Rigid-and-Flexible, Degradable, Fully Biobased Thermosets from Lignin and Soybean Oil: Synthesis and Properties

Developing thermosets from lignin has huge significance due to the abundant renewable resources and rigid polyaromatic structure of lignin; nevertheless, it is still a challenge to develop fully biobased thermosets with high performance. Herein, lignin was modified with glycidol and further reacted with maleic anhydride to produce multicarboxyl lignin (MGL) which possessed improved solubility in green solvents such as ethanol and increased reactivity toward the epoxy group. Fully biobased epoxy thermosets were prepared from MGL, citric acid (CA), and epoxidized soybean oil (ESO) with the assistance of ethanol. The thermosets exhibited superior thermal and mechanical properties and degradability. This study provides a straightforward countermove to achieve rigid and flexible thermosets from lignin and other abundant renewable bioresources and also provides a promising sustainable alternative to conventional epoxy thermosets.