The paint composition affects the rheology of the paint, and changing the concentration of other solid substances dispersed in the paint can adjust the viscosity, but the adjustment range is limited and the cost is high. The viscosity of coatings is mainly adjusted by thickeners . Commonly used thickeners include: hydroxyethyl cellulose ( HEC ), acrylic acid copolymers and associative polyurethane thickeners.
Hydroxyethyl cellulose is a hydrocolloid that swells in water and can provide for matte paints and thick coatings. Acrylic thickener When the pH value reaches 7 to 8 , polyacrylate will undergo hydration, like hydrocolloid, which will cause swelling effect and give the same rheology of pseudoplastic rheological behavior, For semi-gloss, flat paint. Associative thickeners allow the thickener to interact with the latex to give a rheology that imparts more Newtonian properties.
Bentonite. Bentonite is a flaky structure, and the edge of the flaky structure contains oxygen and hydroxide groups. The flakes dispersed in the paint can form hydrogen bonds with the help of these groups, forming a three-dimensional network , giving the paint a structure viscosity. When the shear rate exists, the hydrogen bond structure is easily destroyed , reducing the viscosity; when the shear is cancelled, the hydrogen bond is restored and the viscosity increases again, which is why bentonite has anti-sedimentation effect.
