Non-asbestos diaphragm separator

A bonded non-asbestos chlor-alkali diaphragm comprising one or more water-wettable materials and one or more chemically-resistant materials, which is characterized by having a Macmullin number and average diaphragm thickness such that the product of these is between about 5 and about 30 millimeters when the average diaphragm thickness is measured in millimeters, and by a median pore size between about 0.1 microns and about 1 micron, wherein one or more of the chemically-resistant materials is or are coated with a durable, adherent coating of an ion-containing polymer or a thermoplastic precursor thereof which coating has been bonded into the diaphragm on the one or more chemically resistant materials, such that upon converting the thermoplastic precursor to a hydrophilic, ion-containing polymer and placing the diaphragm in use, the diaphragm exhibits a sustained increase in wettability and a sustained, decreased tendency to dewet and become gas-blinded as compared to a identically-prepared and characterized, bonded diaphragm which does not include such coated materials, or such that the diaphragm as bonded exhibits increased burst strength as compared to a diaphragm including one or more chemically-resistant materials which have been coated with an ion-containing polymer but which is not bonded.