Odor-free kraft lignin-based thermoset with remarkable mechanical properties

Abstract

Future materials should be made from renewable resources and be sustainable without compromising the mechanical properties compared to conventional products. Kraft lignin is an available renewable raw material, sourced globally as a by-product from paper pulp production, and currently burnt at a low value. Kraft lignin has been converted into thermoplastics, however the mechanical properties worsen by degree of blending. Thermosets containing kraft lignin give materials with high strength, where the lignin matrix contributes to the mechanical properties. However, pre-fractionation or multistep chemistries have been applied to give high performance materials. Herein, we have combined kraft lignin with bio-based glycerol 1,3-diglycidyl ether to give a resin with enhanced mechanical properties. This resin – LigniSet® – is odorless, which is a unique property for kraft lignin-based products. The resin is, due to its hydrophilicity, compatible with natural fibers to give strong composite materials. The material can be recycled to give new materials without reduction in performance. Life cycle assessment shows that transformation of lignin to materials instead of burning shows significant benefits with respect to environmental sustainability.