Smoke suppressant effect

Fig. 11 illustrates the smoke suppression effect of the zinc borate when used in conjunction with ATH in a halogen-free ethylene-vinyl acetate (EVA) system. Sumitomo Electric, in a... 

Smoke suppressants effectively reduce the amount of aromatic species released as smoke by promoting char development during a fire. 

In addition to flame-retardancy, zinc borates have a smoke suppressing effect. When used in polyamides, they counteract the reduction in the tracking index (cf. Section 3.2.2.1) caused by the halogenic flame-retardants. ... 

The smoke suppressing effect is attributed to several metal compounds, mainly oxides, hydroxides and salts, but it has also been observed with other chemicals, such as carboxylic acids, aldehydes, alcohols, fluoroborates, sulphur, and silica. Some commercial smoke suppressor additives are listed in Table 5.16. 

The very signifieant smoke suppression effect of the FeOOH in the blends is explained in terms of iron/chlorine compounds formed in situ. The maximum smoke suppression effect was obtained at a blend ehlorine content of about 20%. It was also shown that the char formation is directly related to smoke formation and suppression in these polymer blends. 

This occurs in the condensed phase and interferes with heat feedback from the burning gases in the flame to the decomposing polymer beneath. It also promotes the formation of a layer of char which further protects and insulates unbumed material. The smoke suppression effect may be viewed as a consequence of char promotion (that is carbon-rich particulates that would have otherwise become smoke, are locked up in the condensed phase as char). It is also likely that the very high surface area transition aluminium oxides formed during decomposition of ATH will adsorb many volatile species and fragments that could otherwise become smoke. 

TrialkylPhosphates. Triethyl phosphate [78-40-0] C H O P, is a colorless Hquid boiling at 209—218°C containing 17 wt % phosphoms. It may be manufactured from diethyl ether and phosphoms pentoxide via a metaphosphate intermediate (63,64). Triethyl phosphate has been used commercially as an additive for polyester laminates and in ceHulosics. In polyester resins, it functions as a viscosity depressant as weH as a flame retardant. The viscosity depressant effect of triethyl phosphate in polyester resins permits high loadings of alumina trihydrate, a fire-retardant smoke-suppressant filler (65,66). 

Certain anhydrous stannates are effective as smoke suppressants in glass-reinforced polyester, especially Na2Sn(OH)g [12058-66-1] and ZnSnO ... 

Other flame retardants and/or smoke suppressants can also be used such as magnesium hydroxide, magnesium carbonate, magnesium-zinc complexes and some tin-zinc compositions. Zinc oxide is a common ingredient in many rubber base formulations used as part of the curing system. At the same time, the action of zinc oxide is similar to that of antimony trioxide, but less effective. 

Hence, it is apparent that certain inorganic tin compounds are very effective flame retardants and smoke suppressants for halogenated polymer formulations. Since these additives are generally non-toxic, their potential use as partial or total replacements for existing commercial flame retardants, such as antimony trioxide, is thought to merit serious consideration. 

Green J (1989) Flame retardants and smoke suppressants. In Katz HS, MUewski JV (eds) Handbook of fiUers for plastics. Van Nostrand, New York, chapter 4, p93 Hornsby PR, Watson CL (1986) Plast Rubber Process Appl 6 169 Rothon RN (1995) Effects of particulate fiUers on flame retardant properties of polymers. In Rothon RN (ed) Particulate-fiUed polymer composites. Longman, Harlow, Chap 6,p207... 

The traditional flame retardant is based on organobromine compounds together with antimony trioxide as a synergist. Magnesium hydroxide is a good flame retardant due to its high decomposition temperature and smoke suppression properties. It is widely used in thermoplastic materials. However, magnesium hydroxide must be added in portions of some 60% to achieve a reasonable effect. 

This zinc borate is a more effective flame retardant and smoke suppressant than barium metaborate (Busan 11M1).43 For example, in flexible PVC, a combination of antimony trioxide and the zinc borate results in much better fire test performances than the antimony trioxide and barium metaborate combination (Table 9.4). In contrast to flexible PVC, this zinc borate alone improves both fire retardancy and smoke suppression in rigid PVC.48... 

Elastomers The zinc borate is an effective synergist of halogen sources and smoke suppressants in elastomers such as styrene butadiene rubber (conveyor belting, flooring), neoprene (wire and cable, dampening compound, conveyor belt), EPDM and PVC-nitrile foam (insulation foam), and so on.55 It has also been used in halogen-free silicone elastomer and EPDM, EP (in conjunction with ATH or MDH). 

This anhydrous zinc borate is recommended for use in engineering plastics processed at temperatures higher than 300°C which is the upper limit of Firebrake ZB processing temperature. It is reported to be an effective smoke suppressant in chlorofluoropolymers for plenum cable applications.66 Recently it was claimed that this anhydrous zinc borate can replace antimony oxide (or sodium antimonate) completely in high temperature polyamide applications. Like its hydrated analog, this anhydrous zinc borate can also improve CTI, thermal stability, and the color stability of polyamide containing halogen sources.67 68... 

Owens-Corning claimed the use of ammonium fluoroborate or potassium fluoroborate as smoke suppressant in isocyanurate-urethane.107 It was believed that the fluoroborate decomposition products such as BF3, KF, or NH4F act as free radical chain stopper and add across double bounds of olefinic decomposition products. NASA reported that both ammonium fluoroborate and potassium fluoroborate are the effective endothermic fillers of ablative intumescent coating.108... 

Zinc borate is also an effective SS in combination with phosphate ester plasticiser (130). The combination of ammonium octamolybdate and zinc stannate is also beneficial (435). It has been shown that ATH and MDH functional fillers coated with zinc hydroxystannate give significantly increased combustion resistance and lower levels of smoke evolution (386). Copper (I) complexes have been suggested as smoke suppressants (241). Copper oxides have also been investigated with positive results (60). 

The results are reported of a study of the effect of various polymeric additives and metal oxides on the thermal degradation, flame retardancy and smoke suppression of rigid PVC carried out using a cone calorimeter at an incident heat flux of 25 kW sq.m. Polymeric additives... 

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