Study On The Toughening Of Bismaleimide Resins

In recent years, the bismaleimide resins are widely used in the areas of aviation,mechanical and electronic industries because of their features such as thermal stability,fire retardance and good mechanical property. However, unmodified bismaleimideresins have the low toughness and poor impact resistance, which limit their application.Therefore, BDM-DDM-PO and SiO₂-[P（GMA-co-BA）-g-DDS] were added intobismaleimide resin to prepare high performance resin composites in this paper.Firstly, the BDM-DDM-PO was prepared by using BDM, DDM and POfirstly. The resulted BDM-DDM-PO was used as toughener and added into the4，4’-diphenylmethanedimaleimide. The effect on the thermal and mechanicalproperties of bismaleimide was studied. The research results showed thatBDM-DDM-PO could obviously improve the thermal properties and mechanicalproperties of composites. When mass fraction of BDM-DDM-PO was5%， themechanical properties were best. The SEM showed that the fracture pattern ofcomposites was changed from brittle fracture to ductile fracture.The P （GMA-co-BA） chains were grafted from nano-SiO₂via ATRP method. Thenthe diamino diphenyl sulfone （DDS） was introduced onto the SiO₂surface throughring-opening reaction. The resulted functionalized SiO₂was denoted asSiO₂-[P（GMA-co-BA）-g-DDS], which had toughening effect and could participate in thecuring process of bismaleimide. The FT-IR, TGA,1H NMR and XPS analysis was usedto characterize the SiO₂-[P（GMA-co-BA）-g-DDS]. The results showed that the polymer chainswere grafted onto the SiO₂surface, and the grafting ratio of P（GMA-co-BA） andP（GMA-co-BA）-g-DDS were73.3%and76.5%respectively.SiO₂-[P（GMA-co-BA）-g-DDS] was added into bismaleimide resin to prepareSiO₂-[P（GMA-co-BA）-g-DDS]/BMI composites. And the mechanical properties anddynamic mechanical properties of composites were also studied. The research resultsshowed that SiO₂-[P（GMA-co-BA）-g-DDS] could obviously improve the impacttoughness and bending strength of composites. When mass fraction ofSiO₂-[P（GMA-co-BA）-g-DDS] was0.5%，the impact toughness and bending strengthof composites were best, and increased198.7%and64.5%, respectively. The SEMshowed that the fracture pattern of composites was changed from brittle fracture to ductile fracture.The curing kinetics of SiO₂-[P（GMA-co-BA）-g-DDS]/BMI composite was studied byfourier transform infrared （FT-IR） and non-isothermal DSC. The cure kineticparameters of the apparent activation energy, curing reaction series and curingtemperature are evaluated. A function of curing degree as apparent activation energyEa is more than the constant activation nenergy.