Green Flame Retarding Bismaleimide Resin Based On A Multi-functional Organic Boron Compound

High performance thermosetting resins play a significant role in many front areas(such as aerospace, transportation, electrical information and new energy, etc.) owing to their outstanding process and integrated performances. However, more and more requirements are needed with the rapid development of modern industries, multi-function becomes the development trend of materials. Similar as other heat resistant thermosetting resins, bismaleimide(BMI) resins have poor flame retardancy and processing feature, seriously obstruct their further development. However the improvement of one given property of resins tends to sacrifice other excellent properties of original resins. Therefore, how to improve the flame retardancy while maintaining the original good properties is the key subject. This is also the target of our research reported in this thesis.Firstly, a novel bismaleimide resin was prepared by the copolymerizing 4,4’-bismaleimidodiphenylmethane(BDM) with allyl triphenylborate(ATPB), and comparatively studied with the BDM/o,o’-diallylbisphenol A resin(the molar ratio of imide to allyl groups is 1:0.85, coded as BD). Results show that the BDM/ATPB prepolymers have a good solubility in acetone; their softening points are about 60 oC, and the processing window is as wide as about 90 oC, suggesting that BDM/ATPB resins have good processing characteristics. Moreover, according to the thermogravimeter analyses, wherever in nitrogen or air atmosphere, BDM/ATPB resins have better thermal stability than BD resin. Specifically, for the BDM/ATPB3 resin with the same molar ratio of imide to allyl groups, its initial decomposition temperature is 10 oC and 13 oC higher than the corresponding values of BD resin, respectively, and the char yields are severally increased by 29% and 17%, demonstrating that BDM/ATPB resins have good thermal and thermo-oxidative stability, this is owing to the thermal stability of B-O bond. Compared with BD resin, BDM/ATPB resins have sharply decreased heat release rate(HRR), total heat release(THR) and peak heat release rate(p HRR), specifically, the p HRR and THR of BDM/ATPB3 are only 53.8% and 47.0% of those of BD resin, respectively, showing that ATPB can effectively improve the flame retardancy of BDM resin. Note that the amount of B element is only 1 wt% for BDM/ATPB3, indicating the high effect of boron in flame retardancy. Moreover, BDM/ATPB has 1.2-1.3 times higher impact and flexural strengths than BD resin.In order to overcome the decrease of the anti-moisture property induced by the addition of ATPB into the resin, new BD modified by hyperbranched polysiloxane(a HSi) and ATPB were designed and prepared. Results show the existence of a HSi can effectively improve the water-resistance. The diffusion coefficient is decreased to 3.68032*10-4 mm2/s from 4.53991*10-4 mm2/s, and the permeability coefficient is decreased from 34.28663*10-6 mm2/s to 23.28200*10-6 mm2/s.