Synthesis and Performance of Biobased Polyurethane Adhesives from Epoxidized Soybean Oil and Isosorbide

Biobased polyurethane pressure-sensitive adhesives were produced with polyols based on epoxidized soybean oil (ESO) and isosorbide (ISO). Soybean oil-based polyol was synthesized via epoxide ring-opening with ISO and catalyzed by adding aluminum triflate (Al(OTf)3) - named polyols ESOISO. Two polyurethane recipes were produced by mixing the polyol ESOISO and polylactic acid (PLA) and then reacting with hexamethylene diisocyanate (HDI) - named PU ESOISO and PU ESOISO/PLA. The characteristic molecular groups of polyols and polyurethanes were evidenced using FTIR and NMR techniques (13C NMR and 1H NMR, HSQC, and HMBC-2D NMR). The exothermic peak of ESOISO 0.1 mol % (Al(OTf)3) ranged between 80 and 115 °C. Al(OTf)3 promoted the curing, i.e., lower Ea consumption and increased availability of OH groups in the polyol. The Tg of PU adhesives ranged between -15.45 and -13.86 °C. The H-bond supramolecular structure provided by the polar groups enabled the networks to behave as adhesives, improving the self-healing character when the bonded interface was damaged. PU ESOISO/PLA achieved high-efficiency self-healing and adhesivity performance with the potential for a sustainable adhesive framework design.