This is an excellent video.

This is an excellent video. I know that the RepRap project guys, Bowyer and co, have been working on color-mixing print heads that mix multiple strands of plastic.

That is basically the process at work here, and the concerns they have are similar - this is used, according to the article, in high viscosity polymers where shear stress can damage the long-chain polymers, basically the situation we are in with mixing various plastics.

The method they used for visualizing the results is particularly clever, if a bit destructive.