Comparative Study Investigating Bio-Based Reactive Diluents for Photo-Curing Applications

This investigation provides a comprehensive comparison of the selected and synthesized bio-based curable compounds used in the photocured methacrylated vegetable oil. The chosen reactive diluents are vanillin methacrylate (VMA), cinnamyl methacrylate (CMA), isosorbide dimethacrylate (IDMA), glycerol methacrylate (GMA), and glycerol trimethacrylate (GTMA). We synthesized all the mentioned compounds with high final yields (>85%) except for GMA (reached 72% yield). The structural characterization was provided by 1 H NMR and FTIR. In total, four different functional properties were studied: polymerization reactivity, rheological profile, thermal stability, and mechanical characteristics. The most reactive compound, GMA, achieved the polymerization activation energy of 68.2 kJ/mol. The lowest observable viscosity was observed for the curable system containing CMA (25% in the methacrylated oil), with an apparent viscosity of 405 mPa·s at 25°C. The most thermally stable system comprised 25% GTMA in the methacrylated oil, reaching the heat-resistant index of 184°C. The highest flexural modulus was reached by the GTMA-involving system (596 ± 38 MPa), while the highest flexural strength was reached by the IDMA-involving resin (12.7 ± 0.3 MPa). The best rigid-enhanced system contained 25% IDMA, while the most tremendous increase in flexibility was observed with resin containing 25% of VMA.