Happy Birthday, Delrin

Delrin acetal turns 50 this year, but the material still has plenty of life in it. DuPont, Delrin’s maker, recently introduced enhancements that stand to improve the material’s utility.

Many engineers rightly think of Delrin as a plastic gear material. But it’s more than that. With its high mechanical properties and chemical resistance, acetal is really a versatile metal replacement candidate, according to George Hesser, a business development manager with DuPont’s Mechanical Solutions Group. He’s seen an upswing in the materials’ use on packaging lines and in automobiles. Here’s a look at three recent Delrin upgrades.

UV performance and extra flow

Delrin 327 UV acetal addresses automotive interior requirements with a balance between uv-stability, flow length and mechanical properties. The material offers about 20 percent more flow than Delrin 127 UV, an earlier uv-stabilized grade. And flow is key. Hesser explains that part consolidation in automotive interior parts has resulted in increasing numbers of complex, thin-walled parts than need a high flowing material. “You’re starting to get more complicated tooling that requires easy-to-mold materials,” Hesser says. The fact that these materials will see use in the passenger compartment of cars, though, still requires the uv-resistance (see chart).

Cost-effective friction reduction

Two new lubricated Delrin acetal grades, 100 TL and 500 MP, address a need for lubricity requirements that falls short of what the company’s premium wear-and-friction products offer. Delrin 100 TL and 500 MP both use Teflon fluoropolymer micropowder to impart the added lubricity, while the company’s premium wear-and-friction grades use Teflon fibers. Hesser says both new grades offer significant coefficient of friction reductions (see chart) compared to standard acetal, but they cost roughly half of what the premium Teflon-fiber-filled grades cost. He says office equipment that needs need some “squeak” reduction would be a good candidate for the new grades. So would any other gear trains where standard acetal would bear the loads, but a lubricated grade is needed to reduce noise or solve problems with mating-gear materials.

Low Emissions

Much of the push to reduce the emissions from plastics used in automotive interiors has focused on olefins, which isn’t surprising given their use as skin materials inside the vehicle. But DuPont has nonetheless introduced low-emission Delrin acetal grades. “Acetal is not the principle driver here, but our philosophy is that we should try hard to meet the emissions requirements with our polymers,” Hesser says. And that’s exactly what DuPont has done. Delrin grades with the “E” designation have a 90 percent reduction in emissions — in acetal’s case, formaldehyde — compared to their standard counterparts. “We applied our chemical knowledge to 'cap’ the molecule’s formaldehyde chains to keep them from unzipping, which is what causes the emission,” Hesser explains. In terms of mechanical properties, the low-emissions materials are essentially identical to their standard Delrin counterparts, Hesser says. But cutting emissions doesn’t come for free. He estimates that the materials will initially cost somewhere between 15 and 20 percent more than standard Delrins.