• Hydrophobic PTFE Membrane Cobetter Hydrophobic PTFE membrane is made from pure PTFE membrane bonded to a polypropylene support. The extreme chemical compatibility (pH 1-14) makes them very useful for the filtration of solvents and acids or other aggressive chemicals, for which other membrane filter types are unsuitable. Due to their hydrophobic characteristics, they must be pre-wet with a solvent such as ethanol or methanol before the filtration of aqueous solutions.