Viton Selection Guide - Home - Rainier Rubber Company

1 Technical Information Selection GuideIntroductionViton fluoroelastomer was introduced in 1957 tomeet the needs in the aerospace industry for a high-performance sealing elastomer. Since then, the use ofViton fluoroelastomer has spread quickly to manyother industries, especially in the automotive, fluidpower, appliance, and chemical industries. With40 years of field-proven performance, Viton fluoro-elastomer has developed a reputation for its out-standing performance in very hot and extremelycorrosive Properties of VitonFluoroelastomerVulcanizates based on Viton fluoroelastomers providean exceptional balance of physical property character-istics, including the following features: Resistance to temperature extremes:Heat Viton withstands high temperature andsimultaneously retains its good mechanical proper-ties better than most other elastomers.

2 Oil andchemical resistance also are relatively unaffected byelevated temperatures. Compounds of Viton remainusefully elastic indefinitely when exposed tolaboratory air oven aging up to 204 C (400 F) or tointermittent test exposures up to 260 C (500 F).High temperature service limits are generallyconsidered to be:3,000 hr at 232 C (450 F)1,000 hr at 260 C (500 F)240 hr at 288 C (550 F)48 hr at 316 C (600 F)Cold Viton is generally serviceable indynamic applications down to 18 to 23 C(0 to 10 F), although special formulationspermit its use in static applications down to 54 C ( 65 F). Also, Viton has proven to besatisfactory for static seals used under conditionsapproaching absolute zero.

3 Resistance to degradation by a greater varietyof fluids and chemicals than any nonfluorinatedelastomer, providing the best proven fluidresistance of any commercial Rubber . Excellentresistance to oils , fuels, lubricants, and mostmineral acids. Extremely low permeability to a broad range ofsubstances, including particularly good perfor-mance in oxygenated automotive fuels. Resistance to aliphatic, aromatic hydrocarbons thatare solvents for other rubbers. Exceptionally good resistance to compression set,even at high temperatures. Exceptionally good resistance to atmosphericoxidation, sun, and weather.

4 Excellent resistance tofungus and mold. Good electrical properties in low voltage, lowfrequency applications. Low burning characteristics; inherently moreresistant to burning than other, non-fluorinatedhydrocarbon Various Families and Typesof Viton FluoroelastomerThere are three major families of standard Vitonfluoroelastomer: A, B, and F. The Viton A typesare comprised of vinylidene fluoride (VF2 ) andhexafluoropropylene (HFP). The B and F types aremade with vinylidene fluoride (VF2), hexafluoro-propylene (HFP), and tetrafluoroethylene (TFE). Viton fluoroelastomer products are designated asA, B, or F types according to their relative resistanceto attack by fluids and chemicals.

5 The differences influid resistance that exist among these families are theresult of different levels of fluorine in the polymer,which is determined by the types and relativeamounts of monomers that comprise the general, the standard types of Viton exhibit out-standing resistance to attack by a wide variety offluids, including mineral acids and aliphatic and2aromatic hydrocarbons. The higher the fluorinecontent of the polymer, the less will be the effect, asmeasured by volume increase, for example. The mostsignificant differences between standard types ofViton , in terms of resistance to volume change orretention of physical properties, are noted in lowmolecular weight, oxygenated solvents (such asmethanol and methyl t-butyl ether).

6 As mentioned above, the fluid resistance of Vitonpolymers improves with increasing levels of is shown in Table 1, below (note the volumeincrease after aging in methanol at 23 C [73 F]). Asthe fluorine content increases, however, the lowtemperature flexibility of the polymer decreases, and acompromise must be made between the fluid resis-tance and low temperature flexibility of the those applications that require the best perfor-mance in both fluid resistance and low temperatureflexibility, a number of specialty types of Viton weredeveloped that contain a fluorinated vinyl ethermonomer. Polymers that contain this monomer exhibitsignificantly improved low temperature flexibility,compared to standard types of GLT, introduced in 1976, was the first commer-cial fluoroelastomer to use this fluorinated vinyl ethermonomer.

7 This polymer provides the same excellentresistance to heat and fluids that is typical of the Atypes of Viton fluoroelastomer. Viton GFLT, likeViton GLT, exhibits significantly improved lowtemperature flex characteristics compared to standardtypes of fluoroelastomer, but in addition, provides thesame superior resistance to fluids that is typical of theF types of Viton fluoroelastomer as Types of VitonFluoroelastomers that contain vinylideneflouride(VF2) are subject to attack by high pH materials,including caustics and amines. In addition, standardfluoroelastomers are not resistant to low molecularweight carbonyl compounds, such as methylethylketone, acetone, or methyl tertiarybutyl Extreme , ETP-500 and ETP-900, commer-cialized in 1998, are fluoroelastomers made withethylene, tetrafluoroethylene (TFE), andperfluoromethylvinyl ether (PMVE).

8 This uniquecombination of monomers provides outstandingresistance to fluids. The ETP types of Viton exhibitthe same excellent resistance to acids and hydrocar-bons typical of standard types of Viton . Unlikeconventional fluoroelastomers, however, ETP types ofViton also provide excellent resistance to low molecu-lar weight esters, ketones, and aldehydes. In addition,these unique polymers are inherently resistant to attackby base, and thus provide excellent resistance tovolume swell and property loss in highly causticsolutions and information regarding performance differ-ences between the various families and types of Vitonfluoroelastomer is presented in Tables3 6 to assist in selecting the particular grade of Vitonthat is best suited for both a given end-use applicationand for a specific manufacturing 1 Polymer Fluorine Content versus Fluid Resistance and Low Temperature FlexibilityStandard TypesSpecialty TypesABFB70 GLTGFLTETPN ominal Polymer FluorineContent, wt%66687066646767 Percent Volume Change inFuel C.

9 168 hr at 23 C (73 F)*4325524 Percent Volume Change inMethanol, 168 hr at 23 C (73 F)*90405909055 Percent Volume Change inMethylethyl Ketone, 168 hrat 23 C (73 F)*>200>200>200>200>200>20019 Percent Volume Change in30% Potassium Hydroxide,(Samples too swollen and degraded to test)14168 hr at 70 C (158 F)*Low Temperature Flexibility,TR-10, C* 17 13 6 19 30 24 12*Nominal values, based on results typical of those obtained from testing a standard, 30 phr MT (N990) carbon black-filled,75 durometer Systems for Viton FluoroelastomerIn addition to inherent differences between the varioustypes and families of Viton fluoroelastomer, a numberof compounding variables have major effects on thephysical property characteristics of the final vulca-nizates.

10 One very important variable is the crosslinkingor curing system that is used to vulcanize the curatives were introduced in 1957 (DIAK-1)for crosslinking Viton A. While these diamine curativesare relatively slow curing, and do not provide the bestpossible resistance to compression set, they do offerunique advantages, such as excellent adhesion to metalinserts and high hot tensile fluoroelastomers currently are crosslinked withBisphenol AF, a curative first introduced in 1970, in thefirst commercial curative-containing precompound, Viton E-60C. Compounds of Viton that use this cura-tive exhibit fast rates of cure and excellent scorchsafety and resistance to compression 1987, an improved bisphenol curative was intro-duced, which was made available in several differentprecompounds: Viton A-201C, A-202C, A-401C, andA-402C.