Towards lignin valorization: lignin as a UV-protective bio-additive for polymer coatings

Abstract

Abstract Interest in fossil-free, bio-based materials capable of protecting against the harmful effects of UV radiation is constantly growing. The functional groups within lignin are able to effectively absorb light in the visible and UV range, making lignin a good candidate as a bio-additive in UV-protective polymer coatings. In this work, unmodified and modified (by methacrylation) lignin of different origins (softwood [spruce] and hardwood [eucalyptus]) was used as a bio-additive within epoxy resin to develop UV-blocking coatings. Methacrylation of the lignin, as well as the presence of appropriate functional groups in the coatings was confirmed by FTIR spectroscopy. The colour properties of the coatings were additionally investigated whereby the chemical modification of lignin was found to significantly influence the colour of the biocomposite coating. The thermal properties and morphology were investigated by DSC and confocal microscopy, respectively. The results demonstrate that methacrylated lignin is a promising environmentally friendly UV-protective bio-additive for polymer coatings.