The one application were secondary synthetics works very well and natural flake does not is bi-polar plates (compression moulded polymer binder)...tensile, flexural, and compression strength due to the thin flake morphology verses secondary synthetics from electrode scrap manufactured using needle coke which demonstrates excellent flexural strength...this is from direct experience testing various graphite powders for bi-polar plates and SOFC.
Secondary synthetics are bulky, irregular spheroid morphologies and are limited in purity up to ~99.0%. There are many contaminates in scrap graphite from machining tool wear, oxidation inhibitors (zinc sulfate & aluminum sulfate), and other contaminates which makes secondary synthetics limited on application usage and is not economical to try and purify....mainly used in friction and lubricants.
