Well not yet, and not just any plastic. A few smart people at M.I.T (imagine that!?) have figured out, "By slowly drawing a polyethylene fiber out of a solution, using the finely controllable cantilever of an atomic force microscope, which they also used to measure the properties of the resulting fiber." Perhaps the coolest part about this is that the polymer is only conductive in one direction and is about 300 times more conductive than regular polyethylene along the direction of the fibers. Currently, they've only produced the polymer in a lab setting but they hope to scale the operation up down the road.
This is pretty cool stuff. It will also be great to not have to hang a big heavy chunk of metal off our motherboards. I personally can't wait until the day the OCC CPU Cooling section has some metal vs plastic heatsink comparisons. What do you think about this? Let us know in the comments or forums.