The 6D long vacuum degassing element ensures efficient removal of residual moisture and volatile matter in WPC processing

Processing of WPC with up to 12 % residual moisture

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  • 10% lower melt temperature during processing of shear-sensitive wood plastic composites
  • Side feeder with special vacuum technology enables higher output
  • KraussMaffei Berstorff offers dedicated WPC version of co-rotating twin-screw extruder

Products made of WPC have become increasingly popular in Europe for indoor and outdoor applications with annual growth rates of up to 25 percent. WPC decking profiles in particular are in high demand. For the processing of shear- and temperature-sensitive WPCs, KraussMaffei Berstorff offers a modular screw and barrel system with a co-rotating twin-screw extruder as a basis. In order to achieve higher output while at the same time decrease the melt temperature, KraussMaffei Berstorff has optimized its ZE twin-screw extruder components.

Kneading and multi-process elements keep melt temperature low

A special feature of the extruder is the combination of kneading and multi-process elements in the plasticizing zone that enables a lower melt temperature of about 10 percent while the melting efficiency remains unchanged compared to standard screws. In addition, the company has adapted the screw configuration in the fiber feed area and in the mixing section where also multi-process elements are employed.

Wood Plastic Composites consist of polypropylene and wood fibers with a share ranging between 50 and 90 percent (source: KraussMaffei Berstorff)

Wood Plastic Composites consist of polypropylene and wood fibers with a share ranging between 50 and 90 percent (source: KraussMaffei Berstorff)

6D long vacuum degassing for the removal of 12 % residual moisture

Further process advantages are achieved by the employment of 6D-long combined barrel elements, which are a typical feature of the ZE extruders. These elements allow the wood content to be efficiently incorporated, and air, trapped during the process, to be removed. For the degassing of the 12 % residual moisture content in the natural fibers, the 6D-long degassing openings ensure high process reliability at low gas velocities. A hold-down system, that is frequently needed for this kind of application, is not required.

The extruder is equipped with a ZSFE side feeder with special Ultra Feed vacuum technology that gives higher output rates by increasing the bulk density of light filler materials. With this side feeder design, the total output rate in WPC processing can be increased by a factor of 2.5 compared with conventional lines, according to the company.

Main Picture: The 6D long vacuum degassing element ensures efficient removal of residual moisture and volatile matter in WPC processing (source: KraussMaffei Berstorff)

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