Pigment dispersion stability, both on the shelf and in aqueous coatings, remains a priority for the paint and pigment dispersion manufacturers. Two common measures of pigment dispersion stability are the dispersion’s viscosity over time and color development when mixed in a white base paint. In a recent study with the pigment Phthalo Green (PG7) the E-Sperse® product line demonstrated lower viscosity in pigment dispersions and better color development when introduced to commercial paints than standard dispersants, such as NP9 (nonylphenol + 9 EO) and Disperbyk® 190.
- Viscosity indicates the quality of a pigment dispersion.
The chart below shows the viscosity change measurements 24 hours after making the pigment dispersion and after one week in a 54°C oven. Initially, all viscosities read 433 – 3528 cPs. After one week in the oven viscosities increased dramatically, especially with the Disperbyk® 190 pigment dispersion, which is too high to be measured. Most of the E-Sperse® products maintained 25% of the paste viscosity as the one made with NP9.
- Color development when mixed into a paint reveals the dispersion’s ability to stabilize the pigment particles and its compatibility with the paint.
- Color development is measured by a sheer-stress application. The coating is applied to a coated paper substrate, e.g. a Leneta opacity chart. While the film is still wet, a gloved finger applies shear by rubbing the film in a circular motion. The color difference between the disturbed and non-disturbed dry film surface indicates the extent of the color separation or flocculation. A spectrophotometer determines color difference as expressed by ΔE, a metric for understanding how the human eye perceives color difference. If the ΔE of the non-disturbed surface is greater than the ΔE of the rubbed surface, then the pigment particles are considered stable.
- The color development of the E-Sperse® products in a PG7 pigment dispersion surpass that of NP9 and Disperbyk® 190, when evaluated in two commercial acrylic paints and one commercial styrene-acrylic paint.
- All E-Sperse® products use rates at 100% active and based on the pigment charge are lower than that of NP9. E-Sperse® 1203, 345, and 343 use rates at 100% active and based on the pigment charge are lower than that of Disperbyk® 190, while E-Sperse® 326, 1202, and 1204 are the same recommended use rate as Disperbyk® 190.
Based on the above data, Ethox Chemicals has products within the E-Sperse® product line that can maintain not only a lower viscosity within a paint dispersion over time, but also provide pigment stability once the dispersion is added to a commercial paint.
The E-Sperse® product line is just one of the many technologies coming from the diverse experience of our technical staff, and the reported data is based on our in-house pigment dispersion formulation. In solving new challenges, we leverage our experience to pursue new market opportunities and solve customer problems. Ethox prides itself on developing and optimizing a new dispersant product for a specific customer application. Let us develop something new just for you!
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