| One-component epoxy adhesives are widely used in industry due to their simple use process,low labor load,and easy adoption of automated assembly lines.Among them,the ketimine type one-component epoxy adhesive is favored by the majority of scientific researchers because of its simple preparation,convenient activation,and curing at room temperature in a humid environment.However,the ketone produced by the latent ketimine curing agent during the curing of the epoxy resin is not easy to volatilize from the adhesive,causing it to be enclosed inside the adhesive,thereby reducing the strength of the adhesive.In response to this problem,this thesis designed and prepared five ketodiimide curing agents with different molecular weights,and controlled the performance of one-component epoxy resin adhesives by changing the diffusion rate of the ketone produced during curing in the adhesive.Specific research work includes:First,select the most commonly used methyl isobutyl ketone(MIBK)and m-xylylened DImine(MXDA)to synthesize methyl isobutyl ketone diimide as a one-component epoxy resin latent curing agent.Orthogonal experiments were designed,reaction conditions were optimized,storage stability of curing agent,economy and other factors were integrated,and the best feed ratio of the experiment was 5:1,the experiment temperature was 170 ℃,and the reaction time was 4 h.The infrared spectrum test of epoxy resin under different curing time shows that the latent curing agent can successfully cross-link and cure epoxy resin under the excitation of moisture.When the mass ratio of epoxy resin E-51 and MIBKDI is 2:1,after 7 days of curing at room temperature,the tensile strength and shear strength reach the maximum value,respectively 19.2 MPa and 12.9 MPa,and the elongation at break is 6.5%,which satisfies The strength requirements of general construction adhesive.Its storage stability is more than 30 days in an environment with a relative humidity of 10%.At the same time,the adhesive was placed in a vacuum oven with a constant temperature of 60 ℃ and-0.1 MPa,and the diffusion amount of ketone was detected by the quality of the adhesive.The ketone loss of the colloid was 6% after 15 days.Secondly,select acetone(ACE),butanone(BUT),2-pentanone(MIPK)with smaller molecular weight and higher volatility and MXDA to synthesize three ketodiimides(ACEDI,BUTDI,MIPKDI)for latent curing.After mixing different curing agents and epoxy resins,three types of one-component epoxy adhesives with fast curing and high strength can be obtained.The mechanical performance test shows that as the molecular weight of the curing agent increases,its tensile strength/shear strength gradually decreases(63.5 MPa/36.4 MPa,54.1 MPa/32.4 MPa,25.2 MPa/15.8 MPa),which are higher than those of MIBKDI single Component epoxy adhesive;the curing time at room temperature gradually increases(1,3,5days),which is less than MIBKDI type one-component epoxy adhesive;the loss of ketone after 15 days of curing(70%,41%,25%),Are higher than MIBKDI type one-component epoxy adhesive.Finally,select 2-octanone(OT)with larger molecular weight and lower volatility and MXDA to synthesize octanone diimide(OTDI)curing agent.It was characterized by nuclear magnetic and infrared,and the results showed that its structure was correct.After this latent curing agent is mixed with epoxy resin,a one-component epoxy adhesive with high toughness and long window period can be configured.The mechanical performance test results show that its tensile strength and shear strength are 7.7 MPa and 4.5 MPa,respectively.The curing time at room temperature is 14 days.The elongation at break is 35%,which is much higher than MIBKDI one-component epoxy adhesive.Almost no loss of ketone after 15 days of curing. |
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