| Curing agent is an important and indispensable part in epoxy resin applications. It determines the physical properties of cured products with epoxy resin.This issue is aimed at developing a new curing agent for the Southern hot and humid weather which is used as Senior Wood coating together with epoxy resin. According to process requirements, we selected fatty amine as a raw material for the synthesis of modified curing agent. Polyamine curing agent has two kinds of active hydrogen atoms which is primary amine hydrogen and secondary amine hydrogen. As to the reactivity, the former is much higher than the latter. And the primary amine hydrogen can react with epoxy resin quickly at room temperature which will result in great shrinkage stress and make the film become brittle and crack easily. In order to reduce the activity of polyamine curing agent, it needs to use the blocking agent to close part of the primary amine hydrogen. At the same time, it needs a certain amount of epoxy resin used as chain extender to improve the compatibility of the modified curing agent and epoxy resin. In this paper, firstly we use the single-epoxy compound and acrylic compound to modify the diethylenetriamine (DETA) respectively. Then, we use the Differential Scanning Calorimetry (DSC) to detect the Glass Transition Temperature of the different coatings. Further, we detect the curing time, water resistance, tensile strength, elongation at break, adhesion, gloss of the coatings, etc. We analysis the indicators of the cured products and discovered that the E10 is the best blocking agent. In order to solve the problems existed in practical applications, we adjusted the formulation and synthesis technology of the curing agent. At last we got the best results:(1)the molar ratio of the reactants is n(E10):n(DETA):n(E-51)=1.2: 1: 0.3 and the solid content is 65%;(2)the temperature of the first step is 65~70℃and the temperature of the second step is 75~80℃;(3)in this reaction, the way in feeding is by dropping and the time of dropping E10 is 20~30min;(4) the reaction time of the first step is 2 hours and the second step is 2 hours. In addition, we took a series of measures to optimize the formula such as adjusting the solvent and the amount of curing agent, adding methyl methacrylate (MMA) to improve gloss, using the Nonyl phenol (NP) to improve the curing speed etc. The results are as follows:(1)the formula tree of mixed solvent is much better than others and the performance of the film is excellent; (2)when the ratio of epoxy equivalent weight and amine equivalent is 1.0:1.0,the epoxy groups can not fully respond; when the ratio of them is between 1.0:1.0 and 1.1:1.0, the performance of the cured products is best;(3)when the dosage of MMA is 5%,the gloss is to be improved in a certain extent;(4)NP will shorten the curing time about two hours, but will decrease the hardness of the films. |
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