The material selection platform
Coatings Ingredients
The material selection platform
Coatings Ingredients

Using HSP to Improve the Dispersibility of Pigments and Fillers

Sander van Loon & Beverley Fricker – Nov 29, 2018

Improve Dispersibility using HSPThe selection of a suitable dispersant for a filler or an insoluble pigment can be difficult and time-consuming due to both the variety of dispersants and nature/surface treatment of the solid particle.

Discover an effective method as practically implemented by VLCI. This turns the complex selection task into a predictive, data driven test method, by applying Hansen Solubility Parameters (HSP) to your paint, coating or ink formulation.

The validity of this screening process has been proven using the more conventional optimum dispersant concentration (ODC) test methodology.

As you will see in this article, the more HSP data you build up about particles and dispersants, the quicker you can formulate, by screening effective combinations.

Selection of Dispersants: How is it Done in the Industry?

The Most used but Least Efficient Method: Optimum Dispersant Concentration (ODC)

When a suitable dispersant is introduced into a pigment dispersion, there is a dramatic reduction in the viscosity of the paste or slurry, as the particles become more mobilized in the solvent (usually water). As the dispersant is gradually added into the slurry under mixing, there can be a fairly rapid decrease in the viscosity, which is visually seen as a larger vortex develops.

So, one dispersant is added to the slurry and then its effect on the viscosity is tested. Then repeat with the next dispersant, and the next dispersant, until you have tested a wide range of commercial grades. With so many dispersants and filler combinations to choose from, combining them drop wise in the slurry, wastes a lot of time and material.

An Improved Method Available to All

dispersant selection processIn a tutorial by Jochum Beetsma, we show how to rationalize your dispersant selection process by starting with looking at Technical Datasheets and limiting your compatibility study to candidates that have matching characteristics.

This method will allow you to work with fewer candidates, and to start with an estimation of the loading needed.

Watch tutorial now!

Using Hansen Solubility Parameters

Predictive Selections Using HSP

This selection method is based on the use of Hansen Solubility Parameters (HSP) to get accurate predictions of the compatibility between solid particles & dispersants, as well as between dispersants and solvents. The goal is to take into consideration the chemical and physical characteristics of particles and dispersants, to predict the relative compatibilities of particle-dispersant combinations.

To learn more about the theory behind HSP see Professor Steven Abbott's tutorial.

 » Continue reading to understand how to save time using HSP to determine suitable dispersant for your coating formualtion! 

2 Comments on "Using HSP to Improve the Dispersibility of Pigments and Fillers"
Sander van L Apr 25, 2016
Thanks, Titus! Indeed, these are dispersants for waterbased applications and even their HSP is determined when in water. This makes it practical for their use in waterbased formulations such as coatings. HSP gives you guidelines to a much smaller area to test, compared to when just performing the same with trial and error. But indeed, not everything can be taken into account, so practical tests always needs to be done! Same approach works for the carbon black indeed (mentioned in the HSPiP book) and might be more challenging, but the process is more or less the same. Hope this helps!
Titus S Apr 22, 2016
Nice work, though it leaves out some important points for practical applications. This makes it of course much simpler for start and introduction of the concept, which is well done. An obvious problem is and hard to believe that dispersant efficiency should be independent on continuous phase (water or a specific solvent(composition). Continuous phase did not played any role in the sketched selection process. Seemed to work well for water because dispersants tested likely are products developed for aqueous media. It is easy to compute HSP's for dispersant mixtures, however, due to preferential adsorption this approach will likely fail if dispersants differ much in composition and structure. In case of pigments like talc, process of dispersion and input of energy will be of second order and the effect of stabilization by dispersants is easily modeled. For pigments highly agglomerated and aggregated (e.g. carbon black, aerosil) situation is much more complex.

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