Common Types of Thickeners and Their Applications in the Coating Industry

In the coatings industry, thickeners, also known as gelling agents, play an indispensable and key role. Its main function is to increase the viscosity of the paint to ensure that the paint can maintain a uniform suspension state, opacification state, or even form a gel. Thickeners play a key role in paint printing, latex paint manufacturing and other fields, affecting the performance and quality of paint in various ways.

The role and importance of thickeners

In the field of pigment printing, the preparation of printing paste usually includes thickener, water, binder and pigment paste. The shear force generated by the printing machinery will instantly reduce the viscosity of the printing paste. The thickener plays a key role in this process, allowing the viscosity to change with the shear force. This ensures crisp outlines of fabric prints and is an essential component of the printing process.

In latex paint manufacturing, thickeners play a multi-faceted role in coordinating the performance of latex paint. It can act as a colloidal protective agent during latex polymerization and improve the stability of the emulsion. In the dispersion stage of pigments and fillers, thickeners can increase the viscosity of the dispersed material and better disperse the pigments and fillers. In addition, thickeners also improve the stability and freeze-thaw resistance of coatings during storage and transportation, and prevent the deposition and agglomeration of pigments and fillers. During the construction process, it can adjust the viscosity of latex paint, exhibit thixotropy, and affect the fluidity of the paint.

How thickeners work

Thickeners usually achieve thickening and viscosity effects through two principles: physical water absorption and expansion and chemical reaction.

Physical water expansion: This type of thickener is based on the principle of physical water expansion. It expands when absorbing water through its molecular structure, thereby increasing the viscosity of the paint. This swelling agent is widely used in water-based systems and can change the viscosity of the system as water is absorbed.

Chemical Reaction: On the other hand, some thickeners work based on the principle of chemical reaction, connecting molecules in the liquid to each other through specific chemical reactions to form a gel or thickened structure. These thickeners are typically found in high molecular weight polymers and serve a variety of purposes, including maintaining viscosity, improving dispersion and increasing flow.

Common types of thickeners

• Here are some common thickener types:

• Cellulose ethers and their derivatives: including polyanionic cellulose, hydroxyethyl cellulose, methyl hydroxyethyl cellulose, ethyl hydroxyethyl cellulose, etc. By introducing hydrophobic groups, hydrophobic modified cellulose achieves an associative thickening effect and improves the viscosity and stability of the coating.

• Alkali swelling thickeners: include non-associative and associative types. Associative thickeners are water-soluble polymers with hydrophobic groups that can form an association structure in the aqueous polymer solution, thereby increasing the viscosity.

• Polyurethane thickener: It is a non-ionic associative thickener that forms associations through the intramolecular structure to increase the viscosity of the paint and exhibits extremely strong Newtonian flow characteristics.

• Bentonite: It is a common inorganic thickener that works through the principle of physical water absorption and expansion. It quickly absorbs water and expands, increasing the viscosity of the paint and improving the ability to suspend particles.

Thickener selection and application

Selecting the appropriate thickener often depends on the specific requirements of the product, including flow, clarity, viscosity, gelability, and requirements for suspended particles. The amount of thickener used, compatibility with the host ingredients, lack of phase separation, and storage stability are also factors to consider. In the coatings industry, the selection and use of thickeners directly affects the performance and quality of the final product. It is regarded as a key technology in coatings manufacturing and provides solid support for the development of the coatings industry. The research and application of thickeners will continue to promote innovation in the coatings industry and provide more choices and solutions for various coatings.