Maleated Technical Lignin Thermosets and Biocomposites Designed for Degradation

Abstract

Maleated kraft lignin has been explored as a building block for degradable thermosets. The maleation procedure allows for a facile and atom-efficient way to install functional handles into the lignin structure, rendering the obtained lignin amenable for cross-linking via amine-Michael addition and thiol-ene coupling. Since lignin modification leads to the formation of an ester linkage, the final thermosets are susceptible to hydrolytic degradation, demonstrated under basic conditions (NaOH, 0.6 M, acetone/water (1/2.5, v/v) for 2.5 h at 75 °C). We also extended the study to biocomposite formulations with cellulose nanofibrils as reinforcing agents. The final biocomposites demonstrated strengths of 110-150 MPa and moduli of 4-5.5 GPa at 55-65 wt % of nanocellulose. This work offers a cradle-to-grave approach for biobased and degradable thermosets and composites from technical lignin.