I want to grind flexible polyurethane foam to a size of about 50-100 microns. The feedstock is shredded 1.5 lb/ft^3 polyurethane foam.
I tried a commercial meat grinder, which works but is very slow, and I tried a hammermill, which works, especially if it's mixed with ice, but nothing's really been effective.
Have you considered a Industrial Plastics grinder? they are typically a series of metal plates that have teeth on them that spin in one axis with two sets in opposite directions. you can typically find them that take things down to i think 1/4 inch but you could probably find one that would take it down even smaller or even use a secondary meat grinder to take it further from your initial grinder size. i have a link to a place that sells them below and a video of an extremely large one crushing a car.
http://www.jordanreductionsolutions.com/plastic-grinder.html : Plastics Grinder
https://www.youtube.com/watch?v=tPDLX0koXFs : Car Crush
Have you considered adjusting the nozzle on a pressure washer to create a coaxial (zero degree) exit angle and using it like a fluid powered knife?
