Preparation And Properties Of Bio-based Bismaleimide Self-repairing Polymer

Bismaleimide(BMI)is a thermosetting resin widely used in many fields.It uses maleimide(MI)as the active end group,and its resin is easy to synthesize and process.The processing method is similar to epoxy resin.In this thesis,based on bio-based diamines,a highly flexible bismaleimide resin was prepared by azeotropic dehydration cyclization method using ionic liquid as catalyst.The bio-based sterol resin PFA,UF was separately prepared.The Diels-Alder reaction of resin UF produces a bio-based self-repairing polymer containing a thermoreversible covalent bond,which is separated from the traditional synthetic route of petrochemical industry,and realizes the recyclability of thermosetting resin.Its synthesis,structure and performance was studied.It mainly includes the following contents:1.Firstly,different structures of bismaleimide resin were prepared by azeotropic dehydration cyclization method using ionic liquid as catalyst.The optimum preparation conditions are:one-step synthesis,catalyst ionic liquid(triethylamine p-toluenesulfonate),solvent is xylene,reflux temperature:137-140℃,reactant ratio maleic anhydride:diamine=2.3:1,the post-treatment was extracted with n-heptane,and the obtained product was a dark brown resin with a yield of74.4%.Characterization of the product by ~1H NMR and FTIR indicated that the bio-based bismaleimide resin has been successfully prepared.2.A cross-linked self-repairing material(PFA-BMI)was prepared by the reaction of bio-based sterol resin PFA and bio-based bismaleimide BMI,and its structure and properties were characterized.The results show that the polymer can be crosslinked by DA reaction,and the optimum crosslinking reaction temperature is 70℃.Polymer sample only swells and dissolves,the gel content can reach 83.10%.The sample has good flexibility and the elongation at break can reach 88.31%.Elongation after breaking through simple self-repair can still reach 85.71%,which indicates that the prepared PFA-BMI sample has good self-repairing performance.In addition,ma-terial recovery and repeated reprocessing can also be achieved by simple comminution and hot pressing.3.Design and synthesis of three self-repairing polymers(PFA-BMI,UF-BMI,UF-BMI PACM),comparing the differences in cross-linking reaction temperature,gel content,self-repairing temperature and toughness.The self-repairing polymer(UF-BMI)prepared by bio-based UF resin and bio-based bismaleimide resin BMI has an optimum crosslinking reaction temperature of 80℃and a gel content of 90.03%.Sample has good flexibility and the elongation at break can reach 97.59%.Elongation at break after self-repair at 90℃for 12 h still reached89.16%.The self-repairing polymer(UF-BMI PACM)prepared by BMI PACM and bio-based UF resin has the best crosslinking reaction temperature of 70℃and gel content of 97.54%.Sample has good flexibility and the elongation at break can reach 80.56%.Elongation at break after self-repair at 90℃for 12 h still reached 73.83%.The properties of such self-healing polymers can be adjusted by molecular structure design.