Controlling the assembly of graphene based nanosheets within a rubber matrix: Nanocomposite morphology probed by measuring gas permeation and dielectric properties AIP Conference Proceedings 1736, 020066 (2016) Abstract. The use of graphene as a filler in thermoplastics has already been investigated extensively. The mechanical properties as well as electrical and thermal conductivity of thermoplastics can be improved due to graphene. However, these studies were carried out in experimental scale, which allows a good dispersion of graphene because of a long residence time during melt mixing and because of the use of almost ideal graphene, which has a high specific surface and low number of layers. In this study the scientific findings are transferred into industrial practice. For that purpose, a corotating intermeshing twin screw extruder with limited residence time and limited shear energy input is used to produce graphene based polyamide 6 composites and short carbon fibre reinforced graphene based polyamide 6 composites. These composites are further processed by injection molding to produce specimens in order to determine the mechanical properties. In addition to the scale-up to industrial production, two types of graphene platelets are used, which are commercially available. This investigation reveals that the addition of 1 wt.-% commercially available graphene platelets to polyamide 6 improves Young´s modulus and tensile strength. Compared to pure polyamide 6 an improvement up to 20 % with regard to Young´s modulus and up to 15 % with regard to tensile strength can be achieved. The combination of short carbon fibre with graphene platelets in polyamide 6 enables an increase of Young´s modulus, which is higher than the additive effect.

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Abstract The main goal in the design of spiral mandrel dies for blown film extrusion is to achieve a homogeneous velocity distribution of the plastics melt at the die outlet. However, thermal inhomogeneities in the die can lead to an uneven flow distribution despite a rheologically optimized design of the die. The thermal inhomogeneities are especially dominant in the predistributor of spiral mandrel dies. Against this background, the temperature influence on the melt distribution in the predistributor is investigated for different polyolefins with the help of flow simulations in Polyflow (Ansys). The simulation models the whole predistributor and takes both the heat transfer in the predistributor and the shear heating in the melt into account. Afterwards, simulations are conducted in which the thermal design measures for the homogenization of the flow in the die are applied. With the combination of heating cartridges, brass inserts, and isolating gaps in the die, a significant homogenization of the predistribution can be achieved. Finally, the simulation results are validated in practical tests, whereby a good agreement between simulation and measurement can be observed.