November 27, 2012 – Driven by the need to provide solutions for increasingly harsh environments in filtration for the aerospace and fuel cell industries, Dexmet Corporation, a manufacturer of precision expanded metals, foils and polymers, added a high performance polymer to its PolyGrid* portfolio. Dexmet chose APTIV® film made with VICTREX® PEEK polymer to add to their portfolio where an expansion procedure using specifically designed proprietary equipment and processes are used to produce diamond configured, open area mesh products.
“APTIV film was selected to expand our high temperature PolyGrid product line,” said Ken Burtt, VP of Sales and Marketing at Dexmet, “But we consider it more of a ‘high performance’ PolyGrid material since its unique performance capabilities provide chemical resistance and mechanical strength combined with high temperature capabilities which is especially beneficial in certain applications in harsh environments.”
Critical applications requiring high temperature stability to filter caustic gases or fluids, such as in the semiconductor, chemical processing, and petroleum/gas industries, have traditionally used polymers such as polytetrafluoroethylene (PTFE), perfluoroalkoxycopolymer (PFA), and ethylene chlorotrifluoroethylenecopolymer (ECTFE). “All of these materials provide excellent temperature and chemical resistance but none match the mechanical strength provided by the expanded APTIV films,” explained Burtt. “With the continual increase in demands on filter performance, VICTREX PEEK-based PolyGrid is the solution to meet the critical performance challenges.”
In the fuel cell industry, manufacturers continue to increase the performance of the membrane electrode assembly (MEA) used in a fuel cell. “Manufacturers are experimenting with different materials as a membrane substrate to adhere the catalyst, which is typically made up of a mixture of carbon and platinum,” explained Burtt. “They need a material that has high temperature capability along with good mechanical strength. As manufacturers increase the performance of their cell, the pressures will increase and mechanical strength of the membrane will become more critical.
Current materials typically used are polyimides (PI) and sulfonatedtetrafluoroethylene (TFE) but as these materials reach their performance limits, APTIV film has become the next logical choice.” “When Dexmet approached us they were familiar with PEEK but our ability to offer them this performance capability in a thin film format was revolutionary,” said Tim Herr, Global Films Business Leader, Victrex Polymer Solutions. “Combining our material with their processing capability represents a significant advantage for Dexmet’s customers to tailor a solution to their end use application requirements.”
To reduce weight and increase efficiency, aerospace manufacturers are using more and more carbon fiber to replace aluminum in structural components. “By putting carbon materials together with either copper or aluminum, a galvanic reaction occurs causing the materials to corrode. To alleviate the corrosion, structural engineers are looking at different polymer materials as a barrier layer between the carbon fiber and expanded material,” explained Burtt. “APTIV film is an option because it’s thin, strong and has excellent high temperature and dielectric properties. Plus, the high temperature characteristics are essential when heat setting the adhesive on carbon fiber components. Incorporating an expanded APTIV film is an even better option because it reduces the weight even more.”
Dexmet utilizes a precision expansion process which combines a ‘slit and stretch’ function to produce the high performance mesh product. “It’s a process that’s been around for over 100 years,” said Burtt. “What makes it unique to Dexmet is our ability to produce an expanded product on very thin materials with very small openings at wide widths. There are no other expanders in the world that can expand thin materials, especially polymer films under 0.127mm (0.005in) with opening sizes down to 25 microns.” The process has infinite variability which enables Dexmet to tailor a product to exact performance requirements, whether it is opening (pore) size, open area, weight per area, or overall thickness.
While variability is the major advantage of the expansion process, another is the yield per pound or linear foot of raw material. Because it’s an expansion process, it will always yield more finished product than the initial raw material amount. “Unlike a perforation process that produces an open area product by punching holes in the material and producing scrap, the expansion process doesn’t ‘punch out’ material to produce the hole so yield increases while minimizing waste,” continued Burtt. “The expansion process becomes a more economical solution when using precious raw materials such as silver, nickel, titanium or even the APTIV PEEK films.”
Another advantage especially important in a filter design is that the material is one homogenous unit. “The strands don’t move relative to the other strands so opening sizes don’t change,” said Burtt. “And, the material has a three dimensional geometry, which allows for multiple flow directions, improving cross flow while reducing pressure drop.”
Victrex Polymer Solutions helps customers and end users achieve the greatest possible benefit from the use of its high performance PEEK materials to achieve cost effective, reliable solutions for long-life applications. All of this, backed by more than 30 years of experience, makes Victrex the only company in the world that can offer this level of specialized support. For more information, please visit www.aptivfilms.com.