Physicochemical characterization of lignin recovered from microwave-assisted delignified lignocellulosic biomass for use in biobased materials
Lignocellulosic biomass (Moso Bamboo, Chinese tallow tree wood, switchgrass, and pine wood) was subjected to a novel delignification process using microwave energy in a binary glycerol/methanol solvent. The physicochemical properties of the recovered lignin were analyzed prior to its application in the fabrication of polylactic acid (PLA)–lignin composites. The results showed that the samples had a high Klason lignin content (>75%) and retained their natural structure. Thermogravimetric analysis revealed that the recovered lignin exhibited a different thermal decomposition pattern from that of commercial lignins. All the recovered lignins had good solubility in common organic solvents (acetone, 1,4-dioxane, THF, DMSO, and ethanol/water) and 1 mol/L NaOH solution. The addition of lignin into the PLA matrix resulted in the improvement in tensile properties of PLA–lignin composites. PLA films with low lignin content had good UV light-resistant properties, indicating that the recovered lignin has potential in packaging of light-sensitive products.