Thermoset membranes incorporate principal polymers that are chemically cross linked or vulcanized. One characteristic of true thermoset polymers is once they are cured, they only can be bonded to similar materials with adhesives. The most common thermoset roof membrane is EPDM. EPDM roof membranes can be installed fully adhered, mechanically attached, or ballasted. Most EPDM membranes do not receive additional surfacing.