Epoxy thermosets from model mixtures of the lignin-to-vanillin process

Abstract

Epoxy thermosets were prepared from mixtures of phenolics modelling the product stream of the lignin-to-vanillin process. Vanillin is one of the only mono-aromatic compounds produced on an industrial scale from lignin. This process leads to mixtures of phenolic compounds. Isolation of pure vanillin is costly both economically and environmentally. The present work demonstrates that these purification steps are not necessary in order to prepare high-performance epoxy thermosets from biomass. Model mixtures of depolymerization products of lignins from both softwood and hardwood were prepared. These mixtures were subjected in a first step to a Dakin oxidation in order to increase their phenolic functionality. In the second step, they were glycidylated to obtain mixtures of epoxy monomers. Each of the components of the mixtures was individually subjected to the same reactions to provide further insights on their reactivity. Epoxy thermosets were conveniently prepared from these epoxy monomer mixtures. These potentially bio-based epoxy thermosets displayed outstanding thermo-mechanical properties while avoiding environmentally damaging purification steps. Thus, their production could advantageously be integrated in a biorefinery as a high value added product from lignin processing.