Chemically modified lignin through epoxidation and its thermal properties

Chemical modification of lignin could improve lignin's performance as a biopolymer and offer new fields of lignin application to biomaterials. In the present work, a novel chemical modification process was developed to modify a reductively degraded organosolv lignin by epoxidation- grafting an epoxide group onto lignin. The chemical structure of the resulting epoxy-lignin was characterized with FTIR to confirm the present of epoxied groups on the lignin structure and also the reduction of hydroxyl groups compared with the original lignin sample before grafting. To optimize the process and to achieve the optimal number of epoxy groups on the lignin structure, the effects of reaction time, reaction temperature, and epichlorohydrin/lignin ratio were investigated. The as-prepared epoxy-lignin samples were characterized using gel permeation chromatography (GPC) for their molecular weights and distribution, differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA) for their thermal properties.