Overcoming waterborne coating formulation challenges with novel additives

Cynthia Challener reports on the market, current challenges and demand for waterborne coatings in North America

Prior to the COVID-19 pandemic, demand for waterborne coatings in North America was rising at a healthy pace. Due to the impact of the novel coronavirus on nearly all downstream sectors, however, the trajectory of the market for water-based paints and coatings is uncertain at this time. It may not be until a vaccine is developed and widely deployed but demand will return and the key drivers for use of waterborne coatings will once again lead to their growing use: a rising interest in sustainability and the desire to improve human health and air quality by reducing emissions but without compromising on performance.

Sceptical of performance
Water-based paint products have already been widely adopted for decorative application due to their ease of use and ability to beautify. There is a perception, however, that outside of these applications, waterborne coatings do not perform as well as solventborne systems, even though there is ample technical evidence to the contrary, according to Ron Grieb, Application Development Leader for Coating Resins–Americas at Arkema. Monet Talesara, Global Segment Leader for GIF/PC at Dow Coating Materials agrees: “Despite the fact that we have seen waterborne products that exceed the corrosion resistance of their solventborne counterparts, many are still sceptical of applying a waterborne product to a metal substrate in order to increase corrosion resistance.” A lack of experience with waterborne coatings in these applications and a belief that powder coatings offer superior performance and environmental benefits are two reasons for the lack of confidence. “While waterborne coatings do have an extra layer of complexity, that complexity can and is being managed. There really is no downside or upside to waterborne coatings; it depends a great deal on what the paint formulator requires or needs,” states Michael T Venturini, Marketing Director for Coatings at Sun Chemical.

Wider range of applications
In fact, advances in the performance of waterborne coatings are also enabling their use in a wider range of applications traditionally dominated by solventborne coatings, according to Grieb. Dow is starting to see competitive or better performance of waterborne coatings in lighter duty applications, despite the general perception that waterborne coatings haven’t achieved the performance of solvent-based systems, Talesara adds. Progress is also being made on waterborne systems for heavy-duty applications. “As a result, waterborne industrial coatings are quickly picking up traction and beginning to transform the common misconception that they cannot withstand the rigorous performance requirements necessary to compete against their solventborne counterparts,” Grieb observes.

Advances in additive technologies have been important for the development of higher-performing waterborne coatings. The high surface tension of water creates a need for specially designed additives to ensure optimal performance during production and application and by the applied film, according to Petra Lenz, Technical Support Manager for Paint Additives from BYK. Indeed, the physical properties of water make it necessary and challenging to control properties, such as defoaming, flow and levelling, hiding, and mar and block resistance, adds Frank Cangelosi, Vice President of Marketing for Troy Corporation. Additives, particularly multifunctional materials, that overcome surface tension barriers and macro/micro foam formation have enabled water-based coatings to achieve the same performance as solventborne systems. New dispersant technologies, for instance, enable better colour development and even deliver functional properties, such as water resistance, notes Nick Sterne, Marketing Manager for Lubrizol Performance Coatings. Advances in rheology modifiers, meanwhile, enable formulators to develop coatings with performance properties, such as coverage with one coat application, smooth finish and uniform appearance and colour, according to Melanie Bauer, Global Marketing Director for Coatings at Michelman. Rheology modifiers and coalescents based on soya bean and linseed oil derivatives that have zero VOCs and more than 95% renewable content are some examples highlighted by Grieb. He also points to new surfactants based on epoxide chemistry that enable higher performance standards for early water resistance, adhesion, and durability of waterborne coatings and elastomers.

Innovative surfactant replacements

Many new additives are designed to be easier to incorporate, while also improving durability, feel and appearance, adds Sterne. Innovative replacements for APEO/NPEO surfactants that offer improved ease of use over initial generation materials while advancing performance in areas, such as leaching and open time are having a big impact as well, according to Marc Chan, Regional Marketing Manager for Industrial Applications with Clariant. New additive technologies have also been introduced that reduce dirt pick up, providing better anti-fingerprint performance, and imparting ice resistance, particularly for windmills and ACE applications, adds Ruediger Mertsch, Market Segment Automotive/Transportation with Evonik. Advanced wet-state preservatives are also available that do not compromise sustainability standards, Cangelosi says. Dry-film preservation has also advanced with the development of controlled-release, encapsulation technology that offers enhanced resistance to leaching, he adds. Looking out into the future, Eric Fu, Innovation Manager for Waterborne Coatings at Huntsman Advanced Materials, sees exciting developments in additives based on nanomaterials and graphene.

Much work still needs to be done, however. Reducing the costs of overall coating formulations and the environmental impacts of drying, as well as increasing the sustainability of raw materials – particularly through the use of biobased ingredients – are important issues that must be tackled,” Mertsch asserts. The main challenge lies in the use of water. Meeting reduced VOCs and HAPs requirements while still achieving desired attributes with respect to reproducible film formation and adhesion is difficult at low solvent levels. “Coating formulators must rely more on the inherent properties of newly developed waterborne resins and additives to tackle these challenges,” asserts Steven Reinstadtler, Infrastructure Marketing Manager with Covestro LLC.

Author: Cynthia A Challener, PhD, Principal Consultant, C & M Consulting
Email: challener@vtlink.net

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