Viscosity-increasing agents polyvinyl alcohol

Surfactants act as wetting agents by lowering the surface tension of the waterborne epoxy. Silanes can be used to increase adhesion to certain substrates and fillers, as shown in Table 14.4, formulation C. Water-compatible thickeners and protective colloids such as polyvinyl alcohol, substituted cellulosics and sugars, and some acrylics improve application properties and offset viscosity decrease seen with water dilution. 

An efficient suspen.sion also requires a. suspending agent, normally a protective hydrophilic colloid, used in low concentration to avoid significant viscosity increases in the suspension, as compared to that on water. Very viscous vehicles provoke painful injections the same can be said about suspensions formed by too large particles. The most frequently used colloidal protectors are sodium car-boxymethylcellulose, potyvinylpyrrolidine. polyvinyl alcohol, or gelatin. These are all first choice when a new formulation is designed however, for very insoluble panicles like hydrocortisone butyl acetate or prednisolone butyl acetate, sorbitol has proven useful. 

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