Study On The Development Of High-parameter Impregnating Agent And Impregnation Process

Heat exchange equipment is widely used in the production process of modern chemical and petroleum industries.The production safety problem caused by the explosion and leakage of heat exchange equipment needs to be solved urgently,so the heat exchange equipment with superior performance parameters is the necessary guarantee for the smooth operation of various industries.Compared with other heat exchanger materials,artificial graphite has better corrosion resistance and thermal conductivity,and is increasingly used in the production of heat exchange equipment.However,artificial graphite has about 10%to 30%of pores,which is permeable to gas and liquid.To be used to manufacture graphite heat exchanger,artificial graphite should be made into impregnated graphite by impregnation.The performance of the impregnant has become a key factor affecting the performance of graphite heat exchange equipment.In view of the shortcomings of existing phenolic resin impregnating agents,research and develop new impregnating materials with better performance,and make a reasonable impregnation curing process with reference to the existing impregnation curing process and the characteristics of the new impregnating agent.This is of great significance for the development of graphite heat exchange equipment with good corrosion resistance,good temperature resistance and high mechanical strength.In this study,three new impregnating agents with excellent properties:epoxy resin（EP）,polytetrafluoroethylene（PTFE）and water glass are used as graphite impregnating agents.The preparation of epoxy resin impregnant and its effect on the properties of impregnated graphite were studied.The modified epoxy resin was used as waterborne epoxy resin for the study of the effect of impregnated graphite on graphite properties.In order to optimize the PTFE impregnated graphite process,the effect of the number of PTFE immersion and the number of plasticization on the properties of impregnated graphite was studied.In order to improve the comprehensive performance of graphite,the effect of composite impregnation of polytetrafluoroethylene and epoxy resin on the properties of graphite was studied.Optimize and compare the water glass heat curing,the sodium fluorosilicate curing and the ethylene glycol diacetate curing process based on the properties of impregnated graphite,and determine the suitable curing process for water glass.The main conclusions were summerrized as follows:1.The reactive diluent 660A or 692 and the latent curing agent 594 are selected to be an epoxy resin（EP）impregnating agent;a waterborne epoxy resin was prepared by using emulsifier 2（PEG6000）and a curing agent dinitrileamine.2.When the graphite is impregnated twice with epoxy resin,the porosity of the impregnated graphite can be reduced to less than 1%,the impregnation effect is very good,and the compressive strength after the two impregnations is more than 70 MPa,and the thermal stability is good.Compared with the traditional solvent-based epoxy resin,the aqueous epoxy resin has small viscosity,environmental protection and good impregnation effect,but increases the cycle of impregnating and solidifying graphite.3.Studying the PTFE impregnation and plasticizing process,it is found that the process of one plasticization after n times of immersion has better impregnation effect than that of n times of immersion and n times of plasticization process,and the compressive strength of one plastic process after n times of immersion is high.The compressive strength of the three times of impregnation is 50.1 MPa,which is higher than the three impregnation and three plasticization processes,and is 0.4 MPa higher than the four impregnation and four plasticization processes.The heat resistance of the impregnated graphite of the two processes is good,and the one plasticizing process after n times of immersion shortens the production cycle and achieves a better impregnation effect compared with the n times of the n-time immersion plasticizing process.4.In the PTFE/EP composite impregnated graphite process,the composite impregnated graphite with PTFE impregnated twice and then EP impregnated has the highest weight gain rate（16.750%）and the lowest porosity（1.006%）,and its compressive strength is compared with PTFE alone.It is 10 Mpa higher and its thermal stability is higher than that of PTFE twice impregnated graphite and EP alone impregnated graphite.The corrosion resistance is higher than that of EP alone impregnated graphite.The composite impregnation process of polytetrafluoroethylene and epoxy resin combines the advantages of two impregnants,effectively improving the comprehensive performance of impregnated graphite.5.The heat curing process of the water glass is optimized to be subjected to pickling treatment after curing,and the water resistance of the graphite treated by the optimized process is improved;The Na₂SiF₆ curing process is optimized for the alternate impregnation process of water glass and Na₂SiF₆,and the water glass impregnant can be reused,but the curing process time is increased;The EGDA curing process is optimized to alternately impregnate water glass and EGDA,then pressurize and program temperature cure to improve the overflow of the immersed water glass.6.After comparing and optimizing the three water glass curing processes,it was found that the heat resistance of the three processes is excellent,and the water resistance of the heat curing process is poor.For the impregnation effect,the Na₂SiF₆ process is poor,and the weight gain,density and compressive strength are the smallest,but the open cell porosity is the highest;The immersion graphite of EGDA curing process has relatively good effect with high compressive strength and high residual rate of corrosion quality.Therefore,the curing process of water glass impregnated graphite adopts optimized EGDA curing process.