Flame-retardant effect

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

Additives. Because of their versatility, imparted via chemical modification, the appHcations of ethyleneimine encompass the entire additive sector. The addition of PEI to PVC plastisols increases the adhesion of the coatings by selective adsorption at the substrate surface (410). PEI derivatives are also used as adhesion promoters in paper coating (411). The adducts formed from fatty alcohol epoxides and PEI are used as dispersants and emulsifiers (412). They are able to control the viscosity of dispersions, and thus faciHtate transport in pipe systems (413). Eatty acid derivatives of PEI are even able to control the viscosity of pigment dispersions (414). The high nitrogen content of PEIs has a flame-retardant effect. This property is used, in combination with phosphoms compounds, for providing wood panels (415), ceUulose (416), or polymer blends (417,418) with a flame-retardant finish. 

Du, M.Gao and Jia, D. (2006) Thermal stability and flame retardant effect of halloysite nanotubules on Poly(propylene). European Polymer Journal, 42, 1362-1369. 

An efficient flame retardant effect was demonstrated with 2-mil zinc coatings on polyphenylene oxide-polystyrene blends (Notyl) by Nelson (21). The action may relate to enhanced char formation by chemistry specific to this blend. However, other metal coatings on some other polymers also appeared to contribute a measurable flame retardant effect. 

Table IV. Flame Retardant Effect of Some Metal Compounds...

Illustrative performance properties for a "general purpose polycarbonate," and for the same resin modified with the additive formulations "700" (without PTFE) and "800" (with PTFE) are summarized in Table IV (adapted from reference 32). It is clear that the objective of minimal effect on performance properties has been attained for this system. It is evident that flame retardant effectiveness attained with minimal levels of additive can provide optimum solutions to the problem of decreasing flammability without sacrifice in performance properties. Work documented to date suggests that in depth studies of thermal degradation such as reported for aromatic sulfonates in polycarbonates (28) would be rewarding for other systems. 

Raldua D, Padros F, Sole M, Eljarrat E, Barcelo D, Riva MC, Barata C (2008) First evidence of polybrominated diphenyl ether (flame retardants) effects in feral barbel from the Ebro River basin (NE, Spain). Chemosphere 73(l) 56-64... 

It is self evident that mineral fillers need to be stable at the temperatures (up to 350 °C) experienced in processing thermoplastics. Most fillers are stable to much higher temperatures and so this is not usually an issue. However, it is a very important topic for flame retardant fillers which function by decomposing endothermically with the release of inert gasses. To be effective, this decomposition must occur near to the temperature at which the polymer begins to decompose and release flammable volatiles. This is usually not too much above the processing temperature in the case of thermoplastics and hence the exact temperature at which decomposition commences is of great importance. The size and position of the endotherm and the rate at which the inert gas is released are also of importance to the flame retardant effect itself [23]. 

Aluminium hydroxide has a Moh hardness of about 3 and a specific gravity of 2.4. It decomposes endothermically with the release of water at about 200 °C and this makes it a very useful flame retardant filler, this being the principal reason for its use in polymers. The decomposition temperature is in fact too low for many thermoplastics applications, but it is widely used in low smoke P VC applications and finds some use in polyolefins. For these applications low aspect ratio particles with a size of about 1 micron and a specific surface area of 4-10 m g are preferred. The decomposition pathway can be diverted through the mono-hydrate by the application of pressure, and this may reduce the flame retardant effect [97]. This effect can be observed with the larger sized particles. Although it is chemically the hydroxide, it has for many years been known as alumina trihydrate and by the acronym ATH. 

Wyman, R, Crook, V., Ebdon, J., Hunt, B., and Joseph, P., Flame-retarding effects of dialkyl-p-vinylben-zyl phosphonates in copolymers with acrylonitrile, Polym. Int., 2006, 55, 764-771. 

Banks, M., Ebdon, J. R., and Johnson, M., The flame-retardant effect of diethylvinyl phosphonate in copolymers with styrene, methyl methacrylate, acrylonitrile and acrylamide, Polymer, 1994, 35, 3470-3473. 

Zhu, W. and Weil, E.D., A paradoxical flame-retardant effect of nitrates in ATH-filled ethylene-vinyl acetate copolymer, J. Appl. Polym. Sci., 56, 925-933, 1995. 

To further explore the influence of silica material properties (morphology, surface area, silanol concentration, and surface treatment) on the silica flame-retardant properties, various types of silicas (silica gel, fumed silicas, and fused silica) were investigated.50 51 Material properties of the various silicas are summarized in Table 8.6. These different types of silicas were added to polypropylene and polyethylene oxide to determine their flame-retardant effectiveness and mechanisms. Polypropylene was chosen as a non-char-forming thermoplastic, and polyethylene oxide was chosen as a polar slightly char-forming thermoplastic. Flammability properties were measured in the cone calorimeter and the mass loss rate was measured in the radiative gasification device in nitrogen to exclude any gas phase oxidation reactions. 

FIGURE 15.16 THE and PHRR of PA 66-GF and PA 66-GF/Pmd plotted against irradiation. With increasing irradiation the flame retardancy effect vanishes with respect to THE and increases with respect to PHRR. The THE correlates to the ML during burning, which converges for PA 66-GF and PA 66-GF/Pred with increasing irradiation. The PHRR is determined more by the barrier properties of the char than by its quantity. 

It is striking that this system shows such a clear differentiation between the behavior of the two probably most important fire risks PHRR and THE, when the external heat flux is varied. The flame retardancy effect with respect to the THE decreases with increasing irradiation, whereas the relative flame retardancy effect with respect to the PHRR increases. The latter clearly indicates the predominant influence of the barrier effect on the HRR. 

The relationship between other flammability characteristics and the polymer tendency for carbonization has also been studied Flame retardant effective-... 

According to Eq. (4.3), the slope of the straight line obtained from a plot of the LOI versus the coke yield during pyrolysis or combustion of a polymer may be a measure of the ability of coke to improve the flame retardancy of polymers. Fig. 15 demonstrates that, when siloxane monomers are introduced into aromatic polycarbonates, the flame retardant effect of the coke increases considerably as compared with polymers not containing such monomers. It has been noted, however... 

The effect of volatile phosphorus-containing compounds in polymer flames has not yet been studied. For gas systems it has been found that the flame retarding effect of the additives depends on the concentration (trimethyl phosphate, phosphorus halides and thiohalides). HPO fragments were detected in the radiation spectrum of a H2/O2 flame, upon the introduction of trimethyl phosphate Pj, PO, POj and HPO, P and PH fragments in low concentrations were discovered in a CH /Oj flame inhibited with triphenylphosphine oxide. As regards the flame retardation effect, phosphorus in triphenylphosphine occupies an intermediate position between Sb and As. Triphenyl phosphate is less effective than SbClj. Most effective are POQ3, PCI3 and PBrj. 

Other types of finishes typically reduce the main effect of a finish type, for example the flame retardant effect is decreased by nearly all other types of chemical finishes as they add flammable components to the fabric. 

Very little in the way of review material has appeared in the time frame under consideration the only exceptions being a detailed discussion of the reactions of (NPCl2)34 with polyfunctional nucleophiles and a brief survey in Japanese of the flame retardant effects of cyclophosphazenes. 

The flame-retardant effect of magnesium hydroxide and ATH is based on the endothermic decomposition to magnesium or aluminum oxide, see reactions (11.1) and (11.2). This decomposition effectively acts as a heat sink cooling the surface of the polymer. 

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