Materials: Automotive PP Compound Combines Glass & Wheat Fibers

A. Schulman Inc. in Akron, Ohio (aschulman.com), commercialized the first wheat-fiber/PP compound last year to replace 20% talc-filled PP in an automotive part. The 20% wheat-fiber compound retained mechanical properties while reducing density by 10%. Now Schulman has filled PP with 15% wheat fiber and 15% glass for another automotive application, designing the compound as a match for 20%-glass/10%-mica filled PP and achieving a similar 10% density advantage. Schulman’s renewably sourced Agriplas compounds were developed with Ford Motor Co.; the Univ. of Waterloo, Ont.; and Omtec Inc., Mississauga, Ont. (omtecinc.ca), which supplies the Biofiller wheat straw. Biofiller has the same density as PP.

The first Agriplas compound was used in the 2010 Ford Flex rear quarter trim storage bin and inner lid. Developing the compound required innovations in fiber chopping, compatibilization, and dispersion. The material has about 10% lower tensile strength than 20% talc-filled PP, but slightly higher stiffness, the same or better HDT, lower shrinkage, and much higher MFR and notched Izod impact at -40 F. It molds at 30° F lower tool temperature, saving energy and cycle time.

Wheat-fiber/PP is spreading into other applications, like small engine covers, lawnmower housings, and possibly pallets. In pallets, wheat straw provides the same mechanical properties as wood fiber but reportedly injection molds much easier.