For polyester I was thinking of the fluffy batting that WalMart sells for stuffing cushions and bedspreads that I used to wrap my absorbers with.
I don't usually think of it as foam, and that I have absorbtion coefficients for at the usual http://www.bobgolds.com/AbsorptionCoefficients.htm .
- Polyurethane ether
- Polyurethane ester
- Reticulated polyurethane (stranded - air filter little resistance)
Brian wrote a few interesting things about chemistry here http://forum.studiotips.com/viewtopic.php?p=13505#13505