Hyperbranched Polyurethanes with Flammability Resistance for Leather Retanning

In this study, diethyl bis(2-hydroxyethyl) aminomethyl phosphonate was modified by hexamethylene diisocyanate, and then was utilized to partly replace the isocyanates to prepare hyperbranched polyurethanes (HPU-DPAs). The hyperbranched polyurethanes were then employed in the retanning process of wet blue. The shrinkage temperature, average thickness as well as mechanical properties of leather before and after retanning were acquired. The flammability of retanned leather was measured by cone calorimeter test. The morphologies of wet blue and leather after retanning by HPU-DAP were obtained using a scanning electron microscope. Results showed that the average thickness, tensile strength and elongation at break of leather were all improved after retanning. Retanning by HPU-DAPs can effectively increase flame retardancy of final leather.