Synthesis And Properties Of Biobased Benzoxazine Resin

With the rapid development of society and the increasing awareness of environmental protection,human demand for green and sustainable materials is increasing.Bio-based benzoxazine is a resin which using sustainable biomass as a raw material and has very important research significance.A bio-based benzoxazine(DPA-F-BOZ)was synthesized from a biobased substance-derived furfurylamine and a bio-based platform compound derivative,bisphenolic acid;A part bio-based benzoxazine(PTL-F-BOZ)was synthesized from furfurylamine and petrochemical-based phenolphthalein.The chemical structures of the two monomers were characterized by using Fourier transform infrared spectroscopy(FTIR)and nuclear magnetic resonance spectroscopy('H-NMR,13C-NMR).Non-isothermal DSC and in-situ infrared method were used to test the curing behavior of the above two monomers.The results show that,First,a ring-opening reaction occurs under heating condition to form a Schiff base structure,and then the furan ring,the ortho position of the benzene ring,and the O in the oxazine ring attack the structure,and three different electrophilic substitution reactions occur.Forming three different polybenzoxazines,furfuryl-based polybenzoxazine,phenoxy polybenzoxazine and phenolic polybenzoxazine.The first curing peak corresponds to the ring opening reaction and the electric reaction,the second curing peak corresponds to the rearrangement and diffusion steps of the phenoxy structure to the phenol structure.The presence of a furan ring in the furfurylamine increases the crosslink density of the polymer,which in turn slows down the diffusion of molecules during molecular structure rearrangement,the diffusion step plays a controlling role,so there is a second curing peak.Non-isothermal DSC was used to determine the corresponding curing process,and finally prepared three benzoxazine resins:PBPA-A-BOZ,PDPA-F-BOZ and PPTL-F-BOZ.Using the thermogravimetric analyzer(TG),vertical combustion,the limiting oxygen index(LOI),the micro-combustion calorimeter(MCC),and the cone calorimeter(Cone)to test the heat resistance and flame retardance.and comparing with the traditional petrochemical benzoxazine,bisphenol A aniline benzoxazine(PBPA-A-BOZ).The results show that under the nitrogen atmosphere,the T5%of PPTL-F-BOZ and the carbon yield at 800? are the highest,up to 380? and 63.0%,respectively,the T5%of PDPA-F-BOZ and the carbon yield at 800? was 340 C and 50.2%,respectively,while the T5%of the PBPA-A-BOZ and the carbon yield at 800? were the lowest,respectively 331 C and 30.6%.According to the DTG,PPTL-F-BOZ resin has the lowest decomposition rate,PDPA-F-BOZ resin is the second,and PBPA-A-BOZ resin is the highest,indicating that PPTL-F-BOZ resin has excellent thermal stability.PDPA-F-BOZ resin is the second,PBPA-A-BOZ resin has the worst thermal stability.In terms of flame retardant performance,PPTL-F-BOZ resin has an limiting oxygen index of up to 36.2%,passing UL-94 V-0 level,while PDPA-F-BOZ resin and the PBPA-A-BOZ resin have no grade,and their limiting oxygen indexs are 27.4%and 32.2%,respectively.DOPO was used to have flame retardancy modification of PDPA-F-BOZ and PBPA-A-BOZ.The PDPA-F-BOZ resin system adds 10%DOPO of its mass to V-0,and its limiting oxygen index is 35.1%.PBPA-A-BOZ resin system was added with 8%to reach the V-0,and its limiting oxygen index was 41.5%.The results shows that DOPO is a good flame retardant modifier for benzoxazine resin.