Issue: Nov 2009


Despite the Buzz, Nano Is Not Always Best



by Steve Barclay

Trelleborg Sealing Solutions, a worldwide leading supplier of high-quality sealing and bearing systems, today announces its research proves that the traditional fillers used in the majority of its Turcon(R) polytetrafluoroethylene-based sealing materials as additives to improve wear reduction outperform nanoparticles as additives.

Current industry buzz is all about the enhancement of seal performance by using nanoparticles as fillers for polytetrafluoroethylene-based sealing materials. Responding to this, Trelleborg Sealing Solutions researched and compared the wear reducing ability of its traditional Turcon(R) additives to nanoparticles as additives. In these tests the optimized Turcon(R) additives outperformed the nanoparticles.

"Despite the results showing that our traditional additives outperform nanoparticles, Trelleborg Sealing Solutions will continue to work on sealing nanotechnology," says Thomas Larsen, who headed up the test program at Trelleborg Sealing Solutions. "Our Turcon(R) compounds are optimized for service conditions using traditional fillers and are generally difficult to beat. Even so, we will continue to investigate if improvements can be made using nanoparticles."

Trelleborg Sealing Solutions 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 1wt%. Performance was compared to both virgin PTFE and Turcon(R) T05.

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 though were capable of out-performing the wear resistance of Turcon(R) T05, dry-running or lubricated.

Background information:

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.

Background to Trelleborg Sealing Solutions and Trelleborg Group

Trelleborg Sealing Solutions is one of the world's leading developers, manufacturers and suppliers of precision seals. It support its aerospace, industrial and automotive customers through over 20 production facilities and more than 40 marketing companies globally. Within its portfolio are some of the longest established sealing brands, including Busak+Shamban, Chase Walton, Dowty, Forsheda, GNL, Palmer Chenard, Shamban, Skega and Stefa along with a large number of proprietary products and materials such as Turcon(R), Zurcon(R), Orkot(R), Isolast(R), Stepseal(R) and Wills Rings(R). www.tss.trelleborg.com

Trelleborg is a global industrial group whose leading positions are based on advanced polymer technology and in-depth applications know-how. Trelleborg develops high-performance solutions that seal, damp and protect in demanding industrial environments. The Trelleborg Group had annual sales 2008 of approximately SEK 31 billion, with approximately 20,000 employees in 44 countries. The Group comprises four business areas: Trelleborg Engineered Systems, Trelleborg Automotive, Trelleborg Sealing Solutions and Trelleborg Wheel Systems. The Trelleborg share has been listed on the Stockholm Stock Exchange since 1964 and is listed on the OMX Nordic List. www.trelleborg.com.

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