Chain polyphosphates

Condensed phosphates are derived by dehydration of acid orthophosphates. The resulting polymeric stmctures are based on a backbone of P—O—P linkages where PO tetrahedra are joined by shared oxygen atoms. The range of materials within this classification is extremely broad, extending from the simple diphosphate, also known as pyrophosphate, to indefinitely long-chain polyphosphates and ultraphosphates (see Table 1). Both weU-defined crystalline and amorphous materials occur among the condensed phosphates. 

Sodium tripolyphosphate is produced by calcination of an intimate mixture of orthophosphate salts containing the correct overall Na/P mole ratio of 1.67. The proportions of the two anhydrous STP phases are controlled by the calcination conditions. Commercial STP typically contain a few percent of tetrasodium pyrophosphate and some trimetaphosphate. A small amount of unconverted orthophosphates and long-chain polyphosphates also may be present. 

Phosphates, which react with calcium to reduce the calcium ion activity, assist in stabilizing calcium-sensitive proteins, eg caseinate and soy proteinate, during processing. Phosphates also react with milk proteins. The extent of the reaction depends upon chain length. Casein precipitates upon addition of pyrophosphates, whereas whey proteins do not. Longer-chain polyphosphates cause the precipitation of both casein and whey proteins. These reactions are complex and not fully understood. Functions of phosphates in different types of dairy substitutes are summarized in Table 9 (see also Food additives). 

A rather different structure-motif is observed in the chain polyphosphates these feature comer-shared PO4 tetrahedra as in the polyphosphoric acids (p. 522). The general formula for such anions is [Pn03 4.i] + , of which the diphosphates, P2O7 ", and tripolyphosphates, PsOjo , constitute the first two members. Chain polyphosphates have been isolated with n up to 10 and with n infinite , but those of intermediate chain length (10 < n < 50) can only be obtained as glassy or amorphous mixtures. As the chain length increases, the ratio (3n + l)/n approaches 3.00 and the formula approaches that of the polymetaphosphates [P03 ]oo-... 

The general formula of these new oxynitrides M2M1(PX3)3 suggests as for the previous series a cyclophosphate-type structure or a long-chain polyphosphate-type structure, where nitrogen would be structurally equivalent to oxygen. 

See also van der Waals forces Long-chain aliphatic acids, 20 97 Long chain amphiphiles, 24 123 Long-chain branching, 19 840 extent of, 19 839 in HDPE, 20 160-162 in LDPE, 20 220, 232-234 in LDPE resins, 20 215 quantifying, 20 228-229 Long-chain polyphosphates,... 

ATP -I- (phosphate)n = ADP -h (phosphate)rn-i (<12> mechanism [10] <12> short chain polyphosphates are incorporated at the ends of the long chain product [9] <12> both polyphosphate synthesis and polyphosphate utilization follow a processive mechanism [10])... 

Fig. 16.29 Separation of polyphosphate anions by paper chromatography. The ions are first allowed lo migrate ki a bask solvent and subsequently in an acidic solvent. The straight-chain polyphosphates lie on the ascending branch of the Y." the meuiphosphates on the lower branch. (From Van Wazer. i. R. Phosphorus and Its Comp,ntnds. Wiley New York. 1958 Vol. (. p 702. Reproduced with per mission.J...

A Gel Chromatographic Study on the Interactions of Long-Chain Polyphosphate Anions with Magnesium Ions... 

In spite of much information available for the interactions of various metal ions with small oxoanions of phosphorus, relatively little information has been obtained for the complex formation of long-chain polyphosphate ion. This may be due to the fact that the conventional methods useful for the study of the complex formation of a relatively small ligand are not always applicable to the polyanion complex formation system. Since a gel chromatographic method based on the same principle as the equilibrium dialysis method has been proved to be applicable in the field of inorganic complex chemistry (1), this method has been applied to the study of the binding of long-chain polyphosphate ions to magnesium ion. 

This work was undertaken in order to evaluate the binding of middle units of long-chain polyphosphate to magnesium ion from a view point of the mass action law. 

