Volume expansion ratio

A chemical blowing agent was well dispersed in a linear low density polyethylene matrix, in pellet form. The pellets were rotationally moulded to produce foams, the morphology of the foams being studied using optical microscopy. The quality of the cell structures in terms of cell size, cell population density and volume expansion ratio was superior to that of foams produced by drying blending. 28 refs. 

The simplest technique for determination of the average by volume expansion ratio (and density) is the direct measurement of the total foam volume and the liquid volume in it (or its mass). Using barbotage methods for foam production the foaming process can be run until the initial solution is completely transformed into foam. Foam expansion ratio and its density are calculated by the formula... 

An equivalent volume expansion ratio of 3.0 to 3.2 has been measured due to the formation of corrosion products on steel bars embedded in concrete [16]. 

In the study of HMSPP foaming blown by butane, Naguib, Park, and Reichelt (2004) discussed the effect of die temperature on volume expansion ratio and cell density of PP foams. The different optimum die temperature that produced the maximum expansion ratio was observed for the different gas content injection. For the cell density of PP foams, however, they did not change with the die temperature, which indicated the decreased die temperature did not induce the enhanced cell nucleation. In the case of PP/clay (Zhai et al., 2010), PP/silica (Zhai, Park, and Kontopoulou, 2011), and nanocomposites extrusion foaming, however, Zhai et al., (2010), found that the decreased die temperature not only increased the expansion ratio of PP foams but also increased their cell densities. This phenomenon resulted from the enhanced cell nucleation and the suppressed cell coalescence, and the mechanisms will be discussed in the next section. In addition, for PP nanocomposite foaming systems, a typical mountain shape of foam expansion relative to the die temperature was also observed. 

Assure adequate ventilation. Since liquified cryogenic gases have a high volume expansion ratio (see Table 17.1) when evaporated (in other words, a very small amount of liq-... 

Because of the high volume expansion ratios available across the leakage path with hydrogen and helium, use of labyrinths was considered for the high-pressure plunger seal. While theoretical analysis of an ideal labyrinth shows... 

Both cell-population density and volume expansion ratio increased as the die pressure-drop rate increased. The nucleation and expansion behaviors showed little difference within the same die group. 

Figure 5(a) shows the effect of the cell density on the radiative conductivity by fixing the volume expansion ratio at 42 and the foam density at 25 kg/ml It is noted that an elevated cell density leads to a weak radiative conductivity. Figure 5(b) describes the effect of the foam density on the radiative conductivity with the cell diameter of 350 pm, 300 pm and 250 pm, respectively. It is believed that there exists an optimum foam density to obtain a minimum radiative conductivity. This optimal foam density tends to shift toward a low value as the cell size increases. 

The particle volume fraction as a function of temperature, (pp(T) was determined from swelling experiments. The change in linear size of the microgels as it swells was converted into a particle volume expansion ratio ap(T, and was then modeled using an empirical sigmoid equation with the results presented in Figure 4a. The results were subsequently used to calculate (pp(T) as shown in Figure 4b. 

Figure 4 (a) Volume expansion ratio for microgels in squalane obtained from swelling experiments modeled with an exponential-sigmoid equation with the temperature in an absolute scale. X represents observed data, — represents an empirical sigmoid model with the following eoefficients E 3.21, Eq = 1.36, Ti = 351.2, and m = 70.95. (b) Particle volume fraction in a 5 wt% microgel suspension. 

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