Facile fabrication and tribological properties of self-lubricating polyurethane based on expanded graphite/paraffin for water lubricated bearings

Abstract

To improve the tribological properties of polyurethane (PU) based water-lubricated bearings specifically under severe conditions, expanded graphite/paraffin (EG/paraffin) is synthesized as self-lubricating additives and incorporated into the polyurethane matrix. The tribological performance of the PU-EG/paraffin composites at dry and water-lubricated conditions is investigated systemically. Results show that the friction coefficient of PU-EG/paraffin composites can reach a minimum value of 0.18 and 0.08 under dry and water lubricating conditions, respectively, with a reduction of 77% and 62% compared to that of pure PU. Meanwhile, the wear rate of these composites also exhibits a significant decrease under both conditions. The wear surface morphology indicates that a lubricating film can be formed by paraffin or paraffin-water emulsion between the friction pairs, thereby significantly enhancing the lubrication state under dry and water lubricating conditions, respectively. The present work puts forward a practical and effective approach for manufacturing self-lubricating water-lubricated bearing materials.

Keywords

• Polyurethane
• Expanded graphite/paraffin
• Self-lubricating
• Tribological properties