Membrane latex

In other areas, POD has been used to improve the wear resistance of a mbber latex binder by incorporation of 25% of Oksalon fibers. Heat-resistant laminate films, made by coating a polyester film with POD, have been used as electrical insulators and show good resistance to abrasion and are capable of 126% elongation. In some instances, thin sheets of PODs have been used as mold release agents. For this appHcation a resin is placed between the two sheets of POD, which is then pressed in a mold, and the sheets simply peel off from the object and mold after the resin has cured. POD-based membranes exhibit salt rejection properties and hence find potential as reverse osmosis membranes in the purification of seawater. PODs have also been used in the manufacturing of electrophotographic plates as binders between the toner and plate. These improved binders produce sharper images than were possible before. 

Membrane-retained components are collectively called concentrate or retentate. Materials permeating the membrane are called filtrate, ultrafiltrate, or permeate. It is the objective of ultrafiltration to recover or concentrate particular species in the retentate (eg, latex concentration, pigment recovery, protein recovery from cheese and casein wheys, and concentration of proteins for biopharmaceuticals) or to produce a purified permeate (eg, sewage treatment, production of sterile water or antibiotics, etc). Diafiltration is a specific ultrafiltration process in which the retentate is further purified or the permeable sohds are extracted further by the addition of water or, in the case of proteins, buffer to the retentate. 

Electroultrafiltration (EUF) combines forced-flow electrophoresis (see Electroseparations,electrophoresis) with ultrafiltration to control or eliminate the gel-polarization layer (45—47). Suspended colloidal particles have electrophoretic mobilities measured by a zeta potential (see Colloids Elotation). Most naturally occurring suspensoids (eg, clay, PVC latex, and biological systems), emulsions, and protein solutes are negatively charged. Placing an electric field across an ultrafiltration membrane faciUtates transport of retained species away from the membrane surface. Thus, the retention of partially rejected solutes can be dramatically improved (see Electrodialysis). 

Porous membranes with selective permeabiUty to organic solvents have been prepared by the extraction of latex films prepared with moderate ratios of PVA—PVAc graft copolymer fractions. The extracted films are made up of a composite of spherical cells of PVA, PVAc microgel, and PVA—PVAc graft copolymers (113). 

Latex Latex particles of loiovvm size are available as standards, Thev are useful to challenge MF membranes. 

A method of concentrating latex by passing an electric current through the latex contained in a rectangular tank. The rubber particles move toward the anode and also tend to rise because of their lower specific gravity. The separation is facilitated by a large number of semi-permeable membranes fitted between the electrodes. 

Adsorption Isotherms. The adsorption isotherms were determined using the serum-replacement adsorption or desorption methods (7). For the adsorption method, the latex samples (50 or 100 cm 2% solids) containing varying amounts of PVA were equilibrated for 36 hours at 25°C, placed in the serum replacement cell equipped with a Nuclepore membrane of the appropriate pore size, and pressurized to separate a small sample of the serum from the latex. For the desorption method, the latex samples (250 cm 2.5% solids) were equilibrated for 36 hours at 25°C and subjected to serum replacement with DDI water at a constant 9-10 cm /hour. The exit stream was monitored using a differential refractometer. The mean residence time of the feed stream was ca. 25 hours. It was assumed that equilibrium between the adsorbed and solute PVA was maintained throughout the serum replacement. For both methods, the PVA concentration was determined using a An-C calibration curve. 

The specific resistances obtained are independent of applied load, suspension concentration and membrane type, as expected for non-compressible filter cakes. Tests with uniform latex particles have given permeabilities in very good agreement with Equation 2, using a value of 5 for the Carman-Kozeny constant. 

Place a small piece of nonabsorbent paper (the paper separating the nitrocellulose sheets works well) over the section to protect the membrane from fingerprints. In some instances, latex gloves maybe required. When printing a thin section (200-300 pm), placing a piece of membrane on top of the section instead of the nonabsorbent paper frequently gives better results. 

Batch latex manufacturing, 14 721 Batch membrane system, 21 638 Batch microcarrier cell culture systems, 5 350, 352-354... 

Bansal, I. K. 1976. Concentration of oily and latex waste waters using ultrafiltration inorganic membranes. Ind. Water Engr. 13(5) 6-11. 

Enzymatically active, partially purified (washed) rubber particles can be isolated such that, when provided with an appropriate APP primer, magnesium ion cofactor, and IPP monomer, rubber is produced in vitro [253-255]. Fresh latex can be separated by centrifugation into three phases. The bottom fraction (20% of the latex) contains membrane-bound organelles. The middle fraction is called the C-serum. The top fraction phase contains the rubber particles. Biochemical smdies have established that latex in this fractionated form is unstable. These smdies also suggest that the bottom fraction is required for initiation of polymer synthesis. 

Other polymer materials which can be prepared include latexes, or particle agglomerates, by dispersed phase polymerisation. These can be either hydrophilic or hydrophobic in nature, or may have core-shell morphologies. They can be employed as support materials for a number of catalyst systems. Polymerisation of both phases of the emulsions produces composite materials, which have found use as selective membranes for the separation of mixtures of liquids with similar physical properties. 

An apparatus lor carrying out a dialysis usually consists of two chambers separated by a semipermeable membrane of parchment paper latex, animal lissue. or oilier colloid. In one chamber the solution is placed, and in Ihc other, the pure solvent. Crystalline substances diffuse from the solution through the membrane and into the solvent much more rapidly than amorphous substances, colloids or large molecules. 

Similar results were obtained in the pervaporation separation of acetic acid-water mixtures using blended polyacrylic acid-nylon 6 membranes [22], poly(4-vinylpyridine-co-aciylonitrile) membranes [11] and in the permeation and separation of aqueous alcohol solutions through PVA-AN-HEMA latex membranes [5],... 

G.H. Hsiue, Y.S. Yang, J.F. Kuo, Permeation and separation of aqueous alcohol solutions through grafted poly(vinyl alcohol) latex membranes, J. Appl. Polym. Sci. 34 (1987) 2187-2196. 

A typical plot illustrating the slow decrease in flux that can result from consolidation of the secondary layer is shown in Figure 6.5 [14], The pure water flux of these membranes is approximately 50 gal/min but, on contact with an electrocoat paint solution containing 10-20% latex, the flux immediately falls to about 10-12 gal/min. This first drop in flux is due to the formation of the gel layer of latex particles on the membrane surface, as shown in Figure 6.4. Thereafter, the flux declines steadily over a 2-week period. This second drop in flux is caused by slow densification of the gel layer under the pressure of the... 

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