Fibers flame retardation

Flame emissivity Flame ionization Flameproofing cotton Flame resistance Flame-resistant fibers Flame retardancy Flame retardant... 

Incorporation of Flame Retardants in Fiber. Flame retardants suitable for cotton are also suitable for rayon. A much better product is obtained by incorporating flame retardants in the viscose dope before fiber formation. The principal classes of flame retardants used in viscose dope are tabulated aimuaHy (111). 

The most common route for making cellulosic fibers flame retardant is the use of catalysts such as antimony trichloride and phosphoric acid that enhance the formation of char. Because of the major role of cellulosic fibers in the textile market, flame retardation of cellulose has been the subject of several reviews (10, 11, L5). 

According to new research, made protective clothing fabrics and flame retardant fiber, flame retardant and antistatic properties are very good, has the broad prospects for development, the study on people s life and property security, promote the sustained and steady development of the coal industry in China, speed up the process of our socialist modernization construction has the very vital significance. Hope this paper the uniform national standards and industry stand-... 

Wood flour Nylon fibers Flame retardants... 

Acryhc and modacryhc fibers are sold mainly as staple and tow products with small amounts of continuous filament fiber sold in Europe and Japan. Staple lengths may vary from 25 to 150 mm, depending on the end use. Eiber deniers may vary from 1.3 to 17 dtex (1.2 to 15 den) 3.2 dtex (3.0 den) is the standard form. The appearance of acryhcs under microscopical examination may differ from that of modacryhcs in two respects. Eirst, the cross sections (Eig. 1) of acryhcs are generally round, bean-shaped, or dogbone-shaped. The modacryhcs, on the other hand, vary from irregularly round to ribbon-like. The modacryhcs may also contain pigment-like particles of antimony oxide to enhance their flame-retardant properties. 

An example of a commercial semibatch polymerization process is the early Union Carbide process for Dynel, one of the first flame-retardant modacryhc fibers (23,24). Dynel, a staple fiber that was wet spun from acetone, was introduced in 1951. The polymer is made up of 40% acrylonitrile and 60% vinyl chloride. The reactivity ratios for this monomer pair are 3.7 and 0.074 for acrylonitrile and vinyl chloride in solution at 60°C. Thus acrylonitrile is much more reactive than vinyl chloride in this copolymerization. In addition, vinyl chloride is a strong chain-transfer agent. To make the Dynel composition of 60% vinyl chloride, the monomer composition must be maintained at 82% vinyl chloride. Since acrylonitrile is consumed much more rapidly than vinyl chloride, if no control is exercised over the monomer composition, the acrylonitrile content of the monomer decreases to approximately 1% after only 25% conversion. The low acrylonitrile content of the monomer required for this process introduces yet another problem. That is, with an acrylonitrile weight fraction of only 0.18 in the unreacted monomer mixture, the low concentration of acrylonitrile becomes a rate-limiting reaction step. Therefore, the overall rate of chain growth is low and under normal conditions, with chain transfer and radical recombination, the molecular weight of the polymer is very low. 

In addition to dyeabiHty, polyesters with a high percentage of comonomer to reduce the melting poiat have found use as fusible biader fibers ia nonwoven fabrics (32,34,35). Specially designed copolymers have also been evaluated for flame-retardant PET fibers (36,37). 

Alloy Rayons. It is possible to produce a wide variety of different effects by adding materials to the viscose dope. The resulting fibers become mixtures or aUoys of ceUulose and the other material. The two most important types of aUoy arise when superabsorbent or flame retardant fibers are made. 

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). 

Physical Dilution. The flame retardant can also act as a thermal sink, increasing the heat capacity of the polymer or reducing the fuel content to a level below the lower limit of flammabiHty. Inert fillers such as glass fibers and microspheres and minerals such as talc act by this mechanism. 

Several commercial polyester fabrics are flame retarded using low levels of phosphoms additives that cause them to melt and drip more readily than fabrics without the flame retardant. This mechanism can be completely defeated by the presence of nonthermoplastic component such as infusible fibers, pigments, or by siUcone oils which can form pyrolysis products capable of impeding melt flow (27,28). 

