Spartanburg, South Carolina, is home to one of the largest privately owned chemical and textile research establishments in the world, Milliken & Company. The firm's innovative research that combines textiles and chemistry has now produced a thermoplastic composite called Tegris that is cheap, recyclable and tough. These properties make Tegris an attractive alternative to (or composite partner for) carbon fiber, and it's already proving to have wide ranging applications in the automotive, military and sporting industries.
Tough, cheap and 100 percent recyclableWith increasing demand for lighter and more fuel efficient vehicles using more environmentally-sustainable products, newer polypropylene-based products lay claim to being both green and cheap. Recent developments in additive and resin technologies have improved the performance, ease of production and range of applications for polymers such as polypropylene, particularly Tegris and a rival product named Pure from Dutch textiles manufacturer The Royal Lankhorst Euronete Group.
By collaborating with its clients, Milliken has been able to leverage its new technologies in interesting ways. One example is a carbon fiber/Tegris/carbon fiber sandwich that has equal stiffness to a carbon fiber-only structure, yet is 18 percent lighter, more damage tolerant and requires twice the energy to break. Another is an aluminum/Tegris/aluminum sandwich construction, which takes three times the energy to break.
The production processTegris starts out as a series of polypropylene (PP) films that form a tape yarn within a polymer matrix - for composite processing - before being woven into fabric. This is then pressed under heat and pressure to form a single piece approximately 0.005 inch (0.13 mm) that weighs just 0.02 lbs/sq.ft (0.11 kg/sq.m).
Sheet and plate is typically available in 0.125 inch, 0.250 inch and 0.500 inch thick sizes, so multiple layers are added depending on the required thickness. The NASCAR Aero splitters made from the material are typically 100 layers thick (1/2 inch or 12mm).
The outer layers are melted together to perform a similar function to that of resin in fiberglass products. From here, the sheet can be formed into a variety of shapes using heat and pressure, depending on the mold. The end result contains no fragment-producing glass, has high impact resistance and retains strength from around 180 degrees F down to -40F, as well as being easier on the production molds.
To put this into perspective, whilst having similar properties to carbon fiber, (the company claims 70 percent of the strength) Tegris won't shatter on impact, is approximately a tenth the cost, and is fully recyclable.
ApplicationsTegris is already seeing use as protective armor by the U.S. military in its vehicles, primarily against IEDs. There's also such diverse applications as small watercraft, helmets, outdoor furniture and baggage.
Tumi, a high end luggage manufacturer which holds Tumi the exclusive rights for Tegris in the travel goods market, is already using the material in its new Tegra-Lite collection. This includes a range of packing cases and smaller carry-on baggage that claim enhanced durability, impact resistance and less weight. All very desirable attributes for baggage when traveling.
Another outfit that appreciates the lightness and toughness of the material is Riddell, makers of body armor for football players. Its Lightspeed Shoulder Pads are claimed to be the lightest in the business without compromising protection.
In the automotive racing world, as mentioned, Tegris is being used in NASCAR racing for Aero splitters, as well as some door panels. Powerstream Industries has further developed the process to suit the equally harsh road racing environment, using CNC-machined pockets in a sheet of Tegris which is inlayed with high density foam and covered with a cap layer of Tegris that is then heat formed back into one piece, achieving a high level of rigidity.
Custom race Aero Splitter before the second layer of Tegris is added (machined recesses for hi-density foam clearly visible)
"Much of our development is to create advanced duplex composite panels to compete against carbon fiber," says Powerstream's Chris Meurett. "But with approximately 50 times the impact resistance."
Tegris can also be glued or threaded to accept mechanical fasteners. "We have done extensive testing with various adhesives designed for polypropylene and have found the bond unsatisfactory for our use," Meurett adds. "The very best way to bond Tegris to Tegris is through a consolidation process using heat and pressure on a platen press which when heated to the correct temperature essentially turn 2 pieces into 1."
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