Flame melamines

Different behavior was found for SBS-MEL microcomposite, which had a TTI similar to that of pure SBS (85 s), but after 100-110 s a decrease in the HRR was observed, resulting in a delay in the PHRR (TTP = 239 than 204 s). Moreover, SBSMEL shows a PHRR similar to that for pure SBS. The mechanism of the fire retardant action of melamine derivatives is under investigation by many academic and industrial research groups however, it is well known that when exposed to heat and flames, melamine and derivatives decompose, absorbing heat and causing a cooling effect [46,47]. 

Melamine is most commonly used in flexible polyurethane foams in combination with chloroalkyl phosphates and in intumescent coatings in combination with ammonium polyphosphate and pentaerythritol. Nevertheless, there is extensive patent literature on the use of melamine in thermoplastics and elastomers, which was reviewed by Weil and Choudhary. The review gives good insight into the mechanism of flame retardant action of melamine. It is known that melamine does not melt, but sublimes at about 350°C (actual volatilization starts at a lower temperature). Upon sublimation, significant energy is absorbed, which decreases the surface temperature of the polymer. This is especially important for polyurethane foams having very low thermal inertia. In a hot flame, melamine may decompose further, with creation of cyanamid, which is also a very endothermic process. 

C2HgNg H4O2P2 (60). The pyrophosphate is reported to be only soluble to the extent of 0.09 g/100 mL water, whereas melamine orthophosphate is soluble to 0.35 g/mL. The pyrophosphate is the most thermally stable. Melamine orthophosphate is converted to the pyrophosphate with loss of water on heating. AH three are available as finely divided soflds. AH are used commercially in flame-retardant coatings (qv) and from patents also appear to have utihty in a wide variety of thermoplastics and thermosets. A detaHed study of the thermal decomposition of the these compounds has been pubHshed (61). 

THPC—Amide Process. The THPC—amide process is the first practical process based on THPC. It consists of a combination of THPC, TMM, and urea. In this process, there is the potential of polymer formation by THPC, melamine, and urea. There may also be some limited cross-linking between cellulose and the TMM system. The formulation also includes triethanolamine [102-71-6J, an acid scavenger, which slows polymerization at room temperature. Urea and triethanolamine react with the hydrochloric acid produced in the polymerization reaction, thus preventing acid damage to the fabric. This finish with suitable add-on passes the standard vertical flame test after repeated laundering (80). 

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. 

Melamine—Formaldehyde Resins. The most versatile textile-finishing resins are the melamine—formaldehyde resins. They provide wash-and-wear properties to ceUulosic fabrics, and enhance the wash durabiHty of flame-retardant finishes. Butylated melamine —formaldehyde resins of the type used in surface coatings may be used in textile printing-ink formulations. A typical textile melamine resin is the dimethyl ether of trimethylolmelamine [1852-22-8] which can be prepared as follows ... 

Flame retardants (qv) are incorporated into the formulations in amounts necessary to satisfy existing requirements. Reactive-type diols, such as A/ A/-bis(2-hydroxyethyl)aminomethylphosphonate (Fyrol 6), are preferred, but nonreactive phosphates (Fyrol CEF, Fyrol PCF) are also used. Often, the necessary results are achieved using mineral fillers, such as alumina trihydrate or melamine. Melamine melts away from the flame and forms both a nonflammable gaseous environment and a molten barrier that helps to isolate the combustible polyurethane foam from the flame. Alumina trihydrate releases water of hydration to cool the flame, forming a noncombustible inorganic protective char at the flame front. Flame-resistant upholstery fabric or liners are also used (27). 

Melamine cyanurate is useful in preparation of flame retardant polyamide resins and compositions (133). It also is useful as a soHd lubricant (134). 

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. 

There is also growing interest in multi-phase systems in which hard phase materials are dispersed in softer polyether diols. Such hard phase materials include polyureas, rigid polyurethanes and urea melamine formaldehyde condensates. Some of these materials yield high-resilience foams with load deflection characteristics claimed to be more satisfactory for cushioning as well as in some cases improving heat resistance and flame retardancy. 

The tetrakis(hydroxymethyl)phosphonium chloride so formed is the major ingredient with urea-formaldehyde or melamine-formaldehyde resins for the permanent flame-proofing of cotton cloth. 

The need to paint the blends has also resulted in new painting systems. Recently, a nonpolar color coat based on a hydrogenated polybutadiene diol and melamine resin for TPO bumper fascia was invented. The breakthrough technology allows the elimination of the TPO pretreatment step such as adhesion promoter, flame, or plasma during manufacturing. The paintability of two different types of E-plastomers was evaluated. The olefinic white paint was found to provide excellent paint adhesion for both types of metallocene plastomers. Paint peeling was not observed in any of the test... 

Melamine fiber is mainly used in heat- and flame-resistant applications, especially in the manufacture of protective clothing for the iron, steel, and automobile industries, in aircraft and... 

