Polyurethane adhesive based on polyol monomers BHET and BHETA depolymerised from PET waste

During the development of the polyurethane (PU) industry, one of its biggest challenges has been synthesis and formulation-related due to a lack of renewable resources and thus an over-reliant dependence on fossil reserves which has led to considerable research effort focused on alternative renewable sources of supply. In this study, PET bottle waste and castor oil have been considered as alternative sources for the synthesis of a PU adhesive. A cheap and environmentally friendly synthesis pathway for polyols is provided using depolymerization reactions of recyclable materials. The structures of the polyols have been demonstrated using Fourier-transform infrared spectroscopy (FTIR) and nuclear magnetic resonance (NMR) spectroscopy. Different NCO/OH ratios with calculated amounts of MDI were used to prepare polyols which were then employed during PU preparation and their effects on the resultant PUs were investigated. Solvent-free polyurethane adhesives were synthesized. Changes in the properties of PU synthesized by the addition of castor oil and boron species to the structure were also determined. The thermal behaviour of PU samples were characterized by DSC-TG; and functional group detection and covalent bonding formation were investigated via FTIR analysis.