Study On Preparation And Properties Of Modified 2-Phenylimidazole Curing Agent

As a kind of epoxy resin curing agent,the imidazole compounds with many advantages,such as non-polluting,low volatility,less solvent,low toxicity and the solid product show excellent physical and chemical properties.However,most imidazole compounds have significant disadvantages.Imidazole compounds is not well-mixed with epoxy resin because it is solid at room temperature.The pot life and latency of materials made from epoxy resin and imidazole are short.Aiming at these problems of imidazole curing agents,the following work has been carried out in this paper.(1)Modified 2-phenylimidazole by propylene carbonate(PC-PI)was synthetized via substitution reaction of 2-phenylimidazole with propylene carbonate(PC).The curing system was prepared by PC-PI and epoxy resin.The effects of synthesis process conditions on the performance of modified curing agent PC-PI were investigated by measuring DSC,tensile shear strength,curing time,60 ? gelation time at 60 ? and hardness and adhesion of the cured coating.Based on this,the synthesis process of PC-PI was optimized.And the product structure was characterized by FTIR and 1H-NMR.The results show that PC-PI of good performance can be obtained when the molar ratio of 2-PI to PC is 1:3,and they reacted at 140 ? for 4 h.The hydrogen atom of 1 bit nitrogen of 2-PI imidazole ring is replaced,and the hydroxyl group is introduced into modified 2-phenylimidazole.(2)The curing process of PC-PI was optimized.PC-PI and 2-PI was compared in four aspects as follow,material state,the pot life of epoxy curing system at room temperature,physical properties and tensile shear strength of cured resine.Kinetic analysis of PC-PI epoxy curing system was investigated by DSC,and the kinetic equation and apparent activation energy were determined.The results shows the properties of epoxy resin curing system cured at 140 ? for 45 min are ideal when the mass ratio of PC-PI to epoxy resin is 6:100.The compatibility of 2-phenylimidazole is improved by modifying the 2-PI to the liquid PC-PI.The PC-PI is a liquid and 2-PI is solid powder.The former is more easily mixed with epoxy resine,and the purpose of modification is achieved.Compared PC-PI with 2-PI,the activity increases,the storage period at room temperature of 2-PI and PC-PI is 30 and 21 days,respectively.And the shear strength of the adhesive cured by 2-PI and PC-PI are 7.3 MPa and 16.41 Mpa.The apparent activation energy of PC-PI epoxy curing system is 76 kJ/mol.Its kinetic equation and rate constant are as follow:d?/dt=k(T)(1-?)0.915,k(T)=1.282×109 exx(-76000/RT).(3)The complex modified 2-phenylimidazole(CAM-PI)were prepared by complex Reaction PC-PI with copper acetate.The synthesis process was also optimized.The complexation reaction was proved by FTIR and 1H-NMR.The results showed that CAM-PI synthetized at 100 ? for 60min is of good performance when the molar ratio of 2-phenylimidazole,PC and copper acetate was 1:4:0.3.(4)The curing process of CAM-PI was optimized.The kinetics of CAM-PI epoxy curing system was analyzed by DSC,and the kinetic equation and apparent activation energy were also determined.CAM-PI and PC-PI were compared as follow,material stat,storage period of epoxy curing system at room temperature,physical properties of solidified coating,tensile shear strength and acid resistance.The results show that when the mass ratio of CAM-PI to epoxy resin is 7:100,the cured product prepared at 100 ?for 60min shows an ideal performance.The apparent activation energy of CAM-PI epoxy curing system is 78.38 kJ/mol.Its kinetic equation and rate constant are as follow:d?/dt=k(T)(1-?)0.917 and k(T)=1.8×109 exp(-78380/RT),respectively.The storage life of CAM-PI reached 140 rather than 21 days of PC-PI,showing a good latent property.