Mean specific extinction area

Unlike halogenated additives silica gel /K2CO3 does not significantly affect the specific heat of combustion when added to PP [227]. Furthermore, since the CO yield and the soot (mean specific extinction area) are not significantly increased by these additives, the use of this system may represent an improvement over halogenated and some phosphorus based additives, which commonly tend to increase CO yield and soot [227]. These data indicate that these additives most likely act primarily in the condensed phase not in the gas phase. The cone calorimeter results for PP are summarized in Table 5.5 along with data for the other polymers examined [227]. 

A conclusion has been drawn in [67] that the extinction of the luminous flux (7//o, where, 7o is the intensity of the incident light and 7 is the intensity the light passed through the foam) is a linear function of the specific foam surface area. A similar dependence has been used also for the determination of the specific surface area of emulsions [68]. Later, however, it has been shown [69,70] that the quantity 7//o depends not only on the specific surface area (or dispersity) but also on the liquid content in the foams, i.e. on the foam expansion ratio, that during drainage can increase without changing the dispersity. Since foam expansion ratio and dispersity are determined by the radii of border curvatures and film thicknesses, all the structural elements of the foam will contribute to the optical density of foams. This means that... 

---