Smoke polymer flammability

The symposium was planned as a state-of-the-art meeting, focusing on the basic science. Program areas included high heat polymers, fire performance of polymers, hazard modeling, mechanism of flammability and fire retardation, char formation, effects of surfaces on flammability, smoke assessment and formation mechanisms, and combustion product toxicity. 

In an attempt to look for alternatives to the use of halogenated fire retardants, which function in the gas phase, an approach has been pursued which controls the polymer flammability by modifying the condensed phase chemistry. Silica gel combined with potassium carbonate have been reported to be an effective fire retardant for a wide variety of common polymers, such as polypropylene, nylon, poly(methylmethacrylate), poly(vinyl alcohol), cellulose, and to a lesser extent, polystyrene and styrene-acrylonitrile.49 The cone calorimeter data shown in Table 8.5 indicate that the PHHR is reduced by up to 68% without significantly increasing the smoke or carbon monoxide levels during the combustion. 

Polymer Flammability Flame Odor of Smoke Indication... 

A relatively large amount of unfavourable publicity has appeared in the media related to their flammability, smoke and toxicity aspects. Examples are the major fire in 1992 at a vegetable processing facility in Yuma (Arizona, USA), in 1996 at the international observatory in Hawaii, in 2002 in nightclubs in Chicago, Rhode Island and Bali. Producers of polymer foams have made determined efforts to demonstrate that these products do not present an unacceptable fire hazard when properly installed and maintained [153,154]. 

Records show that more fatalities occur through victims being suffocated by smoke or poisoned by toxic gases emitted during a fire than by being burnt to death. This is particularly worrying when it is realised that many additives incorporated into a polymer to retard its flammability are often found to increase the amount of smoke emitted as the rate of flame propagation decreases. Most... 

The markets for polyetherimides arise to an extent from stricter regulations concerning flammability and smoke evolution coupled with such features as high strength, toughness and heat resistance. Application areas include car under-the-bonnet uses, microwave equipment, printed circuit boards and aerospace (including carbon-fibre-reinforced laminated materials). The polymer is also of interest in flim, fibre and wire insulation form. 

The major improvement sought in polymers in terms of their fire behaviour is reduction of flammability. For certain applications, however, reduction in smoke evolution is sought but these two aims tend to be mutually incompatible. Reduction in flammability is brought about by making the combustion process less efficient. A penalty for inefficient combustion is increased smoke production. Similarly a reduction in smoke evolution may be achieved by increasing the efficiency of any accidental combustion that is, by increasing the flammability. 

Aryloxyphosphazene copolymers can also confer fireproof properties to flammable materials when blended. Dieck [591] have used the copolymers III, and IV containing small amounts of reactive unsaturated groups to prepare blends with compatible organic polymers crosslinkable by the same mechanism which crosslinks the polyphosphazene, e.g. ethylene-propylene and butadiene-acrylonitrile copolymers, poly(vinyl chloride), unsaturated urethane rubber. These blends were used to prepare foams exhibiting excellent fire retardance and producing low smoke levels or no smoke when heated in an open flame. Oxygen index values of 27-56 were obtained. 

Substances applied to or incorporated in a combustible material (e.g. organic polymers, nylon, vinyl and rubber, etc.) to reduce flammability. Act by retarding ignition, control/douse burning, reduce smoke evolution. Slow down or interrupt the self-sustained combustion cycle when the heat-flux is limited. Flame retardants (FRs) improve the combustion behaviour and alter the combustion process (cool, shield, dilute, react) so that decomposition products will differ from nonflame retarded articles. FRs are usually divided into three classes ... 

Hence, the zinc stannates have been shown to impart"5beneficial properties to this polymer system, in terms of flammability and smoke/carbon monoxide evolution, and the improvements in performance are clearly superior to those exhibited by the commercially available antimony trioxide. 

Hirschler, M.M. and Thevaranjan, T.R., Effects of magnesium oxide/hydroxide on flammability and smoke production tendency of polystyrene, Eur. Polym. J., 21(4), 371, 1985. 

Polylactic acid based fibres have various attributes that make them attractive for many traditional applications. PLA polymers are more hydrophilic than PET, have a lower density, and have excellent crimp and crimp retention. Shrinkage of PLA materials and thermal bonding temperatures are easily controllable. These polymers tend to be stable to ultraviolet light resulting in fabrics that show little fading. They also offer low flammability and smoke generation characteristics. 

The burning behavior of a polymer cannot, therefore, be regarded as an intrinsic property of the material. Rather do the major variables in the case of a fire — flammability, propagation of the fire, production of heat, smoke and toxic or conosive decomposition products — depend on all the factors mentioned above. 

Thermal analysis experiments have clearly shown that tin-based fire retardants markedly alter both the initial pyrolysis and the oxidative burn off stages that occur during polymer breakdown These changes have been interpreted as being indicative of an extensive condensed phase action for the tin additive, in which the thermal breakdown of the polymer is altered to give increased formation of a thermally stable carbonaceous char at the expense of volatile, flammable products. The consequent reduction in the amount of fuel supplied to the flame largely accounts for the beneficial smoke-suppressant properties associated with zinc stannates and other tin-based fire retardants. 

The polymer eomponent, whieh is a thermosetting resin, forms eross-linked bonds between chains of molecules, whieh enhanees the eharacteristic of the produet. Unsaturated polyesters and vinyl esters are primarily used as resin systems. Epoxies are also used in some eases, but the eure eyele is longer. Phenolic resins have gained importanee these days because of their inherent properties, especially in applications that require lower flammability, reduced smoke generation, and higher thermal stability. New resin systems such as... 

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