SÍNTESE DE RESINA EPÓXI A PARTIR DE LIGNINA KRAFT FENOLADA
Epoxy adhesives are used in many applications as structural applications on automotive industry, construction industry, equipments and tools repair, encapsulation and potting of medical and electrical devices and other many other applications. The main epoxy resin used globally are epoxy resin from bisphenol A, the diglycidyl ether of bisphenol A (DGEBA). These resins are produced from fossil resources, and many interesting studies are increasing to replace this source for a renewable material, such as lignin. Lignin is a biopolymer widely present in plants and it is the second most abundant organic molecule in the Earth, after cellulose. It is composed of monolignols, which is characterized by phenolic groups, so lignin presents itself as an excellent candidate for replacing bisphenol A in the production of DGEBA. Bisphenol A, besides being a resource of fossil origin, has a negative contribution to human health, since it causes damage to the human endocrine system. In this context, this study proposes the epoxidation of kraft lignin and its application as a partial substitute for DGEBA in epoxy adhesive formulation. The kraft lignin was epoxidized following two distinct routes: i. direct epoxidation of the kraft lignin; ii. phenolation of the kraft lignin followed by epoxidation. The epoxidized samples were characterized by nuclear magnetic resonance (NMR), Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC) and thermogravimetry (TG). The results confirm the lignin modification, having the highest conversion efficiency for the previously phenolated samples. As a next step, the lignins will be incorporated into epoxy adhesive formulation and will be characterized for practical adhesion. Finally, it is expected to relate the practical adhesion with the chemical structures of the modified lignins.