Study On Resin Synthesis And Performance Based On Benzoxazine Chemistry

With the development of science and technology,people not only have higher requirements for the performance of materials,but also increasingly demand for the wide range of application fields of materials.Benzoxazine resin is a new thermosetting resin developed on the basis of phenolic resin.It has good heat resistance,low moisture absorption,flame retardancy,and excellent mechanical property.During the curing process,there is no release of small molecules and the volume shrinkage rate is basically zero.It is a thermosetting resin with excellent comprehensive performance.It is widely used in compound material,copper clad plate matrix resins,friction braking materials,etc.In addition to these application fields,we have studied the solventless synthesis of benzoxazine resin,foam prepared with benzoxazine resin,and benzoxazine surfactants.The main content and research results of this dissertation are as follows:1.Solventless synthesis and properties of benzoxazine resinAt present,traditional benzoxazine resins are mostly synthesized by solvent method.Use of organic solvents causes environmental pollution and requires treatment and purification after synthesis.This chapter studies the solventless synthesis of benzoxazine monomers.Four liquid benzoxazine monomers were synthesized using phenol and cashew nut phenol as phenol sources,ethanolamine and diethylene glycol amine as amine sources.The benzoxazine monomers compared with the same monomers synthesized by solventless method.A series of benzoxazine resins were prepared by thermal ring opening polymerization of four benzoxazine monomers.The viscosity of benzoxazine monomer and the thermal properties of benzoxazine resin were studied.The results showed that the purity of benzoxazine monomers synthesized by solventless method is equivalent to that synthesized by solvent method.The yield of solventless method is slightly higher than that of solvent method.The results indicated that the properties of benzoxazine monomers synthesized by solvent-free method are comparable to those obtained by solvent method.Among the synthesized benzoxazine monomers,benzoxazine monomer synthesized from diethylene glycol amine and cashew phenol(DYBZ)has the lowest viscosity,with a viscosity of 250 mPa·s at 25℃.Among the prepared benzoxazine resins,benzoxazine resin synthesized from ethanolamine and phenol(Co-EBZ)has the highest glass transition temperature(Tg)of 249℃,which is similar to the Tg of benzoxazine resin synthesized by solvent method in the reference.It can be applied in the field of high-temperature resistant resins.2.Preparation and properties of benzoxazine resin foam synthesized from cardanolIn order to solve the corrosion problem of strong acid or strong base in the curing process of phenolic foam,a new method of preparing foam by crosslinking benzoxazine oligomer with isocyanate is proposed in this chapter.Using cardanol and diethylene glycol amine as raw materials,DYBZ and oligomer(QDYBZ)were synthesized.A series of benzoxazine resin foam synthesized from cardanol(PBZFs)were prepared by polyurethane foaming process using QDYBZ as polyol and polyether polyol 4110.The effects of polyol ratio,foaming agent content,and foam stabilizer content on the apparent density,thermal conductivity,mechanical properties,and thermal properties of PBZFs were studied.The results showed that when the molar ratio of QDYBZ to polyether polyol 4110 is 1:1,the overall performance of foam PBZFs with foaming agent(30%)and foam stabilizer(1%)is the best.At this time,the apparent density of PBZFs is 42 kg/m3,which is equivalent to the commercial phenolic foam.The compression strength of PBZFs is 0.68 MPa,which is 170%higher than that of the commercial phenolic foam.The tensile strength of PBZFs is 0.78 MPa,and the elongation at break of PBZFs is 4.2%.The larger the proportion of QDYBZ in polyols,the thermal stability of foam is better.At this time,its carbon residue rate is 12.3%.benzoxazine resin foam synthesized from cardanol PBZFs prepared in this chapter has better performance than the commercial phenolic foam.3.Synthesis and performance of PMMA-PBA core-shell toughening agent based on polymerizable benzoxazine surfactantThis chapter proposes a new method for preparing PMMA-PBA core-shell toughening agents using polymerizable benzoxazine surfactants to address the issue of removing surfactants in the preparation of core-shell toughening agents.DYBZ was synthesized using cashew nut phenol and diethylene glycol amine as raw materials.A carboxyl and double bond benzoxazine monomer(DYBZM)was synthesized by reacting DYBZ with maleic anhydride,and then ionized with saturated sodium bicarbonate solution to synthesize a polymerizable benzoxazine surfactant(DYBZM-Na).A polymerizable cashew phenolic surfactant(YM-Na)was prepared using the same method with cashew phenolic as the comparison.Two core-shell toughening agents(CRS-DYBZM,CRS-YM),were prepared using these two surfactants.They were added to the epoxy resin system to prepare cured products(CRS-DYBZM-EP,CRS-YM-EP).The effect of the amount of core-shell toughening agent added on the mechanical and thermal properties of the epoxy resin was studied.The results show that the toughening effect of CRS-DYBZM is better than that of CRS-YM.Among them,when the addition amount of CRS-DYBZM is 7.5 wt%,CRS-DYBZM-EP has the highest elongation at break,which is 17.25%.The elongation at break of CRS-DYBZM-EP is 112%higher than pure epoxy resin.At this time,the impact strength of CRS-DYBZM-EP is also the highest,which is 53.5 KJ/m2.The impact strength of CRS-DYBZM-EP is 157%higher than pure epoxy resin.When the same content of toughening agent is added,the Tg,thermal stability and plastic deformation performance of CRS-DYBZM-EP are higher than those of CRS-YM-EP.This polymerizable benzoxazine surfactant can solve the problem of removing surfactants when preparing core-shell toughening agents.It will not affect the toughening performance of the core-shell toughening agent,and is more cost-effective and environmentally friendly.