Valorization of enzymatic hydrolysis lignin for the multifunctional stabilization of polypropylene

Environmental toxicity of conventional stabilizers for polymers and their degradation products is raising severe concerns. There is an urgent need for the development of environmental-friendly, high-efficiency, and multifunctional stabilizers for polymers. Herein, Lignin nanoparticles (LNP), which were produced from enzymatic hydrolysis lignin (EHL) isolated from corncob residue, were demonstrated as a multifunctional stabilizer for polypropylene (PP). LNP fabricated by the anti-solvent method has distinct surface properties from the raw EHL, which lends it a better dispersion state in PP, and a higher free radical scavenging and UV absorption ability. The addition of 1 wt% LNP significantly enhances the thermo- and photo-oxidation stability of PP. The oxidation induction time of PP increases from 6.1 min to 12.3 min by 102 % with the addition of 1 wt% EHL, while it further increases to 20.1 min by 230 % for PP/LNP. Compared with PP, the oxidation degree of PP/EHL during thermo-oxidation for 8d is reduced by 27 % while that of PP/LNP is reduced by 60%. In addition, the UV degradation diffusion from the surface to the inner part of PP/LNP is significantly suppressed. These results highlight the excellent stabilization effects of LNP on PP and provide a promising path for the high-value-added lignin.