Advancing sustainable adhesive: potential use of recycled polyethylene terephthalate (PET) polyols for the synthesis of polyurethane hot melts adhesive

The word "versatility" defines polyurethane. The reaction between di-isocyanate and polyester polyol led to the formation of polyurethane. The focus of this work is to generate eco-friendly, sustainable polyols by using waste material, such as polyethylene terephthalate (PET) which was further used to prepare hot melt polyurethane adhesive. PET was degraded via the chemical degradation method under controlled conditions, as prepared polyol was further used to prepare hot melt polyurethane adhesive with di-isocyanate (MDI), polyol (PEG), and chain extender (BDO). By taking into account the advantage of nanotechnology SiO 2 nanoparticles were incorporated to impart mechanical strength to prepared hot melt polyurethane adhesives. FTIR and NMR spectrographs confirm the formation of the final product by the absence of -NCO- peak and the presence of -NH- peak. Surface morphology and crystallinity results through AFM and XRD represent well-stabilized formulations by the continuous distribution of PET polyol, and SiO 2 in polyurethane matrix. The addition of PET polyol and SiO 2 provides mechanical stability to the prepared sample, by resisting the deformation at elevated temperatures, indicated by TGA/DSC thermograms. A remarkable improvement in adhesion properties and chemical resistance was observed in the prepared hot melt adhesives with an increase in melting viscosity and T-peel strength. These enhancements were attributed to the increased content of PET polyol and the incorporation of SiO₂ into the adhesive formulations. The current research provides evidence that recycled PET, when combined with optimized adhesive formulations, can be effectively used in hot melt adhesive applications across a variety of uses.