Synthesis And Characterization Of Waterborne Epoxy Curing Agent Modified By Silane

A novel waterborne epoxy curing agent was prepared using 3-glycidoxypropyltrimethoxysilane (GPTMS) as a termination agent of the adduct, which was synthesized by triethylene tetramine (TETA) and liquid epoxy resin (E-51). All factors which affect the synthesis and the properties of the waterborne epoxy curing agent were analyzed in detail. Furthermore, the curing process of curing agent with different content of GPTMS was studied. In order to obtain top-quality film, the physical properties of the cured film were measured. Meanwhile, the effects of different termination agents, the content of GPTMS, and the amount of acetic acid on the properties of curing agent and the performance of the cured film were studied.The structure of the products was characterized by Fourier Transform Infrared Spectroscopy (FTIR) and ¹H-NMR, respectively. The results show that the diagnostic peaks of epoxy group and N — H₂ disappeared, and that the reaction has indeed occurred between the oxirane ring of AGE or GPTMS and the amino group of the adduct of TETA and E-51. The structure was also confirmed by ¹H-NMR spectra. The effects of time, temperature and the molar ration of the starting materials towards the reaction could be investigated from the mensuration of the change of epoxy value. The results show that E-51 could completely combine with TETA after a 4h-reaction at 75℃, the mass ratio of TETA to E-51 is 1:1.2. The appropriate conditions of the termination reaction of the adduct of TETA/E-51 by AGE and/or GPTMS are as follows: reaction temperature is 75-85℃, the reaction time is 3-4 h, the molar ratio of epoxy group of terminator to -NH2 group is 1:1, the amount of GPTMS is 3-5%, and the amount of HAc is 5%. The yield coefficient is 95%. The particle size is round 5nm, and the theoretic amine value is about 140 mgKOH/g.The DSC results show that the curing process of waterborne epoxy resin system is diffudion-controlled. There are three stages in the curing process, and the difference of the curing process with GPTMS and without GPTMS exists in first stage: the activation energy of the system without GPTMS drop to 60 KJ/mol from 75 KJ/mol atthe beginning but that of system with GPTMS rise to 85KJ/mol from 60 KJ/mol. The activation energy and the curing rate increase with increase of content of GPTMS. The TGA result shows that the degradation of cured film can be divided into two steps. The thermal stability is also improved by GPTMS in a way. The property content of GPTMS is about 5%The rheological property, the particle size and the distribution of waterborne curing agent, the heat stability, water resistance, adhesion, and flexibility of the cured film made from the waterborne curing agent modified by silane were investigated. The results show that the termination agent AGE can improve the flexibility and adhesion. The particle size of waterborne curing agent is stable after 90 days. The viscosity increases with increase of the content of GPTMS, and decreases with increase of the amount of HAc. On the premise of water solubility and the appropriate viscosity, the optimal amount of HAc should be about 5%.