Preparation And Properties Of Self-Healing Waterborne Polyurethane Based On Click-Reaction And Dynamic Disulfide Dond

At present,the preparation methods of self-repairing polymer materials mainly include two categories: extrinsic type and intrinsic type.Reversible covalent bond self-repairing in intrinsic self-repairing polymer materials is an effective method to prepare self-repairing polymer materials.By introducing reversible covalent bonds into polymer materials,the fracture and recombination of reversible chemical bonds can be used to repair the materials for many times.In reversible covalent bonds,Diels-Alder(DA)reaction is widely used without additional catalyst,with few side reactions,high yield and mild reaction conditions;Disulfide bond(SS)has low bond energy and can achieve dynamic equilibrium of reversible exchange under mild conditions,which provides the possibility for self-repair of polymer materials.Based on the characteristics that DA bond and SS bond can undergo reversible transformation under mild transformation conditions,this paper mainly studied the preparation and selfrepairing properties of waterborne polyurethane containing DA bond,SS bond,DA and SS synergistic effect,and explore its self-repair mechanism,the research results show that:(1)The DA bond was introduced into the polymer material to prepare the waterborne polyurethane material containing DA bond.The particle size and potential of the dispersion were analyzed to prove that the dispersion had good stability;FT-IR was used to verify the DA reversible reaction;TGA test showed that the introduction of DA bond is beneficial to the improvement of thermal stability of materials;It was found by optical microscope that the furan ring and maleimide ring with the content of 1:1(WPU-DA1/1)had the best repair effect,and the scratches were repaired after heating for 10 min under the condition of130℃;A quantitative evaluation of the self-healing results of the films showed that the WPU-DA-1/1 with tensile strength of 16.89 MPa had a self-healing efficiency of 72.76%,and after four cycles of repair,the repair efficiency was still49.73%,and had certain reprocessing performance.(2)A waterborne polyurethane material containing SS bond was prepared by introducing SS bond into the polymer material.The particle size and potential of the dispersion were analyzed to prove that the dispersion had good stability;FTIR was used to verify the successful introduction of SS bond;TGA test showed that the introduction of hard segment SS bond is not conducive to the thermal stability of WPU-SS film.It was found by optical microscope that when the content of polytetrahydrofuran(PTMG)and Bis(2-hydrocarbon ethyl)disulfide(HEDS)was 1:1(WPU-SS-1/1),the film scratches could be completely repaired after heating at 70 ℃ for 3min;A quantitative evaluation of the self-healing results of the films showed that the self-healing efficiency of WPU-SS-1/1 with tensile strength of 2.85 MPa at heat treatment of 70℃ for 6h was 96.49%,The films also had a repair efficiency of up to 84.56% when placed at room temperature for 24 h,and had good reprocessing performance.(3)In order to prepare a self-repairing polyurethane material with good mechanical properties and self-repairing effect,DA and SS bonds were introduced into the structure of waterborne polyurethane at the same time,and WPU-DASS waterborne polyurethane material was prepared.The particle size and potential of the dispersion were analyzed to prove that the dispersion had good stability;FTIR was used to verify the successful introduction of DA bond and SS bond;TGA test showed that the introduction of difurfuryl disulfide containing both furan ring and disulfide bond increased the content of DA bond in the polymer,and the thermal stability of WPU-DASS films was improved;It was found by optical microscope that the scratches on WPU-DASS film had a good repair effect when heated at 70℃ for 10min;A quantitative evaluation of the self-healing results of the films showed that the self-healing efficiency of WPU-DASS film with tensile strength of 16.15 MPa at heat treatment of 70℃ for 6h was 87.55%.After further inverse DA heat treatment,the self-healing efficiency of the film can be up to99.94%,WPU-SS-1/1 films had good reprocessing performance.