In Situ Synthesis of Flowerlike Lignin/ZnO Composite with Excellent UV-Absorption Properties and Its Application in Polyurethane

In this work, lignin-decorated ZnO composite was prepared via an in situ synthesis method using industrial alkali lignin (AL). First, the AL was modified by quaternization to prepare quaternized alkali lignin (QAL). The microstructure and optical properties of the QAL/ZnO composite were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), and UV–vis and photoluminescence (PL) spectroscopy. These results showed that the prepared QAL/ZnO composite possessed a flowerlike structure and showed excellent synergistic UV-absorbent properties. Interestingly, the anti-UV performance and mechanical properties of polyurethane (PU) were significantly improved when it was blended with the resulting QAL/ZnO. In comparison with pure PU film, the UV transmittance of the PU film was rapidly reduced. Furthermore, the tensile strength and elongation at break of PU film blended with QAL/ZnO were significantly improved, which was due to good compatibility between QAL/ZnO and PU matrix. Results of this work provide a significant and practical approach for the high value-added utilization of lignin as a functional material.