Replacing Materials of Concern

Adhesives, sealants, and coatings companies should have a robust protocol in place for determining the optimal replacements for materials of concern.

By Douglas Corrigan, Ph.D., Vice President, ChemQuest Technology Institute

Replacing Materials of Concern

Adhesives, sealants, and coatings companies should have a robust protocol in place for determining the optimal replacements for materials of concern.

Volatile organic compounds (VOCs). Isocyanates. Crystalline silica. Regulations regarding materials of concern are becoming increasingly complex all around the world, and the list of “concerning” materials only continues to grow.

For this reason and others (e.g., supply chain constraints), developing a protocol for materials replacement is a necessity for those operating in the CASE sector. This can be challenging, particularly considering the widespread loss of know-how due to the retirement of experienced personnel or restructuring initiatives.

Case in Point: PFAS

Though PFAS (per- and polyfluoroalkyl substances) have been used extensively in numerous applications for decades, concerns have grown recently regarding their potential long-lasting health and environmental impacts. In addition to their ubiquity in our everyday lives, the term PFAS is used to encompass chemical compounds containing carbon-fluorine bonds that number anywhere between 3,700-14,000 different substances.

The sheer volume and variety make categorizing and evaluating these materials a daunting task (and well beyond the scope of this column). Suffice it to say, increasing global scrutiny will surely lead to additional regulations regarding PFAS use at some point.

The bad reputation PFAS have for being “forever chemicals” is the result of their exceptionally strong carbon-fluorine bond. The stability of that bond makes PFAS difficult to break down chemically, thermally, photochemically, or even biologically. For formulations in the CASE sector, this same strength enables PFAS to impart highly desirable properties, including durability, temperature and chemical resistance, and flame retardancy. Their chemical resistance and durability can be particularly beneficial in caulk formulations, for example.

PFAS also feature quite a low surface energy, which makes them not only hydrophobic (water repelling) but also lipophobic (oil repelling, also known as oleophobic). Adhesive formulations can rely on this omniphobicity in the form of surfactants to help improve wettability.

While we don’t yet know which PFAS compounds will become restricted or even banned (and this is sure to vary depending on geography), proactive work should begin now to investigate potential replacement materials. The question then becomes: Where to start?

The Search Is On

The process of investigating a replacement material is essentially the same whatever your reason for replacement. It could be avoiding a material of concern, mitigating a scarcity issue due to a supply chain shortage, or perhaps offering a bio-based alternative to a traditional petrochemical-based molecule. Once you have a thorough scientific process in place, or access to a trusted third-party partner, you can follow the same procedure across the board.

The first step is to identify the key properties associated with the material to be replaced. Why are you using the material of concern in the first place? Then consider what your product needs to do. What environment does it operate in, and what standards do you need it to meet (e.g., ASTM or ISO)? In the example of PFAS, is it giving your adhesive the wettability mentioned previously? Is it water and oil repellency, or chemical resistance? Is the UV resistance of your PFAS molecule providing weatherability for an outdoor application?

Once those details are determined, the next step is to develop a screening program for alternative materials that exhibit those required properties and can operate effectively in those environments. It’s important to keep the other components of your formula in mind here. What kind of resin are you using? Is it waterborne or solventborne? Are there other components in the system (e.g., additives like pigments or fillers) to be aware of? These materials will likely influence which alternatives will work and which could cause problems down the line.

When looking at alternate materials, keep an open mind. Instead of one single molecule, the optimal solution could be a blend of additives that address various properties depending on what the original material is providing. In other situations, the solution may be a different polymer or resin backbone. An outside perspective can often make a big difference, with third-party expertise identifying previously unfamiliar options and possibilities.

During a scientifically designed screening program and design of experiments, you’ll begin with your original formula and systematically make replacements with the options you’ve identified, testing for the required properties. Let’s say you’ve identified 12 potential replacement materials; this step will help you narrow the field to perhaps three remaining options. A key to accelerating this screening process may be in the development and use of novel test methods that serve as quick proxies to rapidly rule in, or rule out, certain molecules.

To further investigate the final candidates, you’ll generate data to gain a better understanding of the optimal dose of your new material(s). You’ll continue to study, analyze, and compare the options until you determine which material seems to perform the best. With an experienced third-party partner that understands your formula and needs, this process can involve rapid or novel tests that help screen through the formulations more quickly in order to reach the end point faster. Once the ideal formula is identified, ASTM or ISO tests can then be performed to ensure that the final product meets any necessary standards.

Of course, cost is another important factor. In the case of PFAS, for example, their numerous performance benefits often result in a more expensive molecule. However, keep in mind that the ideal replacement material may be something more exotic, or you may need to include multiple new components in your formulation in order to achieve the desired properties.

Consider All the Variables

No matter how rigorous your procedures, there will never be a single, one-size-fits-all solution to material replacement. CASE formulations involve too many variables, particularly when you consider water- or solvent-based formulations, as well as 100% solids. Additives simply work differently in those dissimilar environments.

Whatever material you’re adding to your formula must work effectively with all of the other components. Without a thorough, scientific process in place, it's entirely possible that what you thought was the ideal replacement material actually results in unforeseen consequences to the performance of your formulation. For example, perhaps the new material changes the end product’s flexibility. If this is the case, you may need to explore yet another additive, resin, or curative to solve that new problem.

Innovate with Confidence

Between the need to replace a seemingly never-ending list of materials of concern, the supply chain shortages that plagued the industry over the past several years, and the loss of internal subject matter experts, many R&D teams in the CASE sector are struggling. Developing an internal material replacement protocol or trusting in expertise from a knowledgeable third-party technology development partner results in efficiencies and solutions that loosen that bottleneck, giving companies increasing opportunities to focus on product innovations and the new technologies they need for a much-needed competitive edge.