Preparation And Application Of Water Soluble Boron Phenolic Resin

Water-soluble boron phenolic resin(BPF)is highly heat-resistant,safe and environmentally friendly.The application of graphite impregnants can improve the long-term heat resistance,ablation resistance and mechanical properties of graphite;it is of great significance for its application in graphite materials.This study is mainly divided into two parts.One is to use phenol and formaldehyde as raw materials and boric acid as a modifier to synthesize water-soluble BPF by the salicyl alcohol method,and compare the thermal weightlessness data of different phenolic resins(PF)at 270? for 200 h;Using water-soluble BPF to impregnate graphite,the factors affecting the weight gain of impregnation,the tensile,compression and mechanical properties of graphite after impregnation were discussed.The following main conclusions were reached:(1)Through the experimental process,the optimal synthesis conditions are: n(phenol): n(formaldehyde): n(boric acid)= 1: 1.3: 0.2?0.3,the catalyst is Na OH,and the amount is3?5%,phenol and formaldehyde in the reaction stage at 55?60? for 2h,boron esterification stage at 95? for 1h,and finally pumping water at 65?80? for 0.5?1.5h.Under these conditions,the synthesis process is easy to control.The synthetic BPF has good water solubility,performance meets relevant enterprise standards,namely viscosity 10?40s,gel time120-240 s,free phenol content ?21%,free aldehyde content ?4%,and water content ?20%.(2)The transition from the small-scale test to the pilot-scale process,the total amount of raw materials will be enlarged from 200 g to 40 kg,and the exothermic heat of the reaction will also increase sharply.In order to ease the synthesis process and obtain the water-soluble BPF meeting the standard,the combination of boric acid and phenol The ratio is reduced to 0.2?0.3,the preheating temperature of the reactor is adjusted to 35?40 ?,the formaldehyde is added in four times,and the Na OH is added in two times to control the reaction of phenol and formaldehyde at 45?55 ° C for 4?5h,and the esterification of boron The stage is a reaction at95 ° C for 30 minutes,and pumping water for 3?5 hours.(3)The viscosity of the resin is greatly affected by temperature.When the ambient temperature is less than 20 ° C,the resin viscosity rapidly increases and cannot be a graphite impregnating agent.In order to reduce the resin crosslinking degree and control the molecular weight of the synthesized product,the ratio of boric acid to phenol is further reduced to0.15?0.2,the formaldehyde can be adjusted to two feedings,reduce the pumping time to 2?4h,and add furfuryl alcohol to adjust the resin viscosity.(4)The water-soluble BPF synthesized in this study has the smallest thermal weight loss at 200 h at 270?,which is only 37.92% of ordinary water-soluble phenolic resin and 78.69%of commercially available BPF.(5)IR and TG-DSC characterization analysis shows that in this study,a high ortho-substituted,highly heat-resistant water-soluble BPF was synthesized.(6)The impregnation weight gain rate is proportional to the solid content of the resin,which changes with the addition of wetting agent and the curing process.Among them,it is kept at 100? for 3h,120?,150?,and 180? for 2h and 200?.Under the curing process under heat treatment,the highest is 18.33%.(7)Through long-term adjustment of the resin synthesis process,impregnation process and curing process,the graphite tensile strength after BPF impregnation is 14.33 Mpa,compressive strength is 59.91 Mpa,and flexural strength is 28.63 Mpa,which basically meets the enterprise standard technical indicators.This experiment has undergone dozens of 40kg-level pilot tests.Water-based BPF-impregnated graphite workpieces have been put on the market,and they have the conditions for the next ton-scale amplification.