Classification of thickeners used in architectural coatings
Thickeners can be classified in many different ways, including organic and inorganic according to biological properties, natural and synthetic according to production methods, swelling/dissolution and association type according to silk thickening methods. The commonly used thickeners for architectural coatings include HEUR (such as PU), HASE (ASE), HEC (HMEC), inorganic bentonite, attapulgite, etc.
Characteristics of various thickeners:
Polyamide ester or HEUR thickener, non-ionic type, has the characteristics of surfactant, and water, cosolvent and surfactant have great influence on the thickening effect. Splash resistance, good leveling, improve the film fullness; Good scrub resistance, alkali resistance, thickened emulsion paint is uniform and non-flocculating, this non-flocculating coating has luster potential, and the coating film formed by non-flocculating coating is compact, good penetration resistance and corrosion resistance; It is insensitive to electrolyte and has no biodegradation.
Alkali-soluble or alkali-swelling HASE (ASE) thickener: anionic thickener, sensitive to pH, thickened latex paint is a flocculating non-uniform system, with matt potential. Water resistance, alkali resistance and corrosion resistance are not good. They are sensitive to electrolytes and have no biodegradation.
Cellulose HEC (HMEC): non-ionic type, insensitive to pH, thickened latex paint is a non-homogeneous system with flocculation, matt potential and biodegradation.
Inorganic: Bentonite has great thixotropy, and has little effect on medium and high shear viscosity compared with alkali soluble or alkali swelling type and cellulose.
Formulation selection, coating with different decorative effects has different requirements for convexity:
In mercerizing, semi-gloss and high-gloss coatings, HEUR with luster potential is selected to avoid the use of a large amount of cellulose and other thickeners with flocculating properties to reduce the gloss and limit the improvement of PVC.
For the system with fine particle size, high lotion and high pigment, the thickener with Newtonian thickening curve shall be selected, and the thickener with low and medium shear viscosity shall be avoided.
Strong thixotropic roughening coating is selected with strong thixotropic thickener.
