Small bubbles elimination

Although oven temperatures between 282°C and 357°C have been successfully tried for rotomolding ECTFE, the recommended range is 288°C-315°C.1 1 At temperatures above 321°C, small bubbles are formed that are difficult to eliminate from the part. Cycle time has to be determined experimentally. The... 

Defoamer de- fom- (defoaming agent) n. A substance that, when added in small percentages to a liquid containing gas bubbles, causes the small bubbles to coalesce into larger ones that rise to the surface and break Additive used to reduce or eliminate foam formed in a coating or a coating constituent. 

Due to the insolubility in the solid state, small bubbles are formed in the welding seam during cooling. These pores lead to poor welding seams, which is why the zones to be welded must be carefully brushed in order to eliminate any surface contamination. Furthermore, it is necessary to work under controlled temperature and humidity... 

Isocyanates can also undergo a wide variety of primary reactions. For example, they can react with alcohols to form urethanes and react with amines to give ureas. Isocyanates can also undergo secondary reactions reacting with urethanes and ureas to give allophanates and biurets, respectively. Isocyanates can also release carbon dioxide that can appear as small bubbles or micropopping in the clearcoat film. The use of moisture scavengers and other additives can help reduce or completely eliminate these defects in baked systems. 

Flow surges in the seal drum are likely generated by the cyclic formation of large bubbles as the flare gas is discharged into the drum. These pulsations can be virtually eliminated by the use of a horizontal sparger ineorporating many small diameter holes arranged specifically to allow the open area to increase as flow increases. These holes must be spaced sufficiently far apart to avoid interference between bubbles. 

Air pockets or bubbles are left on the surface of all concrete. Good vibration and placing techniques will reduce their number but not eliminate them. Many air pockets have a small opening on the surface in relation to their size. Paints will not penetrate into such holes, with the result that air or solvent is trapped and subsequent expansion will cause the coating to blister. In addition, some air pockets are covered with a thin layer of cement that also has no strength and will cause loss of adhesion. 

One final test was conducted on a heat treated sample to elucidate the effect of heat treatment and sensitization on the fracture behavior of this steel. A CF sample was heated for 24 hours at 650°C to see if the fracture mode would continue to change with an even larger amount of carbide precipitation. Note in Figure 15-a this heavily sensitized steel has a fracture appearance that is completely dominated by small microvoids associated with carbides. The bimodal distribution of microvoids like those in Figure 7 has been eliminated. In fact, the fracture appearance is remarkably similar to that of the tritium-exposed-and-aged steels albeit at a different magnification (Figure 15-b). It appears that carbides in the microstructure affect the fracture mode in a similar manner as the decay helium bubbles but on a different scale. 

Immediate benefits of switching to the larger-volume cell (Fig. 25) include the formation of larger-area deposits, 2-3 cm, versus the 0.1-0.2 cm deposits obtained using the thin layer flow cell. The thicker layer of solution eliminated problems with IR drops, bubbles, and edge effects except at the top of the deposit. Some nonuniformity at the top of the deposit resulted from small variations in the levels of different solutions pumped into the cell. Rinse solution levels, for instance, were always raised to a slightly higher level than the reactant solutions in order to make sure that the reactants were completely removed after each deposition. 

Air bubbles in the system carried small amounts of solvent extract out the phase separator with the aqueous phase. This loss was eliminated by moving the pumps to a position lower than the other parts of the extractor, as recommended by the manufacturer, and ensuring that all Teflon connections were airtight. 

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