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Water-based coating, paint, and ink formulators must optimize for many performance aspects based on application, including adhesion, leveling, abrasion resistance, gloss, and more. Among these, one aspect governs commercial viability in practically every case, regardless of the end application: storage stability. A paint, coating, or ink formulation that does not exhibit adequate storage stability based on the required time or temperature will be unusable for the end customer, despite the other optimized conditions. |
Most types of coatings, paints, and inks used for decorative and informational purposes use pigments to display an aesthetic or information on materials. Compared to the rest of the contents in a formulation, pigments are extremely large particles with a higher propensity to settle under gravity and agglomerate together. When this happens, an uneven appearance will result, and surface defects may arise on the material to which paints, coatings, or inks are applied.
In general, a few factors govern the settling of particles in liquids: the rheology of the continuous phase, the density of the particles, and the size of the particles. Given that the density and size of a chosen pigment cannot be changed, a rheology-modifying, stabilizing agent must be used in coating and ink formulations to adjust viscosity and provide resistance against sedimentation.
SeaSpen® IN Rheology Modifiers and Stabilizing Agents for Coatings, Paints, and Inks
There are three main reasons why
SeaSpen® IN is the ideal rheology modifier and stabilizing agent to provide long-term stability and performance in water-based coatings and inks. These are presented below.
1. Sustainability and Ease of Use
SeaSpen® IN is a natural rheology modifier and stabilizing agent based on iota-carrageenan harvested from sustainable red seaweed farms. It is a biodegradable material designed to be easily solubilized in cold water, simplifying blending processes and making it compatible with all types of water-based systems, even beyond coatings, paints, and inks. Besides the sustainability and workability improvements SeaSpen® IN provides, there are also significant functional improvements to consider.
2. Excellent Stabilization of Pigments at Low Use Rates
One of the most common pigments in paint and coating formulations is titanium dioxide (TiO2), prized for its brightness and high refractive index. However, TiO2 is insoluble in water and extremely dense at approximately 4 g/cm3. Therefore, it presents a significant stability challenge.
SeaSpen® IN was evaluated for its ability to provide long-term stability for a TiO2 dispersion by preparing samples with and without minimal content (0.15 wt%) of SeaSpen® IN. An accelerated stability test was conducted, where the samples were stored in containers and aged for two weeks at 54°C. After two weeks, the samples were compared for visual settling analysis and flow characteristics by inverting the containers.
As seen above on the left, the TiO2 dispersion without SeaSpen® IN resulted in significant settling and caking, where a large crust of pigment developed at the bottom of the container that could not be mixed back into the dispersion. The sample containing SeaSpen® IN on the right did not exhibit separation and maintained free-flowing characteristics, demonstrating that the uniformity and fineness of the dispersion were preserved.
In tandem, a quantitative analysis was made using a Turbiscan LAB stability analyzer, where the two samples were evaluated at 25°C. In this test, a lower Turbiscan Stability Index (TSI) indicates better long-term stability.
Since only a minimal increase of TSI resulted, it is clear that SeaSpen® IN dramatically increased stability and did so at very low use levels.
3. Shear-Thinning Rheology
The basis by which SeaSpen® IN functions as a stabilizing agent is the ability of its carrageenan polymer to form a three-dimensional matrix. This matrix provides associative thickening that viscosifies water-based formulations.
At low or no shear, SeaSpen® IN imparts high viscosity to formulations and its three-dimensional matrix helps suspend particles, such as pigments, fillers, and other large solid particle ingredients, so they do not agglomerate or settle. At high shear, the system rapidly loses viscosity. When the shear is removed, the system rapidly reforms the polymer matrix and recovers its viscosity. This property, referred to as shear-thinning, is important for paint and coating applications. Lower viscosities are necessary to allow good spreadability and leveling onto substrates when paints and coatings are subjected to high shear while being applied. Higher viscosities are necessary after the paint or coating has been applied to prevent dripping and sagging, which is especially important on vertical or overhead surfaces.
A three-interval thixotropy test was conducted on the TiO2 samples below to demonstrate the thixotropic effect of SeaSpen® IN for paint applications.
At 0.15%, SeaSpen® IN provided a significant decrease in viscosity at high shear, which is important to achieve smooth application in paints. When shear was removed, the sample quickly recovered at nearly the same viscosity prior to shear. This demonstrates that a shear-thinning and thixotropic rheology can be achieved using SeaSpen® IN at an extremely low use level.
Summary
SeaSpen® IN is one of the most sustainable rheology modifiers and stabilizing agents available that water-based coating and ink formulators can incorporate to gain excellent long-term stability. Made using carrageenan sourced from renewable seaweed farms, SeaSpen® IN is natural, biodegradable, and extremely effective at very low use rates to thicken solutions, prevent the settling of pigments, and provide shear-thinning rheology. Click below to request a sample or more information on SeaSpen® IN.
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