What kinds of thickeners are commonly used in waterborne polyurethane?

What kinds of thickeners are commonly used in waterborne polyurethane?

2024-03-01 17:36:22
admin

There are four common waterborne polyurethane thickeners:
①Inorganic thickeners, such as flake silicates, fumed silica, etc.;
②Natural organic thickeners, such as cellulose ethers;
③Synthetic organic thickeners, such as polyacrylates, polyvinylpyrrolidone;
④associative thickener. This paper mainly introduces the associated emulsion thickener.
Associative emulsion thickeners are non-ionic synthetic water-soluble polymers, alkali-soluble emulsions and other thickeners with hydrophobic groups. Hydrophobic groups are generally composed of alkyl groups with a carbon atom number of 12 to 22. In view of the association between hydrophobic groups to form a network and thicken, they are called associated thickeners. By adjusting the relative molecular mass of the hydrophobic group or the polymer main chain to thicke, from the inclined flow to the pseudoplastic flow transformation, from the properties of some polymer surfactants found that this has a strong thickening, such rheological characteristics can be freely designed.
The advantages of association thickeners used in waterborne polyurethanes are:
①High thickening effect;
②The flow is closer to the cow inclination fluid;
③The viscosity of low shear rate is relatively low, and the flattening property is good;
④The viscosity of high shear rate is better and the film forming property is good;
⑤It is not easy to form a spatter effect
⑥It will not be degraded by microorganisms.
The disadvantage is that the thickening effect is more sensitive to the formulation of water-based coatings, including the size of latex particles, emulsifiers, additives, and cosolvent types.
The association type thickener has been successfully applied in waterborne polyurethane system for several years, and there are industrial products in China. This association type thickener is dissolved in water/organic solvent (such as propylene glycol) to form polymer solution. Among them, the role of organic solvents is to reduce the viscosity of concentrated solutions and improve operability. However, organic solvents also become part of the VOC in the paint. The new development direction is to make the association thickener solvent-free. The role of the solvent is replaced by a polymeric surfactant that acts as a solubilizer for polymers in water.

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