coating rheological property solution
coating can be divided into water-based paint and solvent based coatings according to performance. water-based paint use water as solvent or dispersion medium, including water-soluble coating, water dilutability coating and water dispersibility (latex paint). solvent-based coating uses organic solvent as dispersion medium.
coating rheological property is mainly embodied in the storage stability and coating properties. the additives can improve coating rheological properties are all called rheological modifier, also known as rheological agent. the main function of rheological agent in coatings is to prevent the sedimentation of filler and pigment in the process of storage, packing, and to avoid paint from splashing down during coating process, improve leveling properties of the coating, etc.
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commonly used rheology modifiers coating types: (1) bentonite (2) fumed silica (3) polyvinyl alcohol, polyamide wax type of organic polymer.
coating rheology modifiers-bentonite has two categories: organic bentonite and water-based bentonite (inorganic gel)
organic bentonite: special rheology modifiers used in solvent based coating system.
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water-based bentonite (inorganic gel): special rheology modifiers used in water-based coating system.
mechanism of bentonite in coating: organic bentonite swelling, scattering, stripping to form "card room" type irregular interpenetrating network structure in solvent , and wrap up the solvent, fillers within the network structure to prevent the sedimentation of fillers, which has a good storage stability and thickening property. "network structure" forming by organic bentonite in the solvent, the "node" is connected with electrostatic interaction between each other with weak force. "network structure" can be rapidly damaged under the weak intensity external force, showing obvious shear dilution properties, which is good for coating. after the external force is disappeared, “net structure” of organic bentonite can be rapidly formed under the action of hydrogen bond interaction, which plays a good coating sagging prevention performance.
