Spreading factor 442 INDEX

The uncertainty of the calculated spreading factor A(o q) depends upon the accuracy of the inhomogeneity index of the sample and that of the total variance of experimental chromatogram. It may be expressed as... 

TABLE 14.14 Flame Spread Index (ESI), Flame Spread Factor (FSF), and Heat of evolntion valnes (determined according to ASTM E 162) for two HDPE-based composite materials, one filled with rice hulls, another with rice hulls and a mineral filler. Detailed on the compositions are given on page 484. Data by the author. 

In this small-scale test method, 460-mm (18-in.) x 150-mm (6-in.) wide and up to 25-mm (1-in.) thick vertical sample is used. The sample is exposed to a temperature of 670 + 4 °C at the top from a 300-mm (18-in.) x 300-mm (12-in.) inclined radiant heater with top of the heater closest to and the bottom farthest away from the sample surface. The sample is ignited at the top and flame spreads in the downward direction. In the test, measurements are made for the arrival time of flame at each of the 75-mm (3-in.) marks on the sample holder and the maximum temperature rise of the stack thermocouples. The test is completed when the flame reaches the full length of the sample or after an exposure time of 15-min, whichever occurs earlier, provided the maximum temperature of the stack thermocouples is reached. Flame spread index (7s) is calculated from the measured data, defined as the product of flame spread factor, F, and the heat evolution factor, Q. 

The surface burning characteristics (flame spread index and smoke developed index) for wood and wood products as measured by American Society for Testing and Materials (44) can be reduced with fire retardant treatments, either chemical impregnation or coatings (48). Fire retardant treatments also reduce the heat release rate of a burning piece of wood (49,50). The heat release rates (51) of the burning materials are an important factor in fire growth. 

The ratio MMD/SMD is generally recognized as a good measure of droplet size range. In addition, various indices and factors have been defined to describe the spread of droplet sizes in a spray, for example, droplet uniformity index LVfSAMD -Z),)/MMD 433 and relative span factor (D09 -Z)01)/MMD, etc. 

ASTM D 3675 Surface Flammability of Flexible Cellular Materials Using a Radiant Heat Energy Source This method may be used on cellular elastomeric materials such as flexible polyurethane foam and neoprene foam. It employs a radiant panel heat source consisting of a 300 by 460-nun (12 by 18 in.) panel in front of which an inclined 150 by 460-m (6 by 18 in.) specimen of the material is placed. The orientation of the specimen is such that ignition is forced near its upper edge, and the flame front progresses downward. Factors derived from the rate of progress of the flame front and heat liberated by the material under test are combined to provide a flame spread index. The method was developed to test cellular elastomeric materials which could not be tested by ASTM E 162. 

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. 

When the Hamaker constant is positive, it corresponds to attraction between molecules, and when it is negative, it corresponds to repulsion. By definition, 3 = 1 and n3 = 1 for a vacuum. As we know from McLachlan s equation (Equation (92)), the presence of a solvent medium (3) rather than a free space considerably reduces the magnitude of van der Waals interactions. However, the interaction between identical molecules in a solvent is always attractive due to the square factor in Equation (567). On the other hand, the interaction between two dissimilar molecules can be attractive or repulsive depending on dielectric constant and refractive index values. Repulsive van der Waals interactions occur when n is intermediate between nx and n2 in Equation (566). If two bodies interact across a vacuum (or practically in a gas such as air at low pressure), the van der Waals forces are also attractive. When repulsive forces are present within a liquid film on a surface, the thickness of the film increases, thus favoring its spread on the solid. However, if the attractive forces are present within this film, the thickness decreases and favors contraction as a liquid drop on the solid (see Chapter 9). 

Traditionally, information on inflation expectations has been obtained by survey methods or theoretical methods. These have not proved reliable however, and were followed only because of the absence of an inflation-indexed futures market. Certain methods for assessing market inflation expectations are not analytically valid for example, the suggestion that the spread between short- and long-term bond yields cannot be taken to be a measure of inflation expectation, because there are other factors that drive this yield spread, and not just inflation risk premium. 

The most reasonable way to measure bondholder value appears to look at the spread versus government bonds financial markets process information in a fast and anticipative way. Additionally, considering the spread to an index or benchmark bond representing the sector of the corporation allows to largely eliminate sector specific and general interest market related factors. 

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