Sal (Shorea Robusta) Leaves Lignin Epoxidation and Its Use in Epoxy Based Coatings

Lignin was extracted from Sal leaves by treating with alkaline solution followed by acidification at room temperature. The extracted lignin was first purified by hot water extraction followed by soxhlet extraction with cyclohexane and ethanol mixture. This purified lignin was epoxidized with epichlorohydrin in alkaline medium. FTIR, UV-Visible, TGA and DTA techniques were used to characterize the lignin and its epoxidized form. FTIR spectra are comparable with other lignin structure in the literature. UV-Visible spectra show a long absorption band in the visible region other than the usual absorption in the UV region. The epoxidized form was mixed with epoxy based primer coating and coated on metal panel for corrosion studies by electrochemical analyzer. The Tafel plot shows that the corrosion rate increases with increase in lignin content in the paint composition.