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Organoclays: Additional possibilities offered to formulators thanks to new clay sources

SpecialChem / Dec 24, 2008

Organoclays have long been used as rheological modifiers for solvent and oil based systems requiring pigment suspension and other thixotropic properties associated with the paint and ink markets. The unique properties of organoclays give good film-application thickness to paints with no sagging and good self-levelling to remove brush marks. The rheological profile provided by the clay is developed by hydrogen bonding between hydroxyl groups on the organoclay platelet edges. It can probably best be visualized as a card house structure. To establish the hydrogen bonding, the presence of (molecular) water is necessary for the bridging of hydroxyl groups of adjacent platelets to be able to form the card house structure and provide the typical rheological properties. The hydrogen bonding structure is reversible: it breaks down under shear forces and regenerates in the rest state. This behavior gives organoclays the typical rheological profile. The profile of the organoclay gel structure strongly reduces sedimentation of pigments and extenders while preventing sagging.

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