Polymer Composites with Enhanced Thermal Conductivity and Mechanical Properties for Geothermal Heat Pump Pipes

In this article, we report a robust strategy to prepare polymer composites with enhanced thermal conductivity and mechanical properties for geothermal heat pump pipes, in which high density polyethylene (HDPE) used as matrix, various inorganic fillers including zero-dimensional (0D) aluminium spherical particles (Al-SPs), one-dimensional (1D) carbon fibres (CF) and two-dimensional (2D) graphite platelets (GPs), used alone or blended as modifier. The as-prepared polymer composites are GPs/HDPE, GPs/CF/HDPE, GPs/Al-SPs/HDPE and GPs/CF/Al-SPs/HDPE. Thermal conductivity and mechanical properties of these polymer composites were characterised. The results indicate that of all these as-prepared polymer composites, GPs/CF/Al-SPs/HDPE composites are the only one which possesses preferable and comprehensive properties both in thermal conductivity and mechanical properties due to the synergistic effect of filler. The thermal conductivity, elongation at break and tensile strength of GPs/ CF/Al-SPs/HDPE composites prepared with GPs (9 wt%), CF (3 wt%) and Al-SPs (3 wt%) were 0.803 W m ⁻¹ K ⁻¹ , 70.6 % and 26.69 MPa, respectively, which could meet the commercial requirements of the geothermal heat pump pipes.