Thermoplastic fluoroelastomers

In general the nitroso rubbers also suffer from a poor resistance to ionising radiation, sensitivity to degradation by organic bases, highly toxic degradation products and an exceptionally high cost. The advent of the rubbers based on perfluoro(methyl vinyl ether) considered above and of the phosphonitrilic elastomers considered below would appear to put the commercial future of these materials in extreme doubt. 

These last named materials may be considered as derivatives of the inorganic rubber, polyphosphonitrilic chloride, discovered by Stokes in 1895. This was prepared by the reaction of phosphorus pentachloride with ammonium chloride as follows  

This material had poor hydrolytic stability and was no more than a laboratory curiosity. Treatment with sodium trifluoroethoxide and heptafluorobutoxide has recently been found to yield a useful fluorophosphazene polymer  

The rubber has a very low Tg of -68°C, excellent hydrolytic stability and excellent resistance to ozone, solvents and acids. In addition the rubber does not bum even in an oxidising atmosphere. Although its properties are virtually unchanged in the range -75 to + 120°C it does not possess the heat resistance of other fluoroelastomers. This polymer was marketed by Firestone in the mid-1970s as PNF rubber, but in 1983 the Ethyl Corporation obtained exclusive rights to the Firestone patents and the polymer is now marketed as Eypel F. 

In addition to the elastomers already described, others, have been produced on an experimental scale. These include the perfluoroalkylenetriazines with their unsurpassed thermal oxidative stability for an elastomer but with many offsetting disadvantages, and poly(thiocarbonyl fluoride). It is probably true to say that material does not have any outstanding desirable property that cannot now be matched by an alternative and commercially available material. 

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FIGURE 8.5 O-rings from thermoplastic fluoroelastomer. (Courtesy of Dai kin.)... 

The third period since mid 70s might be called as the era of functional polymers. The commercialized examples are membranes, a thermoplastic elastomer, weather resistant paints and some cyclopolymers. The thermoplastic fluoroelastomer developed by Daikin involves a quite interesting technology. This is a very unique block copolymer with hard and soft segments based on the specially designed iodine-containing living fluoropolymer (1). 

Uses. Vinyhdene fluoride is used for the manufacture of PVDF and for copolymerization with many fluorinated monomers. One commercially significant use is the manufacture of high performance fluoroelastomers that include copolymers of VDF with hexafluoropropylene (HFP) (62) or chlorotrifluoroethylene (CTFE) (63) and terpolymers with HEP and tetrafluoroethylene (TEE) (64) (see Elastomers, synthetic-fluorocarbon elastomers). There is intense commercial interest in thermoplastic copolymers of VDE with HEP (65,66), CTEE (67), or TEE (68). Less common are copolymers with trifluoroethene (69), 3,3,3-trifluoro-2-trifluoromethylpropene (70), or hexafluoroacetone (71). Thermoplastic terpolymers of VDE, HEP, and TEE are also of interest as coatings and film. A thermoplastic elastomer that has an elastomeric VDE copolymer chain as backbone and a grafted PVDE side chain has been developed (72). 

Natural mbber comes generally from southeast Asia. Synthetic mbbers are produced from monomers obtained from the cracking and refining of petroleum (qv). The most common monomers are styrene, butadiene, isobutylene, isoprene, ethylene, propylene, and acrylonitrile. There are numerous others for specialty elastomers which include acryUcs, chlorosulfonated polyethylene, chlorinated polyethylene, epichlorohydrin, ethylene—acryUc, ethylene octene mbber, ethylene—propylene mbber, fluoroelastomers, polynorbomene, polysulftdes, siUcone, thermoplastic elastomers, urethanes, and ethylene—vinyl acetate. 

Over the past 40 years there have been a number of developments that have resulted in the availability of rubbery materials that are thermoplastic in nature and which do not need chemical cross-linking (vulcanisation or setting) to generate elastomeric properties (see also Section 11.8 and 31.2). This approach has been extended to the fluoroelastomers. 

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). 

HMX HMX HMX HMX HMX HMX HMX HMX HMX HMX HMX HMX HNS NTO NTO/HMX NTO/HMX NTO/HMX PETN PETN PETN PETN PETN PETN PETN PETN PETN PETN RDX RDX RDX RDX RDX RDX RDX RDX RDX RDX RDX RDX RDX TATB/HMX Cariflex (thermoplastic elastomer) Hydroxy-terminated polybutadiene (polyurethane) Hydroxy-terminated polyester Kraton (block copolymer of styrene and ethylene-butylene) Nylon (polyamide) Polyester resin-styrene Polyethylene Polyurethane Poly(vinyl) alcohol Poly(vinyl) butyral resin Teflon (polytetrafluoroethylene) Viton (fluoroelastomer) Teflon (polytetrafluoroethylene) Cariflex (block copolymer of butadiene-styrene) Cariflex (block copolymer of butadiene-styrene) Estane (polyester polyurethane copolymer) Hytemp (thermoplastic elastomer) Butyl rubber with acetyl tributylcitrate Epoxy resin-diethylenetriamine Kraton (block copolymer of styrene and ethylene-butylene) Latex with bis-(2-ethylhexyl adipate) Nylon (polyamide) Polyester and styrene copolymer Poly(ethyl acrylate) with dibutyl phthalate Silicone rubber Viton (fluoroelastomer) Teflon (polytetrafluoroethylene) Epoxy ether Exon (polychlorotrifluoroethylene/vinylidine chloride) Hydroxy-terminated polybutadiene (polyurethane) Kel-F (polychlorotrifluoroethylene) Nylon (polyamide) Nylon and aluminium Nitro-fluoroalkyl epoxides Polyacrylate and paraffin Polyamide resin Polyisobutylene/Teflon (polytetrafluoroethylene) Polyester Polystyrene Teflon (polytetrafluoroethylene) Kraton (block copolymer of styrene and ethylene-butylene)... 

