Effect of siloxane chain length on thermal, mechanical, and chemical characteristics of UV (ultraviolet)-curable epoxy acrylate coatings

Abstract

In this research, high-performance epoxy acrylate (EA) coating formulations that contain various acrylate-modified diepoxy siloxane (DESA) intermediates were synthesized and characterized. Firstly, diepoxy siloxane (DES) intermediates, which have varying chain lengths (Mw = 370-3300 Da), were modified by acrylic acid via the ring-opening reaction oxirane group. DESA intermediates were then used in the preparation of ultraviolet (UV)-curable EA formulations. EA was also synthesized via acrylic acid modification of a commercial bisphenol-A-based epoxy resin, used as the standard formulation. EA-based UV-curable formulas were applied on substrates and then cured by UV irradiation for investigating the coating performances. Subsequently, performances of the UV-cured coatings were evaluated by the various test techniques, such as hardness, gloss, cross-cut adhesion force scratch resistance, contact angle, yellowing resistance, abrasion resistance, chemical resistance, and color measurement. The effect of DESA variety on the formations was examined compared to both themselves and the standard formulation. The results showed that the varying amounts and chain lengths of DESA influenced UV-curable coatings' properties; particularly, the scratch resistance, contact angle, and yellowing resistance significantly enhanced with the increasing chain length of DESA. High-performance UV-curable EA formulations could be produced with the scratch resistance of 4 N, the contact angle of 95 degrees, and high yellowing resistance (Delta E = 0.35).