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

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 ligno-sulfonates 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 pre-viously 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.

Automated summary

An aqueous dispersion strategy using nano-scaled ligno-sulfonates was proposed to overcome the dilemma between self-healing capacity and mechanical strength for polyurethane materials. The prepared self-healing polyurethane showed an ultra-high tensile strength and elongation at break, even after undergoing thermal processing. Atomic Force Microscope (AFM) and Variable-Temperature Infrared Spectroscopy (V-FTIR) confirmed the presence of nano-scaled ligno-sulfonate aggregates and discussed the reinforcing mechanism. V-FTIR further revealed the origin of self-healing from the dissociation of oxime-carbamate bonds with increased temperature. This nano-scaled aqueous dispersion strategy has the potential to design polyurethane materials with balanced self-healing performance and mechanical properties.