There is a material called Asaclean that they use for industrial extruders, though I don't know what it is made of. The idea is that it doesn't stick to metal, but it bonds really well to any kind of plastic, so as it passes through the barrel, it bonds to the leftover plastic and drags it out without leaving any of itself behind on the inner surfaces of the barrel and screw. I've tried it out on my Filastruder, with pellets I found on Ebay. I don't know how much need there is for it in a printer extruder, but it might be worth a try if jamming becomes a common problem.