Bio-based organic-inorganic hybrid UV-curable hydrophobic coating prepared from epoxidized vegetable oils

Abstract

Bio-based coatings gradually become an ideal substitution for the non-renewable petroleum-based coatings due to the features of environmental friendliness and low cost, and the preparation of high-performance bio-based coatings via a facile method is highly desirable. Herein, bio-based organic-inorganic hybrid UV-curable coatings with self-cleaning property were prepared in a solvent-free one-pot method. In this coating system, synthesized epoxidized castor oil (ECO) was used as a coating precursor, glycidyl methacrylate (GMA) and 3-glycidoxypropyltrimethoxysilane (GPTMS) were used as reactive diluents, and triarylsulfonium salt (TAS) was used as an effective cationic photoinitiator. Besides, commercial epoxidized soybean oil (ESO) was employed as another coating precursor to compare with ECO. The chemical structure of the synthesized ECO was confirmed by 1H NMR and FT-IR. The occurrence of double bond radical copolymerization, epoxy ring-opening copolymerization and trialkoxysilyl sol-gel reaction in the cured films was proved via ATR-FTIR. The properties of the films cured with different GPTMS contents were investigated. Dynamic mechanical analysis (DMA) results revealed that EC films showed better performance than ES films, and the addition of GPTMS reduced the glass transition temperature (Tg) and crosslinking density (νe) of the cured films. However, the addition of GPTMS increased the peak temperature (Tp) and char yield (Wchar) of the cured films, indicative of the enhancement in thermal stability. SEM results indicated that the incorporation of GPTMS in the cured films facilitated the obtainment of a smooth surface. Furthermore, all of EC films were hydrophobic, and they also exhibited self-cleaning property. In addition, they showed excellent hardness and acid resistance. Therefore, this study provided a facile approach to preparing bio-based organic-inorganic hybrid UV-curable films with self-cleaning property, and the high performances of these cured films made them potential for practical applications.