Abstract: The invention is directed to an open celled polyurethane foam article, which initially is generally non-absorbent, the surface of which is subsequently rendered absorbent by decreasing the average pore cell size to a critical range while preferably also simultaneously or subsequently achieving a critical range of a wetting agent in such surface. This can be accomplished in either of two ways. The first method is to permanently collapse the cells in the surface region of the original foam so that the concentration of any residual wetting agents initially present in the structure increases in the compressed surface region, thus rendering said surface more readily absorbent. For a surgical dressing, the surface cells should be permanently but only partially collapsed to substantially less than the original size to form a microporous skin.

Abstract: A foam material for use especially as a surgical dressing of the formula containing stannous octoate and a chlorofluoromethane and comprised of a polyether based polyurethane having a compressed dense surface which is absorbent to fluids as contrasted with the remaining uncompressed foam which is non-absorbent; the compressed dense surface containing foam cells which have only been partially collapsed as compared to the uncollapsed foam cells of the non-absorbent material.

Abstract: A polyurethane foam article, preferably a surgical dressing, at least one surface of which is rendered lyophilic by applying pressure and heat to said surface.