Royaltherm 1721 Silicone modified ethylene-propylene diene terpolymer Chemtura (Crompton-Uniroyal Chemical) Acrylic Monomers Coil Coating ROYALTHERM® 1721 ROYALTHERM 1721 a modified EPDM with a special silicone rubber. ROYALTHERM is supplied as a base compound that can be vulcanized with peroxides or sulfur/accelerator systems. ROYALTHERM 1721 is 55 - 65 Durometer when vulcanized with 1.8 phr of dicumyl peroxide. It can be blended with 1421 for intermediate hardness applications. ROYALTHERM 1721 is recommended for applications that require higher tensile strength than 1421. ROYALTHERM 1721 is also recommended for applications that require retention of mechanical strength at elevated temperatures, weather and moisture resistance, electrical stability and compression recovery at low temperatures. It has superior overall heat resistance to 1711. coil coating. Ethylene-propylene diene terpolymer modified with a special silicone rubber. Used as a base compound in coil coatings. Can be vulcanized with peroxides or sulfur/accelerator systems. Provides high tensile strength, retention of mechanical strength at elevated temperatures, weather and moisture resistance, electrical stability and compression recovery at low temperatures. Possesses superior overall heat resistance.