Trelleborg Sealing Solutions has researched and compared the wear reducing ability of its traditional Turcon® additives to nanoparticles as additives. Trelleborg tested PTFE filled with the following nanoparticles: carbon nanotubes (MWCNT), alpha Aluminum Oxide (Al2O3, alpha), beta Aluminum Oxide (Al2O3, beta), Tin Oxide (SnO2), Copper Oxide (CuO), Zinc Oxide (ZnO) and Iron Oxide (Fe2O3) - in all cases at 1 wt%. Performance was compared to both virgin PTFE and Turcon T05. In these tests, the optimized Turcon additives outperformed the nanoparticles. The Turcon compounds are optimized for service conditions using traditional fillers. Even so, the company will continue to investigate if improvements can be made using nanoparticles.
The results demonstrate that different types of nanoparticles have different effects on the wear resistance of PTFE, going from virtually no effect to wear reductions beyond a factor of 50. For some, nanoparticles performance was dependent on whether systems were running dry or lubricated. For instance, MWCNT performed very well when dry-running but poor in lubricated conditions, while others, such as Al2O3 alpha, gave good overall performance. None of the nanoparticle filled materials were capable of outperforming the wear resistance of Turcon T05, dry-running or lubricated.
Virgin polytetrafluoroethylene (PTFE) has very low wear resistance and fillers are added to PTFE to increase its wear resistance in dynamic sealing applications. Nanoparticles, which have at least one dimension in the size range of one to 100 nanometers, offer an alternative to traditional fillers. These are currently receiving much attention as fillers for polymers and are promoted as improving mechanical and tribological properties at a low degree of fill as well as reducing the risk of abrasive action against mating counter surfaces. The comparative results are illustrated below:
The results demonstrate that different types of nanoparticles have different effects on the wear resistance of PTFE, going from virtually no effect to wear reductions beyond a factor of 50. For some nanoparticles performance was dependent on whether systems were running dry or lubricated. MWCNT performed very well when dry-running but poor in lubricated conditions while others, such as Al2O3 alpha, gave good overall performance.
None of the nanoparticle filled materials though were capable of out-performing the wear resistance of Turcon® T05 PTFE compound, dry-running or lubricated.