Abstract: A polishing pad material is provided with a cellular polymeric layer containing elongated cells normal to the major surfaces of the material, such that the cell openings on the polishing surface of the material comprise a majority of the surface area, and the cells have a mean diameter of about 50 to 200 microns with the diameter of the surface openings being preferably larger than the cell diameters below the surface. The cells are preferably cone-shaped and have a depth at least 1.5 times the diameter of the surface openings. The pad material is formed from a poromeric material, preferably polyurethane elastomer, with microporous cell walls having pore diameters less than 0.1 times the diameter of the cells.

Abstract: An air filter assembly including an electret filter sheet of material which exhibits electrical charges of opposite sign on opposite faces thereof and a non-electret conventional filter sheet of material combined with and disposed upstream from the electret filter sheet of material, whereby particles of a large diameter are collected by the non-electret filter sheet of material and particles of a small diameter are collected by the electret filter sheet of material without causing clogging or air pressure loss.