{"id":7491,"date":"2017-12-01T08:00:46","date_gmt":"2017-12-01T14:00:46","guid":{"rendered":"https:\/\/www.ulprospector.com\/knowledge\/?p=7491"},"modified":"2021-12-30T09:02:34","modified_gmt":"2021-12-30T15:02:34","slug":"pc-rheology-waterborne-paints","status":"publish","type":"post","link":"https:\/\/ulprospector.ul.com\/7491\/pc-rheology-waterborne-paints\/","title":{"rendered":"Rheology of waterborne paints"},"content":{"rendered":"

Let\u2019s start with a definition: Rheology<\/strong><\/em>\u00a0is the study of flow and deformation of materials under applied forces which is routinely measured using\u00a0various methods.<\/p>\n

More simply put, rheology is part of our daily life, observed in things like yogurt that has fruit suspended or shower gel coming out of a bottle.<\/p>\n

In waterborne paints, rheology is determined only after all the ingredients have been mixed thoroughly into the final product. Your specifications should already be set for your target viscosity.<\/p>\n

At this point, you need to select what type of thickener you need to use. You will start to see which type of thickener and the different shear level required. These methods of incorporation are extremely important as the higher the shear, the more potential foaming issues may have to be addressed.\u00a0 Figure 1 below illustrates four specific attributes that the viscosity of your product addresses.<\/p>\n

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SOURCE: BASF1<\/sup><\/figcaption><\/figure>\n

In the above example, you see the direct relationship that paint rheology has on specific attributes. The thickener selection and chemistry type determine the shear rate needed to incorporate into the paint.<\/p>\n

After you chose your ingredient for viscosity build, levelling and sagging directly affect the final paint\u2019s performance.<\/p>\n

With the newest paint and coating formulations reducing volatile organic compounds (VOC), waterborne paint formulations have become extremely complex. Older versions of many coatings contained a mere five to seven ingredients and were loaded with glycol ethers. That is no longer the case, with zero-VOC paints flooding the market. Chemists must ensure that EVERY ingredient is VOC-free. So today, the chemical manufacturers have modernized additives to meet these requirements.<\/p>\n

So, as you look for solutions to your rheology targets, search UL Prospector for a list of different thickeners and review the traits that each have. Your choice of additives, such as wetting aids, dispersing aids, and the products that address sagging and viscosity consistency, will affect that overall formulation.<\/p>\n

Now, let\u2019s discuss what additives are available and how they affect these flows. Most people refer to these as associative thickeners.<\/p>\n

Rheology modifiers<\/strong><\/h3>\n

Rheology modifiers that thicken by volume exclusion include cellulosic ethers and alkali soluble (or swellable) emulsions (ASE). Cellulosic ethers are nonionic, water soluble polymers derived from natural fibers. They thicken by absorbing water and creating chain entanglement and flocculation.<\/p>\n

There are basically three types that are commonly used in waterborne paints to control overall viscosity and flow. They are:<\/p>\n