Viscosity modifiers

Emulsion Adhesives. The most widely used emulsion-based adhesive is that based upon poly(vinyl acetate)—poly(vinyl alcohol) copolymers formed by free-radical polymerization in an emulsion system. Poly(vinyl alcohol) is typically formed by hydrolysis of the poly(vinyl acetate). The properties of the emulsion are derived from the polymer employed in the polymerization as weU as from the system used to emulsify the polymer in water. The emulsion is stabilized by a combination of a surfactant plus a coUoid protection system. The protective coUoids are similar to those used paint (qv) to stabilize latex. For poly(vinyl acetate), the protective coUoids are isolated from natural gums and ceUulosic resins (carboxymethylceUulose or hydroxyethjdceUulose). The hydroHzed polymer may also be used. The physical properties of the poly(vinyl acetate) polymer can be modified by changing the co-monomer used in the polymerization. Any material which is free-radically active and participates in an emulsion polymerization can be employed. Plasticizers (qv), tackifiers, viscosity modifiers, solvents (added to coalesce the emulsion particles), fillers, humectants, and other materials are often added to the adhesive to meet specifications for the intended appHcation. Because the presence of foam in the bond line could decrease performance of the adhesion joint, agents that control the amount of air entrapped in an adhesive bond must be added. Biocides are also necessary many of the materials that are used to stabilize poly(vinyl acetate) emulsions are natural products. Poly(vinyl acetate) adhesives known as "white glue" or "carpenter s glue" are available under a number of different trade names. AppHcations are found mosdy in the area of adhesion to paper and wood (see Vinyl polymers). 

BASF/Luviskol, KoUidon Cross-hnked stabUizer, crystallization inhibitor, dye scavenger, detoxi-cant, viscosity modifier... 

The product is a mistuie of various polyoxyethylene chain lengths (29—31). Glycol diesters ate used as vinyl plasticizers the monoesters as surface-active agents and viscosity modifiers for alkyd resins (qv). 

Applications Over the last 20 years, ICP-AES has become a widely used elemental analysis tool in many laboratories, which is also used to identify/quantify emulsifiers, contaminants, catalyst residues and other inorganic additives. Although ICP-AES is an accepted method for elemental analysis of lubricating oils (ASTM D 4951), often, unreliable results with errors of up to 20% were observed. It was found that viscosity modifier (VM) polymers interfere with aerosol formation, a critical step in the ICP analysis, thus affecting the sample delivery to the plasma torch [193]. Modifications... 

TDBHI 1,3,5-Tris(3,5-di-f-butyl-4-hydroxybenzyl)isocyanurate VM Viscosity modifier... 

In the case of 2-octanol and cyclohexanol, differences in stereochemistry might be due to a lower hydrogen availability. In the case of cyclohexanol, its high viscosity, modifying the substrate adsorption step on the surface, may also play a role. 

For suspensions of fine particles, or systems containing a significant amount of fines, the suspending fluid can be considered to be homogeneous, with the density and viscosity modified by the presence of the fines. These properties depend primarily on the solids loading of the suspension, which may be described in terms of either the porosity or void fraction (s) or, more commonly, the volume fraction of solids, buoyant force on the particles is due to the difference in density between the solid (ps) and the surrounding suspension (p ), which is... 

Films of PATE were cast on copper plated circuit boards. Typical solutions contain from 8% to 17% PATTE solids and 0.02% Flourad FC 135 surfactant. No other additives, such as adhesion promoters, sensitizers, viscosity modifiers or stabilizers, were employed in the formulations. Films of 0.001 to 0.008 inches wet film thickness were cast on abrasively cleaned circuit boards and then oven dried for 5 minutes at 105 °C. Thus, in each case the... 

Stabaxol P is used normally as a hydrolysis stabilizer in non-food polyester applications. One of the main applications is the stabilization of monofilament. An additional advantage of Stabaxol P is that it also works as a viscosity modifier. Stabaxol P has no FDA approval, and this means that it can be used only for technical applications. 

Displacement injection is usually the preferred method because analyte ions are present in the sample zone in proportion to their concentration in the bulk sample. In addition, injection efficiency is less sensitive to variations in sample ionic strength. However, it should be noted that the presence of high salt can affect detector response and variations in the sample viscosity due to temperature, or the presence of viscosity-modifying components can affect displacement injection efficiency. 

Tannins are polyphenols that occur only in vascular plants such as leaves, needles, barks heartwood, seeds and flowers. Tannins exist primarily in condensed and hydrolysable forms. Natural tannin extracts have been employed since the turn of the last century in leather industry. Recent development of their industrial uses as adhesives, flocculants, depressants, viscosity modifier agents and more recently as corrosion inhibitors reflects their importance as industrial raw materials. Electrochemical studies have shown that tannins extracted from the barks of mangrove trees are excellent corrosion inhibitors of steel at very low pH. The mechanism of inhibition at this pH was due to the chemisorption of tannin molecules while at higher pH, inhibition was achieved via formation of ferric-tannates [6]. 

FIGURE 7.8 Viscosity as a function of molecular weight of a low molecular weight oil (extreme left), high molecular weight oil (extreme right), and of the low molecular weight oil to which an appropriate viscosity modifier has been added (middle). 

FIGURE 7.9 Polymer composition along a single pol5mier chain for the ethylene-propylene copol5mier employed in most motor oils as the viscosity modifier. 

The majority of resins are composed of two dimethacrylate monomers, 2,2 -bis [4(2-hydroxy-3-methacryloyloxypropyloxy)phenyl] propane (Bis-GMA) and triethylene glycol dimethacrylate (TEGDMA) [22-28]. Typically, TEGDMA or other methacrylate monomers are added as viscosity modifiers to Bis-GMA to make the solution less viscous and more appropriate for clinical use. These diluents also allow for better distribution of the components during manufacture of these composite systems. Another common monomer used to make dental composites, especially those manufactured in Europe, is urethane dimethacrylate [24,29, 30], Ethoxy bisphenol A dimethacrylate is another modification of the Bis-GMA monomer that can be used to make a more hydrophobic polymer that would better withstand the wet oral environment. Other diluents include low viscosity diacrylates and dimethacrylates. Table 1 lists some of these monomers [31-37]. 

Poly(vinyl alcohol) is used in films, coatings, fibers, and as a viscosity modifier of a variety of aqueous systems such as certain cosmetics. Its films, formulated with dichromate salts, may be cross-linked by exposure to ultraviolet light. This property has found application in photoengraving and related fields [6],... 

Nanomaterials were used by Zhang et al. (4) as a replacement for polymer-based viscosity modifiers for automotive lubricants. Compared with traditional polymer-based viscosity modifiers, nanomaterials induce a more even viscosity increase across engine operating temperature ranges. In addition, nanomaterials provide a viscosity modifier that exhibits temporary shear loss that can contribute to fuel economy. 

The synthesis of various multi-arm star polymers has long been of growing practical and theoretical interest to a variety of industries. Star polymers have shown to be useful as surfactants, lubricants, rheology modifiers, and viscosity modifiers. Actually, star polymers are considered as viscosity modifiers and oil additives (15). 

Regular PIB may be used as a viscosity modifier, particularly in lube oils, as a thickener, and as a tackifier for plastic films and adhesives. PIB can also be functionalized to produce intermediates for the manufacture of detergents and dispersants for fuels and lube oils (14). 

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