Nylons flame retardants

Red Phosphorus. This aHotropic form of phosphoms is relatively nontoxic and, unlike white phosphoms, is not spontaneously flammable. Red phosphoms is, however, easily ignited. It is a polymeric form of phosphoms having thermal stabiUty up to ca 450°C. In finely divided form it has been found to be a powerful flame-retardant additive (26,45—47). In Europe, it has found commercial use ia molded nylon electrical parts ia a coated and stabilized form. Handling hazards and color have deterred broad usage. The development of a series of masterbatches by Albright Wilson should facihtate further use. 

Usage of phosphoms-based flame retardants for 1994 in the United States has been projected to be 150 million (168). The largest volume use maybe in plasticized vinyl. Other use areas for phosphoms flame retardants are flexible urethane foams, polyester resins and other thermoset resins, adhesives, textiles, polycarbonate—ABS blends, and some other thermoplastics. Development efforts are well advanced to find appHcations for phosphoms flame retardants, especially ammonium polyphosphate combinations, in polyolefins, and red phosphoms in nylons. Interest is strong in finding phosphoms-based alternatives to those halogen-containing systems which have encountered environmental opposition, especially in Europe. 

Nylon Finishes. Halogens are less effective flame retardants on nylon than on polyester. Most of the flame retardants effective on ceUulosics... 

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. 

Flame Retardants. Flame retardants are added to nylon to eliminate burning drips and to obtain short self-extinguishing times. Halogenated organics, together with catalysts such as antimony trioxide, are commonly used to give free-radical suppression in the vapor phase, thus inhibiting the combustion process. Some common additives are decabromodiphenyl oxide, brominated polystyrene, and chlorinated... 

Noryl. Noryl engineering thermoplastics are polymer blends formed by melt-blending DMPPO and HIPS or other polymers such as nylon with proprietary stabilizers, flame retardants, impact modifiers, and other additives (69). Because the mbber characteristics that are required for optimum performance in DMPPO—polystyrene blends are not the same as for polystyrene alone, most of the HIPS that is used in DMPPO blends is designed specifically for this use (70). Noryl is produced as sheet and for vacuum forming, but by far the greatest use is in pellets for injection mol ding. 

Nylon. Nylons comprise a large family of polyamides with a variety of chemical compositions (234,286,287). They have excellent mechanical properties, as well as abrasion and chemical resistance. However, because of the need for improved performance, many commercial nylon resins are modified by additives so as to improve toughness, heat fabrication, stabiUty, flame retardancy, and other properties. 

Also of interest are salts of melamine (see Chapter 24). In the nylons these can be used with bright colours (unlike red phosphorus) and do not adversely affect electrical properties. They do, however, decompose at about 320°C. Similar materials are very important in giving flame-retardant properties to polyurethane foams. 

It is possible to determine components in complex EPs where matrix effects can be severe. For example, zinc (as zinc borate), chlorine (as dechlorane flame retardant), antimony (as oxide) and fibre-glass have been determined in nylon using just one standard. Many users have refined the universal precalibrated programmes for standardless XRF and made them more efficient for matrix correction by using variable correction coefficients. OilQuant offers possibilities for analysing polymers [243]. Software packages usually provide ... 

Table 8.45 Surface effects on flame-retardant nylon mouldings...

Substances applied to or incorporated in a combustible material (e.g. organic polymers, nylon, vinyl and rubber, etc.) to reduce flammability. Act by retarding ignition, control/douse burning, reduce smoke evolution. Slow down or interrupt the self-sustained combustion cycle when the heat-flux is limited. Flame retardants (FRs) improve the combustion behaviour and alter the combustion process (cool, shield, dilute, react) so that decomposition products will differ from nonflame retarded articles. FRs are usually divided into three classes ... 

Zinc Borate (2Zn0-3B203-3.5H20) is a unique multifuntional fire retardant. It can function as a flame retardant, smoke suppressant, afterglow suppressant, as well as an anti-tracking agent in polymers. It has been used extnesively as a fire retardant in PVC, polyolefin, nylon, polyester, epoxy, acrylic, urethane, rubbers, etc. 

Cold cure" or high resilience PU foams tended to liquify before igniting were developed and gave good results in standard tests such as BS 4735(25) (similar to the discontinued ASTM D1692) but could still burn when used with flammable fabrics in furniture (Table IV). However they have been used most successfully in the UK in combination with flame retarded cotton interliners and fabrics of low flammability e.g. wool, nylon, FR cotton etc. and formed the basis of public area furniture used in the UK since the early 1970 s (Table V). 

Uses. As a flame retardant on Nylon 6 fibers intermediate in the production of pesticides and herbicides as a stabilizer in oil and plaster an additive to lubricants... 

Lead dichloride occurs in nature as the mineral cotunnite. The compound is used in making many basic chlorides, such as Pattison s lead white. Turner s Patent Yellow, and Verona Yellow, used as pigments. Also, it is used as a flux for galvanizing steel as a flame retardant in nylon wire coatings as a cathode for seawater batteries to remove H2S and ozone from effluent gases as a sterilization indicator as a polymerization catalyst for alpha-olefins and as a co-catalyst in manufacturing acrylonitrile. 

Dimethyl hydrogen phosphite is used as a flame retardant on nylon 6 fibres, as a chemical intermediate in the production of pesticides and in lubricant additives and adhesives. No data on occupational exposure levels were available. A potential source of exposure to this chemical is from its occurrence as a degradation product of the chemical intermediate trimethyl phosphite and of pesticides such as trichlorphon and malathion (lARC, 1990). 

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