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).

• Publication type
• Journal Article MeSH

Bio-based cross-linkers can fulfill the role of enhancing additives in bio-sourced curable materials that do not compare with artificial resin precursors. Isosorbide dimethacrylate (ISDMMA) synthesized from isosorbide (ISD) can serve as a cross-linker from renewable sources. Isosorbide is a bicyclic carbon molecule produced by the reaction modification of sorbitol and the optimal conditions of this reaction were studied in this work. The reaction temperature of 130 °C and 1% w/w amount of para-toluenesulfonic acid (p-TSA) were determined as optimal and resulted in a yield of 81.9%. Isosorbide dimethacrylate was synthesized via nucleophilic substitution with methacrylic anhydride (MAA) with the conversion of 94.1% of anhydride. Formed ISD and ISDMMA were characterized via multiple verification methods (FT-IR, MS, 1H NMR, and XRD). Differential scanning calorimetry (DSC) proved the curability of ISDMMA (activation energy Ea of 146.2 kJ/mol) and the heat-resistant index of ISDMMA (Ts reaching value of 168.9) was determined using thermogravimetric analysis (TGA). Characterized ISDMMA was added to the precursor mixture containing methacrylated alkyl 3-hydroxybutyrates (methyl ester M3HBMMA and ethyl ester E3HBMMA), and the mixtures were cured via photo-initiation. The amount of ISDMMA cross-linker increased all measured parameters obtained via dynamic mechanical analysis (DMA), such as storage modulus (E') and glass transition temperature (Tg), and the calculated cross-linking densities (νe). Therefore, the enhancement influence of bio-based ISDMMA on resins from renewable sources was confirmed.

• Keywords
• PHB, alkyl 3-hydroxybutyrates, cross-linker, enhancement, isosorbide, isosorbide dimethacrylate,
• Publication type
• Journal Article MeSH