Abstract
Recent advances in the automotive, petroleum, and energy-related industries have created applications for high-performance elastomers, which often require chemically resistant elastomers with improved high-temperature operating capability. Fluoroelastomers are uniquely capable of withstanding high temperatures in conjunction with aggressive chemicals, fuels, and lubricants. While a number of reviews concerning fluoroelastomers have been published in the last three years, this paper will concentrate on recent developments that have improved fluoroelastomers to meet the requirements of new high-performance applications. Three types of fluorine-containing elastomers—fluorocarbon, fluorosilicone, and fluoroalkoxyphosphazene (phosphonitrilic)—are commercially available. The fluorocarbon elastomers have the highest fluorine content, with general grades having between 53 and 70% fluorine. The high fluorine content of these specialty elastomers imparts exceptional resistance to attack by fuels, oils, and corrosive chemicals. The excellent resistance to high-temperature aging for extended periods of time results in a temperature use range of −46 to 320°C. Fluoro-carbon elastomers are produced in the United States by 3M (“Fluorel” Brand fluoroelastomer) and Du Pont (“Viton” Brand fluoroelastomer) and outside the United States by Montedison (Italy, “Technoflon” Brand fluoroelastomer), Daikin (Japan, “Daiel” Brand fluoroelastomer), and Asahi Glass (Japan, “Aflas” Brand elastomer, a copolymer of tetrafluoroethylene and propylene). Fluorosilicone and fluoroalkoxyphosphazene elastomers contain 30–40% fluorine. Although the fluorine content of these elastomers is less than that of fluorocarbon elastomers, it is high enough to provide moderate chemical resistance to many fluids. The flexible nature of the heteroatoms of the polymer chain backbone in fluorosilicone and fluoroalkoxyphosphazene elastomers results in excellent low-temperature flexibility, giving them a temperature use range of −54 to 230°C. Fluorosilicone elastomers are produced by Dow Corning (“Silastic”) and General Electric (“FSE”), while fluoroalkoxyphosphazene elastomers are produced by Firestone (“PNF”). This paper is a discussion of developments in fluorocarbon elastomer technology that have led to successful use in demanding applications which require high-performance elastomeric parts. Typical properties of fluorocarbon elastomers and improved properties resulting from cure system development and variations in the fluorine content of this type of elastomer will be presented. Applications for fluorocarbon elastomers in the automotive, petroleum, and energy-related industries will be illustrated.
