Study On The Preparation And Properties Of Curing Agent And Its Epoxy Adhesive In Water Environment

Epoxy resin adhesives have been widely used in car industry,civil construction,machine and electronics,and aerospace field due to their high adhesion strength,outstanding adhesion to many kinds of substrates,excellent mechanical properties,low curing shrinkage rate,good heat resistance and chemical stability.So it becomes well-known as "all-purpose adhesive".After decades of development,the epoxy resin adhesives are in the direction of customization,high performance and functionalization.In order to prepare underwater-curing adhesives with high adhesion strength,curing agent is synthetized by Mannich reaction between the mixed pehenol(phenol,nonyl phenol,m-cresol),the mixed amine(hexanediamine and triethylene tetramine)and paraformaldehyde,the optimization of experimental conditions is phnol:amine:paraformaldehyde=0.7:1.6:1,reaction temperature and time are 80℃ and 3h,respectively.When the mass ratio of the above-mentioned curing agent:E-44 is 40%(base on epoxy resin weight,similarly hereinafter),the shear bonding strength in air and water is 10.0-12 MPa,7.2～7.6 MPa,respectively.And its tensile strength,bending strength and impact strength of casting specimens made at room temperature are 57MPa、116MPa、15.6KJ/m2,respectively;the water absorptions at room temperature and boiling water are 0.8～1.5%、2～6.5%,respectively.The experiments about selecting of fillers showed that the addition of filler can obviously improve the bonding strength,especially,underwater curing bonding strength and the effect of using composite fillers is better than that using single filler.The dosage of filler is 60～80%,the shear bonding strengths(steal to steal)are up to 23MPa in air and 14MPa in water under a certain ratios of epoxy resin E-44,the curing agent,the fillers and the coupling agent,respectively when the curing time is 24h.The effect of certain frequency and heating rate on E’,E",tanδ by using DMA,curves move to low temperature with the increasing of dosage of curing.agent,The curing process is studied by DSC,Ea(59KJ/mol,61.8KJ/mol)and reaction order(0.9)are decided by Kissinger,Flynn-Wall-Ozawa,Crane equations,the property of heat-resistance of cured products is detected by TGA,the characteristic temperatures move to low temperature with the increasing of dosage of curing agent,An increase of curing agent dosages makes the TGA curves shift to lower temperature,the brittle fracture surface is observed by SEM,the change occurs from a brittle fracture to a ductile fracture with the increasing of dosage of curing agent.