Synthesis of Hybrid Epoxy Methacrylate Resin Based on Diglycidyl Ethers and Coatings Preparation via Cationic and Free-Radical Photopolymerization

Abstract

A series of difunctional epoxy methacrylate resins (EAs) containing at least one epoxy and at least one methacrylate group were synthesized by means of an addition reaction between epoxy-terminated diglycidyl ethers and methacrylic acid. In order to investigate the impact of polymer architecture on the course of addition reactions and further coating properties, several different types of diglycidyl ethers, i.e., linear, containing aliphatic or aromatic rings, with a short or polymeric backbone, were employed in the synthesis. The carboxyl–epoxide addition esterification reactions have been found to, in a relatively straightforward manner, control the extent of acrylation depending on the substrate feed ratio and reaction time. The structure of obtained pre-polymers was evaluated by FT-IR and NMR methods. At the same time, the extent of addition reactions was validated via quantitative analysis, including non-volatile matter content (NV), acid value (PAVs), and epoxy equivalent value (EE) analysis. The modification was carried out in a manner likely to create a compound with one epoxy and one carbon–carbon pendant group. Hence, due to the presence of both functionalities, it is possible to crosslink compositions based on synthesized EAs via two distinct mechanisms: (i) cationic polymerization or (ii) free-radical polymerization. Synthesized epoxy methacrylate pre-polymers were further employed for use in formulate photocurable coating compositions by the cationic or radical process. Furthermore, the photopolymerization behavior and properties of cured coatings were explored regarding some structural factors and parameters. The investigated polymeric materials cure in a short time to obtain coatings with good properties, which is why they can be successfully used to produce protective and decorative coatings for many industries.

Epoxy (Meth)acrylate-Based Thermally and UV Initiated Curable Coating Systems

“…A significant difference was observed for CHMEDE-AA, whose value of EGC was approximately 31%. The difference in results can be the result of distinct chain architecture, reactivity, viscosity, molecular weight and molecular mobility, which was also observed in one of our recent studies [30]. Therefore, it is impossible to state any single factor that determines the rate of response, as well as the degree of conversion of EG and AA or MAA (Table 2).…”

“…In our previous studies [ 7 , 21 , 26 , 30 ] we described in detail the dual-curing process of epoxy (meth)acrylate (EA) coatings, specifically the use of two different photopolymerization mechanisms, i.e., radical and cationic. In turn, this study presents a dual-curing process that takes into account various initiation methods, i.e., using electromagnetic radiation and elevated temperature.…”

“…Comparative FTIR spectra of the uncured formulations and cured films are illustrated in Table 3 . The analysis centered on specific absorption bands: epoxy ring stretching vibration (-C-O) at 915 cm −1 and C-O-C (~825 cm −1 ) stretching vibrations [ 31 , 32 ]; ether groups (-C-O-C) at 1036 cm −1 [ 33 ]; and carbonyl stretching mode (-C=C) from 1607 cm −1 to 1635 cm −1 [ 34 , 35 ] and 809 cm −1 [ 30 ] associated with acrylic or methacrylic acid. Moreover, the absorption peak corresponding to C=O stretching vibrations was observed at 1718 cm −1 .…”