Self-healing polyurethanes with ultra-high-strength via nano-scaled aqueous dispersion of lignosulfonates

Abstract

How to overcome the dilemma between self-healing capacity and the mechanical strength for polyurethane materials is an intriguing but challenging topic. Taking advantage of the nano-scaled dispersion of the lignosulfonates in tailored waterborne polyurethane (WPU) emulsion, herein an aqueous dispersion strategy was proposed. Different from the previously reported methods, it is simple, efficient and environmentally friendly. The prepared self-healing polyurethane exhibited an ultra- high tensile strength of 51.4 MPa (higher than previously reported results) combined with a elongation at break of 670% when merely 6 wt% of lignosulfonate was introduced into the WPU system. Upon undergoing three cycles of thermal processing, a tensile strength higher than 30 MPa was still remained. Atomic Force Microscope (AFM) combined with Variable-Temperature Infrared Spectroscopy (V-FTIR) confirmed the existence of the nano-scaled lignosulfonate aggregates within the WPU matrix and the reinforcing mechanism was discussed from a viewpoint of the intermolecular interactions. V-FTIR further revealed the origin of the self-healing from the detected dissociation of the oxime-carbamate bonds with the increased temperature. This nano-scaled aqueous dispersion strategy demonstrates a high potential in designing polyurethane materials with balanced self-healing performance and mechanical properties.