UV-Shielding Performance and Color of Lignin and its Application to Sunscreen

The balance between sunscreen performance and color is a main obstacle in the preparation of high-quality lignin-based sunscreens. In this study, five lignin samples (i.e., NaOH-L, EG-L, G-L, 1,3-PDO-L, and 1,4-BDO-L) are extracted from sugarcane bagasse by using five different solvent systems. The lignin extracted by organic solvents clearly shows light color and excellent UV-shielding performance, and the 1,3-PDO-L sample reveals the lowest total color difference (Delta E is 30.4) and highest sun protection factor (SPF 3.99) among the samples obtained. The SPF of commercial facial creams significantly increases after addition of 5 wt% lignin samples, and the colors of these creams are lighter than that of 10 wt% lignin-modified cream samples. Moreover, the lignin-modified creams exhibit excellent broad-spectrum UV absorbency. The synergistic effects of lignin and the active substances of commercial sunscreen dramatically enhance the UV shielding effect of the commercial sunscreen. The aging test confirms that the lignin-based sunscreens have good photostability. This study provides a reliable reference for the development of lignin-based sunscreens and high-value utilization of lignin.