Novel Multifunctional Epoxy (Meth)acrylate Resins and Coatings Preparation via Cationic and Free-Radical Photopolymerization

Abstract

In this work, a series of novel multifunctional epoxy (meth)acrylate resins based on a low-viscosity aliphatic triepoxide triglycidyl ether of trimethylolethane (TMETGE) and acrylic acid (AA) or methacrylic acid (MMA) have been synthesized. Thanks to the performed modification, the obtained prepolymers have both epoxides as well as carbon–carbon double bonds and differ in their amount. The obtained results indicate that the carboxyl-epoxide addition esterification occurs in the presence of a catalyst (triphenylphosphine) at a temperature of 90 °C, whilst the required degree of conversion can be achieved simply by varying both the reagents ratio and reaction time. The structure of synthesized copolymers was confirmed by spectroscopic analyses (FT-IR, 1H NMR, 13C NMR) and studied regarding its nonvolatile matter content (NV), acid value (PAVs), as well as its epoxy equivalent value (EE). Due to the presence of both epoxy and double carbon–carbon pendant groups, one can apply two distinct mechanisms: (i) cationic ring-opening polymerization or (ii) free-radical polymerization to crosslink polymer chains. Synthesized epoxy (meth)acrylate prepolymers were further employed to formulate photocurable coating compositions. Hence, when cationic photoinitiators were applied, polyether-type polymer chains with pending acrylate or methacrylate groups were formed. In the case of free-radical polymerization, epoxy (meth)acrylates certainly formed a poly(meth)acrylate backbone with pending epoxy groups. Further, photopolymerization behavior and properties of cured coatings were investigated regarding some structural factors and parameters. Moreover, reaction rate coefficients of photo-cross-linking by both cationic ring-opening and free-radical photopolymerization of the received epoxy (meth)acrylate resins were determined via real-time infrared spectroscopy (RT-IR). Lastly, basic physicomechanical properties, such as tack-free time, hardness, adhesion, gloss, and yellowness index of cured coatings, were evaluated.

Photocurable Epoxy Acrylate Coatings Preparation by Dual Cationic and Radical Photocrosslinking

“…Hence, when cationic photoinitiators were applied, polyether-type polymer chains with pending (meth)acrylate groups were formed. In the case of free-radical polymerization, epoxy (meth)acrylates certainly formed a polymethacrylate backbone with pending epoxy groups [ 23 ]. The process of photopolymerization of the obtained resin was tested by both photo differential scanning calorimetry (photo-DSC) and Fourier transform infrared spectroscopy for real-time process monitoring (RT-IR) methods.…”

“…The viscosity tests were carried out using a cone-plate viscometer LAMY RM-100 plus CP 2000. The test methods were described in detail in our previous article on epoxy acrylate prepolymers [ 23 ]. The molecular weight studies were performed in tetrahydrofurane with a liquid chromatograph LaChrom system, RI Detector L-7490 and LaChrom UV Detector L-7400 from Merck-Hitachi, equipped with a PLgel 106 Å column from Hewlett-Packard.…”

Synthesis of Epoxy Methacrylate Resin and Coatings Preparation by Cationic and Radical Photocrosslinking

“…The final reaction temperature was set to 90 • C, and the process was conducted for 5 h in a nitrogen atmosphere, with stirring. The above synthesis parameters were established based on a literature survey [10,[20][21][22][23] and our own experience [19,36]. The reaction products appear as colorless, transparent, viscous liquids.…”

“…Partial acid values (PAVs) were determined by colorimetric titration according to EN ISO 2114:2000 standard, following the procedure described in detail elsewhere [19].…”

“…According to the manufacturer, the latter can be employed in rapid set adhesives, patching compounds, and wear-resistant coatings. In our previous study [19], a series of novel trifunctional epoxy (meth)acrylate resins (EAs) containing at least one epoxy group and at least one acrylate group were synthesized via the addition of (meth)acrylic acid to the triglycidyl ether of trimethylolethane (TMETGE). In addition, the photocurable compositions based on synthesized EAs with cationic and radical photoinitiator were investigated in terms of UV-curing kinetics and coatings performance.…”