Acid resistant filter media

A composite porous filter membrane comprising:

• a porous hydrophobic polymeric filter media having a coating thereon which at least partially coats surfaces throughout the porous hydrophobic polymeric filter media,
• wherein said coating is a polyamide polymer possessing a repeat unit structure of the formula —[(CH2)xC(O)NH]n—, wherein x is an integer of from about 8 to 12, and n represents the number of repeat units in the polyamide polymer, and
• wherein the composite porous filter membrane has the following characteristics:
• (i) a surface energy of from greater than 30 to 100 dynes/cm;
• (ii) an isopropanol flowtime of about 150 to about 20,000 seconds/500 mL, measured at 14.2 psi;
• (iii) a bubble point of about 20 to about 200 psi, when measured using ethoxy-nonafluorobutane HFE 7200 at a temperature of about 22° C.;
• (iv) a capacity to bind Ponceau S dye of between about 1 and about 30 μg/cm2 and the capacity to bind methylene blue dye (MB DBC) of between about 1 and about 30 μg/cm2;
• and
• (v) after exposure of the composite porous filter membrane to a >96% formic acid solution for 24 hours and flushing of the composite porous filter membrane with de-ionized water until a stable pH is obtained, the composite porous filter membrane retaining the surface energy of from greater than 30 to 100 dynes/cm.