Thickener viscosity

There are also hundreds of additives used as process aids to improve such things as air release, cure rate, thickening, viscosity reduction, mold release, wetting and dispersion of fillers, thixotropy, shrinkage and static reduction. 

When describing dilatant behavior, the maximum stretch rate, e, in the converging flow at the contraction is a better parameter, but more difficult to be calculated. Instead of the term stretch rate, other authors also used deformation rate (e.g., Chauveteau, 1981) or elongational rate (e.g.. Sorbic, 1991). The shear-thickening viscosity is also called elongational viscosity (often referred to as the Trouton viscosity Sorbie, 1991) or extensional viscosity in the literature. James and McLaren (1975) reported that for a solution of polyethylene oxide (a flexible coil, water-soluble polymer physically similar to HPAM), the onset of elastic behavior at maximum stretch rates was of the order of 100 s and shear rates of the order of 1000 s. In this instance, the stretch rate is about 10 times lower than the shear rate. However, some authors use shear rate instead of stretch rate in defining the Deborah number—for example, Delshad et al. (2008). 

Greater film build promotes better hiding. Spatter resistance, also a high-shear application property, does not depend on thickener viscosity but does depend on the elasticity of the aqueous phase. Higher molecular weight thickeners are more elastic therefore, lower molecular weights are more resistant to spatter during roll application. 

Irrespective of the free surfactant s effect on the maxima in associative thickener viscosity efficiency, the sum of the maxima in the viscosity of the associative thickener and surfactant and of the latex does not equal the viscosity of the combined components in a coating. A synergistic viscosity increase from an interaction between the thickener and the latex is required to account for the total viscosity observed (26). The most popular mechanism for association is the adsorption of the thickener s hydrophobe(s) on the surface of the latex. 

It is generally known that aqueous solutions of true amphoterics can be difficult to thicken. Viscosity control is best achieved by using either the amphoteric salts or by combining with anionic surfactants. The traditional thickening aids, the alkanolamides, are not particularly effective with amphoterics. Nonionic surfactants offer the best thickening support for amphoteric surfactants, especially those based on fatty acids or alcohols ethoxy-lated with 50-200 moles of ethylene oxide, but like all nonionics, they could exert a foam depressing effect if used at a higher level. When amphoteric surfactants are combined with anionic surfactants, the traditional alkanolamides are effective. The final pH adjustment can also make a difference to the viscosity of the product. 

LCP s often display a range of phenomena not often seen, if at all, with Isotropic polymers. These Include the existence of negative first normal stress difference, regions of shear thickening viscosity, and secondary maxima In transient shear flow [2,19]. 

Oil thickening Viscosity, TAN, TEN, insolubles, glycol, metal, oxidation... 

Due to the highly efficient nature of these polymer types as thickeners, viscosity-based characterisation studies are usually carried out on dilute solutions, typically at a concentration of < 1% polymer in water. Despite the non-Newtonian behaviour of these solutions (which is covered in more detail later in this chapter) useful information reflecting the character of the polymer present in solution can be obtained using cheap, simple and reliable equipment such as glass U-tube viscometers. 

Guar gum has a very wide range of applications and is the most commonly used gum of plant seeds. It is used as a thickener, viscosity modifier and stabiliser of dispersions in foods and beverages. It is used not only in the food industry, but also in the paper industry as a glue, and is often used in cosmetics. 

Chitosan is used as an emulsifier (for margarine) and an emulsion stabiliser (it is added to hamburgers, ice creams and cheeses), thickener (viscosity increases), foam stabiliser, gelling agent, clarification agent for fruit juices and also in the pharmaceutical industry and in cosmetics. 

Traditionally, hydroxy ethyl cellulose was the most commonly used thickener ( viscosity increaser ) for emulsion systems. The cost was low and delayed action grades were easy to incorporate. Very small additions can produce large changes in viscosity. However, the rheology of these solutions is far from Newtonian and can lead to thixotropic final products. Solvents also have a marked effect on the viscosity of hydroxy ethyl cellulose. 

Uses Emollient for creams/lotions, bath care thickener, viscosity control agent, pigment dispersing vehicle for cosmetics, pharmaceuticals Features Food grade material Regulatory Japan listed... 

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