Preparation Modification And Performance Test Of Benzoxazine/Epoxy Resin

Benzoxazine（BOZ）is a new thermosetting resin,Ring-opening polymerization can take place in pressure,catalyst and heating environment to form polymer with network structure.Epoxy resin（EP）,has good adhesion,electrical insulation,toughness and other excellent properties.Therefore,When the BOZ and EP are modified,their advantages and disadvantages are complementary,which is of great research value.Based on the synthesis of bisphenol A benzoxazine and linear epoxy resin,the blending system preparing by blending and mixing copolymerization method for the first time,and Finally,it was applied to the preparation and performance investigation of coated sand.The main contents of the study are as follows:1、Synthesis of benzoxazine:bisphenol A benzoxazine was synthesized from bisphenol A,formaldehyde and aniline with toluene as solvent by step feeding method.The optimum technological conditions were as follows:（1）The reaction temperature was 95℃,（2）The reaction time was 5 h,the yield was 92.3%,and the T_d5%（A temperature of 5%of the mass loss for the material）after curing was 299℃.2、Synthesis of epoxy resin:linear phenolic resin were synthesized under the condition of 92℃with phenol and formaldehyde as raw materials,dihydrated oxalic acid as catalyst,then epoxy resin is prepared by modification with epichlorohydrin,The optimum conditions were as follows:（1）the reaction temperature was 82℃,（2）the reaction time was 5.5 h,（3）the concentration of strong sodium hydroxide was46%,and the final epoxide value was 0.464,the T_d5%was 313℃measured by DSC.3、Blending modification of benzoxazine and epoxy resin:dispersion and copolymerization of benzoxazine and epoxy resin were carried out in different proportions,and the curing process of BOZ blends modified by EP was studied by FT-IR.The results showed that,The epoxy group in EP participates in the reaction at180℃.the thermal stability of the cured compounds was measured by non-isothermal DSC,the T_d5%was 355℃,and the T_d10%was 381℃.The mechanical properties of the modified system were tested by using universal testing machine and other mechanical instruments.It was found that the thermal stability was greatly improved;the impact resistance was increased by 40.9,the tensile strength by 30.1,the shear strength by 26.1,the bending strength by 17.3 when the best modified system resin was compared with the unmodified BOZ resin.4.The modified system was used in making sand coating and performance testing:the blending system is milled into powder,mixed with quartz sand,heated stirring mix evenly,cooled quartz sand body grinding,farce production,curing is obtained,and then,researching the best production formula by taking the mechanical performance as the index.The optimum preparation conditions are as follows:（1）the amount of resin used in the blend system is 8%（relative to the total mass of）,（2）the particle size of quartz sand is 0.6⁰.8mm,（3）the curing temperature is 210℃（4）and the curing time is 5h.The flexural strength can reach 9.7MPa and the compressive strength reach 19.9Mpa.The consolidation body has good thermal stability and medium resistance（except for high concentration alkaline environment）,and it can be used in the field of brake pad,sand control pipe and so on.