Fumed Silica Controls Rheology of Adhesives and Sealants
Rheological properties of liquid polymer systems are of enormous industrial importance. For adhesives and sealants, proper rheological control is an important aspect of their formulation technology. The most common way to control rheological properties of adhesives and sealants is to use so-called “rheological control agents” or “thixotropes” as additives. A number of commercially available thixotropes, such as fumed silica, talc, asbestos, modified bentonite, colloidal silica and certain hydrated magnesium aluminum silicates, can be utilized to impart the desired rheological characteristics for the end-use application.
One of the best and most popular thixotropes is fumed silica.1,2 It has the advantages of being an effective rheological control agent, which will not undergo swelling and which exhibits chemical inertness. This article gives a brief review of the use of fumed silica in adhesives and sealants as thixotropes with emphasis on three areas: basic rheological properties of adhesives and sealants, physical and chemical nature of fumed silica, and the use of fumed silica as thixotrope in general.