Sugar cane bagasse lignin in resol-type resin: Alternative application for lignin-phenol-formaldehyde resins

Lignin can be recovered from sugar cane bagasse, which is widely available in Brazil as a residue from sugar mills. Many reports can be found in the literature on the partial replacement of phenol by lignin in phenolic-type resins, but normally only their application as an adhesive is considered. This work is part of a study intended to look for other uses for lignin-phenol resins; for instance, in molded materials. Resols were prepared with the partial replacement of phenol by organosolv sugar cane bagasse lignin (10, 20, 40, 100% w/w), and the pre-polymers were characterized by TGA and DSC. The cure reaction was performed in a mold in a process monitored by infrared spectroscopy. The resins obtained were characterized by TGA, DSC, and DMTA. TGA and DSC results revealed that endothermic and exothermic steps are probably involved in the cure reaction. From infrared results it can be inferred that lignin is really incorporated to the phenol polymer chain, where it acts as a chain extender. DMTA analyses showed that lignin-phenol-formaldehyde resins retain their modulus at elevated temperatures. The overall properties show that the partial substitution of phenol by lignin in phenolic molded-type resins is feasible.