Flame retardants mineral-based

Mining conveyor belts are based on CR where stringent flame retardance requirements must be fulblled. Flame retardant mineral bllers used in combination with a chlorinated wax are recommended along with a silica bller for abrasion and tear resistance. 

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... 

Herbiet, R., Luther, D.W., and Thomas, S.G. Jr., Benefits of brominated mineral based flame retardants for wire cable in Proceedings of the 50th IWCS/Focus International Wire Cable Symposium, Lake Buena Vista, FL, 2001, pp. 807-815. 

The next major class of flame retardant additives that are nonhalogenated is the phosphorus-based flame retardants, but even these materials have some regulatory environmental concerns.Other nonhalogenated flame retardants that are not phosphorus-based exist, including mineral fillers (i.e., Al(OH)3, Mg(OH)2), expandable graphite, mela-mine, and polymer nanocomposites combined with other flame retardants.Each of these materials has its own advantages and disadvantages, and effectiveness in one polymer system often does not translate into another system. 

A common disadvantage of chlorine-containing flame retardants is that they have to be added in quantities, which in turn decrease mechanical properties of the polymer materials. The same sitnation in terms of large amount that should be added into the base material holds for mineral flame retardants as well (ATH, Mg(OH)2) however, minerals typically improve both flexural modulus (stiffness) and flexural strength of composites. 

Alcan Chemicals Europe, a major source of flame retardants, mainly mineral based aluminium and tin compounds, has been put up for sale by parent Alcan Canada. 

To achieve typical flame retardancy for cables required by the most important international cable fire test (lEC 60332-3-24, Tests on electrical cables imder fire conditions - Part 3-24 Test for vertical flame spread of vertically-mounted bunched wires or cables) demands a high loading of a mineral FR filler such as ATH. 65wt% of ATH with 35% of a suitable polymer like EVA must often be used for cable jackets. A similar compound of EVA (with 28% VA content) with ATH and 5% of a nanocomposite can pass the same test. It was found that the ATH could be reduced to only 45% of the composition. The reduction in the total amount of the fillers results in improved mechanical and rheological properties of typical EVA-based cable compoimds. The char formed is... 

The chemistry of flame-retardant additives is highly varied and is optimised not only for specific polymer chemistries, but also to address flammability effects such as flame spread, dripping, smoke release and so on. Flame-retardant chemistry includes classes of compounds such as halogenated organics, char formers, crosslinking compounds, mineral fillers, intumescent packages, phosphorus compounds, nitrogen-based compounds and even certain metal and boron compounds. 

This represents a specialty filler which contributes to paper brightness, ink receptivity and acts as a flame retardant. The effect on flame retardancy can be explained by the 35% of bound water based on material weight. The bound water is released at temperatures above 150 °C. The raw material source for the production of aluminum trihydrate (ATH) is bauxite. Bauxite is a blend of AI2O3, Fc203, Si02, H2O, Ti02 and other minerals. To produce ATH it is necessary to stabilize the alumina content and to separate out the other minerals. This is done by the so-called Bayer process. After final filtration, the clear liquor of sodium aluminate is seeded with specially prepared fine crystals of ATH. This seeding causes the sodium aluminate to decompose to ATH or Al(OH)3 which forms a precipitate. 

PPE-based resins are relatively resistant to burning, and judicious compounding can increase their burn resistance without fee use of halogenated flame retardants. In addition, these blends could be modified wife glass fiber and mineral fillers. Because of low moisture absorption, dimensional stability. 

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