The role of bio-based constituents in additive manufacturing with thermosetting polymers and vitrimers: a review

Abstract

This review focuses on the additive manufacturing of thermoset polymers incorporating at least one bio-based constituent, whether as a filler or as the thermoset polymer itself. In this work, bio-based thermosets reviewed are mostly epoxy, acrylate, methacrylate and thiol–ene resins. The micro-scale fillers developed in additive manufacturing mainly source from woody biomass, with wood particles but also cellulose powder and lignin. Nano-scale fillers use is also reported with cellulose nano crystals, chitin nano crystals and carbon dots derived from cellulose. Additive manufacturing was chosen as the focus due to its broad range of applications and significant sustainability advantages, including reduced waste, shorter value chains, and easier repairability. Furthermore, the growing demand for bio-based polymers is driven by the anticipated shortage of fossil-based alternatives. This review demonstrates the relevance of this timely topic and highlights the extensive research efforts dedicated to bio-based thermosets and thermosets with bio-based fillers, showcasing a diverse array of innovative approaches explored across 83 studies. Overall, despite significant progress in the development of bio-based thermosets, the dependence on petroleum-derived photoinitiators, together with the limited understanding and control of curing kinetics and rheological behavior of neat and composite precursors, remain major challenges that must be addressed to enable the industrial scale-up of these additive manufacturing materials.