Fibers, flame-retardant treatments

Flame-Retardant Treatments For Wool. Although wool is regarded as a naturally flame-resistant fiber, for certain appHcations, such as use in aircraft, it is necessary to meet more stringent requirements. The Zirpro process, developed for this purpose (122,123), is based on the exhaustion of negatively charged zirconium and titanium complexes on wool fiber under acidic conditions. Specific agents used for this purpose are potassium hexafluoro zirconate [16923-95-8] [16923-95-8] K ZrF, and potassium hexafluoro titanate [16919-27-0], K TiF. Various modifications of this process have been... 

Flame relardanls are used in smolder-resistant upholstery fabric, combination flame retardant-durable press performance, flame-retardant treatments for wool, thermoplastic fibers (Tris. decabromodiphenyl oxide-polyacrylate finishes. Antihlu/e 19. nylon finishes), polyester-cotton fiber blends (THPOH-ummonju-Tris finish, decabromodiphenyl oxide-polyacrylate finish. THPC-amide-polytv illy I bromide) finish, THPOH-NHi and Fyrol 76. LRC-UX) finish, phusphonium salt-urea precondcn-satej. cotton-wool blends, and core-yam fabric,... 

Dermeik E, Braun R, Lemmer KH and Lung M (2006), WO 2006/102962, Process for the flame-retardant treatment of fiber materials. 

Ramie reinforced PLA biocomposite with flame retardancy by using APP on preserving the environmental fiiendly character of biocomposites has been studied. Here, natural fibers can be used as char formers in association with APP to increase the char yield of biocomposites. The flame retardancy of biocomposites is obtained by three means (Fig. 4.36). PLA is blended with APP, then the resulting flame-retarded PLA is combined with ramie fibers (ramie fibers with flame retardant treatment by APP is compoimded with PLA) PLA and ramie both of which have been flame-retarded by APP are blended together. 

A limited number of finishes are used to correct deficiencies in acetate and triacetate. Delusterants, antioxidants, and/or antistat finishes as outlined previously are added to the spinning solution prior to fiber formation. Plasticizers (nonvolatile aromatic esters) can also be added to the spinning solution to improve the flexibility of the fiber. When flame retardant treatment is required, haloalkylphosphonates are added to the spinning solution or padded onto the yarns to effectively lower the flammability of these fibers. 

Flame Retardant Treatments Although the protein fibers are naturally flame retardant, additional flame retardancy is required in some appl ica-tions. Wool can be effectively rendered flame retardant through treatment with halogenated organic acids, organophosphonates, and complex inorganic salts of zirconium, titanium, tungsten, etc. 

Antimony Oxide as a Primary Flame Retardant. Antimony oxide behaves as a condensed-phase flame retardant in cellulosic materials (2). It can be appHed by impregnating a fabric with a soluble antimony salt followed by a second treatment that precipitates antimony oxide in the fibers. When the treated fabric is exposed to a flame, the oxide reacts with the hydroxyl groups of the cellulose (qv) causing them to decompose endothermically. The decomposition products, water and char, cool the flame reactions while slowing the production and volatilization of flammable decomposition products (see Flaa retardants for textiles). 

One concern in conventional processing is the achievement of uniform reagent appUcation and uniform cross-linking (18). An area in which adequate treatment of aU fibers is necessary is in flame-retardant finishing. One means of obtaining thorough treatment has been the use of vacuum impregnation, in which the fabric is first passed over a vacuum slot to remove air from the fabric interstices, foUowed by exposure to the phosphoms flame-retardant solution in the precondensate ammonia system (19). 

Other fibrous and porous materials used for sound-absorbing treatments include wood, cellulose, and metal fibers foamed gypsum or Portland cement combined with other materials and sintered metals. Wood fibers can be combined with binders and flame-retardent chemicals. Metal fibers and sintered metals can be manufactured with finely controlled physical properties. They usually are made for applications involving severe chemical or physical environments, although some sintered metal materials have found their way into architectural applications. Prior to concerns regarding its carcinogenic properties, asbestos fiber had been used extensively in spray-on acoustical treatments. 

Borax pentahydrate is an effective flame retardant for wood/cellulosic materials in terms of surface flammability. However, due to the Na20 moiety, it can promote smoldering combustion in cellulose. Thus, in cellulosic material and wood products, it is commonly used in combination with boric acid, which is an effective smoldering inhibitor. For example, the treatment of wood fibers with a partially dissolved boric acid and borax pentahydrate slurry (-1.75% by wt. of boron) results in Medium Density Fiberboard (MDF) that is claimed to pass the ASTM E-84 Class 1 surface flammability standard.12 The additional examples of using borax pentahydrate and boric acid combination are presented in Section 9.2.2.1. 

Wool Wool, though not as flammable as cotton, still needs flame retardation for specific applications, e.g., carpets, upholstered furniture in transport, etc. Ammonium phosphates and polyphosphate, boric acid-borax, and ammonium bromide can be successfully used in nondurable FR finishes for wool. Various commercial products have been reviewed by Horrocks.3 The most successful durable treatment for wool is Zirpro, developed by Benisek, which involves exhaustion of negatively charged complexes of zirconium or titanium onto positively charged wool fibers under acidic conditions at 60°C. The treatment can be applied to wool at any processing stage from loose fiber to fabric using exhaustion techniques. 

Wool has been regarded as a relatively safe fiber from the flammability point of view. However, it could be flame retarded to a higher degree if required. Hendrix et al. (26) suggested a large improvement in fire resistance of wool by treatment with 15% H PO. Beck et al. (27) showed that weak acidic materials, such as boric acid and dihydrogen phosphate, are effective additives for flame retarding wool by the condensed-phase mechanism (increased char residue). 

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