Introduction to the chemistry, synthesis, manufacture and characterization of epoxy resins

Effects of composition of hardener on the curing and aging for an epoxy resin system

“…The pre-existing secondary amine groups increase the concentration of secondary amine groups and, therefore, increase the chance of secondary amine-epoxide reaction. In hot environments, the difference between the reaction rate for primary amine-epoxide reaction and secondary amine-epoxide reaction is small, 8,9 so the total secondary amine-epoxide reactions can be more than the total primary amine-epoxide reactions due to higher concentration of secondary amine groups compared to primary amine groups. Since the amount of heat generated by per mol secondary amine reactions is more than the amount of heat generated by per mol primary amine reactions, the exothermic heat per mol epoxide in the studied system can be more than the reported 107 kJ obtained from the conventional epoxy-diamine system, in which the amount of reactable primary is equal to the amount of reactable secondary amines.…”

“…5(a)] is the lowest among the studied systems. While T g and modulus usually increase with the increase of degree of cure, the contradiction can be explained as follows: According to Ellis,9 at 22°C, the rate of the reaction between secondary amine and epoxy is just equal to one-fourth of the rate of the reaction between primary amine and epoxy. Thus, during the initial curing stage at room temperature, the main reaction is the reaction between primary amines and epoxide unless there is not enough primary amine to react.…”

“…7 Grillet and coworkers 8 found that the reaction rate constant for secondary amines [Scheme 1(b)] is about 0.8 ϳ 0.9 of the reaction rate constant for primary amines [Scheme 1(a)] in a DGEBA/DDS diamine system. Ellis 9 found that the relative rates of reaction of secondary to primary amines increased with cure temperature, 0.25 at 22°C and 0.75 at 50°C. The etherification reaction [Scheme 1(c)] is usually much slower than the amine-epoxy reactions.…”

“…The etherification reaction [Scheme 1(c)] is usually much slower than the amine-epoxy reactions. 9,10 Therefore, for a hardener-rich system, the reactions between the epoxy group and the primary amine dominate the curing reaction, and the etherification reaction can be ignored. For epoxy-rich systems, the etherification reaction might dominate the curing reaction after most of the primary amines and secondary amines are consumed during the initial curing stage.…”

Carboxy Derivative of Dioxydiphenylpropane Diglycidyl Ether Monomethacrylate as an Additive for Composites

“…The main demand for such products is the presence of reactive groups capable to react with functional groups of the composite at room temperature and at heating [3,4]. Epoxy compounds are widely used as the initial materials [5].…”