porous polymers

Does anyone know which polymer is used to make porous plastic parts such as filters on sanders? Also are they processed in a special way?
Thanks in advance tom gardega
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snipped-for-privacy@optonline.net wrote:

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
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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,
Simon

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In theory, you can achieve a cellular (porous) structure in any plastic via injection molding or extrusion, by "using an appropriate foaming agent". Have a look at http://www.cromptoncorp.com/foaming-agents.html , for example, and Google for more suppliers of foaming agents for the plastic of your choise.
snipped-for-privacy@optonline.net wrote:

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