Aqueous paints viscosity

We therefore have a mechanism that could, at least in principle, exist in drying paint films containing non-spreading antifoam drops. It would clearly mainly concern aqueous paint films on hydrophobic surfaces. However, it would not be confined to oils of low viscosity—the phenomenon occurs in aqueous films even with oils of viscosities as high as 10 mPa s [39], although the effect of the high viscosities of the aqueous phase likely to prevail in drying paint films is not apparently known. 

Emulsion polymerization also has the advantages of good heat transfer and low viscosity, which follow from the presence of the aqueous phase. The resulting aqueous dispersion of polymer is called a latex. The polymer can be subsequently separated from the aqueous portion of the latex or the latter can be used directly in eventual appUcations. For example, in coatings applications-such as paints, paper coatings, floor pohshes-soft polymer particles coalesce into a continuous film with the evaporation of water after the latex has been applied to the substrate. 

The differences in composition between water-borne and solvent-bome air-drying paints necessitate change in driers and drier combinations. Since traditional driers are dissolved in mineral spirits, xylene, or other aUphatic/aromatic solvents, they are not readily dispersed in an aqueous system. If traditional driers are used, they must be dissolved in the vehicle before neutralization, which may result in a severe viscosity increase and processing problems. 

Viscosity of Polymer Solutions. Polymer solutions are very common. Glues, pastes, and paints are just a few examples of commercially available aqueous suspensions of organic macromolecules. Also, recall from Chapter 3 that certain types of polymerization reactions are carried out in solution to assist in heat removal. The resulting polymers are also in solution, and their behavior must be fully understand in order to properly transport them and effect solvent removal, if necessary. 

The binders used for silicone resin emulsion paints [16] are almost exclusively methylsilicone resins, R-SiOsa (R = CH3), in combination with an organic polymer binder. Aqueous silicone resin emulsions predominate. As a solvent-free solution cannot be produced from a solid resin, high-viscosity silanes/siloxanes/silicone resin mixtures are used that differ initially from the solid resin in the degree of polymerization. 

PBT/elastomer blends display a unique combination of high impact strength, dimensional stability due to their non-hygroscopic namre, excellent resistance to automotive fluids such as gasoline, oils, paint solvent, aqueous salt solutions and good heat resistance. In addition, their easy processability (low melt viscosities) lends... 

The most outstanding property of alginic acid is the high viscosity shown by aqueous solutions of its soluble salts even at low concentrations (0.25 to 1.0%), and it is chiefly this property which has made the alginates so important in the food, pharmaceutical, medical, dental, textile, rubber, paint, and paper industries. 

Aqueous viscosity was measured at room temperature with a Brookfield and Ubbelohde viscometer. Intrinsic viscosities were measured by a five-point dilution method no shear-rate corrections were made for the data. Interfacial tension was measured with a DuNouy ring tensiometer against toluene at various polymer concentrations. The formulations used to evaluate the HMHECs for latex paints have been described elsewhere (5). 

In aqueous dispersion media, the preparation of high solids dispersions that are stabilized electrostatically is often fui d by the gel-hke nature of the product. This is a consequence of the interactions between the double layers surrounding each particle. No comparable increase is evident in the viscosity of sterically stabilized dispersions at high solids content. Of course, in certain applications, such as in paints, the rheological properties exhibited by electrostatically stabilized dispersions at high solids may be a decided advantage rather than a drawback. 

Versions which function in aqueous media are also used in automotive refinishing metallic paint to give high viscosity immediately after application to prevent sagging and aluminium flotation. Their use has enabled the development of water-borne car refinishes, which might otherwise only have achieved solvent reduction by the high solids route. 

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