There is a huge range of commercially available carbon filled plastics – people mold them on standard equipment all the time. I am a bit confused by your reference to carbon powder as “powdered grit” though: commercial carbon powder is essentially soot. I’m not sure what you mean by “electrochemical” either, but if you want to experiment with electrical properties, you might consider carbon fiber – aspect ratio of the fibers has a major effect on properties. If you have deep pockets, you could even look at carbon nano-fibers, which have very large aspect ratios and give useful electrical properties (ESD or conductivity) at much lower loading than powder, so they have less effect on the mechanical properties of the resin.

Effect of the carbon on equipment depends on its chemical structure. Commercial carbon powder is structurally graphite and has no effect. Carbon fibers are abrasive, so in mass production you’d want to use an abrasion resistant screw and barrel. If your “powdered grit” is pulverized industrial diamond, you may have a bit more of a challenge. Effects also depend on loading and on base resin – LDPE with 10% (by weight) carbon powder is no problem; 30% carbon fiber loaded polycarbonate will eat OEM screws.

In any case, if you have specific property requirements, and unless your powdered grit is something very special, I would strongly recommend talking to a commercial resin compounder before you try to reinvent the wheel.