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11.09.2017 Granulating technology for conditioning of short carbon fibres

Maschinenfabrik Gustav Eirich, Hardheim, Germany, reports that carbon fibres in the form of continuous fibre fabrics or cut fibres are used to strengthen and reinforce other materials, such as plastics. Plastics like epoxy resin can be reinforced, providing a material which is widely used in the aviation industry. Short fibres are produced from production leftovers, but this material needs to be conditioned via granulation before it can be put to further use. Eirich technology is well suited for this task.
Large quantities of so-called carbon fibre prepregs are used in the manufacture of commercial aircraft. In order to process the hardened prepreg leftovers, they are cut or ground, often to fibre lengths below 500µm. Unavoidably, a certain amount of dust is produced in the process. The fibres tend to form clumps, and the demixing that occurs makes accurate feeding very difficult. This is why it is advantageous to improve processability of the ground fibres through granulation. For granulating, preferably very small amounts of liquids are added in which binding agents are either dissolved or suspended. In the sizes used for granulating, the Eirich mixer has only one moving mixing tool, the rotor, which can run at a speed of up to 30m/s. This makes it possible to generate high shear forces and distribute liquids quickly and uniformly.
As a result, dust-free granulates that offer good flow properties and are easy to feed are manufactured from cut or ground fibre leftovers. Another advantage: the system-related properties of Eirich mixing technology also make it easy to scale up this solution, with the process parameters originally determined in the Eirich test centre being transferable to larger production machines. 
Fibre leftovers are normally very difficult to feed into a process

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