High Performance and Repeatable Adhesion Property of Biobased Isosorbide Nonisocyanate Polyurethanes

Because of the potentially dangerous isocyanate monomer, the utilization of polyurethanes (PUs), despite their advantages, remains restricted in many applications. To address this limitation, nonisocyanate polyurethanes (NIPUm-x/y), composed of a high percentage of biobased components with exceptional overall performance, adhesion, and recyclable properties, were synthesized via a solvent-free and environmentally friendly melt polycondensation process. The reaction employed diamine modified carbamate (DC), dimethyl 1,6-hexamethylene dicarbamate (DHMD), and biobased isosorbide (IS) as primary components. The chemical structures of NIPUm-x/y were verified by using Fourier transform-infrared spectroscopy, proton nuclear magnetic resonance, and gel permeation chromatography. The performance of NIPUm-x/y could be adjusted by controlling the dimer amine structure and the DC content. These NIPUm-x/y materials exhibited excellent mechanical properties, with tensile strength observed to range from 0.7 to 12.2 MPa and strain at break varying from 95.8 to 1151.9%. The NIPUm-x/y also exhibited great thermal properties. Representatively, the decomposition temperature (Td), measured at a 5% weight loss, exceeded 238 °C. An increase in DC content resulted in greater molecular chain flexibility, which reduced the mechanical strength of NIPUm-x/y while increasing the elongation at break. The synthesized NIPUm-x/y possessed on-demand and repeatable adhesion properties, as well as recyclability, presenting promising opportunities for industrial applications, such as the packaging of electronic devices and adhesion of various substrates.