As a result of tribochemical reactions and the presence of oxygen or hydroperoxide in oil, adsorbed ZDDP and LI-ZDDP on the surface are thermo-oxidatively decomposed to give long-chain polyphosphates Zn(P03)2. 

As the rubbing continues, the polyphosphate layer comes into closer contact with water in oil and is hydrolyzed to give a short-chain polyphosphate, e.g., Zn2P207 (Fuller et al., 1998). During the mechanically activated processes (friction coefficient, p > 0.4), a nascent surface is generated, and in the presence of oxygen, an iron oxide is formed. The acid - base reaction between polyphosphate glasses (hard Lewis bases) and the oxides (hard Lewis acids) is... 

The XANES spectra of the tribofilms were recorded in the bulk FY mode, and in the surface TEY mode from the ZDDP and calcium phenate. The (S) L-edge and (P) L-edge XANES spectra indicate that sulfur in sulfide form was only present on the topmost part of the film the phosphorus signaled that the topmost surface contained relatively long polyphosphates, and the bulk chemistry of the film contained mostly shorter-chain polyphosphates. Using a range of concentrations of two detergents, it was concluded that calcium phenate influences the film formation much more than calcium sulfonate, and thus calcium phenate solubilize excess ZDDP from film surfaces more effectively (Yin et al., 1997). 

PIBS-PAM surfactant RMs (c 1%) + ZDDP -> short chain polyphosphate tribofilm only. 

ZDDP tribofilms are composed of inorganic polymer material on the top surface the long chain polyphosphate is a zinc phosphate and in the bulk the short chain polyphosphate is a mixed Fe/Zn phosphate with a gradient concentration. 

The current understanding of the structure of ZDDP-based tribofilms derives mainly from XANES spectroscopy (Armstrong et al., 1997 Bancroft et al., 1997 Ferrari et al., 1999a Fuller et al., 1995, 1998 and 2002 Martin et al., 2001 Yin et al., 1993 and 1997a), infrared spectroscopy (Harrison and Brown, 1991 Lindsay et al., 1993 Willermet et al., 1992 and 1995b), and a comprehensive multi-technique (AES/XPS/XANES) approached on the basis of the hard and soft acids and bases (HSAB) principle (Martin, 1999, Martin et al., 2001 ). Most prominent models involve a two-layer structure. The layer in contact with the metal surface is thought to be composed of short-chain polyphosphates, and a top layer, consists of long-chain zinc polyphosphate. 

EXAFS Tribofilms were amorphous with long-chain polyphosphates with Fe as the cation (Belin et al., 1989 and 1995 Martin et al., 1986a). 

A recent XANES experiment showed that the ZDDP tribofilm generally has a two-layer structure a short-chain phosphate layer covered by a thin, long-chain polyphosphate layer. XANES spectra analysis of tribofilms did not show a substantial difference between neutral and basic ZDDPs (Fuller et al., 1997 Martin, 1999 Martin at al., 2001 Varlot et al., 2000 Willermet et al., 1991 and 1992 Yamaguchi et al., 1993 and 1996). 

At lower temperature, thermally generated film has more similarity to tribofilm. The thermal films, as in the case of the tribofilms, contain mostly a mixture of short-and long-chain polyphosphates. The chemical states of phosphorus and sulfur in each neutral and basic pair were very comparable. The aryl phosphate films contain long-chain polyphosphate throughout the film, whereas the alkyl phosphate films are composed of long-chain polyphosphates in the bulk. Also, the aryl polyphosphate films contain more unchanged ZDDP. 

Thermal film in oil solution Mixture of short and long chain polyphosphates. Sulfur is absent at 200°C present as sulfate at low temp. Mixture of polyphosphates. Above 200°C, sulfur is absent in the film present as sulfate at low temp. Mixture of polyphosphates. Above 200°C, sulfur is absent in the film present as sulfate at low temp. 

Tribochemical film in oil solution Long chain polyphosphate on the topmost surface and short chain polyphosphates in the bulk. S is present as sulfide. Long chain polyphosphate on the topmost surface and short chain poly-phosphates in the bulk. S is present as sulfide. Long chain polyphosphate throughout the tribofilm. Contain more unchanged ZDDP. 

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