Wilmington, Del. – Oct. 14, 2008 – Molders can cut cycle time for PBT parts up to 30 percent with new super-fast grades of DuPont™ Crastin® PBT thermoplastic polyester. Designated Crastin® SF, the new resins come in non-reinforced form and in reinforced versions with 15 or 30 percent glass fiber.

“The shorter molding cycles achieved with Crastin® SF can deliver cost savings ranging up to 20 percent,” said Dave Donofrio, global business manager for Crastin® at DuPont Engineering Polymers. “The super-fast molding resins are particularly advantageous in molding thin-wall parts such as connectors and large parts such as structural housings.”

The key to the cycle time reductions provided by the new resins is their exceptionally high flow. For example, the melt viscosity of a 30 percent glass Crastin® SF grade is 43 percent lower than that of a comparable standard grade at 250°C and a typical molding process shear rate of 1000/s Pa.sec.

The high flow of Crastin® SF grades opens the way for major reductions in melt temperature, thus saving precious seconds in the duration of hold pressure and cooling. The chart below shows a typical example.

In this example comparing glass-reinforced grades, use of DuPont™ Crastin® SF enables a 30 percent drop in cycle time.

In addition to reducing cycle time, the enhanced flow of Crastin® SF resins can also enable the design and production of parts with thinner walls. For large parts, this can lead to substantial savings in material consumption and part weight. In the case of small parts, it can permit new part designs with longer, more intricate flow paths. The higher flow of Crastin® SF resins also opens the way to cost savings through the use of molds with more cavities. Alternatively, because Crastin® SF requires lower injection pressure, the molder can employ a smaller machine, which costs less to buy and to operate.

The mechanical properties of the new resins are very similar to those of comparable standard grades, according to Donofrio. “We achieve that impressive result with new technology that enhances the flow of polymer chains at the molecular level while maintaining the properties expected for comparable PBT resins,” he said.

About DuPont
DuPont Engineering Polymers manufactures and sells Zytel® nylon and Zytel® HTN PPA, Crastin® PBT, Rynite® PET, Delrin® acetal, Hytrel® TPC-ET, DuPont™ ETPV engineering thermoplastic vulcanizates, Minlon® mineral reinforced nylon, Thermx® PCT, Tynex® filaments, Vespel® parts and shapes, Zenite® LCP, to global aerospace, appliance, automotive, consumer, electrical, electronic, industrial, sporting goods and other diversified industries.

DuPont is a science-based products and services company. Founded in 1802, DuPont puts science to work by creating sustainable solutions essential to a better, safer, healthier life for people everywhere. Operating in more than 70 countries, DuPont offers a wide range of innovative products and services for markets including agriculture and food; building and construction; communications; and transportation.

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