Biochar as a sustainable and renewable additive for the production of Poly(ε-caprolactone) composites

Abstract

Sustainable poly(ε-caprolactone) (PCL) composites can be produced via initiation of polymerization using the surface hydroxyl groups of oxidized biochar nanostructures obtained after liquid-phase exfoliation of biochar. Biochars are stable, renewable, and sustainable carbon-based materials, which in large-scale applications have the potential to mitigate climate change. The biochar used herein is produced by pyrolysis of hardwood waste biomass (e.g. sawdust, branches, bark) and then converted using nitric acid to oxidized biochar (oxbc). Oxbc is directly sonicated in ε-caprolactone to produce the exfoliated analogue (Eoxbc), which is used to promote the ring-opening polymerization of ε-caprolactone. Eoxbc is highly dispersible in this monomer, and thus reactions can be performed under neat conditions. Eoxbc presents sufficient surface hydroxyl groups (−OH) to initiate and facilitate the ring-opening polymerization of ε-caprolactone using tin octoate, organic bases or lipase enzymes as catalysts. The PCL/Eoxbc composites produced present higher crystallinity and increased stiffness when compared to pure PCL. In preliminary studies, Eoxbc also shows a positive effect upon the degradation of PCL under various conditions.