Design and Preparation of a High Mechanical Strength Recyclable Polyurethane Adhesive Based on Dynamic Disulfide Bonds

To overcome the major limitations of poor mechanical properties of traditional polyurethane adhesives and improve their low reuse efficiency, a series of thermoplastic polyurethane adhesives, named 2SPU, were obtained by combining polyester polyols: poly-1,4-butanediol adipate (PBA), self-made soybean oil-based polyols (MESO), and toluene diisocyanate (TDI), and incorporating dynamic disulfide bonds to introduce thermal cycling function. Properties analysis shows that when the synthesized polyurethane adhesive contain 5% 2,2 '-dithiodianiline (2-AFD), it exhibits great mechanical strength and good self-healing ability (compared to the adhesive without disulfide bonds, its shear strength increases from 43.38 to 118.08 MPa and its initial repair efficiency could increase from 24.4% to 96.6%). SEM clearly shows the self-healing process. These polyurethane adhesives based on S-S chain exchange reaction has great application potential as a dressing for promoting the recycling of high bonding strength adhesives.