Flame retardants molybdenum

Flame letaidancy can be impaited to plastics by incorporating elements such as bromine, chlorine, antimony, tin, molybdenum, phosphoms, aluminum, and magnesium, either duriag the manufacture or when the plastics are compounded iato some useful product. Phosphoms, bromine, and chlorine are usually iacorporated as some organic compound. The other inorganic flame retardants are discussed hereia. 

Molybdenum Oxides. Molybdenum was one of the first elements used to retard the flames of ceUulosics (2). Mote recently it has been used to impart flame resistance and smoke suppression to plastics (26). Molybdic oxide, ammonium octamolybdate, and zinc molybdate ate the most widely used molybdenum flame retardants. Properties ate given in Table 5. These materials ate recommended almost exclusively for poly(vinyl chloride), its alloys, and unsaturated polyesters (qv). 

Molybdenum trioxide is a condensed-phase flame retardant (26). Its decomposition products ate nonvolatile and tend to increase chat yields. Two parts of molybdic oxide added to flexible poly(vinyl chloride) that contains 30 parts of plasticizer have been shown to increase the chat yield from 9.9 to 23.5%. Ninety percent of the molybdenum was recovered from the chat after the sample was burned. A reaction between the flame retardant and the chlorine to form M0O2 012 H20, a nonvolatile compound, was assumed. This compound was assumed to promote chat formation (26,27). 

Molybdenum Oxide. Molybdenum compounds incorporated into flexible PVC not only increase flame resistance, but also decrease smoke evolution. In Table 10 the effect of molybdenum oxide on the oxygen index of a flexible PVC containing 50 parts of a plasticizer is compared with antimony oxide. Antimony oxide is the superior synergist for flame retardancy but has Httle or no effect on smoke evolution. However, combinations of molybdenum oxide and antimony oxide may be used to reduce the total inorganic flame-retardant additive package, and obtain improved flame resistance and reduced smoke. 

Table 10. Effect of Flame Retardancy of Molybdenum Oxide and Antimony Oxide ...

Flame and Smoke Retardants. Molybdenum compounds are used extensively as flame retardants (qv) (93,94) in the formulation of halogenated polymers such as PVC, polyolefins, and other plastics elastomers and fabrics. An incentive for the use of molybdenum oxide and other molybdenum smoke and flame retardants is the elimination of the use of arsenic trioxide. Although hydrated inorganics are often used as flame retardants, and thought to work by releasing water of crystallization, anhydrous molybdenum oxides are effective. Presumably the molybdenum oxides rapidly form... 

In 1826 J. J. Berzelius found that acidification of solutions containing both molybdate and phosphate produced a yellow crystalline precipitate. This was the first example of a heteropolyanion and it actually contains the phos-phomolybdate ion, [PMoi204o] , which can be used in the quantitative estimation of phosphate. Since its discovery a host of other heteropolyanions have been prepared, mostly with molybdenum and tungsten but with more than 50 different heteroatoms, which include many non-metals and most transition metals — often in more than one oxidation state. Unless the heteroatom contributes to the colour, the heteropoly-molybdates and -tungstates are generally of varying shades of yellow. The free acids and the salts of small cations are extremely soluble in water but the salts of large cations such as Cs, Ba" and Pb" are usually insoluble. The solid salts are noticeably more stable thermally than are the salts of isopolyanions. Heteropoly compounds have been applied extensively as catalysts in the petrochemicals industry, as precipitants for numerous dyes with which they form lakes and, in the case of the Mo compounds, as flame retardants. 

The antimony oxide/organohalogen synergism in flame retardant additives has been the subject of considerable research and discussion over the past twenty-five years (1-17). In addition to antimony oxide, a variety of bismuth compounds and molybdenum oxide have been the subject of similar studies (18-20). Despite this intensive investigation, relatively little has been conclusively established about the solid state chemical mechanisms of the metal component volatilization, except in those cases where the organohalogen component is capable of undergoing extensive intramolecular dehydrohalogenation. 

Addition of fillers such as alumina trihydrate, antimony trioxide, molybdenum oxide [315], zinc borate and zinc borate complex [316] leads to increase in TS but decrease in elongation and NG migration/absorption. Addition of inorganic fillers also leads to increase in flame retardance. 

Molybdenum compounds can act as flame retardants and smoke suppressants in textiles and in plastics233,275. Heteropoly compounds have been found to act as... 

