Smoke density index

Gross et al. (1967) and Imhof and Stueben (1973) developed a smoke density index (Dm) based on the maximum specific optical density, ranging from 0 to 1000. High Dm values are found for polymers with LOI values between 0.18 and 0.30. 

Smoke density index. This is calculated from the light absorption vs, time curves as in the above procedure. 

In the procedure of ASTM E 286-1969 (reapproved 1975), a horizontal light beam is measured in the vertical vent pipe of the 2.44-m tunnel furnace (cf. Section 3.2.1, Fig. 3.94). The smoke density index (4) is determined in a similar way as in the method of ASTM E 84-198la. 

Elame-spread and smoke-density values, and the less often reported fuel-contributed semiquantitive results of the ASTM E84 test and the limited oxygen index (LOI) laboratory test, are more often used to compare fire performance of ceUular plastics. AH building codes requite that ceUular plastics be protected by inner or outer sheathings or be housed in systems aH with a specified minimum total fire resistance. Absolute incombustibHity cannot be attained in practice and often is not requited. The system approach to protecting the more combustible materials affords adequate safety in the buildings by aHowing the occupant sufficient time to evacuate before combustion of the protected ceUular plastic. 

As an example, a foam prepared from III, alumina trihydrate as a filler, benzoyl peroxide as a curing agent, and azobis formamide as a blowing agent, leads to a material with an oxygen index of 48, a long-term stability to at least 150 °C, and a smoke density about one fifth that of a commercial foam [284]. 

The unfilled grade of PAI is rated UL 94 V-0 at thicknesses as low as 0.008 in. and has an oxygen index of 45%. PAIs are extremely resistant to flame and have quite low smoke generation. Some reinforced grades have surpassed the FAA requirements for flammability, smoke density,... 

Flame retardance is another important property and is defined by different test methods. Some of the small-scale methods include horizontal flame spread (FMVSS 302, ASTM D-1692) vertical flammability (ASTM D-3014, so-called Butler Chimney Test), limiting oxygen index (ASTM D-2863), and smoke density (ASTM D-2840). 

This is called the Radiant Panel Test. A Flame-Spread Index is calculated as a product of the flame-spread and heat-evolution factors. Smoke density is also obtained. 

Metal chelates lower decomposition temperature (decrease thermal stability of material), increase char yield and limiting oxygen index, and improve smoke density rating. They are useful S5mergistic additives for Al(OH)3 and Mg(OH)2. Their two major functions are catalysts of dehydrochlorination and char formers. 

Eigenmann [26] presents data on oxygen index, toxicity index and smoke density of polymers, which contain different flame-retardants. Other flame-retardant polymers can also be used. 

Domine [30] reported on the property profile of Ardel D-lOO polyarylate (the first domestic commercial entry), in addition to the remarks of Sakata above, Domine mentioned the excellent retention of properties of polyarylate exposed to uv. The combustion characteristics determined by a number of different tests were observed to be quite favorable relative to most other non-flame retarded polymers (e.g. V-0 at 1/16", limiting oxygen index - 34, low flame spread index, and low smoke density). The creep resistance of polyarylate was shown to be much better than polycarbonate but inferior to polysulfone. 

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