Study On Temperature Resistance And Alkali Resistance Of Impregnated Water-based Phenolic Resin

The production of industrial products with low smoke,low toxicity,economy,and less pollution is the only way for human sustainable development.Water-based phenolic resin is a thermosetting phenolic resin,which is used for impregnating graphite,paper,asbestos and other materials.However,traditional water-based phenolic resins,due to the limitations of raw materials and process conditions,have a structure that directly connects the hydroxyl group and the benzene ring.Due to the?-?conjugation,hydrogen atoms can easily become H⁺,and react with OH^-in alkaline solutions to destroy the molecular structure.This leads to poor storage stability,insufficient alkali resistance,insufficient temperature resistance,and more free phenol and aldehyde pollutants,which cannot meet the requirements of the growing impregnation industry and hinders further development.For this reason,the research of this subject is mainly based on the design of the production process of water-based phenolic resin,and the modified water-based phenolic resin with improved temperature resistance,alkali resistance and storage stability has been prepared.On the one hand,investigate the influence of process conditions on the performance of water-based phenolic resin,establish a new catalytic system,and explore the influence of the number of phenolic hydroxyl groups,the number of methylene groups and their ratio on the performance of water-based phenolic resin;on the other hand,use chemical and physical modification phases The combined method explores the influence of different functional groups on the temperature resistance,alkali resistance and storage stability of water-based phenolic resin.The main research results are as follows:(1)A water-soluble phenolic resin solution was prepared based on the"two bases and two aldehydes"method.The different molar ratios of phenolic aldehydes and the types of catalysts were explored,and it was determined that the resin with a phenolic ratio of 1:1.5under the catalysis of KOH has thermosetting properties.As well as the high ortho-position feature of oxidation resistance and heat resistance,the free phenol content is only 4.11%,and the solid content can reach 66.95%.Further molecular simulation and nuclear magnetic analysis have determined the positional relationship between the methylene and hydroxymethyl groups of the resins with different ratios.In the resin with a phenolic molar ratio of 1:1.5,the ortho-and para-connected methylene groups of the phenol ring are 0.28.There are many para-attachments,0.91 of the ortho-hydroxymethyl group of phenol is much larger than 0.16 of the para-hydroxymethyl group,indicating that the ortho-para-connection of phenol is much larger than the para-hydroxymethyl group in this ratio.Position connection provides the possibility for further connection of molecules.And the relative ratio of-CH₂-to-CH₂OH is 0.44,which is lower than the other ratios,indicating that the water-soluble phenolic resin has a low oxidation rate and good water solubility and thermosetting properties.(2)the energy change of the hybrid resin was obtained by molecular simulation,and the feasibility of the hybrid resin reaction was determined.On the basis of boric acid modification,the hybrid hybrid process was carried out.On the one hand,the highest weight loss temperature of boron-TEOS water-based resin is about 520°C,and the Alkali resistance of the resin decreases with the increase of curing temperature.On the other hand,the highest weight loss temperature of boron-TEOS water-based resin is 530°C when epoxy and Phenol formaldehyde resin are mixed,at the highest pyrolysis temperature,the net weight loss of ordinary water-based resin is as high as 60%,while that of hybrid resin is controlled at15%?20%.The volatility of blend resin is not very high due to high temperature pyrolysis,and after 900°C,the residual carbon rate of blend resin can be more than 35%,ordinary resin is only about 10%.The alkali tolerance of 5?20%epoxy was increased,the Alkali Resistance of 20%EP was 53.02%.The average viscosity of the blends was 12.94s and the storage period was more than 120 days.(3)using blending resin as impregnating agent,the impregnation and solidification of graphite in high pressure reaction kettle were studied.With the increase of impregnation times,the open porosity decreased gradually,and the open porosity was only 4.87%after impregnation for 3 times,after oxidation heat treatment,it was found that the impregnated graphite moved towards high temperature,the curve of oxidation pyrolysis temperature became wider and wider,the rate of thermal weightlessness decreased,and the anti-oxidation pyrolysis performance improved.