Melamine polyphosphate

A small amount of Melapur 200 (melamine polyphosphate) with a metal hydrate leads to a strong reduction in the rate of heat release. The combination allows a lowering of the loading to 50% instead of 65% and still retains the same peak rate of heat release as with 65% magnesium hydroxide in EVA. The effect of Firebrake ZB has been shown to further reduce the overall level of heat release and create a hard, cellular protective structure. In vertical bum tests like UL94, however, this stmcture is not created and leads to a loss of classification. Current work is endeavouring to improve vertical burning behaviour of these formulations. 

Zinc borate (ZB) added to an ATH/nanoclay combination can convert a V-1 classifieation at 1.6 mm in UL94 to a V-0 rating. 5% of ZB replacing some of the 60% ATH present in EVA with 5% nanoclay has been reported. 

It is also a good smoke suppressant. The addition of 9% to polystyrene reduces the maximum smoke density in the NBS Smoke Chamber from 2556 to 375. In a test on an EPDM compound, a mixture of 75% magnesium hydroxide and 25% ATH produced significantly less smoke than ATH alone in Smouldering Mode NIST (ASTM 2843) smoke chamber testing. 

Magnesium hydroxide is low in toxicity and non-corrosive compared with halogen or phosphorus containing compounds. 

The main sectors for magnesium hydroxide use are in elastomers and thermoplastics, since they cause excessive thickening in the main thermoset application of unsaturated polyester systems. It is also much more expensive than ATH with which it shares comparable properties and flame retardancy, and so ATH will be preferred by processors wherever possible. As a result the principle opportunities are in applications where the extra thermal stability is essential, mainly in PP and polyamides. 

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The TG and DTG curves of Figure 12 show that melamine polyphosphate undergoes a complex degradation process between 330-650 C. In step 3 of the DTG curve (max. rate 390 C), water, ammonia and melamine are evolved. In this step the thermal behaviour of polyphosphate is somewhat similar to that of the sulphate in the same range of temperature (300-400 0. Indeed evolution of melamine indicates that thermal dissociation of polyphosphate giving free melamine takes place above 330 C. However, evaporation of melamine competes with its condensation as shown by evolution of ammonia. 

Moreover, simultaneous evolution of water implies that condensation of melamine is combined with that of polyphosphoric structures. Assuming the reaction scheme proposed above, melam polyphosphate and ammonium polyphosphate groups should be formed from melamine polyphosphate ... 

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

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. 

Braun, U., Schartel, B., Fichera, M.A., and Jaeger, C. 2007. Flame retardancy mechanisms of aluminium phosphinate in combination with melamine polyphosphate and zinc borate in glass-fibre reinforced polyamide 6,6. Polym. Deg. Stab. 92 1528-1545. 

In the presence of co-additives, such as polydimethylsiloxane, melamine polyphosphate, the zinc borate is expected to form borosilicate, or zinc borophosphate residue. 

Zinc borate in PC/ABS and polyamide—when zinc borate is used in conjunction with bisphenol-A-bis-diphenyl phosphate in PC/ABS, it was reported that borophosphate and zinc phosphate were generated during polymer combustion.111 The formation of these materials could be beneficial for passing the more stringent Are tests, such as UL-95 5 V. When Firebrake 500 is used in conjunction with aluminum diethylphosphinate and melamine polyphosphate in polyamide, Schartel et al. reported the formation of boron aluminum phosphate in the condensed phase.112... 

The same method is applicable to control critical temperature where the reaction between polyphosphates and polyols takes place. For example, melamine polyphosphate-polyol system, which is stable at the degradation temperature of PP, has been activated for application in polyolefins [47], An activating effect is ascribed also to the char-forming polymers in intumescent nanocomposites, according to the blending approach [48],... 

The main gases evolved from PA6 and PA6 + NC in nitrogen are e-caprolactam, hydrocarbons, carbon dioxide, water, and ammonia. Other composites namely PA6 + FR and PA6 + FR + NC evolve the same volatiles with an additional phosphorous containing species. PA6 + FR yields diethylphosphinic acid (from aluminum diethylphosphinate), and the water and carbon dioxide arise from the decomposition of melamine polyphosphate through condensation and hydrolytic decomposition. 

Melamine and melamine derivatives, such as melamine cyanurate or melamine polyphosphate, are representatives of nitrogen-containing flame retardants (Fig. 11.20). Melamine is an inert diluent and removes heat through decomposition melamine polyphosphate provides an isolating barrier through an intumescent mechanism. 

Mixture of aluminum salts of diethylphosphinate and melamine polyphosphate ... 

Melamine cyanurate in combinatimi with magnesium hydroxide (Mg(OH)2 or MH) or even with talcum (Japanese patents), melamine polyphosphate (DSM, type Melapur 200), also suitable for PA 6.6 GF, are two examples of more recent developments. Zinc sulfide can replace antimony trioxide in some cases. 

The general paucity of FR polyamides reflects their high melt reactivities and hence poor potential flame retardant additive compatibilities. The only additive currently marketed as a potential flame retardant for polyamide fibres is Clarianf s Exolit OP930/935, which is based on a fine particulate (Dj(, 2-3pm), aluminium diethyl phosphinate. This phosphinate may be used alone or combined with melamine polyphosphate, although in bulk polymers total levels of 15wt% or so are required for acceptable levels of flame retardancy. To date it is not known whether commercially successful PA6 and PA6.6 fibres based on this agent are available. 

Short glass fibre reinforced polyamide-6,6 - melamine polyphosphate (30%) 48... 

As a resnlt of this and further studies by thermogravimetric analysis (TGA), solid-state NMR and electron probe microanalysis, Dabrowski and co-workers [27] conclude that melamine polyphosphate is an efficient flame retardant additive in polyamide-6,6 (glass fibre reinforced or not). The glass fibres are shown to strongly inflnence the fire performance of the intumescent FR material. A reactivity between the additive and the glass fibre and the formation of alumino-phosphates was demonstrated. These species might be responsible for the improvement of the FR behaviour particularly in the conditions of the LOI test. 

Tests have been reported for polyamide-6,6 formulations containing melamine polyphosphate as flame retardant [4], ethylene-vinyl acetate copolymer containing ammonium polyphosphate as flame retardant [5], and elastomer materials [6]. 

A more recent member of this family is melamine polyphosphate (MELAPUR 200, originally from DSM, now from Ciba), which has a thermal stability advantage for use in polyamide 6 and 66 (61) and in combination with char-assisting additives, in polyolefins such as those used for stadium seating. 

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