Aryloxyphosphazenes

The aryloxyphosphazene polymers, on the other hand, have been used primarily ia wire and cable coatings and jackets and as fire-resistant, low smoke, closed-ceU foams and sound-barrier sheets. 

Properties and Applieations. Aryloxyphosphazene elastomers using phenoxy and J-ethylphenoxy substituents have found interest in a number of appHcations involving fire safety. This elastomer has a limiting oxygen index of 28 and contains essentially no halogens. It may be cured using either peroxide or sulfur. Peroxide cures do not require the allyhc cute monomer. Gum physical properties are as follows (17) ... 

Economic Considerations. Gum production by Ethyl Corp. is under 20 metric tons per year. Products are sold primarily for use in U.S. and N.A.T.O. naval appHcations. The materials are sold as finished goods, and thus elastomer pricing is not appropriate. Ethyl Corp. has aimounced that it will either divest or exit this business. Atochem has developed their technology and has constmcted a pilot plant to produce aryloxyphosphazenes. 

Allcock HR, Kugel RL, and Valan KJ. Phosphonitrilic compounds. VI. High molecular weight polyalk-oxy- and aryloxyphosphazenes. Inorg Chem, 1966, 5, 1709-1715. 

Allen RW and Allcock HR. Conformational analysis of poly(alkoxy- and aryloxyphosphazene) [J]. Macromolecules, 1976, 9(6), 956-961. 

Fire retardancy is an often occurring theme in phosphazene chemistry and numerous reviews have focused on this subject over the years [ 10,44,387,393,396, 582]. In this article we will treat only aspects related to the flame-retardant properties of aryloxyphosphazene copolymers, which are the subject of the greatest number of applications. 

The development relative to the flame-retardant properties of polyphosphazenes has been principally centred around the aryloxyphosphazenes copolymers II. 

Table 10 Glass transition temperatures and limiting oxygen index values for selected aryloxyphosphazenes copolymers [284,584,585] ...

Aryloxyphosphazene copolymers can also confer fireproof properties to flammable materials when blended. Dieck [591] have used the copolymers III, and IV containing small amounts of reactive unsaturated groups to prepare blends with compatible organic polymers crosslinkable by the same mechanism which crosslinks the polyphosphazene, e.g. ethylene-propylene and butadiene-acrylonitrile copolymers, poly(vinyl chloride), unsaturated urethane rubber. These blends were used to prepare foams exhibiting excellent fire retardance and producing low smoke levels or no smoke when heated in an open flame. Oxygen index values of 27-56 were obtained. 

Aryloxyphosphazene polymers, such as compound 1 or its mixed-substituent analogs, are also hydrophobic (contact angles in the region of 100°). These too show promise as inert biomaterials on the basis of preliminary in vivo tissue compatibility tests (13). 

First, at the simplest chemical level, aryloxyphosphazene polymers have been surface-sulfonated, as illustrated in Fig. 1 (21). This reaction results in a deci se in the contact angle from 101° for the surface of compound 15 to 0° for the surface of compound 16. 

Allcock, H. R., Kugel, R. L., and Valan, K. J., High molecular weight poly (alkoxy- and aryloxyphosphazenes), Inorg. 

Polyphosphazene-Phthalocyanlne Structures. Thus, a related study was carried out with copper phthalocyanine units linked covalently to a poly(aryloxyphosphazene) (44). Non-polymeric copper phthalocyanine forms ordered stacked structures in the crystalline state. When... 

Polv(Arvloxyphosphazene) Elastomers. Poly(aryloxyphosphazene) elastomers, III, prepared by the reaction of chloropolymer with mixed phenoxides, offer excellent fire resistance without the incorporation of halogens in the polymer or as an additive. In addition, in a fire situation smoke evolution from these polymers... 

Poly(aryloxyphosphazene) elastomers can be cured with peroxides, sulfur and radiation. The resulting vulcanizates are resistant to attack by moisture and oils and have been found to have desirable characteristics for electrical insulation applications where fire safety is a concern (Table II) (12). Fire resistant, low smoke, closed cell foams with excellent properties (Table III) have also been developed from poly(aryloxyphosphazene) elastomers (13). Applications for these foams, which can be produced as either slabstock or tube stock, are being developed for military, aerospace and commercial uses. (See Table II and III.)... 

Poly(aryloxyphosphazene) elastomers offer outstanding fire resistance without the presence of halogen. In a fire these elastomers produce low levels of smoke as well as low toxicity and non-corrosive off-gases. 

Table II. Properties of Poly(aryloxyphosphazene) Wire and Cable Insulation/Jacketing...

Fire Resistant Elastomers. The poly(aryloxyphosphazene) elastomers offer excellent fire resistance without incorporating halogen in the polymer or as an additive. These polymers are self-extinguishing in air and generate only moderate non-corrosive smoke and a minimum of toxic combustion products upon combustion (50-53). The poly(aryloxyphosphazene) elastomers (APN ) have excellent potential for applications such as... 

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). 

Figure 7. Aryloxyphosphazene elastomers (APN) offer excellent potential.

Other crystalline inorganic polymers such as poly(dichlorophosphazene), poly(aryloxyphosphazenes), liquid crystalline polysiloxanes and poly(dichloro-silane) have also been studied by X-ray diffraction methods, enabling the conformations in the crystallites in the solid state to be established. 

Figure 3.2 Cross section of an expanded foam rubber heat- and sound-insulation tube of a poly(aryloxyphosphazene). Reproduced by permission of Ethyl Corporation.

Three examples of polyphosphazenes that function as proton conductors are shown in 3.80-3.82.181 185 All three are aryloxyphosphazenes with acidic functional groups on the aryl rings. Their performance in operating fuel cells is comparable to that of Nation, but they are much more resistant to methanol crossover. The sulfonimide derivative (3.82) functions as a proton conductor at higher temperatures than Nation, and this is an advantage for future developments. 

Two commercial phosphazene elastomers were developed and marketed in the mid-1980s, namely, poly(fluoroalkoxyphosphazene) elastomer (ASTM International designation FZ) and poly(aryloxyphosphazene) elastomer (ASTM International designation PZ) [109]. The structure of the fluorinated product is as follows [110] ... 

Patents describing specific applications or formulations are available. Specific items which appeared include aryloxyphosphazenes for flame-retardant panels and fibers, MEEP-LiCFjSOj based thermally actuated secondary hydrogen... 

Sicka, R.W., Thompson, J.E., Reynard, K.A. and Rose, S.H., "Poly(aryloxyphosphazene) Foam Insulation Materials," pp. 244-249 in Proceedings, 6th National SAMPE Technical Conference, Vol. 6 Materials on the Move, held at Dayton, OH, Oct. 8-10, (1974). (Work supported by the Naval Ship Systems Command (NAVSHIPS 03421) and The Firestone Tire and Rubber Co.). 

The formation and properties - of aryloxyphosphazene polymers have received less attention than the analogous fluoroalkoxy-polymers. Polymers have... 

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