Flame Retardancy of Phosphorus-Containing Polymers

Ho Tsung-Han, Leu Tsu-Shang, Sun Yih-Min, and Shieh Jeng-Yneh. Thermal degradation kinetics and flame retardancy of phosphorus-containing dicyclopentadiene epoxy resins. Polym. Degrad. Stab. 91 no. 10 (2006) 2347-2356. 

PMMA - Red Phosphorus System. The initial reaction that was investigated was that between PMMA and red phosphorus (4-51. Phosphorus was chosen since this material is known to function as a flame retardant for oxygen-containing polymers (1 2). Two previous investigations of the reaction of PMMA with red phosphorus have been carried out and the results are conflicting. Raley has reported that the addition of organic halides and red phosphorus to PMMA caused moderate to severe deterioration in flammability characteristics. Other authors have reported that the addition of chlorine and phosphorus compounds are effective flame retardant additives (12). 

Isobutyl bis(glycidylpropylether) phosphine oxide has been used as a crosslinking agent for phenolic novolac resin [77] in the production of phosphorus containing novolac-epoxy systems. It was shown that samples containing more than 2% phosphorus content produced a VO material, the industry standard for flame retardancy, bnt phosphorus-free polymers and those containing less than 2% phosphorus were consumed in the first ignition. 

The study of nonvolatile residues after pyrolysis and combustion of phosphorus-containing polymer systems indicates the presence of acids of phosphorus [77, 79]. Additional possible schemes of phosphoric acid formation during the pyrolysis of polymers containing inorganic derivatives of phosphorus flame retardant will be given below ... 

Flame Retardants. Bromine compounds make up an important segment of the market for flame retardants used in polymers. Additive flame retardants are added to polymers during processing reactive flame retardants react chemically to become part of the polymer chain itself In addition to the compounds listed in Table 3, a number of proprietary mixtures and phosphorus—bromine-containing flame retardants are also sold (see Flame retardants, HALOGENATED, FLAME RETARDANTS). 

Like other elements important in inorganic chemistry, phosphorus is used mainly in combination with other elements in a polymeric chain 43,44 Small amounts of phosphorus in a polymer can be greatly advantageous, imparting flame retardancy, improved adhesion to metals, and ion-binding characteristics. Phosphorus-containing polymers are therefore extensively used as flame retardants for fabrics, as adhesives, and as ion-exchange resins. 

In this paper, the surface grafting of rayon fabrics with nitrogen and phosphorus containing polymers in cold plasma is studied. The analytical data (IR spectroscopy, TGA, electron microscopy, elemental analysis, etc.) indicate the formation of grafted copolymers. The grafted rayon fabrics present improved flame-retardant properties, the best behavior was proved by those grafted with polyurea of phosphinic acid. 

K.J. Bullett (formerly Pyrrah), Flame retarding acryhc and styrenic polymers by modihcation with phosphorus-containing compounds, PhD thesis, University of Salford, 2002. 

Price, D., Pyrah, K., Hull, T. R., Milnes, G. J., Ebdon, J. R., Hunt, B. J., and Joseph. P., Flame retardance of poly(methyl methacrylate) modified with phosphorus-containing compounds, Polym. Degrad. Stab., 2002, 77, 227-233. 

Horrocks, A.R., Wang, M.Y., Hall, M.E., Sunmonu, E, and Pearson, J.S. 2000. Flame retardant textile back-coatings. Part 2. Effectiveness of phosphorus-containing flame retardants in textile back-coating formulations. Polym. Int., 49 1079-1091. 

Simionescu, C.I., Denes, F., Macoveanu, M.M., Cazacu, G., Totolin, M., Percec, S., and Balaur, D. 1980. Grafting of rayon fabrics with phosphorus containing polymers in cold plasma in order to obtain flame-retardant materials. Cell. Chem. Technol., 14 869-883. 

Padbury, S.A., Horrocks, A.R., and Kandola, B.K. 2003. The effect of phosphorus-containing flame retardants and nanoclay on the burning behaviour of polyamides 6 and 6.6. Proceedings of the 14th Conference Advances in Flame Retardant Polymers, Stamford, Norwalk, CT Business Communications 2003. 

The effect of volatile phosphorus-containing compounds in polymer flames has not yet been studied. For gas systems it has been found that the flame retarding effect of the additives depends on the concentration (trimethyl phosphate, phosphorus halides and thiohalides). HPO fragments were detected in the radiation spectrum of a H2/O2 flame, upon the introduction of trimethyl phosphate Pj, PO, POj and HPO, P and PH fragments in low concentrations were discovered in a CH /Oj flame inhibited with triphenylphosphine oxide. As regards the flame retardation effect, phosphorus in triphenylphosphine occupies an intermediate position between Sb and As. Triphenyl phosphate is less effective than SbClj. Most effective are POQ3, PCI3 and PBrj. 

Halogen-, phosphorus- and metal-containing substances as flame retardants of polymers may exert their action at the different stages and zones of combustion, by chemical as well as by physical mechanisms. 

Besides the phosphazenes other polymers containing nitrogen and phosphorus are known [9]. Some of such polymers are used as flame retardant additives to other polymers (see Section 5.4). 

Morgan, A.B. Tour, J.M. Synthesis and testing of nonhalogenated alkyne/phosphorus-containing polymer additives potent condensed-phase flame retardants. J. Appl. Polym. Sci. 1999, 73, 707-718. 

When I started working at Victor Chemical Works in 1942, my boss. Dr. Howard Adler, wanted me to look into the possibility of making some phosphorus-containing polymers. It is known that organic phosphorus compounds have flame retarding properties. To put things in the proper historical perspective, at that time vinyl polymers and nylon were relatively new commercial products. (Polymers such as the ethylene terephthalate polyesters and polycarbonate were not introduced to the market place until many years later.)... 

Our original goal of making thermoplastic phosphorus containing polymers was considered a technical success. However, we weren t able to commercialize any of them. So this technical success was a commercial failure for us. About twenty some years later, the Japanese chemists from Toyobo Ltd. (6) prepared a polymer using phenylphosphonic dichloride and sulfonyl bisphenol as the dihydroxy reactant. That polymer called Heim Additive (equation 11) was considered seriously for use as an additive type of flame retardant for polyester fibers. 

Phosphorus-containing reactive flame-retardants are mainly phosphonates or phosphates with hydrogen atoms which can be substituted by hydrocarbon groups, so that they are capable of bonding to molecules of the matrix polymer. A notable example is the series of phosphorus-containing polyols. Their alcoholic hydroxyl groups are involved in a polyaddition reaction of the polyurethane foam production. 

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