The work reported demonstrates that the yellowness of UV-curable epoxide resins can be improved by adding certain tertiary amines in appropriately determined amounts. According to the results of our experiments, 2.0 we% benzoyl peroxide added to a resin effectively enhances the crosslinking density, and phenolic free radicals are produced during UV curing, which consequently induce yellowness via the reaction of oxygen and the free radicals. Imidazole (1-amine) and tertiary amines, including 1,2-dimethylimidazole (2-amine), 2,4,6-tris (dimethylaminomethyl)phenol (3-amine), 1-methylimidazole (4-amine) and 2-methylimidazole (5-amine), were chosen to be added to resins, and their effects on UV conversion and yellowness were investigated. According to the experimental results, tertiary amines in the resin can provide a certain degree of improvement in yellowness index (ΔYI) and color parameter (ΔE*ab) of the resin sample. Whatever the type of tertiary amine, it is found that the optimum content of amine in resin is 1.0 wt%. Also, among the studied amines, the 3-amine exhibits the highest UV reactivity and the best efficiency for yellowness improvement with values of Δa·, Δb*, AYI and ΔE*ab as low as - 1.4, 6.23, 11.27 and 6.48, respectively.
- Tertiary amines
- UV-curable epoxide resin