Study On The Mechanism Of The Synthesis Of Phenylbiguanide And The Kinetics Of Curing Epoxy

Monocomponent epoxy resin has excellent properties and has broad application prospects in many areas.Based on modifying dicyandiamide with aromatic amines, a series of biguanide latent curing agent was synthesized and a detailed study on its synthesis and curing reaction has been carried out in this paper. Including:(1) Adopting of the additive reaction of aromatic amines with dicyandiamide, phenylbiguanide and seven of its derivatives have been synthesized. Its structure was characterized by IR spectrum. Their purity as well as their melting point and solubility were determined.(2)The additive reaction kinetics of aniline and its derivatives with dicyandiamide was studied. The influence of reaction order and acidity on the reaction rate was determined. On the basis, the mechanism of the nucleophilic addition reaction of aniline with dicyandiamide was brought forward. The reaction rate equation is derived from the mechanism. Its form is consistent with the experimental results, and the deduction of the equation is well approximation with the experimental results. Morever, it is also found the side reaction of dicyandiamide hydrolyzing to guanylurea during the synthesis of phenylbiguanide and its derivatives. The trend of the hydrolysis is significant with the increasing acidity.(3) Based on the mechanism of the main reaction and the side reaction, the synthesis technology was optimized. Compare with the traditional method, higher yields have been got in a relatively short period.(4) The theoretical analysis shows that, ideal latent curing agent have reaction kinetics characteristics of higher curing reaction activation energy and higher apparent frequency factor; or the curing reaction activation energy increases significantly with the decreasing temperature.(5) Monocomponent resin system was prepared with phenylbiguanide and its derivatives with epoxy resin. The apparent activation energy and apparent frequency factor of the curing reaction system were determined. The storage applicable period and the curing reaction activity were also studied. The results show that the relationship between system latent with the curing reaction activation energy and the apparent frequency factor is consistent with preceding theoretical analysis. What's more, the influence of diverse structure of the curing agent and their amount as well as different diluent on the curing reaction kinetics parameters in the systems. The above change rules were explained combined with the collision theory and the transition state theory of the chemical reaction rate.(6)The curing epoxy resin mechanism.of phenylbiguanide and its derivatives was discussed. The curing reaction of the system mainly include two parts: the addition of epoxy resin with amino group and the addition of epoxy group with hydroxide group. The addition of amino group is a relatively fast reaction, while the addition of hydroxide group is relatively slow. It is more obvious in the later curing, but its role should not be overlooked. The results of IR spectrum and mechanical test provide support for the above mechanism.