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Development of Perfluoroether Rubber FFKM (Brief Discussion)
Perfluoroethyl ether rubber (FFKM) is a copolymer composed mainly of tetrafluoroethylene (TFE), perfluoroethyl (methyl vinyl) ether (PMVE), and a small amount of vulcanization point monomer (CSM). It is the most excellent variety of rubber with high temperature and chemical medium resistance [1]. Perfluoroether rubber was invented by DuPont Company in the United States in 1968 and officially sold to the public in 1975 under the trade name Kalrez. It is still a major global supplier, and is also produced in bulk by SolvaySolexis in Europe, Daikin in Japan, and the Lebedev Synthetic Rubber Research Institute in Russia. A domestic research institute began the development of perfluoroether rubber in the 1970s. Due to a lack of technical information, difficulties in purchasing raw materials, and outdated experimental conditions, the progress of the experimental work was slow, and samples were not synthesized until the early 1980s. Later, due to various reasons, research work completely ceased. In 2006, the synthesis of PMVE and CSM and the research on rubber polymerization technology were completed, and a batch production device was established, making China one of the few countries in the world to master the synthesis of perfluoroether rubber monomers and rubber polymerization technology.
There are two technical routes for the industrial production of PMVE, one is the hexafluoroepoxypropane (C3F6O)/fluorophosgene (COF2) route, and its basic raw materials are hexafluoroepoxypropane, anhydrous hydrogen fluoride (HF), and carbon monoxide (CO) [2]; The other route is dichlorodifluoroethylene (CFCl=CFCl)/fluoroxytrifluoromethane (CF3OF), starting with difluorotrichloroethane (F112), HF, and CO [3]. CSM is a key monomer in the synthesis of perfluoroether rubber, and its structure and synthesis method are highly confidential by various manufacturers. Generally speaking, CSM has several types: perfluorophenoxy (- OC6F5), nitrile (- CN), and bromine (- Br). The vulcanization mechanism of different CSMs varies, and the properties of rubber also vary. TFE, PMVE and CSM are polymerized in free radical lotion in aqueous solution containing surfactant, initiator and other additives to obtain ternary copolymer, in which PMVE content is about 20%~35% (mol) and CSM content is about 0.5%~3% (mol). The main chain of perfluoroether rubber is a C-C bond, and all H on C is replaced by F, with – OCF3 group on the branch chain. Its main chain structure is completely identical to that of polytetrafluoroethylene. Perfluoroether rubber has excellent comprehensive properties, with the best high-temperature resistance among all rubbers. Its long-term use temperature is 280 ℃, and special varieties can reach over 300 ℃; Extremely excellent medium resistance, able to withstand various strong oxidizing and corrosive media, various organic solvents and oils; The weather resistance and airtightness are also very good.
Perfluoroether rubber is a widely adaptable rubber variety mainly used in the petroleum, chemical, pesticide, mechanical, and semiconductor industries. It is used as an “O” ring and “V” ring for mechanical seals, pumps, and valves