Polymer drainage

Since viscometer drainage times are typically on the order of a few hundred seconds, intrinsic viscosity experiments provide a rapid method for evaluating the molecular weight of a polymer. A limitation of the method is that the Mark-Houwink coefficients must be established for the particular system under consideration by calibration with samples of known molecular weight. The speed with which intrinsic viscosity determinations can be made offsets the need for prior calibration, especially when a particular polymer is going to be characterized routinely by this method. 

Retention aid polymers are used in a very high shear environment, so floe strength and the abiHty for floes to reform after being sheared (43) is important. The optimum floe size is a compromise. Larger floes give better free drainage, but tend to produce an uneven sheet due to air breakthrough in... 

Examples of nir analysis are polymer identification (126,127), pharmaceutical manufacturing (128), gasoline analysis (129,130), and on-line refinery process chemistry (131). Nir fiber optics have been used as immersion probes for monitoring pollutants in drainage waters by attenuated total internal reflectance (132). The usefulness of nir for aqueous systems has led to important biological and medical appHcations (133). 

Although expansion and drainage are still increasing together, it can be easily seen that the polymer-stabilized foam has a drainage far below that of the typical foam (each with the same basic formulation) shown in Table III. The foam base is an alkoxy/1 inear alkyl sulfate, fatty alcohol, and glycol/glycol ether mixture, as outlined in Table VII. 

Figure 2. Foam drainage and water loss from the bubble wall concentrate is diluted into a premix, and the foam is generated from the premix. When foam is generated, hydrophobic R groups become part of the bubble wall (X = width of bubble wall). X decreases as water drains downward under the influence of gravity. The polymer strands prevent narrowing of bubble wall, decreasing drainage time and stabilizing the foam.

Retention and drainage aids are chemicals which are added to the fibre and filler suspension to assist the efficiency of the filtration process. Growth in recent years in the use of retention aids has been greater than that of almost any other paper chemical additive. It has been caused by a combination of factors increased machine speeds, the increased use of filler in alkaline systems, the increased use of recycled paper and the growing tendency to use fillers in newsprint. Retention aids are water-soluble polymers which may be cationic,... 

Dry strength additives are usually water soluble, hydrophilic natural or synthetic polymers, the commercially most important of which are starch, natural vegetable gums and polyacrylamides. These polymers are often made in cationic form by the introduction of tertiary or quaternary amino groups into the polymer, and are therefore polyelectrolytes. They are thus also able to function to some extent as drainage and retention aids. 

Evaporation can be reduced by containing the bubble in a closed bottle. It is also found that, in such a closed system, the bubbles remain stable for a very long time. The drainage of water away from the film is dependent on the viscosity of the fluid. Therefore, such additives as glycerin (or other thickening agents [polymers]) assist in maintaining stability. 

Diverse foam structure applications In foam rubber, foamed polymers, shaving foams, milk shakes, and whipped creams, slowly draining thin liquid films (TLF) are needed. Accordingly, the rate of drainage is the most important factor in such industrial foam applications. 

Nikolov AD, Wasan DT, Denkov ND, Kralchevsky PA, Ivanov IB (1990) Drainage of foam films in the presence of nonionic micelles. Prog Colloid Polym Sci 82 87-98... 

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