VTT Technical Research Centre of Finland Ltd’s cylindrical extruder allows long fibers to be processed without cutting and can also be used to produce long fiber composites.
VTT’s research scientists have been testing the prototype’s performance with various plastics, fibers and textiles. Pirjo Heikkilä, senior scientist at VTT said, “Many textile recycling processes are only suitable for products containing homogeneous fibers. However, textiles are often made of a mix of fibers, and many products are comprised of different layers. The new extruder opens up a revolutionary opportunity to recycle mixed textiles and materials without having to separate fibers or components.”
The new idea that materials can rotate around the device’s hollow cylinder was discovered by Hannu Minkkinen, a research scientist at VTT. The first prototype extruder has a screw diameter of 30 cm instead of the 3–4 cm typically found in conventional devices of the same output. The large diameter of the screw, combined with a shallow screw channel, makes it possible to mix components of porous and lightweight materials and to make the mixed mass compatible with the next stage of the production process.
The extruder offers cost savings in design, as it is less expensive to make than traditional mixing twin-screw extruders. Only two meters long and weighing 1.5 metric tonnes, the extruder is compact, transportable, and can be mounted upright. The design also enables accurate temperature control.
VTT’s cylindrical extruder has the potential to revolutionize the processing of recyclable materials. The first prototype exceeded expectations during initial testing, and VTT is now looking for a commercial partner for the project.