Fluoroelastomers applications

Their physical properties, chemical stability, and resistance to temperatures above 135°C qualify these materials as competitors for sdicone rubber and fluoroelastomers. Applications include hose, tubing, gaskets, and protective covers for use in high-temperature environments. 

In summary, PVDF fulfills special requirements in a variety of niche applications because of its unique characteristics. Hence, the broad and growing usage of this polymer is understandable. VDF usage also is increasing in other fluoropolymer and fluoroelastomer applications. 

As with the fluoroelastomers, applications of the FPM elastomers is limited to those areas where other less expensive elastomers will not perform satisfactorily. These are areas of extreme temperatures and highly corrosive conditions. They are suitable for outdoor applications to resist atmospheric corrosion. 

Application of mechanical stresses, implicitly altering chemical potentials, can also effect further changes, as illustrated by Morgan et al. for a fluoroelastomer in aqueous amine environment at several temperatures this study indicated that a balance existed between the amine attack... 

Abstract In this paper the synthesis, properties and applications of poly(organophos-phazenes) have been highlighted. Five different classes of macromolecules have been described, i.e. phosphazene fluoroelastomers, aryloxy-substituted polymeric flame-retardants, alkoxy-substituted phosphazene electric conductors, biomaterials and photo-inert and/or photo-active phosphazene derivatives. Perspectives of future developments in this field are briefly discussed. 

In the case of poly(alkoxyphosphazenes) (IV) or poly(aryloxyphos-phazenes) (V) a dramatic change in properties can arise by employing combinations of substituents. Polymers such as (NP CHjCF ) and (NP CgH,).) are semicrystalline thermoplastics (Table I). With the introduction of two or more substituents of sufficiently different size, elastomers are obtained (Figure 4). Another requirement for elastomeric behavior is that the substituents be randomly distributed along the P-N backbone. This principle was first demonstrated by Rose (9), and subsequent work in several industrial laboratories has led to the development of phosphazene elastomers of commercial interest. A phosphazene fluoroelastomer and a phosphazene elastomer with mixed aryloxy side chains are showing promise for military and commercial applications. These elastomers are the subject of another paper in this symposium (10). 

Other Applications. Thus far the phosphazene fluoroelastomers (PNF) and aryloxyphosphazene elastomers (APN) have moved to the commercial stage. In addition to elastomers, phosphazenes are being investigated as fluids, resins and plastics. Other areas which hold promise include fire resistant paints (55), fiber blends and additives, agrichemicals and herbicides, drug release agents and electrically conducting polymers (6). 

Report 32 Fluoroelastomers - Properties and Applications, D. Cook and M. Lynn, 3M United Kingdom Pic and 3M Belgium SA. 

Fluoroelastomers. The fluoroelastomers were introduced to the mbber industry in the late 1950s by the DuPont Company. They were made by modification of Teflon polymers and designed to have excellent heat and chemical resistance, but remain elastomeric in nature. They were very expensive and have found use in limited applications. However, with the increasing demand in the automotive and industrial market for improved reliability and longer life, the elastomeric fluoroelastomers have made significant inroads into these applications (see Elastomers, synthetic-fluorocarbon elastomers). ... 

Fluoroelastomers excel compared to all other elastomers in heat, chemical, flame, weathering, fuel, and ozone resistance. In addition oil, oxygen, and water resistance are very good. The fluoroelastomers, however, are attacked by amines and some highly polar solvents. The abrasion resistance and low temperature properties are adequate for most applications. 

Parts made from fluoroelastomers are used in applications that justify their high cost, usually where the maintenance and replacement costs are high enough to offset the initial cost of the part. These include automotive applications such as valve stem seals, fuel injector components, radiator, crankcase and transmission seals, and carburetor needle tips. Numerous seals and gaskets in the marine, oilfield, and chemical processing industries employ fluoroelastomers. In addition, many hoses in the automotive and chemical industry are made entirely of fluoroelastomer compounds or have a veneer of the fluoroelastomer as a barrier exposed to the harsh environment. Seals and gaskets in military applications and the binder for flares and missile applications are made with fluoroelastomers. 

Applications. The P-O- and P-N-substituted polymers have so far shown the greatest commercial promise. The fluoroelastomers possess good rubber properties with the added advantages of being nonhuming. hydrophobic, and solvent- and luel-resistant. In addition lo these, because of flexibility down to about -fi()"C. these polymers have been used in seals, gaskets, and buses in army tanks, in aviation fuel lines and tanks, as well as in cold-climate oil pipeline applications, These polymers have also round application in various types of shock mounts lor vibration dampening. 

A fluoroelastomer manufactured by Du Pont called Kalrez, has mechanical properties and resistance to oxidants which are similar to those of Viton. In contrast with Viton, Kalrez has good resistance to polar molecules such as amines, ethers, ketones, and esters. Kalrez is unique among the elastomers in its tolerance to both polar and nonpolar solvents. The cost of O-rings made from Kalrez is very high, but for certain critical applications this cost can be justified because of the outstanding range of solvent tolerance. 

Smith S (1982) Fluoroelastomers. In Banks RE (ed) Preparation, Properties and Industrial Applications of Organofluorine Compounds, Ellis Horwood Chichester 235... 

In 1994, the total worldwide market for fluoroelastomers was estimated at about 9,000 to 10,000 tons, of which about 60% was automotive, 10% chemical and petrochemical, 10% aerospace, and 20% other markets. Annual growth is estimated at 5 to 8%, mainly for new applications or replacement of parts made previously from inferior elastomers.49 O-rings and gaskets consume about 30 to 40%, shaft seals and oil seals about 30%, and hoses and profiles 10 to 15%.50-54 Typical applications are listed in the following sections. 

Coatings and sealants for varied industrial applications are made by dissolving compounds of low-viscosity FKM elastomers, such as VITON C-10, VITON A-35, or FLUOREL 2145, in methyl ethyl ketone, ethyl acetate, methyl isobutyl ketone, amyl acetate, or other related ketones.47 Such products have typical useful storage life of 7 days at 24°C (75°F) and cure within 2 weeks.58 The subject of coatings and sealants based on fluoroelastomers is covered in more detail in Modern Fluoropoly-mers (Scheirs, J., Ed.), Chapter 23 (Ross Jr., E. W. and Hoover, G. S.), John Wiley Sons, New York (1997). 

As shown in the previons section, many of the fundamental properties of the polymers depend on their structure, mainly on the nature of monomeric units composing them. This section concentrates on the specific properties of individual fluoropolymers— more specifically fluoroplastics—and how they relate to their utility in practical applications. The properties of fluoroelastomers are discussed in Chapter 5. 

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