基于可逆共价键构筑自修复和可重塑橡胶纳米复合材料

Reinforcement, recycling and functional application are three important issues in rubber science and engineering. Traditional rubber products exhibit irreversible covalent cross-linking network, which make the recycling and self-healing of rubber products inherently difficult. In this project, nano-silica, for high-performance rubber, is chosen as filler. Carboxyl groups is grafted onto the surface of nano-silica. Dynamic reversible covalent bonds are constructed between the rubber molecules and at the filler-rubber interface simultaneously through the interaction between the epoxy groups and carboxyl groups. To meet the growing demand for high-performance materials, nanofiller (silica) is incorporated into rubber to improve the mechanical properties. Transesterification reactions at elevated temperature is used to introduce the self-healing and recycling abilities. The constructed method and relationship between structure and properties of modified nano-silica will be intensive verified. Moreover, the structure of reversible covalent bond and its factors and rules on the dynamic reversible interface will be investigated. At last, the influence of dynamic reversible bonds on the self-healing and recycling properties of rubber composite will be explored. The implementation of this project will realize the reinforcement, recycling, and self-healing of general rubber and provide theoretical guidance and technical approaches for production and application of high-performance rubber.

实现交联橡胶的可塑加工、增强和拓展其功能性应用是橡胶科学与技术领域面临的三个重要问题。传统橡胶制品由于共价交联网络的不可逆，不具备重塑加工和自修复功能。本项目拟环氧化天然橡胶为主要研究对象，高性能橡胶填料纳米二氧化硅为载体，通过分子设计，在其表面构筑羧基功能基团，基于羧基与环氧基间的酯化反应，在橡胶分子间、橡胶基体-纳米填料间构建多重动态可逆共价键。基于纳米填料的补强效应，实现橡胶的增强。利用动态共价键的可逆性，赋予橡胶可塑加工和自修复功能。系统研究有机官能团在纳米二氧化硅表面的构筑方法及构效关系；深入探讨橡胶分子间、基体-纳米微粒之间共价键的构成及其对动态可逆界面的作用规律；阐明可逆共价键对橡胶纳米复合材料可塑加工和自修复功能的影响机制。通过本项目的研究，实现化学交联橡胶的增强、可塑加工和自修复，为高性能功能化橡胶的生产和应用提供理论依据及新的技术途径。

本项目针对传统橡胶制品中共价交联网络的不可逆，不具备重塑加工和自修复功能，设计制备羧基改性二氧化硅，通过环氧化天然橡胶环氧基和羧基化纳米二氧化硅羧基间的酯化反应，在橡胶分子间、橡胶-填料界面处构建可逆酯键。基于纳米填料的补强效应，在实现橡胶纳米复合材料增强，利用酯键的可逆性赋予橡胶可塑加工和自修复功能。取得的主要结论如下：.成功在二氧化硅表面引入大量的羧基，其羧基含量为1.23mmol/g。二氧化硅表面的羧基与环氧化天然橡胶（ENR）分子链上的环氧基团在高温下发生反应，在两者界面生成β-羟基酯共价交联键，实现二氧化硅同时补强和共价交联ENR的双重目的，共价交联键的形成有利于改善二氧化硅的分散性。为提高性能，构建更多可逆酯键，加入葵二酸作为交联剂，复合材料的拉伸强度随填料用量增加而增大。添加40phr的二氧化硅，复合材料的强度较纯ENR提高了4.5倍。基于界面羟基酯在高温下的动态交换特性，复合材料同时具有高温重复加工和自修能力。当断面在180℃下愈合3h后，愈合样品仍然可以承受较大的应力而不断裂，表现出优异的自愈合能力。.本项目通过有机-无机界面设计实现传统化学交联橡胶纳米复合材料的增强、可塑加工和自修复。在橡胶分子间、橡胶-填料界面处构建动态共价键，基于纳米填料的补强效应和共价键交联，在实现橡胶纳米复合材料的增强，利用动态共价键的可逆特性赋予其可塑加工和自修复功能，为通用橡胶的高性能化和功能化提高新思路和理论指导。

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