Design And Properties Study Of Tunable,degradable And Self-curing Carboxylated Epoxy Resin

Carboxylic acids are widely used in adhesive,self-healing,recyclable material,shape memory and other fields because they are easy to form hydrogen bonds,easy to coordinate with metal ions,and can react with epoxy resin to form degradable,reversible rearrangement ester bond.In the traditional carboxylic acid/epoxy resin systems,the poor compatibility of different components at low temperature will result in heterogeneous mixing of carboxylic acid and epoxy resin,which makes the properties of the cured products deteriorate.Hence,the cured products are not conducive to the massive application.In order to solve the problem of poor compatibility between carboxylic acid and epoxy resin,the single-component epoxy resin system with self-curing characteristics is preparated through thiol-ene click reaction method.In this paper,a series of self-curing epoxy resin(CSC-EP)systems with both carboxylic acid groups and epoxy groups were synthesized based on the molecular structure design.Then,the curing behavior,network structure and properties of different carboxylic acid/epoxy resin systems were investigated and the relationship between the content of carboxyl groups and macroscopic properties was obtained.On this basis,the enhancement and toughening of self-curing epoxy resin system with high carboxyl group content(HC-SE)were studied.The main achievements of this paper are as follows:(1)DADGEBA was successfully synthesized.Using DADGEBA as basic resin,four kinds of CSC-EP systems with different carboxyl contents and carboxyl structure were prepared by thiol-ene click reaction.The results showed that the CSC-EP system could be adjustable and stored at low temperature for a long time.Then,the curing behavior,network structure and properties of different carboxylic acid/epoxy resin systems were studied.The results showed that the system with monocarboxyl structure or the system with high carboxyl contents had high reactivity during the curing reaction.The CSC-EP system with higher carboxyl contents and double carboxyl groups has higher ve,Tg and E',faster degradation rate and better hydrophilicity of the cured products.The CSC-EP system with single carboxyl group structure and moderate carboxyl group content has excellent thermal stability,tensile strength and elongation at break.(2)By introducing serial contents of epoxy resin system with different functionalities that can react with remaining carboxyl groups in the HC-SE system,the purpose of toughening and strengthening HC-SE system was realized by taking advantage of rigid benzene ring and flexible hydroxyl ester chain.Then the properties of the systems modified by epoxy resin systems of different functionalities were studied by various testing methods.The results showed that the Tg,tensile strength and elongation at break of the cured products with DGEBA are increased by 73.26%,151%and 144%,respectively,and the initial thermal decomposition temperature reaches 331?.This indicates that the modified HC-SE system has the characteristics of high strength and high toughness.