Hydrolysis of polyamide-based formulations with 6 N HC1 followed by TLC allows differentiation between a-aminocaproic acid (ACA) and hexamethylenedi-amine (HMD) (hydrolysis products of PA6 and PA6.6, respectively), even at low levels. The monomer composition (PA6/PA6.6 ratio) can be derived after chromatographic determination of the adipic acid (AA) content. Extraction of the hydrolysate with ether and derivatisa-tion allow the quantitative determination of fatty acids (from lubricants) by means of GC (Figure 3.27). Further HC1/HF treatment of the hydrolysis residue, which is composed of mineral fillers, CB and nonhydrolysable polymers (e.g. impact modifiers) permits determination of total IM and CB contents CB is measured quantitatively by means of TGA [157]. Acid hydrolysis of flame retarded polyamides allows to determine the adipic acid content (indicative of PA6.6) by means of HPLC, HCN content (indicative of melamine cyanurate) and fatty acid (indicative of a stearate) by means of GC [640]. Determination of ethylene oxide-based antistatic agents... 

These criteria were developed by the UK PU foam industry and were intended to differentiate the melamine or exfoliated graphite containing combustion modified PU foams from the standard, high resilience and flame retarded (chloro and bromo phosphate) containing PU foams (Table IV). This distinction was required because large scale burning tests of real arm chairs and furnished rooms had demonstrated the superiority of the combustion modified polyurethane foams. 

Generally, flame retardants for engineering PET compositions are based on bromine-containing compounds (such as brominated polycarbonate, decabro-modiphenyl oxide, brominated acrylic, brominated polystyrene, etc.). Such compounds are available commercially (such as from the Ethyl Chemical Corporation, Great Lakes Chemical Corporation, Dead Sea Bromine Company, etc.) In addition, the flame-retardant package generally contains a synergist, typically sodium antimonate. PET may also be flame-retarded with diarylphosphonate, melamine cyanurate or red phosphorus. 

FLAME RETARD ANTS - PHOSPHORUS FLAME RETARDANTS] (Vol 10) Melamine pyrophosphate [15541-60-3]... 

D. Price, Y. Liu, G.J. Milnes, T.R. Hull, B.K. Kandola, and A.R. Horrocks, An investigation into the mechanism of flame retardancy and smoke suppression by melamine in flexible polyurethane foam. Fire Mater., 26, 201-206 (2002). 

Ammonium polyphosphates, on the other hand, are relatively water insoluble, nonmelting solids with very high phosphorus contents (up to about 30%). There are several crystalline forms and the commercial products differ in molecular weights, particle sizes, solubilities, and so on. They are also widely used as components of intumescent paints and mastics where they function as the acid catalyst (i.e., by producing phosphoric acid upon decomposition). They are used in paints with pentaerythritol (or with a derivative of pentaerythritol) as the carbonific component and melamine as the spumific compound.22 In addition, the intumescent formulations typically contain resinous binders, pigments, and other fillers. These systems are highly efficient in flame-retarding hydroxy-lated polymers. 

There are several classes of amine phosphates commercially available to flame retard a wide variety of polymeric substrates, both natural and synthetic.24 A classic example is the three variations of melamine phosphate melamine orthophosphate, dimelamine orthophosphate, and melamine pyrophosphate. Of these, the pyrophosphate is the least soluble and the most thermally stable. Melamine orthophosphate is converted to the pyrophosphate upon heating, with the loss of water. All the aforementioned variations are available as finally divided solids, are used commercially in coatings, and have utility in a wide variety of thermoplastics and thermosets (mostly presented in the patent literature). 

Pentaerythritol phosphate has an excellent char-forming ability owing to the presence of the pentaerythritol structure. The bis-melamine salt of the bis acid phosphate of pentaerythritol is also available commercially. This is a high melting solid that acts as an intumescent flame-retardant additive for polyolefins. Synergistic combinations with ammonium polyphosphates have also been developed primarily for urethane elastomers. Self-condensation of tris(2-chloroethyl) phosphate produces oligomeric 2-chloroethylphosphate. It has a low volatility, and is useful in resin-impregnated air filters, in flexible urethane foams and in other structural foams.11... 

Cyclic oligomeric phosphonates with the varying degrees of structural complexity (Structure 5.4) are also available in the market.25 They are widely used as flame-retardant finishes for polyester fabrics. After the phosphonate is applied from an aqueous solution, the fabric is heated to swell and soften the fibers, thus allowing the phosphonate to be absorbed and strongly held. It is also a useful retardant in polyester resins, polyurethanes, polycarbonates, polyamide-6, and in textile back coatings. A bicyclic pentaerythritol phosphate has been more recently introduced into the market for use in thermosets as well as for polyolefins (preferably, in combination with melamine or ammonium polyphosphate)... 

Melamine polyphosphate Melapur 200 Ciba (Switzerland) PA66/glass fibers, epoxies, synergistic blends with other flame retardants... 

Liu, Y. and Wang, Q. 2006. Catalytic action of phospho-tungstic acid in the synthesis of melamine salts of pentaerythritol phosphate and their synergistic effects in flame retarded polypropylene. Polym. Deg. Stab. 91 2513-2519. 

Chen, Y.H. and Wang, Q. 2007. Reaction of melamine phosphate with pentaerythritol and its products for flame retardation of polypropylene. Polym. Adv. Technol. 18 587-600. 

Wang, Z. Y., Feng, Z.Q., Liu, Y., and Wang, Q. 2007. Flame retarding glass fibers reinforced polyamide 6 by melamine polyphosphate/polyurethane-encapsulated solid acid. J. Appl. Polym. Sci. 105 3317-3322. 

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