Preparation Of Imidazole Compounds As Latent Curing Agents And Their Application In Epoxy Based Thermal Conductive Coating

2-ethyl-4-methylimidazole(EMI) is widely used as curing agent of epoxy resin,due to the high curing efficiency and excellent mechanical properties of the curing product. However, the storage stability of epoxy resin/EMI system is poor for the high reactivity, which leads the storage, transportation and application of epoxy resin into trouble. Substitution reaction and complexation were adopted to improve the storage stability of EMI as curing agent of epoxy resin in this paper, and the homemade curing agent were applied in the thermal conductive coating based on epoxy resin.Three kinds of EMI derivatives(NAEMI, NBEMI, NCEMI) were synthesized through the reaction of EMI with NA chloride, NB chloride and NC chloride, respectively. The structure of EMI derivatives was confirmed by FTIR and 1H NMR spectra, and the curing properties of EMI derivatives with diglycidyl ether of bisphenol A epoxy resin(DGEBA) were studied by DSC, Viscosity, Izod impact, tensile shear strength and TG test. The results indicated that the substitution reaction had occurred between EMI and acyl chloride; which considerably improved the storage stability of EMI as curing agent, and the DGEBA could be cured by EMI derivatives at the concentration of 10 wt%,. The storage time of DGEBA/NCEMI system at the concentration 15 wt% was 176 d or longer, and the corresponding curing temperature and activation energy is 165 oC and 86 k J/mol, respectively. Besides, the izod impact strength of the DGEBA cured by NAEMI reached up to 25.9k J/m2, which lost 5% of weight at 422 oC.Complex curing agents were synthesized through the reaction between modified EMI(MEMI) and metal salt, and the curing properties of MEMI complexes with DGEBA were studied by DSC, Viscosity, Izod impact strength, tensile shear strength and TG test. The results showed that the MEMI complexes were compatible with DGEBA, and the curing system owned excellent storage stability, which could be cured at 150 oC. The DGEBA with 16.4 wt% of MEMI-M2 maintained flowability for 174 d at room temperature, and the corresponding tensile shear strength on aluminum, steel and copper were 11.5, 18.9 and 17.9 MPa, respectively; besides, the izod impact strength of the the DGEBA cured by MEMI-M2 was 23 k J/m2.Al2O3 and Al N particles as thermal conductive fillers were treated by silane coupling agent(KH-560) and modified Al2O3 and modified Al N were obtained. Thermal conductive coating based on DGEBA was prepared from E-20 epoxy resin, thermal conductive fillers and the homemade curing agent. Tensile strength, adhesion force, thermal conductivity and TG were tested to study the properties of coating, the results indicated that the adhesion force of the coating on aluminum was level 0 or 1, and the coating with modified fillers owned better thermal conductivity and mechanical properties than that with unmodified fillers. When the ratio of the mixture of modified Al2O3 and modified Al N was 1 9, the thermal conductivity of the coating could reach up to 2.11 W/m.K.