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Highly structured graphene polyethylene nanocomposites and their electrical, thermal, mechanical and barrier properties

Gaska Karolina ^(1)*, Kádár Roland ⁽¹⁾, Xu Xiangdong ⁽²⁾, Müller Christian ⁽³⁾, Pandit Santosh ⁽⁴⁾, Mokkapati Venkata R. S. S. ⁽⁴⁾, Mijakovic Ivan ⁽⁴⁾, Gubanski Stanislaw ⁽⁵⁾, Rybak Andrzej ⁽⁶⁾, Siwek Artur ⁽⁶⁾, Svensson Magnus ⁽⁷⁾

⁽¹⁾ Chalmers University of Technology, Department of Industrial and Materials Science, - Goteborg - Sweden, ⁽²⁾ Chalmers University of Technology, Department of Electrical Engineering, - Goteborg - Sweden, ⁽³⁾ Chalmers University of Technology, Department of Chemistry and Chemical Engineering - Goteborg - Sweden, ⁽⁴⁾ Chalmers University of Technology, Department of Biology and Biological Engineering - Goteborg - Sweden, ⁽⁵⁾ Chalmers University of Technology, Department of Electrical Engineering - Goteborg - Sweden, ⁽⁶⁾ ABB Corporate Research Center - Krakow - Poland, ⁽⁷⁾ Wellspect HealthCare - Molndal - Sweden

This research presents an overview of the properties of highly structured, low density polyethylene-graphene nanoplatelets (LDPE-GnP). The influence of nanofiller content, size and processing conditions on the material properties have been investigated. Therefore, mechanical, rheological, electrical, gas barrier, thermal and antibacterial nanocomposite properties were investigated. So called dry-coating method has been used in order to prepare masterbatches which were thereafter extruded by means of single screw extruder resulting in a strong anisotropy in the extruded samples. Graphene nanoplatelets were oriented in the extrusion direction for all shear rates and flow histories investigated, as confirmed by scanning electron microscopy. Samples showed small improvements in mechanical properties due to the weak GnP-PE interface. The rheological percolation was determined via nonlinear parameters to be around 7.5wt%. A significant reductions of the through-plane low field electric conductivity was found in the extruded samples whereas above 20 kV/mm crossover effect was observed where a strong field dependent non-linear behavior dominates, yielding higher conduction currents that increase with increasing filler content. The carbon dioxide and sulfur hexafluoride permeability decreases of this property with increasing filler content. Permeability and free volume fraction correlations were investigated in the nanocomposites, by means of positron annihilation spectroscopy. Thermal conductivity measurements revealed strong anisotropy with in-plane conductivity increasing with GnP content.