Synergistic viscosity increase

It was reported that most cations increase the viscosity and most of anions decrease the viscosity of povidone K 90 solutions [530]. Some polymers such as carragheenan show a synergistic viscosity increasing effect with the high-molecular povidone K 90. 

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. 

When xanthan gum is combined with guar gum, a synergistic viscosity increase occurs (Fig. 6). As can be seen, the viscosity of a mixture of xanthan gum and guar gum has a higher viscosity than expected, especially at a ratio of approximately equal parts of guar and xanthan gum. (12)... 

A synergistic viscosity increase is observed with a solution containing HPC and anionic polymers such as CMC and alginate. On the other hand a lower than expected viscosity is observed with a solution containing HPC and nonionic polymers such as HEC, MC, and guar gum. 

Guar gum is soluble in water giving highly viscous solutions stable in the pH range 4-10. Gel is formed in the presence of small amounts of borates. Guar gum can be combined with almost all natural gums, starches, pectins, cellulose and its derivatives and very often is combined with xanthan gum, which increases (as a synergist) viscosity of dispersions. 

DSC revealed that the XG and starch did not interact synergistically and hence did not promote the formation of three-dimensional network structures. However, the hydrocolloid significantly decreased the retrogradation and syneresis of the starch paste, particularly in blends with a starch/XG ratio of 8.5/1.5. Mixing 1% or 2% tamarind XG with 9% cornstarch resulted in an increase in the paste viscosity from 385 to 460 and 560 BU (Brabender units), respectively [298]. The XG is associated with starch, as was evident from the lowering of the pasting temperature and the synergistic increase in pseudoplasticity and yield value of the blend pastes. However, carboxymethylated and hydroxypropylated XGs showed a diminished interaction. 

Blends of starch and konjac gum (Tye, 1991) and of some modified celluloses (Hercules, Inc., 1980) are synergistic. A ternary dispersion of 1% methylcellulose and 2.9% starch had almost 2.5 times the viscosity of a blend of 0.5% methylcellulose and 2.9% starch, and approximately 20 times the viscosity of 3.9% starch (Hegenbart, 1989). Methylcellulose-starch viscosity synergism was suggested as a formula to decrease caloric content (Henderson, 1989). Guar gum can increase starch paste viscosity tenfold (Christianson et al., 1981). 

Starch is also of interest because it is reported to increase the viscosity of caseinate solutions in a synergistic manner, especially at caseinate concentrations > 10% (Platt, 1988). The increase in viscosity was thought not to be due to any chemical interaction (Jones and Wilson, 1976) but rather to the increase in the swelling volume of the starch (Lelievre and Husbands, 1989). 

One of the means used to modify monomers and polyester acrylates further is to amine modify them. This is normally done using a Michael addition reaction between the acrylate and an amine. The benefits of amine modification are normally seen with increased cure speed since this will tend to overcome the effects of oxygen inhibition in the cure process. Amine oligomers and synergists can also be low viscosity and give improved flexibility to a film. One disadvantage of these materials maybe that perhaps they do not possess the stability required of UV inkjet ink formulations. They are also very prone to yellowing and are unstable with some forms of adhesion promoters. 

The viscosities of solutions of xanthan, unlike those of all other water-soluble polymers, do not decrease as the temperature is raised. They are unaffected by temperature between 0 °C and 100 °C. And even though it is an anionic polymer, its solution viscosity is not affected by pH or most salts, i. e., although ionic, it behaves as if it were a neutral gum. Xanthan interacts synergistically with guar gum and locust bean gum (both galactomannans) (O Sect. 4.2). An increase in solution viscosity results from its interaction with guar gum. Heat-reversible gelation results from its interaction with locust bean gum. 

The viscosity of xanthan gum solutions is increased in the presence of ceratonia. This interaction is used synergistically in controlled-release drug delivery systems. 

U.S. Patent 5,798,324 discloses a glass cleaner containing a synthetic polymer thickener in the presence of certain glycol ethers, nonionic surfactants, and linear alcohols that increases viscosity synergistically. Cited compositions exhibit optimal vertical cling and ease of use. 

There are also specific effects due to the particular properties of certain stabilizers. For example, some stabilizers can retard ice crystal growth during storage (Chapter 7). Finally, there are synergistic effects, which arise from the combination of two stabilizers, for example, greater increases in viscosity than would be expected from either component individually, or gelation, when the separate components do not gel. 

---