The Waterborne Symposium 2025

Abstract

Grinding pigments and fillers using cowles dissolver is a standard practice for breaking down agglomerates and aggregates into primary particles during the production of waterborne paints, especially architectural paints. Serrated disc introduced at the appropriate peripheral speed forces a specific flow in the vessel, which causes the agglomerated particles to rub against each other and collide with each other. The wetting and dispersing additive introduced to this process is supposed to build a double electrical layer according to the DVLO theory, but this is only a theory that has little to do with practice. Of course, the theory of wetting, significant zeta potential and other properties of dispersing additives are true, but their correct use in mill-base formulations and further influence on the parameters of the grinding process itself and the parameters of the paints depends solely on the effectively found dose and balance between mill-base concentration allowing grinding at low viscosity and maximum solids loading, without adding any rheology additives during grinding. The paper discusses examples of grinding of various pigments and fillers used in architectural paints and discusses how to properly balance the ingredients and the grinding process to achieve the lowest possible viscosity, low energy consumption and donut-shaped flow, without using rheological additives that prevent proper grinding and breaking down of pigments and fillers into primary particles. It also presents how to properly control the mill-base slurries obtained after the grinding process and how to combine them with latex polymer dispersions in the let-down process to obtain stable architectural paints.

Co-Authors:
Alann O. P. Bragatto, Suzy S. Alves, Bruno S. Dario

Abstract
"The selection of wetting and dispersing agents in pigment concentrate formulations is a non-trivial task. The vast array of available products and technologies, coupled with a frequent lack of adequate technical information, makes the formulator’s job extensive, intricate, time-consuming, and inefficient due the lack of rationalization in the use of these additives. These factors created a barrier to innovative and more sustainable products since the work required to screen new additives became an art instead of a science.
The present study aims to demonstrate how the use, development, and implementation of physicochemical methodologies, combined with digital tools and high throughput screening, can generate highly useful data for formulators in the additive selection and formula optimization process, making it faster, smarter, and more efficient.
The first and most comprehensive part of the work illustrates how physicochemical techniques and parameters applied to surfactants can be utilized in the selection of wetting and dispersing agents. It is demonstrated the correlation between static surface tension, dynamic surface tension, wetting time, contact angle, and free adsorption energy with performance and process properties in pigment concentrate formulations, such as deflocculation curves, process time, tinting strength, rub-out, and stability.
The second part of the work is focused on the development of a method to create adsorption isotherms and on their use. This data is extremely valuable as it allows for comparisons between additives from different technologies even when the chemical structure is unknown. The study demonstrated how the curves and parameters obtained from this technique can help formulators understand which additive has higher affinity for a given pigment, aiding in the selection of dispersing agents with higher potential to provide good performance and longer stability. Additionally, this methodology helped understanding the versatility of the additive, clarifying whether the same molecule could be used with different types of pigments. The results from the adsorption isotherms were correlated with the stability, tinting strength, and rub-out of the pigment concentrates.
The final part of the work aims to apply Hansen solubility parameters (HSP) to evaluate the compatibility of wetting or dispersing agents with pigments. The current focus is on using high throughput screening to determine the HSP values of a variety of wetting and dispersing agents – such as surfactants and polymerics with or without charges. After the parameters of the additives and the pigments of interest are obtained, formulators could use these data to simulate the interaction between the additive and the pigment, enabling the selection of the most promising candidates for experimental evaluation. The last goal of the work is to provide initial data on the HSP parameters determination and compatibility simulations to then correlate with experimental performance data of pigment concentrates, such as tinting strength, rub-out, and stability. Once the correlation is proven, this methodology will allow a quick determination of parameters without requiring knowledge of product’s composition and will aid the development of better coating formulation."

Co-Author: James Rawlins

Abstract

The effective mitigation of corrosion through the application of protective coatings is of paramount importance, impacting both economic and safety outcomes.  Historically, the detection of coating failure and the ensuing corrosion has largely depended on visual inspection and destructive testing methods, which do not adequately predict onset or service lifetimes.  Current methods also lack correlation to specific polymer characteristics that govern corrosion resistance.  This research introduces a novel, nondestructive method that combines Electrochemical Frequency Modulation (EFM) and Confocal Laser Scanning Microscopy (CLSM).  By studying epoxy-amine coatings through a range of tailored glass transition temperatures (Tgs), ranging from high (269 °C) to sub-ambient (4 °C), these research results work contributes to the predictive modeling of coating lifetimes and advances our understanding of the relationship between polymer properties and performance in mitigating corrosion.
Previously, we have shown that the more hydrophilic a crosslinker was, the faster micro-blister formation around a predefined defect occurred.  Micro-blister with delay times varied from 47.5 to 5.5 hours for coatings with increasing hydrophilicity.¹  These results showed that a coating with a Dry Film Thickness (DFT) of 45 μm reduced micro-blistering and exhibited slower corrosion rates compared to the same materials at 5 μm DFT. These results emphasized the role of mechanical beam integrity and corrosion resistance and confirmed that coatings that limit swelling in water and delay physical state changes during immersion were dramatically better at reducing corrosion activity. Example, a coating designed with a high glass transition temperature (Tg) of 269 °C showed less than 3% swelling under all conditions and preserved mechanical properties, including a storage modulus of 2416 MPa, after exposure to corrosive environments. The results indicate that strengthening the mechanical robustness and reduced swelling and physical state changes (such as from glassy to rubbery) for a given coating during exposure are crucial for corrosion control and substrate protection.

Co-Authors: Roger Mouhanna and Laurent Desfontaines

Abstract

Fluoro resins, commonly used in outdoor coatings, offer exceptional weather resistance, durability, and stain resistance. They help maintain the aesthetic appearance of coated surfaces for extended periods, reducing the need for frequent maintenance and repainting.
However, the use of fluoro resins is increasingly regulated due to concerns about PFAS substances. Regulatory bodies have implemented stricter controls on the manufacture, use, and disposal of PFAS, due to their persistence in the environment and the potential health risks. These regulations aim to minimize the release of harmful substances and encourage the development of safer alternatives.
Hybrid resins, combining inorganic polysiloxane with organic acrylic or polyurethane components, offer a compelling alternative to traditional fluoro resins for outdoor coatings. These advanced resins provide superior long-term protection and aesthetic appeal, significantly reducing maintenance costs. Available in various water-based formulations, including 1K and 2K systems, they meet diverse application needs and regulatory requirements, making them a versatile and effective choice for outdoor coatings. In the frame of this work, we will illustrate these benefits with specific examples and case studies, demonstrating the superior performance and compliance of these hybrid resins with current regulations.