Biobased comb polyurethane hot-melt adhesives consisting of dangling fatty acid chains and H-bonds for tailoring bonding strength

Abstract

Traditional polyurethane hot-melt adhesives often fall short in achieving high bonding strength and recyclability, and their dependence on non-renewable resources poses a significant hurdle for sustainable development. In this study, a palm oil-based diethanolamide (POEA) containing a long aliphatic chain was synthesized to develop comb thermoplastic polyurethane hot-melt adhesives (POPUs) with high biobased content, superior adhesion strength, and reusability. The microphase separation structure of POPUs was manipulated through the incorporation of dangling fatty acid chains and hydrogen bonds, resulting in the adhesives with excellent mechanical properties, with an optimum tensile strength of 5.37 MPa and an elongation at break of 282 %. As a hot-melt adhesive, it achieved a maximum lap-shear strength of 7.34 MPa on steel and maintained an average strength of 95 % of its initial value across multiple bonding cycles. Moreover, its lap-shear strengths with wood and glass remained at 6.57 MPa and 3.57 MPa respectively, fully meeting the requirements for interior decoration. Additionally, it was unexpectedly discovered that the adhesives possessed fluorescence characteristics, which can be applied in fields such as cultural relic restoration and anti-counterfeiting.