Dexmet Corp. has added the Aptiv film made with Victrex PEEK (polyetheretherketone) polymer to its PolyGrid portfolio of precision expanded plastics. Wallingford, Conn.-based Dexmet provides filtration solutions for the fuel cell industry, and expanded plastics are used in filtration applications requiring membrane support, purification, and separation. Dexmet’s PolyGrid portfolio consists of various diamond configured, open area mesh polymer products.
“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 Ken Burtt, vice president of sales and marketing at Dexmet. “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 sulfonated tetrafluoroethylene (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 at 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.”
Dexmet uses 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 0.127 millimeters (0.005 inches) 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 always will 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.”
The material is one homogenous unit, which, according to Dexment, is important in a filter design. “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, which provided the Aptiv film polymer, is based in West Conshohocken, Pa. The company produces high performance polymers for various industries and applications, including medical.