Smoke suppression formulation

Additives that impart smoke-suppressant properties to a composition tend not to be flame retardant. Conventional flame retardant and smoke-suppressant formulations include phosphorus-containing compounds such as a phosphoric acid ester, ammonium poly(phosphate) and red phosphorus, or halogen containing compounds such as tetrabromobisphenol A, decabromodiphenyl oxide and chlorinated polymers, and metal compounds such as magnesium hydroxide, aluminum hydroxide and zinc borate (4). 

Alumina trihydtate is also used as a secondary flame retardant and smoke suppressant for flexible poly(vinyl chloride) and polyolefin formulations in which antimony and a halogen ate used. The addition of minor amounts of either zinc borate or phosphoms results in the formation of glasses which insulate the unbumed polymer from the flame (21). 

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. 

PVC-U formulations have low flammability due to the chlorine content. The addition of plasticiser in PVC-P formulations necessitates the use of flame retardant and smoke suppressant additives. These additives are known as functional fillers and a correct balance is necessary to achieve all the end-use specification requirements. They are predominately used in cable, conveyer belting and roofing membrane formulations to give resistance to fire initiation and propagation. It is also important to reduce dripping in a fire situation and that as little smoke as possible is generated. Antimony trioxide has been used extensively, usually in combination with phosphate ester plasticisers, giving excellent fire performance and mechanical properties. 

Details are given of the addition of flame retardant and smoke suppressant additives to PVC to meet specifications such as oxygen index, heat release, smoke evolution or extent of burning in cable tests. Data are presented for synergistic combinations of additives in PVC formulations. 31 refs. 

Reduced Smoke and Toxicity. The smoke and toxic products of combustion are a problem of growing concern. Until recently, this problem has been overlooked in developing fire retardants. Future formulations will not only have to limit flame spread, but also limit smoke and toxic combustion products. Addition of smoke suppressants to some formulations may improve some systems. Modification of systems may also be necessary to meet possible code restrictions. More research is necessary in this area to understand the mechanism of smoke production and accumulation. 

Magnum-White. [RMc Minerals] Magnesium hydroxide/calcium carbonate blend fire retardant smoke suppressant filler for PVC compds., SBR-latex formulations. 

Chem. Descrip. Zinc borate CAS 1332-07-6 EINECS/ELINCS 215-566-6 Uses Flame retardant, smoke suppressant for plastisols, coatings for cellulosics, textiles, and adhesives synergist in PVC and halogenated polyester formulations, and in elastomers, thermoplastic elastomers, polyamides, and polyolefins strong char promoter Properties Wh. free-flowing powd., nonhygroscopic 6 p avg. particle size 99.9% < 30 p sol. 0.5 g/100 ml water sp.gr. 2.50 bulk dens. 18.1 Ib/ff oil absorp. 39 ref. index 1.48 Zb -237 [Great Lakes]... 

Chem. Descrip. Zinc borate CAS 1332-07-6 EINECS/ELINCS 215-566-6 Uses Flame retardant, smoke suppressant for plastisols, coatings for textiles, adhesives synergist in PVC and halogenated polyester formulations, and in elastomers, thermoplastic elastomers, polyamides, and polyolefins strong char promoter... 

The formulation has oil resistance, good low temperature, smoke suppressing and char forming properties... 

Alumina frihydrafe, by itselfor in combination with antimony trioxide, is an effective fire retardant additive (69,70). Antimony trioxide by itself has been shown to effectively reduce the smoke generated in a flexible formulation of PVC (71), as has zinc borate (72) and barium metaborate (73). Phosphate plasticizers, described earlier, are also effective as char formers (71). Smoke suppressants, as a special class of materials, are designed to reduce the... 

Zinc borates have also found uses in PVC formulations. They have been shown to be effective flame/smoke suppressants when used as partial replacements for the antimony oxide that is normally used in a t3 ical flexible PVC cable jacket, for example. For flexible vinyl and PVC plastisol formulations, a half to two-thirds of the antimony trioxide can be replaced by zinc borate without loss of flame retardancy. If a small decrease in flame retardancy can be tolerated, all of the antimony trioxide can be replaced with zinc borate, leading to smoke reductions of up to 65%. The flame retardancy can be increased and smoke formation decreased by adding aitunonium octamolybdate to the borate-containing formulations. 

CHARMAX LS are zinc-molybdenum complexes targeted as smoke suppressants in PVC wire and cable, PVC plastisols and rigid PVC products. LS Z4A is used in a simple PVC jacket formulation. Aroimd 5% of such additives can replace up to 20% of AOM and reduce the afterglow sometimes seen with antimony oxide containing formulations. Also CHARMAX products are cheaper by weight than primary molybdenum and tin-based additives, AOM and zinc starmate, and lower loadings provide the required level of flame retardancy or smoke suppression that may be specified. The complexes may be used as partial of complete replacements for antimony oxides, whose price and supply has been unpredictable in recent times. 

The conclusion of the EVC work was that ZHS had excellent fire retardant and smoke suppressant properties in a rigid PVC compound, with no detrimental effects on key physical or mechanical properties and so merited further detailed study for rigid PVC formulations. 

Applications In reinforced thermoset applications, the principal properties that ATH imparts are flame retardance, smoke suppression, thermal conductivity, optical translucency, and chemical stability. Aside from the benefits imparted in the above properties, the use of ATH as a resin extender also aflfords lower cost formulations with an acceptable balance of performance properties. 

Some interesting work has been reported using Zn and Mo systems in plenum cable formulations. The use of a zinc molybdenum complex in place of ammonium octamolybdate is described in Ref 61 and the use of ammonium octamolybdate in combination with zinc stannate as a smoke suppressant in plenum cable compounds is discussed in Ref [62]. 

Ferrocene fer-6- Sen [ferro- -F cycV -F -ene] (1952) (dicyclopentadienyl iron) n. (C5H5)2pe. A coordination compound of ferrous iron and cyclopentadiene, soluble in PVC and stable to 400°C. Its uses include smoke suppression, a curing agent for silicone resins, an intermediate for high-temperature polymers, and an ultraviolet absorber. Wickson EJ (ed) (1993) Handbook of polyvinyl chloride formulating. John Wiley and Sons Inc., New York. 

Magnesium hydroxide can impart flame retardancy and smoke suppression to a wide variety of thermoplastics and elastomeric formulations. It is temperature... 

Stannates. Zinc stannate [12036-37-2], Alcan s FLAMTARD S, and zinc hydroxystannate [12027-96-2], FLAMTARD HS, are both white water-insoluble powders useful as smoke suppressants in PVC. They can partly replace antimony oxide as flame-retardant synergists in halogen-containing flame-retardant formulations, with reduced smoke (16,17). 

In polyamide formulations, ferric oxide (Fe203), black iron oxide (Fe304) and yellow iron oxide (Fe203-H20) have been shown to be effective. As with molybdenum trioxide, the colour of iron oxides has been a barrier to commercial use. Iron oxides are not suitable smoke suppressants for PVC because of the (heat) destabilizing effect of iron. 

---