PCTFE

Poly(chlorotrifluoroethylene) (PCTFE) Butadiene-maleic acid copolymer (BMC)... 

Cm.OROCARBONSANDCm.OROHYDROCARBONS - RDIG-Cm.ORINATED TOLUENES] (Vol 6) PCTFE. See Polychlorotrifluoroethylene. 

Many challenging industrial and military applications utilize polychlorotriduoroethylene [9002-83-9] (PCTFE) where, ia addition to thermal and chemical resistance, other unique properties are requited ia a thermoplastic polymer. Such has been the destiny of the polymer siace PCTFE was initially synthesized and disclosed ia 1937 (1). The synthesis and characterization of this high molecular weight thermoplastic were researched and utilized duting the Manhattan Project (2). The unique comhination of chemical iaertness, radiation resistance, low vapor permeabiUty, electrical iasulation properties, and thermal stabiUty of this polymer filled an urgent need for a thermoplastic material for use ia the gaseous UF diffusion process for the separation of uranium isotopes (see Diffusion separation methods). 

The typical mechanical properties that qualify PCTFE as a unique engineering thermoplastic are provided ia Table 1 the cryogenic mechanical properties are recorded ia Table 2. Other unique aspects of PCTFE are resistance to cold flow due to high compressive strength, and low coefficient of thermal expansion over a wide temperature range. 

The high fluorine content contributes to resistance to attack by essentially all chemicals and oxidizing agents however, PCTFE does swell slightly ia halogenated compounds, ethers, esters, and selected aromatic solvents. Specific solvents should be tested. PCTFE has the lowest water-vapor transmission rate of any plastic (14,15), is impermeable to gases (see also Barrierpolymers), and does not carbonize or support combustion. 

PCTFE plastic is compatible withHquid oxygen, remains ductile at cryogenic temperatures (16—22), and retains its properties when exposed to either uv or gamma radiation. PCTFE exhibits a refractive iadex of 1.43 (ASTM D542) and an amorphous sheet can provide over 90% transmittance. 

PCTFE exhibits very good electrical properties ia terms of high iasulation resistance, minimal trackiag, corona formation, and surface flashover due to the polymer s nonwettable surface and ultralow moisture absorption (Table 3). 

The lower molecular weight oils, waxes, and greases of PCTFE can be prepared direcdy by telomerization of the monomer or by pyrolysis of the higher molecular weight polymer (45—54). 

PCTFE plastic is available in products that conform to ASTM 1430-89 Type 1 (Grades 1 and 2) and is suitable for processing into parts that meet MIL-P 46036 (Federal Specification LP-385C was canceled 1988). Standards for fabricated forms are available for compression molded heavy sections (AMS-3645 Class C), thin-walled tubing, rod, sheet, and molded shapes (AMS-3650). PCTFE plastics have been approved for use in contact with food by the FDA (55). 

In general, the PCTFE resins have been found to be low in toxicity and irritation potential under normal handling conditions. Specific toxicological information and safe handling procedures are provided by the manufacturer of specified PCTFE products upon request. 

The principal uses of PCTFE plastics remain in the areas of aeronautical and space, electrical/electronics, cryogenic, chemical, and medical instmmentation industries. AppHcations include chemically resistant electrical insulation and components cryogenic seals, gaskets, valve seats (56,57) and liners instmment parts for medical and chemical equipment (58), and medical packaging fiber optic appHcations (see Fiber optics) seals for the petrochemical /oil industry and electrodes, sample containers, and column packing in analytical chemistry and equipment (59). 

The lower molecular weight PCTFE oils, waxes, and greases are used as inert sealants and lubricants for equipment handling oxygen and other oxidative or corrosive media. Other uses include gyroscope flotation fluids and plasticizers for thermoplastics. 

The high thermal stability of the carbon-fluorine bond has led to considerable interest in fluorine-containing polymers as heat-resistant plastics and rubbers. The first patents, taken out by IG Farben in 1934, related to polychlorotri-fluoroethylene (PCTFE) (Figure 13.1 (a)), these materials being subsequently manufactured in Germany and the United States. PCTFE has been of limited application and it was the discovery of polytetrafluoroethylene (PTFE) (Figure... 

Figure 13.1. (a) Polychlorotrifluoroethylene (PCTFE). (b) Polytetrafluoreoethylene (PTFE). (c) Poly(vinyl fluoride), (d) Poly(vinylidene fluoride)... 

Property ASTM test PTFE PCTFE PVF - PVDF TFE-HFP TFE- ethylene PFA... 

POLYCHLOROTRIFLUOROETHYLENE POLYMERS (PCTFE) AND COPOLYMERS WITH ETHYLENE (ECTFE)... 

Polychlorotrifluoroethylene was the first fluorinated polymer to be produced on an experimental scale and polymers were used in Germany and in the United States early in World War II. PCTFE was used, in particular, in connection with the atomic bomb project in the handling of corrosive materials such as uranium hexafluoride. 

The chemical resistance of PCTFE is good but not as good as that of PTFE. Under certain circumstances substances such as chlorosulphonic acid, molten caustic alkalis and molten alkali metal will adversely affect the material. Alcohols, acids, phenols and aliphatic hydrocarbons have little effect but certain aromatic hydrocarbons, esters, halogenated hydrocarbons and ethers may cause swelling at elevated temperatures. 

PCTFE is marketed by Hoechst as Hostaflon C2 and in the United States by Minnesota Mining and Manufacturing (Kel-F) and Allied Chemical (Halon). Typical values for various physical properties are given in Table 13.1. 

The properties of the nylons are considerably affected by the amount of crystallisation. Whereas in some polymers, e.g. the polyacetals and PCTFE, processing conditions have only a minor influence on crystallinity, in the case of the nylons the crystallinity of a given polymer may vary by as much as 40%. Thus a moulding of nylon 6, slowly cooled and subsequently annealed, may be 50-60% crystalline, while rapidly cooled thin-wall mouldings may be only 10% crystalline. 

PCTFE CF2=CFC1 Actar Aclon Daifloti Kel-F Allied Signal Ausimont Dai kin 3M USA Italy USA Japan USA... 

---