基于热可逆共价化学的木塑复合材料蠕变与热变形调控

以木质纤维与热塑性聚合物为主要原料制备的木塑复合材料（木塑），当长期受荷重和热负荷时，由于线型聚合物固有的粘弹特性而易产生蠕变和热变形，严重影响其使用性能。因而抗蠕变和热变形是木塑产业界面临的重大技术瓶颈，也是学术界关注的核心科学问题。本项目提出将热可逆共价交联网络引入木塑体系中，实现加工温度下可高效塑化，使用温度下可永久交联，从而维持结构稳定，抗蠕变且热可塑。采用固体核磁、显微拉曼、红外光谱等原位变温技术，研究热可逆共价交联体系在升降温过程中拓扑结构的动态化学键演化，采用热分析和流变仪研究可逆转变的热力学和动力学，通过蠕变和热膨胀试验及有限元分析研究木塑抗蠕变和热变形性能。揭示热可逆共价交联单体结构与交联密度等因素对拓扑结构重组温度和交换反应动力学速率、木塑流变特性、抗蠕变、抗热变形等的影响规律，阐明热可逆共价交联网络调控木塑蠕变和热变形的新机制，为高抗蠕变抗热变形木塑技术提供科学依据。

Wood-plastic composite (WPC) fabricated with lignocellulosic fibers and thermoplastics, will undergo creep and thermal deformation when it is subjected to long-term external forces and heat load. This is due to the intrinsic viscoelastic properties of linear macromolecular chains ascribed to their thermodynamic movement. The existence of creep and thermal deformation is the fatal defect of WPC, which restricts its popularization and application. Therefore, increasing the creep resistance and thermal stability is an international technique and academic problem needed to be attacked in both industry and academia. In this project, thermally reversible covalent crosslinked polymer networks will be introduced into WPC. The reversibly crosslinked WPC can be efficiently plasticized at high temperatures and permanently crosslinked at service temperatures, showing remarkable reprocessability, mechanical properties, creep resistance, and thermal stability. In situ variable-temperature high-resolution 13C solid-state NMR, micro-Raman, and FTIR will be used to follow the evolution of dynamic covalent bonds of crosslinked polyolefin networks during thermal cycles. The thermodynamic analysis and kinetics of the crosslinked networks will be characterized by thermal analysis technique. The creep resistance and thermal deformation of the WPC will be tested and simulated by finite element analysis. The influence of reversible covalent bond type, monomer structure, and crosslinking density on the temperature and kinetic rate of topology reconstruction, rheological behavior of WPC melt, crystallization behavior, creep resistance, and thermal deformation of WPC will be revealed. The new mechanism of creep and thermal deformation of WPC regulated by the thermally reversible covalent crosslinked polymer networks will be elucidated. This will provide a theoretical basis for WPC technology with high creep and thermal deformation resistance.