Low-Temperature Foaming Approach for Solvent-free Polyurethane Coating Based on Dual Carbon Strategy

Replacing traditional solvent-based polyurethane with two-component solvent-free polyurethane (SFPU) is an efficient approach to achieving green, low-carbon manufacturing of synthetic leather, but the foaming technology of the coating has always been a challenge. In this study, ZnO nanoparticles (nano-ZnO) were in situ loaded onto the surface of 4,4′-oxibis(benzenesulfonyl hydrazide) (OBSH) first, and then the nano-ZnO-loaded OBSH was further modified with KH-550 to improve its dispersion in the SFPU matrix. Finally, zinc stearate (ZnSt2) was doped with nano-ZnO-modified OBSH to activate OBSH, that is, to reduce its decomposition temperature. By means of a synergistic activating strategy, the as-prepared composite foaming agent (CFA) shows a lower decomposition temperature of around 140 °C, and when applied in the manufacture of synthetic leather, a desirable foaming ratio, high peel strength, superior softness and resilience, as well as enhanced water vapor permeability were achieved. More importantly, compared with solvent-based synthetic leather, no VOC emission, zero solvent usage, and more than half reduction in energy consumption were also obtained. This approach offers a promising solution for the green, low-carbon manufacture of synthetic leather.