KraussMaffei Berstorff in Germany (U.S. office in Florence, Ky.) worked for over six years with Hannover University of Applied Sciences to develop a process for compounding undried natural fibers. It uses new screw elements for corotating twin-screw extruders, developed by the plastics institute at the University of Stuttgart, Germany. These elements "comb" or separate rovings of natural fibers like flax, hemp, sisal, or jute without breaking them. The process is aimed mainly at compounding for automotive long-fiber composites. Undried natural fibers are side-fed into the melt and then separated and degassed under vacuum to remove moisture. According to Berstorff, the comb element also works well with nylon and long carbon or glass fibers, producing less breakage than conventional twin-screw elements. Comb elements (described in U.S. Pat. Application 20040228937 in 2004) use a series of truncated tooth shapes with a pyramidal base. The sides of the elements are covered with axial rows of these teeth about 5 mm high, having sloped sides so the fibers don't get stuck between them. Comb elements on one screw intermesh with elements on the other screw, leaving a 5-mm gap between the tips of the teeth that gently pull fiber bundles apart. Berstorff has a series of different comb elements of different lengths. The comb elements are available for customer trials in Florence, Ky., on a ZE-60 (60-mm) extruder with 44:1 or 48:1 L/D. The first domestic customer installation will come later this year. Tel: (859) 283-0200 . www.berstorff.de
7095 Industrial Rd. P.O. Box 6270
Florence, KY 41022-6270
Phone (859) 283-0200 Fax (859) 283-0290
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