The effect of reactive diluents on curing of epoxy resins and properties of the cured epoxy coatings

The effect of monofunctional, difunctional, and trifunctional reactive epoxy diluents (RDs) on curing of epoxy resins by amine hardeners was studied by DSC and oscillatory rheometry. It was determined that curing of the epoxy resins containing difunctional RD was characterized by the lowest activation energy Ea, and the cure reaction was of first order. The shortest gelation time under curing was characteristic for the epoxy resins containing difunctional RDs, while vitrification time of the cured epoxy resins containing difunctional or trifunctional RDs was similar. The use of difunctional RDs as a part of epoxy resins was the most advantageous since they facilitated curing process enabling to reach high degree of curing faster. The effect of RDs of various functionalities on glass transition temperature Tg of the cured epoxy resins and mechanical properties of the epoxy coatings was noticeable but small. Functionality of RDs had no noticeable effect on adhesion and flexibility of the epoxy coatings. Coatings of the cured epoxy resins containing difunctional RD were characterized by slightly higher hardness and increased abrasion resistance. Difunctional reactive epoxy diluents show great potential to be used in epoxy formulations by facilitating curing process and improving mechanical properties of the cured epoxy coatings.