Thixotropy: increasing with silica

Because most latices have low viscosities by compounding, most of the waterborne rubber adhesives are sprayable. Thickeners such as fumed silicas can be added to increase viscosity and thixotropy. This means that even at relatively large viscosities (over 10 Pas) many water-based rubber adhesives can be sprayed. Dip and curtain applications require viscosities between 0.05 and 0.3 Pas, whereas brush application works with viscosities between 1 and 50 Pa s. 

The decrease in viscosity of conductive adhesives with increased shear rate is a time-dependent property, known as shear-thinning or thixotropy. Some fillers, in particular silica particles, exert an effect that enhances the thixotropy already provided by many silver flake varieties. The metal and inorganic particles dispersed in the organic resin affect the rheological properties by their nature, size and shape, thus allowing the desired thixotropy to be engineered. 

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