Fluoropolymers are thermoplastic and nonrigid materials while fluoroelastomers have elastomeric properties. See Tables 2.1 and 2.2 for a comparison of physical and mechanical properties of select plastics and elastomers including fluorinated materials. 

Uses Protective coating for molds in storage all-purpose, bonded coating esp. useful for PU, epichtorohydrin, EPDM, fluoroelastomers, and thermoplastic rubbers McLube 1733L [McLubej... 

Uses Processing aid, modifier, antiozonantfor high m.w. elastomers and resins, e.g., EPDM, NR, IR, SBR, CR, fluoroelastomers, SBS, SEBS, TPO, TPE, and for adhesives, sealants, coatings for low temp, flexibility Features Reactive produces liq. elastomers used alone or with solid elastomers in thermosetting and thermoplastic applies. features low vise., crosslinking, oxidation resist., good elec, props., ozone and UV resist. Properties Pale yel. vise. Ilq. HC odor m.w. 7500 sol. in nonpolar soivs. sp.gr. 0.84 vise. 690,000 cps (60 C) flash pt. > 400 E iodine no. 19 dielec. str. 740 V/mll dielec. const. 2.11 (1 kHz) ethylene/propylene 46/ 54... 

Furno, J. S. and Nauman, E. B. (1991) A novel heat resistant blend produced by compositional quenching a thermoplastic polyimide impact modified with a fluoroelastomer. Polymer, 32,87-94. 

S.S. Baneijee, K.D. Kumar, A.K. Bhowmick, Distinct melt viscoelastic properties of novel nanostructured and micro structured thermoplastic elastomeric blends from polyamide 6 and fluoroelastomer, Macromolecular Materials and Engineering 300 (3) (2015) 283-290. 

Uses. The variety of fluoropolymers and fluoroelastomers incorporating VDF in the main chain is extensive. The commercially important thermoplastic copolymers are based upon hexafluoropropylene HFP (10,11) chlorotrifluoroethy-lene (CTFE) (12,13) and co- or ter-polymers with tetrafluoroethylene (14). Telomer-ization of VDF to form fluorinated oligomers by radical addition has been reviewed (15). 

The Swiss company, WW Fischer, offers PTFE (Teflon PTFE or Hostaflon), PBT (Celanex, Crastin, Ultradur or Valox) or PEEK (Victrex) insulator material options in its 405 series of cylindrical connectors according to the requirements of working temperature and other criteria. PEEK is an expensive polymer which tends to be employed when other materials fail to meet the specification requirements of the application. Other Fischer connector types use polyamide-imide (Torlon) or POM (Celcon, Delrin or Hostaform). Elastomeric seals used by Fischer in conjunction with their connectors are made from acrylonitrile-butadiene rubber (NBR N BUNA) or to MIL-P-25732, fluoroelastomer (FPM VITON), polychloroprene elastomer (CR Neoprene), ethylene-propylene diene elastomer (EPDM) and styrene-ethylene-butadiene-styrene thermoplastic elastomer (TPE-S or TPE-O) where each compound is followed by its trade name. Fischer s Swiss competitor, Lemo, manufactures a similar range of connectors including the Redel types which have a plastic body. 

Some fluoropolymers prepared by DT with iodo-compounds have already been commercialized such as Daiel, Viton, and Technoflon. Such fluoroelastomers may find applications in high technology such as in O-rings, gaskets, hoses, transportation, medical devices, and electronics. The control of the architecture and functionality of the polymer chains makes possible the preparation of peroxide curable fiuoroelastomer with improved properties as well as the development of advanced fluorinated thermoplastic elastomers. Another application of functional fluoropolymers prepared by DT with iodo-compounds is the preparation of membranes for fuel cells. 

Polychloroprene, nitrile, natural rubber, styrene butadiene rubber and butyl rubber can all be readily bonded with cyanoacrylates. EPDM and fluoroelastomers (such as Viton) can also be bonded, although only with specific grades of cyanoacrylate. The silicone rubbers and thermoplastic elastomers will usually require a primer but will also bond with cyanoacrylates. 

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