Fluorine rubber

Fluorinated rubbers, copolymers of hexafluoropropylene and vinylidene-fluorides, have excellent resistance to oils, fuels and lubricants at temperatures up to 200°C. They have better resistance to aliphatic, aromatic and chlorinated hydrocarbons and most mineral acids than other rubbers, but their high cost restricts their engineering applications. Cheremisinoff et al. [54] provide extensive physical and mechanical properties data on engineering plastics. A glossary of terms concerned with fabrication and properties of plastics is given in the last section of this chapter. 

AU EU CSM T FKM FC, FE, GE FK Polyesterurethanes Polyetherurethanes Chlorosulphanated polyethylene Thiokol Fluorinated rubbers-Vitons Silicone rubbers Fluorosilicone rubbers... 

Forms impact-sensitive explosive mixtures with dichloromethylsilane, May attack, plastics, coatings, and chlorinated rubber materials such as Hypalon , Parlon , Rutile , and fluorinated rubbers such as Viton . Inorganic lead compounds are known human carcinogens. 

LEAD MONOXIDE (1317-36-8) A strong oxidizer. Explosive reaction with 90% peroxy-formic acid, rubidium acetylide. Reacts violently with strong oxidizers, boron, chlorine, fluorine, dichloromethylsilane, calcium sulfide, hydrogen peroxide, hydrogen trisulfide (ignition), hydroxylamine (ignition), lithium carbide, metal acetylides, metal powders (e.g., aluminum, molybdenum, zirconium, etc.), perchloric acid, red phosphorus, selenium oxychloride, sodium. Incompatible with aluminum carbide, barium sulfide, silicon, sulfuryl chloride. Forms impact-sensitive explosive mixtures with dichloromethylsilane. May attack plastics, coatings, and chlorinated rubber materials such as Hypalon , Parlon , Rutile , and fluorinated rubbers such as Viton . 

A series of these rubbers possess polar groups consequently, the corresponding elastomers do not swell in oil. Polyurethane rubbers and polysulfide rubbers, as well as the already mentioned nitrile and chloroprene rubbers (Table 37-5), belong to the good oil-resisting rubbers. Moderate oil resistance with simultaneously improved heat resistance is shown by chlorosulfonated ethylene, acrylic, silicone, and fluorine rubbers. 

None of these rubbers has carbon-carbon double bonds. Consequently, they have relatively good aging properties, but, on the other hand, they cannot be vulcanized by the classical sulfur process. For this reason, some of these rubbers are cross-linked with the aid of peroxides, and, in this case, by polymerization of vinyl groups in the case of some silicone rubbers or by free radical transfer reactions in the case of ethylene/vinyl acetate or acrylic rubbers. Other speciality elastomers are cross-linked by reaction with diamines, for example, in the cases of acrylic, epichlorohydrin and fluorine rubbers. 

The fluorinated rubbers are exceptionally good for high-temperature service, but they are below silicones in this respect. They resist most of the lubricants, fuels, and hydraulic fluids encountered in aircraft a wide variety of chemicals, especially the corrosive variety and also most chlorinated solvents. They have good physical properties, somewhere near those of styrene butadiene rubber (SBR) at the higher hardness levels. FKM is valnable in automotive use for its extreme heat and oil resistance and is on a much higher level in this respect than the acrylic elastomers. It has weathering properties snperior to those of neoprene. However, fluoroelastomers are relatively expensive. 

Fluoroelastomer Fluoropolymer elastomer Fluorocarbon elastomer Fluorine rubber... 

Materials. Polymer and reference samples include propylene-1-butene copolymers, chlorinated poly(vinyl chloride) (PVC), polybenzobisoxazoles (PBO), hydrogen c nide (HCN) polymers, ethoxylated alcohol surfactants [polyethylene oxide (10 moles)/mole ol alcohol (POE-10) and POE-20 (20 moles/mole)], plasticized cellulose acetate butyrate-based propellants, snack food product and a fluorinated rubber composite product. 

K. J. Kim, J. Wasko, and M. Hensel, Mold release additive effects on chlorine and fluorine rubber compound , 2 International Rubber Molding Conference (IRMC2004) (paper no. 7) Cleveland, OH, April (2004)... 

Attention must be given to the volatility of the processing aid when selecting one for FKM fluorinated rubber. A good example is dioctyl phthalate (DOP) since the inclusion of 2.00-3.00 pphr of DOP will result in volatilization of it during demolding and oven post-cure. The finished parts will be undersized, hence the mold cavities must be cut to allow for the increased shrinkage. 

The volatility of stabilizers from polymers is affected by both the properties and structures of the stabilizer and polymer and the external physical conditions of the experiment. Moreover, volatility is governed by diffusion of stabilizer in the polymer since volatilization causes a concentration gradient near the surface and subsequent additive loss from the surface must be replaced by diffusion from the bulk. It was found, for example, that the rate of evaporation of phenyl-2-naphthyl-amine from polymers decreases in the series polyethylene > fluorinated rubber > polybutadiene > butadiene styrene rubber > butadiene acrylonitrile rubber and this parallels the solubility of the naphthylamine in these polymers. The polarity of these polymers increases in the same order which is reflected in a decrease in diffusion coefficient and increasing intermolecular interaction in the polymer-stabilizer system. 

The general effect of cross-link density on the elastic modulus of an elastomer is indicated by Eq. 2.3. In their paper Landel and Fedors [189] consider the influence of a time-dependent cross-link density on the shape of the stress-strain curves of silicon, butyl, natural, and fluorinated rubbers. Introducing an additional shift-factor a related to the cross-link density, they were able to represent reduced breaking stresses as a function of reduced time in one common master curve. 

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