Polymers are often used because of their thermal insulating properties and lightweight. Thermal insulation is enhanced by foaming. The addition of carbon powders being typically carbon black or graphite at extremely low loadings (ca. 3%) can further improve the insulation properties by ca. 20% due to the their capability to absorb and reflect infrared radiation (Glenz 2010). Rigid polystyrene foams (EPS, XPS) are widely used for the construction industry and for lightweight and thermally insulating packaging. Especially trend toward energy efficiency improvements to buildings leads to the increasing demand for “gray” EPS with, thanks to the carbon fillers, improved thermal insulation that allows to reduce the thickness of the insulating EPS layer at a given insulation efficiency.
As for other fillers, the mechanical properties of graphite-filled polymers are strongly modified with regard to the original polymer properties. Due to their flaky morphology, the effect of the graphite loading on the mechanical properties is mainly related to the particle aspect ratio that is in turn dependent on the graphite production process. The mechanical behavior of graphite-filled polymer compounds is similar to talc-filled compounds due to a similar particle shape but with some differences in polymer compatibility due to different surface properties. The incorporation of graphitic fillers in polymers causes a strong increase of stiffness and shows little influence on the tensile strength. Small increases in tensile strength have been reported for PP, PS, and HDPE (Wypych 2009). Decrease in elongation at break is often found together with a decrease of the impact properties (Wang et al. 2001).