化性能。本项目针对功能性桐油衍生物固化环氧大豆油体系，采用固化实验与分子动力学模拟（MD）相结合，准确构建多官能团环氧植物油固化过程交联网络模型，模拟解析桐油衍生物官能基团、分子结构与植物油共轭环氧基团的分子间相互作用，揭示相应固化反交联化历程的复杂交联网络结构形成及演变行为，获得体系交联密度、自由体积、径向分布函数、玻璃化转变温度、弹性模量等随原子电荷、键级键角的时空变化规律；考察固化反应条件对固化过程及产物性能的影响，获得固化过程微观拓扑结构演变与宏观热/机械性能间的构效关系；进一步结合自催化非等温固化动力学，形成桐油基热固树脂固化行为与性能的调控策略，实现可绕性环氧大豆油/桐油衍生物热固树脂的可控制备。项目研究可为高性能生物基热固树脂产品的理性设计及可控制备提供模型基础和理论指导。

Epoxidized soybean oil (ESO) is the bio-based product from the epoxidation of soybean oil obtained by converting the double bonds into epoxy groups with higher chemical reactivity. It has attracted an increasing attention as a green epoxy resin utilizing the reactive epoxy groups into crosslinking polymers preparation with functional hardeners and initiators, which imply its great potential in industrial process. The presence of conjugated double bonds in molecular chain gives the tung oil (TO) more possibilities for synthesising bio-based functional hardeners as polybasic multiple amines, acids and anhydride through Diels-Alder reactions. However, it is a common agreement that desirable performance of bio-based crosslinking polymers must surely arise from an adequate understanding of the crosslink structure-property relationship of the epoxy matrix..In this project, curing experiments combined with molecular simulation method are employed to investigate the relationship of crosslink structure and thermal mechanical properties in crosslinked TO/ESO based epoxy resin. The effects of molecular structure of TO derivatives and process conditions on the curing behavior and properties of the products will be systematically studied by the results of the different characterization, including the heat release behavior, the changes of free volumes and microstructures with curing degree, the temperatures dependence of the loss factor, thermal properties and mechanical properties by using PALS, DSC, FTIR, DMA, TGA and universal mechanical test machine respectively. And the non-isothermal curing kinetics will be established based on the Zvetkov standard with the heat release behavior of TO/ESO during non-isothermal curing process..Then, Molecular Dynamics simulation method that enables generation of thermoset structures by mapping into Fully Atomistic Representation, is applied to the establishment of cross-linked networks for the curing system with ESO and TO derivatives. After the three-dimension network structure is completed, several thermomechanical properties of the model epoxy will be computed such as the curing induced shrinkage, gelation point, free volume, coefficient of thermal expansion and glass transition temperature (Tg). The effects of crosslink density on total potential energy, angle energy, bond energy and thermomechanical properties will also be investigated. Cohesive energy density (CED) will adopted to analyze the relationship between molecular inter-atomic forces and the Tg, while Radial distribution function (RDF) will be used to analyze the distribution of atoms. Molecular dynamics predictions and experimental results of microstructure and thermo-mechanical properties will be compared to verify the correctness of the model. After that, the curing behaviors of ESO with different TO derivatives will be systematically studied through the molecular dynamic simulation. The effect of curing agent structure on curing behavior and the structure and properties of curing resin will be analyzed..Consequently, the crosslink structure-property relationships for TO-based thermosetting epoxy resins can be obtained which can serve as a guidance for designing high-performance bio-based thermosetting resin.