As the global plastic industry's biggest get-together, the K Fair always showcases up-and-coming applications for engineering thermoplastics. For prime examples, consider the new heat-transfer, automotive, and gear technologies that DuPont Engineering Polymers (Wilmington, DE) will emphasize at this month's show.
Cooling things off. As thermal insulators, plastics might appear to be a poor choice for a heat-exchanger material. Yet in the right designs, they can actually top metals with much higher thermal conductivities, according to Dr. William Hsu, DuPont's technology vice president. He explains that a material's thermal conductivity contributes far less to total heat transfer than convective cooling in nylon tubes less than 0.4 mm thick. And convective cooling is something that can be maximized through design—by promoting a large surface area at the air-plastic interface and by increasing turbulent flow of the cooling medium.
That's the reasoning behind Caltrel, a patented DuPont technology that creates heat exchangers from standard extruded nylon. "The overall heat exchange efficiency from these plastic heat exchangers is as good or better than traditional metal tubing and fins," Hsu says. And though nylon heat exchanges have about the same total volume as their metal counterparts, Caltrel takes advantage of plastics' inherent design freedom for "free-form" heat exchangers that can fit in unlikely spaces. Hsu adds that the plastic heat exchanges also offer weight and potential cost reductions.
DuPont has recently licensed the Caltrel technology to Heatcraft for industrial uses. More recently, automotive suppliers—including Visteon, Magneti Marelli, and Valeo—have taken licenses too. Hsu says the Caltrel technology will next year appear in a turbo inter-cooler application and is being evaluated for radiators, air-conditioning units, and cabin heaters. "There's talk among the suppliers about integrating all of these into one," he says.
The shock of 42 volts. DuPont will also show materials in anticipation of the impending shift to 42V vehicles. Upward shifts in heat-resistance and electrical-property requirements will place some new challenges on thermoplastics. "Some existing polymers won't work," Hsu says. For instance, DuPont has developed a translucent grade of nylon to replace PES in fuse applications. Aside from translucency, the material has been formulated to offer better heat resistance and "breakdown strength" than PES—the latter important given that fuses can fail explosively, Hsu points out.
Long wearing gears. Helping plastics withstand higher heat and loads is another focus at the show. Much of the trend is driven by 42V vehicles, which potentially need more plastic gears to serve in electrically actuated systems. Since 42V enables auto makers to move belt-driven systems—like air conditioning units—out of the engine compartment, plastics that couldn't stand underhood heat and mechanical loads might now compete against metal.
But DuPont will also show materials for gears that stay under the hood. "Some 42V systems will bring plastic gears closer to the engine," Hsu says. "And these gears will have to go beyond the standard domain of window lifters." He cites gears for electric steering systems as an area in which DuPont has an ongoing development project with a Japanese supplier. New Zytel WRF materials for these gear applications include nylon 66 and toughened nylons, both of which have been modified with wear-reducing Teflon microbeads.
For more information about engineering thermoplastics from DuPont: Enter 538
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