(315e) Lignin in Ethylene Glycol and Poly(Ethylene Glycol): Fortified Lubricants with Internal Hydrogen Bonding
Lignin, one of the most naturally abundant polymers, has been successfully incorporated into ethylene glycol (EG) and polyethylene glycol (PEG) in this work and fortified lubricating properties were achieved in EG/lignin and PEG/lignin. The molecular interaction between lignin and EG (or PEG) has been revealed as hydrogen bonding, which serves as the dominating factor that determines the thermal, rheological and tribological properties of the mixed systems of EG/lignin and PEG/lignin. The physicochemical properties of the mixed lubricants are tightly related to the state of internal hydrogen bonding (EG-EG, PEG-PEG, EG-lignin, PEG-lignin and lignin-lignin) and are well correlated to their lubrication properties. Generally, larger lignin fraction leads to better lubricating performance in both EG and PEG systems. Lignin liquefaction in PEG has been addressed by catalytic degradation with the presence of sulfuric acid, which was then neutralized by triethanolamine for lubricant development. Lignin in PEG significantly improves the lubricating property at higher pressure conditions, where a wear reduction of 94.6% was observed. Lignin fortified EG and PEG based lubricants show outstanding non-corrosive characteristic to the mostly used metal materials such as aluminum and iron.