Preparation And Properties Of Rosin-based Epoxy Vitrimer Polymers

The synthesis of biomass epoxy resin is of great significance to reduce the generation of polymer waste and to decease the use of petrochemical resources.However,the synthesis of biomass epoxy resins with high mechanical properties,excellent chemical recycling and functionalities is not easy.To address the issues,natural rosin with rigid hydrophenanthrene framework was selected as the matrix,and it was introduced dynamic covalent bonds into the network,giving the rosin-based epoxy networks,to improve the mechanical properties and functionalities（self-healing,shape memory and reprocessing ability）of the network.Networks structures and properties were regulated,by changing the structure of rosin monomer,the structure and dosage of crosslinking agent,the crosslinking degree of the network structure.The epoxy networks with high mechanical properties recycling and functionalities were prepared.The research results and conclusions are as follows:（1）In the second chapter,fumaropimaric acid（FPA）was synthesized.Rosin-based epoxy monomer（FPEG）was synthesized by modification of fumaropimaric acid using ethylene glycol diglycidyl ether（EGDE）.Rosin-based epoxy vitrimers（C-FPEG）with dynamicβ-hydroxy ester bond was obtained by curing reaction between the carboxyl group in FPA and the epoxy group in FPEG.The C-FPEG with high thermal stability(T_5d=268 ℃)and mechanical properties（tensile strength 35.9 MPa）was obtained by optimizing the amount of zinc acetylacetonate（ZAA）in the curing system.Due to the presence of the dynamic transesterification reaction,the surface scratches of the C-FPEG-15 sample were healed completely after heating at 200 ℃ for 1 h.Furthermore,the recovery ratios in terms of tensile strength of the physically reprocessed and chemically recovered samples were 90.7%and 92.1%,respectively.（2）In the fourth chapter,a new type of dicarboxylic acid crosslinking agent（BDCB）containing dynamic boronic ester bond was synthesized.Rosin-based epoxy vitrimers with dual dynamic covalent bonds（β-hydroxy ester bond and boronic ester bond）have been prepared by the reaction of epoxy-carboxyl.Due to the rigid network structure of C-FB,they possess the high thermal stability(T_5d=286 ℃)and excellent mechanical properties（tensile strength 52.5 MPa）,which are comparable to traditional epoxy resins.After thermo-healing at 160 ℃,surface scratches of FB-0.4 sample were completely healed with thermo-healing efficiency near 100%.Furthermore,the recovery ratios in terms of tensile strength of physical reprocessed and chemically recovered samples were 90.2%and 93.4%,respectively.（3）In the third chapter,rosin-based epoxy monomer（FPAE）was synthesized by modification of fumaropimaric acid using epichlorohydrin.The rosin-based epoxy vitrimers（RE）with dual dynamic disulfide bond andβ-hydroxy ester bond were obtained by epoxy-carboxyl curing reaction,using FPAE as matrix,3,3?-dithiodipropionic acid（DTDPA）as cross-linking agent.RE has excellent thermal stability(starting decomposition temperature T_5d=300 ℃)and high mechanical properties（tensile strength 37.5 MPa）.Due to the presence of exchange reaction of dual dynamic covalent bond,the surface scratches of RE-100 sample were completely healed after heating at 170 ℃ for 30 min.Furthermore,the recovery ratio of the reprocessed samples with the first generation was 90.6%after thermal pressing at 160℃ for 3 h.