Biobased Epoxy Thermoset Polymers from Depolymerized Native Hardwood Lignin

Biobased epoxy thermoset polymers were prepared from lignin hydrogenolysis oils produced from native hardwood lignin. Native lignin in Eucalyptus nitens and Eucalyptus saligna wood was reacted in situ under Pd-catalyzed mild hydrogenolysis conditions to give depolymerized lignin oils in yields up to 98 wt %. Reacting these lignin oils with epichlorohydrin produced biobased epoxy resins. Blending these resins with nonrenewable bisphenol A diglycidyl ether (BADGE) in different proportions, and curing with diethylenetriamine, produced a series of epoxy thermoset polymers with varying biobased content. Up to 67% of the BADGE could be replaced with hardwood lignin-derived epoxy resins while achieving superior or equivalent mechanical properties to the BADGE control polymer. Comparing the performance of lignin-based epoxy polymers from eucalyptus and pine wood provided insights into the advantages and disadvantages of using hardwood versus softwood native lignins in the quest for high performance biobased thermoset polymers.