Foaming condition

Free caustic alkalinity usually is not recommended for jet-type electrode, as foaming conditions may develop rapidly because of the high recirculation rate. Where high alkalinity is present and FW contamination from colloidal or organic matter takes place, the foaming that develops quickly causes the boiler to be shut down. 

In some cases, temperature effect may be spectacular, a factor frequendy overlooked in designing for foaming conditions. Influence erf this effect can be evaluated by the use of a foam comparator. 

Fig. 11 Details on the cellular morphology of PPE/SAN blends (foaming conditions time 10 s, temperature 180°C)...

Previous work with Oldershaw columns (209-211), however, spells a note of caution to Fair et al. s conclusion. For a fixed system, higher Oldershaw column efficiencies were measured under cellular foam conditions than under froth conditions. For this reason, Gerster (212) warned that when cellular foam can form, scaleup from an Oldershaw column may be dangerous. The conclusions presented by Fair et al. (208) do not extend to Oldershaw columns operating in the Cellular foam regime. Other considerations for scaleup from pilot columns (above) may also be important. The scaleup procedure recommended by Fair et al. (208) is... 

The initial expansion ratio and dispersity of polyhedral foams are related through the quantitative dependence, given by Eq. (4.9). There at Ap > 103 Pa the content of the liquid phase in the films can be neglected. Thus, the connection of the structure parameters n, a and r can be expressed by the simple relation in Eq. (4.10). It follows from it that under given foaming conditions a definite expansion ratio can be reached by changing the border pressure, foam dispersity and surface tension of the foaming solution. 

Most rigid polyurethane foams are produced in the 2 Ib/ft (32 kg/m ) rai e. COj-blown foams cannot be made with reliably low densities. The lowest practical limit is about 4 Ib/ft (64 kg/m ). Halo-carbon-blown foams also provide better physical properties than COj-blown foams. The greater uniformity of the halocarbon-blown foams is, in part, responsible for their superior physical properties. In addition, the polyisocyanate residue from reaction with water is deleterious in several respects. Foaming conditions are less critical with halocarbons because of the absorption of the heat of reaction by the halocarbons (13). 

One variable in particular is important. The linear superficial gas velocity should be run in a few cases at the levels expected in the full-scale plant. This means that foaming conditions are more typical of what is going to happen in the plant and the fermenter should always be provided with enough head space to make sure the foam levels can be adequately controlled in the pilot plant. As a general rule, foam level is related to the square root of the tank diameter on scaleup or scale-down. 

About 20—30% of the aldehydes in the caustic tower are carried into the next stage of compression. If a foaming condition in the caustic tower is not treated, caustic can cany over into the next stage of compression and catalyze acetaldehyde polymer formation here. As in the quench tower, polyglycol antifoams are very effective at controlling foam, as shown in Figure 13. 

Mild, low foaming, conditioning surfactant with good emuisifying properties used in personal care products Liquid pH = 6.5-7.5. Croda Witco/Oleo-Surf. 

From the experiments described in the previous sections foaming conditions have been foimd that produce a starch foam with small cells and low density. The cell structure and mechanical properties of the resulting foam have been analyzed. All foam samples are conditioned at 20°C at 60% R.H. for one week prior to measurements. 

This gas contribution has to be evaluated case by case since it depends strictly on the actual foaming conditions, such as the chemicals used, the process variables, the refrigerator design and VIP geometry. However, under some circumstances, the pressure increase can be a measurable fraction of the maximum acceptable level, thus causing a deterioration of the VIP thermal insulation properties from the very beginning of the refrigerator life. 

However, qualitative estimations based on the CNT equation were performed sustaining the hypothesis of a predominant pore nucleation inside the PBA core-shell nanodomains. It was established that, depending on the exact critical nucleation radius for each foaming conditions (further studies are required to determine accurately these values), this nucleation should happen inside the PBA phase or around the PMMA inner core (Fig. 9.31). This hypothesis was partially confirmed by some TEM micrographs of the nanostructuration after the foaming process, showing blown micelles in the foamed samples (Fig. 9.32) [101],... 

Figure 9.33 Scanning electron microscopy images of porous poly(methyl methacrylate)/ MAM blends 95/5 (left), 90/10 (middle), and 80/20 (right). Plane perpendicular to the injection direction (up) and plane containing the injection direction (down). Foaming conditions 30 MPa, room temperature. 

Silicones therefore influence the cell structure and consequently the physical properties of the foam. However, adding too much silicone does not give any further improvements. The optimum quantity is dependent upon the constituents, foaming conditions, mixing efficiency, etc. 

The use of NMP and/or plasticizers as well as varying foaming conditions was incorporated in a high-throughput experimental methodology during the downselec-tion for the polymer. For the premade VDC-based copolymer from the polymerization track, an RBl-201 VDC-based copolymer product described in Section 4.3.2 resulted in microcellular structures (Fig. 4.5.2). 

Figure 9. Shear thinning effect on water fractional flow under foaming conditions.

A dimensionless foam parameter, FM, can be formulated to adjust the gas phase relative permeability to foaming conditions. 

Various functional forms of FM have been investigated during this study explicit details will be given later. The primary advantage of this foam modelling approach lies in its simplicity use is made of the phase flow equations plus the surfactant transport equation. In addition, the functional form of FM should mimic suitable foaming conditions. 

A characteristic example in the field of cosmetics is the separation and determination of surfactants in shampoos, which contain various combinations of anionic, cationic, nonionic, and amphoteric surfactants. The surfactant combination is designed to influence the essential characteristics of the shampoo cleansing, foam, conditioning, and viscosity. Laurylether sulfates and alkylben-zene sulfonates are common anionic surfeictants used in shampoos to provide lather and cleansing. The only required sample preparation step is the dilution of the product to be analyzed in deionized water and subsequent membrane filtration (0.45 pm) prior to injection. Figure 10.200 illustrates the gradient... 

Foaming Conditions The foaming time and/or the foaming temperature are important process variables for controlling the density and porous morphology of PLA foams owing to their effects on the viscoelastic properties of the polymer (Figure 17.4) [2]. 

Foaming Conditions" Density (g/cm ) Notched Izod Impact Strength (J/m)... 

High foaming conditioning agent used in shampoos, foam baths, and liquid handsoaps. 

Good wetting and foaming agent. Rapidly builds viscosity and improves foam. Conditions and softens hair while reducing flyaway. Use in shampoos, conditioners and mousses or, as an emulsifier in creams and lotions. 

These low-foaming ethoxylated polyoxypropylene glycols of different molecular weights are designed to meet a variety of low-foam conditions. Members of this series find use as defoamers, dedusters and emulsifiers. They are used in rinse aids, machine dishwashing and laundry detergents as suds control agents. 

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