Influence of the Screw Configuration on the LFT-D Processing of Glass Fiber Reinforced PA6

Long fiber reinforced thermoplastics (LFT) play an important role for accomplishing modern light weight goals. Especially the LFT-D process records a growing marked share due to its time and cost efficiency. Implementing structural applications using the LFT-D process is a main focus of the current development. Therefore, the process is adapted for the compounding of glass fiber reinforced PA6. Optimizing the extruder configuration of the LDT-D line for this specific material combination is a major challenge of the development. The goal of this work is to identify the effects of the screw configuration of the mixing extruder on the composite properties. Therefore, four different screw designs are tested. The screw configuration suggested by the LFT-D line manufacture is used as a benchmark. The other three screws are designed to increase the shear and mixing efficiency of the screw from a low to a high level. To analyse the dependency of the screw performance on the volume fill of the extruder, material is compounded using a fully filled and a particularly filled extruder. The material characterisation consists of fiber length measurements as well as tensile, flexural and impact tests. Through this analysis it is possible to show, that the fiber length plays a minor role and that a high mixing and a high shear level is required to optimize the composite’s strength. Additionally, the scattering of the material properties can be significantly reduced by a high shear and mixing level. Finally, a recommendation for the screw design is given.