Polyester Fibers Containing Phosphorus. Numerous patents describe poly(ethylene terephthalate) (PET) flame-retarded with phosphoms-containing diftmctional reactants. At least two of these appear to be commercial. 

This phosphinic anhydride [15171 -48-9] C H O P, is then reacted with glycol and other precursors of poly(ethylene terephthalate), to produce a flame-retardant polyester [82690-14-0] having phosphinate units of the stmcture —0P(0)(CH2)CH2CH2C00—. Trevira 271 is useflil for children s sleepwear, work clothing, and home flirnishings. A phosphoms content as low as 0.6% is reported to be sufficient for draperies and upholstery tests if melt-drip is not retarded by print pigments or the presence of nonthermoplastic fibers (28). 

Work began in the 1930s on the development of flame-retardant cottons based on chemical systems that either reacted directly with the ceUulosic substrate, or polymerized on or in the cotton fiber. A serious effort in this direction, mounted from the 1950s through the 1970s, resulted in most of the state-of-the-art flame-retardant finishes for cotton available. 

Thermal Theory. The thermal approach to flame retardancy can function in two ways. Eirst, the heat input from a source may be dissipated by an endothermic change in the retardant such as by fusion or sublimation. Alternatively, the heat suppUed from the source maybe conducted away from the fibers so rapidly that the fabric never reaches combustion temperature. 

Ra.dia.tlon. Use of radiation to affect fixation of some flame retardants is being investigated (110). Electron-beam fixation requires the selection of compounds that can be insolubilized inside or outside of the fiber with high yield in a short time. Polyunsaturated compounds, eg, Fyrol 76, have shown promise (see Radiation curing). 

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... 

Antlblaze 19. Antiblaze 19 (Mobil), a flame retardant for polyester fibers (134), is a nontoxic mixture of cycHc phosphonate esters. Antiblaze 19 is 100% active, whereas Antiblaze 19T is a 93% active, low viscosity formulation for textile use. Both are miscible with water and are compatible with wetting agents, thickeners, buffers, and most disperse dye formulations. Antiblaze 19 or 19T can be diffused into 100% polyester fabrics by the Thermosol process for disperse dyeing and printing. This requires heating at 170—220°C for 30—60 s. 

Considerable effort is being made (ca 1993) to develop satisfactory flame retardants for blended fabrics. It has been feasible for a number of years to produce flame-resistant blended fabrics provided that they contain about 65% or more ceUulosic fibers. It appears probable that blends of even greater synthetic fiber content can be effectively made flame resistant. An alternative approach may be to first produce flame-resistant thermoplastic fibers by altering the chemical stmcture of the polymers. These flame-resistant fibers could then be blended with cotton or rayon and the blend treated with an appropriate flame retardant for the ceUulose, thereby producing a flame-resistant fabric. Several noteworthy finishes have been reported since the early 1970s. 

Phosphonium Salt—Urea Precondensate. A combination approach for producing flame-retardant cotton-synthetic blends has been developed based on the use of a phosphonium salt—urea precondensate (145). The precondensate is appUed to the blend fabric from aqueous solution. The fabric is dried, cured with ammonia gas, and then oxidized. This forms a flame-resistant polymer on and in the cotton fibers of the component. The synthetic component is then treated with either a cycUc phosphonate ester such as Antiblaze 19/ 19T, or hexabromocyclododecane. The result is a blended textile with good flame resistance. Another patent has appeared in which various modifications of the original process have been claimed (146). Although a few finishers have begun to use this process on blended textiles, it is too early to judge its impact on the industry. 

Flame retardants designated for nylon include halogenated organic compounds, phosphorous derivatives, and melamine cyanurate (160—163). Generally, flame retardants are difficult to spin in nylon because of the high loading required for effectiveness and their adverse effects on melt viscosity and fiber physical properties. 

Both fiber producers and fabric mills have realized that many of the performance variants that are difficult to iacorporate iato fiber melt spinning can be accompHshed by post-treating yams or fabrics. Mills ia the 1990s can apply flame retardants, softeners, dye-fade inhibitors, and stain- and soil-resisting agents as part of the finishing of a fabric. 

---