Abstract: A cap for sealing evacuated tubes has a plurality of sealing surfaces to seal tubes of various sizes and a septum of self-closing material to permit a needle to pass for the withdrawal or injection of fluids. The sealing surfaces are defined by a plurality of annular bands extending in series from a top wall, as well as a skirt which depends from the top wall and surrounds the annular bands.

Abstract: In a porous structure, a macroporous polyethylene substrate defining a network of interconnecting macropores and a microporous matrix of polyvinyl chloride is formed within and completely fills the network of macropores. The microporous matrix is cast within the network of macropores by impregnating the macropores with a solution of a solvent, a polymeric pore former, and polyvinyl chloride. The solution is caused to imbibe water from the atmosphere so as to separate into two liquid phases, one phase being rich in the polyvinyl chloride and the other phase being rich in water. The microporous matrix is coagulated from the first phase and the solvent and pore former are extracted from the macroporous matrix.