porous polymers

The ones I know about, e.g. submicron syringe filters, are made from polyphenylene ethersulphone. The pores come from phase separation: you use a mixture of polymer, solvent (e.g. NMP) and nonsolvent (e.g. water or IPA). When you spin the mixture, it spontaneously makes hollow porous fibres, which are what the filters are made of. Because of the self-assembly, the holes are uniform enough to use for sterilizing water.

Bigger holes, e.g. styrofoam, are made by gas bubbles--either evolved from the reaction itself, as in urea-formaldehyde foam, or blown in during manufacture, as in styrofoam.

Cheers,

Phil Hobbs

There are a number of cellular materials that you could use; I favour polyurethane foam which is pretty controllable.

The foam would normally be processed into slabstock form then cut to shape, which will expose the cells. You can control the amount of open-cells (i.e. the porosity of the structure) with the formulation and moulding characteristics.

Rgds,