Abstract: Polyurethane sponges were treated by different surface active agents in order to improve coating properties when ceramic foams were prepared by polymeric sponge process. A more reasonable method, in which coating properties were evaluated through measuring the size of struts of green bodies and uniformity of slurry distribution in the struts of green bodies, was employed. Experimental results showed that among the four surface active agents, the effect of carboxymethyl cellulose(CMC) on promoting coating properties was the best, and the polyvinylalcohol (PVA)’s effect was the worst. The mechanism of CMC to improve coating properties lies in the structure formed in the condition of pH>7, in which its hydrophobic groups combine with PU sponge and its hydrophilic groups combine with aqueous slurry. This structure promotes greatly wetting
ability between PU sponge and slurry.

Key words: surface treating, coating properties, silicon carbide ceramic foam, size of struts