Development of adhesives from biopolyols and free of isocyanates

The synthesis of polyurethane adhesives from isocyanates and polyols, which is widely used nowadays, poses a problem for modern society, as both isocyanates and phosgene, their precursor, are extremely toxic and pollutant. With this, there is the need to find a greener alternative process to synthesize these adhesives. In this work, polyurethane adhesives free of isocyanates were synthesized as an alternative to the currently commercialized polyurethane adhesives, using bio-based polyols. Sucrose-based adhesives were first synthesized and characterized, working as models to other bio-based polyols. The methodology used for the adhesive synthesis was developed according to information available in literature and properly optimized. The adhesives were extensively characterized by Fourier Transform-Infrared spectroscopy and Nuclear Magnetic Resonance (proton and carbon) and used in the preparation of lignocellulosic materials. The addition of a cross-linking agent was also tested. The performance of the prepared lignocellulosic materials was evaluated using different techniques, such as Thermogravimetric Analysis and Dynamic Mechanical Analysis, mechanical tests, hydrophobicity, absorption and swelling tests. The results were compared using proper statistical analysis and compared to literature values when possible.