Fully Biobased Thermoset Adhesive Precursor from Itaconic Acid and Propylene Glycol

Photocurable adhesives serve numerous practical applications, such as medical devices, electronics, sealing in LCDs, or glass bonding. This work focuses on a scalable and sustainable engineering of a new reactive precursor for photocurable adhesives, dipropylene glycol itaconate (DPG-IA). Synthesis involved Fischer esterification, with more than 98% conversion measured by convenient and affordable volumetric analyses (acid number and hydroxyl value). The product's structural verification was provided by ¹H Nuclear Magnetic Resonance (NMR) and FT-IR analysis, confirming a highly pure yield (more than 99%). Particularly, ¹H NMR and FT-IR uncovered the presence of unsaturated double bonds, which can by radically polymerized and from cured molecular structure. The rheological profile and curing reactivity were investigated since they are crucial for photocurable adhesives. The apparent viscosity reached 1050 mPa·s at 25 °C, and the calculated flow activation energy reached 70.1 kJ/mol. DPG-IA's reactivity was studied by Differential Scanning Calorimetry (DSC), uncovering the polymerization activation energy reaching 115 kJ/mol. Eventually, the adhesion strength, achieved by the cured DPG-IA on the acryl, wood, and glass adherents, was investigated. The measured adhesion strength for the acryl-wood adhesion reached 53.6 ± 1.5 kPa, and for the acryl-glass system it reached 83.4 ± 4.4 kPa.