Other fire retardants used include aluminum hydrate, antimony oxide, and molybdenum compound. Halogenated phosphate esters used in polyurethane foams and bromine compounds used in polyolefin foams are not used in phenolic foams. Flame retardants are used mostly in powder form, and accordingly, their distribution conditions are dependent on their particle size and shape. 

The worldwide annual production of molybdenum amounts to 100000 tons, most of which is used for the production of alloys. The addition of molybdenum to steel alloys increases their strength and thermal resistance, and also reduces their corrosion potential (gas and steam turbines in power generation, missiles, aircraft). Metallic molybdenum enhances the adherence of siliceous material to metals therefore, molybdenum is useful in metal-ceramic composites. Molybdenum compounds are also used in some chemical products (which may lead to wastes) such as catalysts, flame retardants, smoke repressants, lubricants, and molybdenum pigments. 

Types ammonium octamolybdate, molybdenum trioxide, vanadium oxide, zirconium oxychloride, and inorganic compounds listed as flame retardants... 

Properties Sol. 4 ml in water dens. 3.18 dec. pt. 250 C Uses Flame retardant, smoke suppressant in polymers, esp. PVC and unsat. polyesters, thermoplastic elastomers, wire and cable applies., wall coverings, upholstery ManufJDistrib. Climax Molybdenum Pacific West Trade Names Charmax AOM... 

Perchloropentacyclodecane Tetrabromobisphenol A di-2-hydroxyethyl ether Tetradecabromodiphenoxybenzene Tribromophenyl allyl ether flame retardant, adhesives cables Molybdenum trioxide flame retardant, adhesives construction Molybdenum trioxide... 

Hexabromobiphenyl flame retardant, inks Paraffin, chlorinated flame retardant, insulation Molybdenum trioxide flame retardant, insulation felts Melamine borate... 

Melamine phosphate Molybdenum trioxide Paraffin, chlorinated Pentabromodiphenyl oxide Pentaerythritol Perchloropentacyclodecane Tetrabromobisphenol A bis (allyl ether) Tributoxyethyl phosphate Tributyl phosphate Trichloroethylene Tris (chloropropyl) phosphate Tris (2,3-dibromopropyl) phosphate Zinc borate Zinc molybdate Zinc phosphate flame retardant, plastics, flame retardant, elastomers Zinc sulfide... 

Molybdenum trioxide flame retardant, wall upholstery high risk buildings... 

Molybdenum compounds are effective in PVC, especially when coupled with zinc compounds. In addition, these compositions are flame-retardant. For example, 1.5 phr. of Sb20s and 1.5 phr. of Kemgard 911 in plasticized PVC raised the oxygen index from 28 to 33.5 % while the mass of solid particles filtered from the combustion products in an Arapahoe smoke chamber (cf. Fig. 4.1 in Section 4.1.1.1) lessened by 32.6 per cent. 4 phr. of the same additives in rigid PVC enhanced the oxygen index from 41 to 58 % and reduced smoke production by 48 per cent. ... 

Skinner, G. A., Parker, L. E. and Marshall, P. J. Flame retardant synergism between molybdenum and halogen containing compounds in unsaturated polyesters. Fire and Materials, 1, No. 4, 154 (1976)... 

Molybdenum SmokejFlame Suppressants. Product sheets of Climax Molybdenum Co., 1985 Siegel, D. Flame-retardant PP for engineering applications. Plast. Eng. 40, No. 8, 25 0984) Montaudo, G., Scamporrino, E. and Vitalini, D. Intumescent flame retardants for polymers. II. The polypropylene — ammonium phosphate — polyurea system. J. Polym. Sci. Polym. Chem. Ed 21, 3361 (1983)... 

Representatives of various industries [17] have examined some smoke depressants and flame retardant resins introduced by various US Companies in relation to US legislation. These include smoke suppressed polyvinylchloride (PVC) (BE Goodrich) and polyurethane (PU) foams (Mobay Chemical), and smoke suppressant additives from Climax Molybdenum, and Sherwin-Williams (molybdenum compounds), Solem Industries, and Alcoa Chemicals (aluminium trihydrates, for polypropylene (PP) and PVC), Dover Chemical Corp., (aromatic bromine compound for PP), and US Borax (zinc borate). 

Molybdenum and zine eontaining compounds have been used as flame and smoke suppressants for a variety of polymers. These metal containing species normally act to assist the build-up of char on the pol mier surface. This ehar is presumed to be the main method of flame retardancy. Halogenated systems form a large proportion of the market for molybdenum and zinc compounds. 

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