Fabrication and properties of lignin-reinforced self-healing polyurea elastomer

The preparation of polymeric materials with good mechanical properties and efficient self-healing properties at room temperature has been a difficult challenge. Herein, a lignin-reinforced self-healing polyurea elastomer was prepared by a two-step process (polyurea reaction and schiff base reaction) using natural aromatic-based lignin as the reinforcing phase. The effects of lignin content on the thermal, UV-blocking and mechanical properties of T-L-PUA were investigated and the self-healing property and recyclability based on dynamic reversible imine bonding (C=N) of T-L-PUA were analyzed. The results show that the thermal stability of T-L-PUA is significantly enhanced with the increase of lignin ratio, where the maximum increase of residual carbon is 16.6% compared with the sample without lignin. The low transmittance of T-L-PUA in the UV region(280~400 nm)helps to realize the UV-blocking function. Compared with the average transmittance of T-PUA (41.6%), the average transmittance of all T-L-PUAs is around 0.2%. The best mechanical property appears at 20wt% of lignin addition, and the corresponding tensile strength of T-L-PUA is 12.44 MPa, which is 937% higher than that of pure polyurea elastomer. T-L-PUA exhibits good self-healing properties. When T-L-PUA is repaired at room temperature for 48h, the recovery efficiencies of tensile strength and elongation at break is above 91% and 94%, respectively. In addition, the T-L-PUA can also be recovered by the hot-pressing and solvent dissolution processes, and the mechanical properties remain largely unchanged after remolding.