Photocurable Oil-Based Thermosets Containing Modifiers from Renewable Sources for Coating Applications

Abstract

Coating materials involving nature-inspired compounds or renewable sources have recently attracted vast attention. This article presents the synthesis of modified rapeseed oil (MRO) as a precursor possessing high biobased carbon content suitable for cured thermosets formation. Two reactive diluents based on renewable sources, methacrylated methyl 3-hydroxybutyrate (M3HBMMA) and ethyl 3-hydroxybutyrate (E3HBMMA), were successfully synthesized. Lastly, isosorbide monomethacrylate (MISD) was suggested and produced as a polarity modifier miscible with modified curable oil systems capable of increasing the thermoset surface energy. All synthesized compounds were structurally analyzed via NMR, ESI-MS, and FTIR. The characterized reactive substances were coated on paper, stainless steel, and beech wood to investigate their suitability for forming thin layers. The paper dip coating verified the reactive diluting properties of M3HBMMA, resulting in the average formed coating deviation decrease (87.5% for undiluted MRO and 28.0% for 50 wt % M3HBMMA containing MRO). Also, the additional cured thermoset weight decreased from 350 to 69 wt % for the same systems. The standardized bend test applied on the coated stainless steel specimens revealed the thermoset's flexibility and adhesion increase from a 12 ± 2° bending angle of 100% pure MRO to a 121 ± 2° bending angle measured for 40 wt % E3HBMMA containing the MRO-based thermoset. The coated beech wood samples underwent the standardized cross-hatch test investigating the substrate's coating quality. The 100% MRO reached a level 1 rating (second worst), while the system with 40 wt % of MISD obtained a level 5 rating (the best).