Viscosity modifier effect

Tragacanth is widely used as a natural emulsifier in conjunction with acacia and is an effective viscosity modifier for suspension formulations. It contains a variety of methoxylated acids that upon contact with water become a gel. At around pH 5, it renders the maximum stable viscosity due to aging even though the maximum viscosity occurs at pH 8 with the freshly prepared solution. 

Gressel and Roehrs reported viscosity modifiers for enhancing intended effects on an ocular surface. A polyacrylic polymer was used to increase viscosity to a gel consistency and thereby enhancing the treatment of symptoms for dry eyes. Sullivan reported efficacy of carbomer gel in improving the number of subjective and objective symptoms of moderate-to-severe dry eye syndromes. Such a gel vehicle offered an advantage of reducing frequency of instillation and has resulted in a commercial product (Pilopine HS Gel). 

Piston deposit formation is strongly influenced by the type of base oil used and also by the selection and content of viscosity modifier. Detergent and dispersant selection also have significant effects on reducing the formation of piston deposits. 

Reduced detergent levels can be supplemented by adding ashless dispersants to deliver the necessary piston cleanliness. But the dispersant s high contribution to viscosity means that compromises have to be made elsewhere in the formulation. Dispersants, for example, have a detrimental effect on fuel economy and may lead to restricted choices of basestock and viscosity modifier to meet viscometric requirements. Furthermore, the high active nitrogen content that makes dispersants effective can also cause problems with elastomer compatibility. 

Fatty alkanolamides are mainly used as foam stabilizers, but they can also have a large effect on the viscosity of an LDLD formulation, usually increasing it. Other viscosity modifiers include hydrotropes such as alcohol, SXS, SCS, urea, and water-soluble polymers. However, not all of these have the same magnitude of effect, which depends on the surfactant system in the product. 

Many liquid detergent products contain components that serve as product viscosity modifiers, added to achieve the desired consistency of the commercial product. Cellulosic polymers, for instance, are an excellent example of such an additive and various polysaccharides are capable of gelation under specific thermal conditions. In such cases, heat transfer during manufacture may be required to complete hydration and effect the necessary conformational change in the select polymer system [85], in the appropriate aqueous environment. Products requiring controlled heat transfer processes may include various dental creams, shampoos, built liquid detergents, and hard surface cleaners. 

Additives such as antioxidants and stabilizers are technical mixtures of numerous chemical compounds, which in addition to the effective substance also bring along solvents and sometimes processing residues, all of which are potential emission sources in the flooring material. In the late 1980s PVC flooring materials contained plasticizers in which the proportion of VOCs was up to 29 %, viscosity modifiers (up to 100 % VOCs), and stabilizers (up to 54 %) (Saarela, 1989). 

Bansal, J. G. and McElroy, F. C., Accurate Elemental Analysis of Multigrade Lubricating Oils by ICP Method, Effect of Viscosity Modifiers, SAE Technical paper 932694,1993. 

Stabilizers to maintain the dispersion by different phenomena such as steric repulsion, electrostatic interactions, viscosity, gelling effects (polyolosides, pectins, modified starches, gums, etc.). 

Table 6.11 Effect of two various viscosity modifying agents on the properties of SCC [409]...

Kronecker symbol energy dissipation rate volume fraction of gas phase volume fraction of liquid phase tangential coordinate specific growth rate dynamic viscosity modified dynamic viscosity effective viscosity laminar viscosity turbulent viscosity mixing time density... 

Jain, P. K., Hemalatha, C. Y., Sundarrajan, S., Girija, N., and Sarma, A. S. (2000). Effect of base oil characterization on shear stability of viscosity modifiers. 2nd International Symposium on Fuels and Lubricants, New Delhi. 

In the low conversion regime, considerable effort has been made to study the dependence of the free-radical termination rate coefficient (or the total polymerization rate) on the solution viscosity [e.g. 40, 61-85]. To study this effect, two basic approaches have been carried out. The viscosity can either be varied using different solvents with inherently different viscosities or, alternatively, various amounts of polymer can be dissolved as viscosity modifier. Although the effects of both methods upon the variation of kt can turn out to be quite different, the former method (variation of the type of solvent) is hard to separate from the latter one (variation of the amount of dissolved polymer) in experimental studies, as some conversion must always be tolerated to obtain kinetic parameters. The number of studies on this topic is rather large and therefore only a limited number with typical examples will be discussed. 

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