The Study Of Epoxy Resin Modified By Bismaleimide Containing Phthalazinone Moiety

Cured epoxy resin has been taken advantaged of in aviation and aerospace,electronics and electrics and other areas because it possesses a great many of excellent performances, such as good thermal stability,modulus,mechanical properties and processing.However,the brittleness and the bad impact resistance of it limit the application in lots of high technologies fields.Therefore,it's meaningful for people to modify epoxy resin by toughening. Bismaleimide(BMI) has the desirable heat resistance and mechanical properties,especially when the BMI with extended chains are used to toughen epoxy resin,the toughness of epoxy resin system will be dramatically increased owing to the distance between the two maleimide (MI) rings those can decrease the cross-link density.So it's expected to give attention to two properties,heat resistance and toughness,if high performance poly(aryl ether)(PAE) containing phthalazinone moiety that is heat-resistant and dissolved easily is incorporated in the two MI rings.In this paper,the research method and the general idea about toughening epoxy resin with BMI-terminated PAE containing phthalazinone moiety is come up with based on the fundamental research on thermal plastic resin and BMI resin at home and abroad.In this paper,three kinds of novel Bismaleimdes,DHPZ-BMI monomer,PPEK-BMI and PPES-BMI with the different polymerization degrees were synthesized deriving from 4-(4-hydroxyphenyl)-2,3-Phthalazin-1-one(DHPZ).The structures of BMI obtained were characterized by FT-IR,~1H-NMR and GPC,and the solubility and thermal behaviors were also measured.The results showed all had nice solubility in some solvents,and exothermal peak of PPEK-BMI with the polymerization degree below 10 was appeared obviously at the high temperature area,while that of the one with the polymerization degree more than 10 could not be seen clearly due to the small amount of BMI terminal groups deriving from the long chains.So was PPES-BMI.A series of BMI-terminated PAE with different concentrations or polymerization degrees/DGEBA blends were prepared by mechanical mixing without solvents.Curing kinetics of different blends were measured by differential scanning calorimetry(DSC),which showed all curing reaction began at 150℃,and different blends did not affect the curing reaction of epoxy resin so much that each system could be cured under the same condition. The structure and properties of PPEK-BMI/DGEBA blends were investigated.The glass transition temperatures(Tg) was decreased on some extent from the spectra of DSC.The thermal gravimetry(TGA) represented the thermal stability of the blends with 15phr PPEK-BMI was the best,and its impact strength was the most satisfied because the increment was up to 42.8%in the series of PPEK-BMI/DGEBA blends with the same polymerization degree(DP=5).While in the same addition(10phr),the more increased in the polymerization degree of PPEK,the more increment in increasing toughness of modified resin.The increment in impact strength of PPEK-BMI/DGEBA blends was about 30%,that was because the longer chain,the more damage energy could be absorbed.The structure and properties of PPES-BMI/DGEBA blends were also investigated,and the Tg of the blends also was decreased,however,by the smaller increment than that of PPEK-BMI/DGEBA systems because the homopolymer formed in the later stage would make up the heat resistance of the blends.The heat resistance of blends with 45phr PPES-BMI was the best in the blends with the same polymerization degrees(DP=5),which was because homopolymer would precipitated from systems,especially when the concentration of PPES-BMI was increased to some extent,the amount of cured PPES-BMI precipitated could be increased,which was why the stability of the system could be enhanced.While in the same addition(35phr),the blends(with DP=20) also had the best impact strength.Compare the structure and performance of DHPZ-BMI/DGEBA with those of PPEK-BMI,the constants of thermal stability of DHPZ-BMI/DGEBA blends were both higher than those of PPEK-BMI/DGEBA blends from spectra shown by DSC and TGA. While the toughness of DHPZ-BMI/DGEBA blends was not as excellent as that of PPEK-BMI/DGEBA blends due to the shorter distance between the two MI rings those increased the link-cross density and enhanced the heat resistance of the system resulting in the bad toughness.