The Synthesis Of The Modified Aliphatic Amine And The Study Of The Curing Reaction Of Its Cured Epoxy Resin

Waterborne epoxy coating with water as the dispersion medium, is an environmental friendly development prospect, it maintains excellent physical and chemical properties of epoxy resin. However, epoxy resin can’t have the coating function until turns to the polymer under the using of the curing agent, so the development of the waterborne epoxy resin curing agent becomes a research focus. So far, the waterborne epoxy curing agent is poor compatibility with epoxy resin, which leads to unideal coating apparent and bad water and chemical resistance. The short period of coating increases the difficulty of construction. In this paper, two kinds of modified aliphatic amine curing agent were synthesized, then cured two kinds of epoxy resin. The properties of the coating were systematically studied. Meanwhile, the curing kinetics and the model of the waterborne amine curing agent cured epoxy resin were researched by the differential scanning calorimetry (DSC) in the nonisothermal and isothermal conditions, respectively. The specific contents were as follows:The triethylenetetramine (TETA) was modified with polyoxyethylene glycidyl ether (PEGDE) as modifier, epoxy resin (E44/EPON828) as extender. Subsequently, two kinds of aqueous amine curing agents were synthesized and characterized by FTIR. This thesis discussed the synthesis process of curing agent by single factor method. The waterborne epoxy resin coating was prepared by mixing the waterborne epoxy curing and epoxy resin, and the coating properties were tested. The results showed that the optimal reaction time is 4 h, the proper reaction temperature is 70—75℃. The waterborne epoxy coating were prepared by mixing the two kinds of waterborne epoxy curing agent and epoxy resin (E44, EPON828), and its properties were tested. The optimal dosing quantity of E44 is 0.025 mol, the coating surface is smooth and transparent, the surface drying time of the coating is 2 h and completed drying time is 5 h, the resistance of water and chemical is the best, and the hardness of the coating is 4 H, the flexibility reaches to level 1, which achieve the intended target.The non-isothermal curing reaction of two kinds of curing agent (TETA-PEGDE-E44, TETA-PEGDE-EPON828) cured with epoxy resin (E44, EPON828) have been systematically investigated by using differential scanning Calorimetry (DSC). The results indicated that there is only one single exothermal peak in the nonisothermal curing reaction heat curves of the systems, which demonstate the curing reaction involves epoxy amine without side reaction. The apparent activation energy of the four systems were obtained from the method of Kissinger is 45-65 kJ/mol, which is also consistent with the typical amine curing reaction (50-70 kJ/mol). The relationship between the conversion and the activation energy is analyzed by the Flynn-Wall-Ozawa(FWO) method. The results showed that four systems have similar variation, there is a higher activation energy in the initial reaction but it decreased gradually as the conversion rate increased, which shows the typical characteristics of self catalyzed reaction. At the same time, with the Malek method the reaction kinetic analysis confirms the parameters of SB(m, n) model. The corresponding rate equations were established and used to model the reaction rate. The model values are agree well with experimental values. The conversion rate curve and the reaction rate curve of the systems show that the curing process is self catalytic properties.The isothermal curing reaction process of four systems (TETA-PEGDE-E44/E44 TETA-PEGDE-EPON828/E44, TETA-PEGDE-E44/EPON828, TETA-PEGDE-EPON828/EPON828) were systematically studied by using DSC, the thermal curve of isothermal curing reaction is obtained. The results indicated that in the thermal curves of the isothermal curing reaction, there is one single exothermal peak, all of above systems, which is expressed that only the epoxy amine reaction is involved, no side reaction happens. The self catalytic activation energy Ea2 of the systems are less than the non-autocatalytic activation energy Ea1. Because with the reaction proceeds, hydroxyl was generating, and the transition state of hydroxyl, epoxy group and amido were formed, which will reduce the activation energy of the reaction. The self catalytic reaction getting easier, which means that Ea2 is smaller than Ea1. With the increase of the reaction time, the curing reaction rate of the systems was first increased and then decreased, which is a basic characteristic of the autocatalytic reaction. So the autocatalytic model-Kamal model was selected to simulate the reaction rate of the isothermal curing, the reaction rate equations of curing reaction were established, the reaction rate of test data are in agreement with the Kamal model. The maximum curing rate were observed at conversion of 0.1-0.2 is slightly ahead of other epoxy amine systems(0.2-0.4), which reflects that the hydroxyl content of the waterborne curing agent is relatively high and the reaction systems containing a small amount of phenolic hydroxyl groups, these groups effectively catalyze the isothermal curing reaction of the aliphatic amine/epoxy resin.