Photocurable Adhesive Composed of Modified Castor Oil and Enhanced by Valorized Glycerol from Waste Cooking Oil

Abstract

This article describes the production of a photocurable adhesive from renewable sources, i.e., castor oil and waste cooking oil. An innovative castor oil ethanolamide methacrylate (Oil-EA-Met) was synthesized to form the primary binder precursor. The waste-oil-resourced glycerol derivatives, modified to mono-, di-, and trimethacrylate derivatives (MGLY, DGLY, and TGLY), represent functional additives. All products were cross-analyzed using 1H NMR, ESI-MS, FTIR, and GC-FID. Oil-EA-Met represented 75% of the formulated precursor systems, while the functional additive (MGLY, DGLY, TGLY, and a commercially available 2-hydroxyethyl methacrylate (HEMA)) represented 25% of the curable precursor. MGLY had the best impact on the adhesion performance. This additive exhibited the highest polymerization reactivity (E a = 68.2 kJ/mol), a complete miscibility with water, the highest thermal resistivity, a thermomechanical profile, a flexural character, and the highest ISO 2049 adhesion levels on wood-glass substrates (reaching level 5 (the highest)) and wood-PMMA substrates (level 3). The adhesive containing MGLY reached a similar wood-glass adhesion shear strength of 1400 kPa as the system with HEMA and surpassed the HEMA system for the wood-PMMA system (the MGLY system reached 800 MPa; the HEMA system achieved 530 MPa).