Improved Fire- and Smoke-Resistant Materials for Commercial Aircraft Interiors A Proceedings (1995) / Chapter Skim
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Chapter 9. Meeting FR Goals Using Polymer Additive Systems
Chapter 9. Meeting FR Goals Using Polymer Additive Systems
Pages 129-150
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From page 129... ...
7 TRENDS IN FLAME RETARDANT COMPOUNDING: BUILDING A SYSTEM OF INTERACTIVE INGREDIENTS As shown by research in academic laboratories, and by industrial research as disclosed in the recent patent literature, there is a trend toward more multicomponent flame-retardant systems. A system can be built up using a "tool kits comprising ignition retarders, melt-rheology control agents, mass-transfer retardants, heat-transfer retardants, heat sinks, char initiators, 4; ~, ~" charting catalysts, char-strengthening agents, char-oxidation preventatives, and noncarbon barrier-forming agents.
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From page 130... ...
There is much less background on making these excellent fire-resistant polymers even more flame retardant, because the motivation has not been very great. Programs such as that which the Federal Aviation Administration is developing will "push the limits" in new and relatively unexplored territory.
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From page 131... ...
Raising Ignition Temperature and Effective Heat Capacity by Providing Heat Sinks There is scattered evidence that the heat sink effect is an important mode of action for additives such as melamine in lower-temperature polymers such as urethane foams (Ball and Appleyard, 1989~. The heat capacity effects alone were used to explain the relative effectiveness of halogen compounds in the flame Worsen, 1974, 1975~.
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From page 132... ...
The endothermic contribution of volatilized flame retardants in the preheat and combustion zones of the flame have been given very little notice in the flame-retardancy literature. This neglect is becoming increasingly untenable in the face of some remarkable quantitative calculations, in good agreement with experiment, estimating the efficacy of many flame extinguishants on the basis of mainly endothermic decomposition (Sheinson et al., 1989)
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From page 133... ...
A quantitative study of the thermal effects of flame-retarding cellulose by alkali showed that the reduction of the fuel content of the volatiles counteracted the enhanced rate of degradation and enhanced volatile generation (Chen et al., 1991~. Cross-linking, char enhancement, and water release are probably the main modes of action of phosphorus flame retardants in certain other systems, for example, in rigid urethane foams.
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From page 134... ...
The classical antioxidants do not work at these temperatures. One of the many proposed mechanisms for red phosphorus, an effective flame retardant, is radical scavenging in the decomposing polymer phase; the rather weak evidence is that red phosphorus retards pyrolytic degradation of polyethylene (Peters, 1979~.
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From page 135... ...
This is probably an important part of the flame-retardant action of phosphoms additives. Further Consideration of Charring Catalysis Dehydrogenation and oxidative dehydrogenation catalysts are a generic class of additives that a priori should accelerate char formation under oxidative conditions with water as the byproduct.
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From page 136... ...
In our own recent work at Polytechnic, we have pursued this working hypothesis and have found some synergistic results of known dehydrogenation or oxidative dehydrogenation catalysts with other flame retardants, but have not found any manifestation of this effect strong enough to provide us with a "stand-alone" flame retardant. However, we believe that the advanced thermoplastics should actually respond better to this type of catalytic additive (less heat of combustion to counteract the effect, and inherently higher char yield to assist the effect)
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From page 137... ...
Introduction of Polymeric Additives to Provide Char Although most advanced thermoplastics such as polyetherimides and polysulfones are good char farmers in their own right, they could benefit by further increase in char yield and they may likely need improvement in rate of charring. The addition of a good char-forming polymer to a less charrable polymer has been recognized as a valid approach to building a flame-retardant polymer system.
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From page 138... ...
. We think that it will be found productive to add fast char farmers even to those engineering thermoplastics that provide, by themselves, a good char yield.
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From page 139... ...
In one study, the peak of flame retardancy coincided with a peals of char strength (Kambour et al., 19811. It is significant that some recent research at NIST showed that in polycarbonate modified by silicone, while the rate of heat release was greatly reduced, the piloted ignition time was shortened and the flame-spread rate was increased.
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From page 140... ...
Boron oxide from ammonium borate and boric acid appears protective up to 1000 °C and appears to not only form a coating but actually block the active sites on the carbon where oxygen attack occurs bY several mechanisms (Iones and Thrower, 1988, 19911. A wide range of berates, ~, , , _ .~.
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From page 141... ...
The new idea claimed is to use two different fries with different melting ranges. A recent German patent application refers explicitly to reduced-heat-release and lowsmoke aircraft cabin materials and attempts to cover oxides and oxygen acid salts of groups IlI-V of the periodic table as additives for all possible aromatic thermoplastics.
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From page 142... ...
, but they may prevent vision by being extreme eye irritants and thus inhibit exit from an aircraft cabin. Fonnaalat~ng a Flame Retardancy and Smoke Suppression "Package" The large number of different modes of action for flame retardants (and smoke suppressants)
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From page 143... ...
Journal Of Polymer Science, Polymer Chemistry Edition 17:1129-1144. Buchert, H., G
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From page 144... ...
1991. Numerical model of ignition processes of polymeric materials including gas-phase absorption of radiation.
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From page 145... ...
1990. Char formation in aromatic engineering thermoplastics.
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Pp. 178-183 in Proceedings of the 2nd Beijing International Symposium/Exhibition on Flame Retardants.
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From page 147... ...
1985. Inorganic glass forming systems as intumescent flame retardants for organic polymers.
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From page 148... ...
1979. Phosphine-based flame retardants for polypropylene.
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From page 149... ...
Pp. 285-290 in Proceedings of the 2nd Beijing International Symposium/Exhibition on Flame Retardants.
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From page 150... ...
1989. A strategy for the design of flame retardants: Cross-linking processes.
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