Technology Interchange—Sealing the Deal

by Daniel Henry

Product development is the lifeblood of a specialty chemical company like Sika Corporation. As an innovator in elastic bonding, industrial sealing, and acoustic applications for production, assembly, and repair, it must develop new products, new markets, and new products for new markets, without stifling growth. This is the story of how Sika developed its first product, designed specifically for the powder coating industry, to be integrated into the powder coating process.

Sika is probably best known as a specialty chemical company supplying the construction industry with products for concrete, roofing, waterproofing, sealing, and bonding. Sika also has a robust business supplying the automotive industry as well as many industrial manufacturers, but previously had very little experience with products supporting the powder coating industry—until the development of a seam sealer made specifically to aid and enhance the quality and appearance of powder coated products.

It Began with an Idea
Ideas for new products can come from anywhere: customers, sales, marketing, and of course, research and development. While visiting customers, Sika’s regional sales manager based in Fort Worth, TX, saw how many customers were sealing the seams of powder coated products with general sealants after they went through the bake cycle. Most of these customers would do their best to color match the powder coat, but this is difficult; especially if the powder was not black, white, or grey. With this insight, he started advocating for a sealant that could be applied to metal substrates prior to being coated, negating the need to color match, as the sealant would be covered with the powder. This was not readily received as a potential developmental project as it was a new product, probably using a new chemistry, in a new market with which Sika had very little experience. The idea of a high temperature curing seam sealant bounced around for a few years until, in 2019, the sales manager’s persistence paid off and the chemists on the R&D team agreed to start a development project. This kicked off a global development process that took four years, spanned three continents, and utilized a number of highly skilled chemists to bring to market a sealant that can survive the rigors of the powder coating process.

Sika Corporation produces polyurethane adhesives and sealants, as well as silicones, butyls, and epoxies. The challenge for Sika was to develop a product that could be applied prior to being powder coated, and not only withstand the bake cycle, but maintain all the properties of a sealant that would typically be applied after the bake cycle. Most of the chemistries they were familiar with could not survive these harsh conditions.

Dr. Hong Yao became the principal chemist for the development of what was to become SikaSeal®-330. With a career spanning over 30 years with Sika, Dr. Yao has been involved with the development of over 100 products, but this one proved to be one of the most challenging ones. He worked with chemists from Brazil, Switzerland, and the United States to find the ideal chemical technologies to combine to make a product that could survive the powder coating process while maintaining key attributes. When Dr. Yao started the development process, he started with the challenges and concerns associated with exposing a sealant to high temperatures for a long duration.

The primary issue was the thermal stability of the sealant. The sealant must maintain its basic performance and function, such as elasticity and flexibility, even if applied at low temperatures. If the sealant becomes brittle, it will lead to cracking and subsequent leaking from the seam that was sealed. Second, it must be compatible with the powder coatings that will be applied on top of the sealer, and then cure at the same time as the powder when it is baked at temperatures above 350°Fahrenheit. Poor compatibility can cause adhesion failure of the coating to the sealant, the cracking of the coating, or aesthetic inconsistence. In addition, the sealant, when baked at high temperature, should not emit any smoke for environmental and health considerations. Finally, when all the performance criteria are met, the product must be easy to apply, easy to tool, and have good storage stability. Piece of cake, right?

From the beginning of the development cycle, all the required performance and property criteria were used to screen the technology bases that could be used for the backbone of the product. Several technologies were considered as the basic platform for development. The company’s knowledge from sealant chemistries used primarily within the construction industry such as polyurethane, silicon and silane terminated polyurethane, as well as toughened epoxy, PVC plastisol, acrylic plastisol, and their hybrids used in the automotive industry, were very useful for the development. These learnings provided the basics for thermal stability, adhesion, flexibility, storage stability, and many other aspects of a one-component seam sealer.

Breaking Through
The breakthrough came during a meeting in Brazil, where fellow Sika chemist Michael Schlumpf was reviewing potential chemistries that were being used on applications for automotive customers. While not being powder coated, these products had to survive higher temperatures while still maintaining a level of flexibility and elasticity. This enabled Dr. Yao and the R&D team to lay out a roadmap for the base formulation. From there, the team met with colleagues at Sika’s technical center in Switzerland to gain more insight into the chemical technologies that were going to be used in the seam sealer. This proved critical, as the chemists in Switzerland had done extensive work in high temperature environments with epoxies and other technologies. This gave the team necessary insight and additional data to consider in selecting the additional components to give the sealant it’s key characteristics. At the same time, visits were made to a handful of potential customers to gain familiarization with their production processes, applications, substrates, and their need for this product.

Once the backbone of the chemistry was identified and tested, Dr. Yao and his fellow chemist, Carlos Noboa, began the process of creating and perfecting the recipe for the sealant. This process is much like baking bread both in terms of ingredients and process. Begin with a cup of this, add three ounces of that, a pinch of spice, and a “secret ingredient” or two to give the recipe that little extra that makes it better than others. Then the chemist needs to make sure that everything is added at the right times, in the correct sequence, and mixed using the proper process for the exact amount of time. Unlike the recipe you make in your kitchen, this one took a little longer to perfect. In fact, it wasn’t until Sample #17 that the R&D team found a formulation that met all criteria to move to the next step. As Dr. Yao states, “The formulation work is a process of optimization and balance of application properties, performance characteristics, manufacturing feasibility, and the financial impact to our business.” In total, Dr. Yao estimates that over 4,000 hours were spent optimizing the product for commercialization.

Putting it to the Test
Much like a new recipe you try at home, you can’t just assume it tastes great. The Sika product development team now had to go test it out in the real world to make sure it performed as intended, meeting or exceeding the required performance attributes for adhesion, sag, flexibility, elasticity, and in this case, ensuring that powder coatings maintained an electrostatic bond throughout the process. The team turned to customers with whom the company had built strong relationships to conduct field trials and get the necessary feedback from end users to ensure that the product is viable. With the prototype made, the company started those field trials and got feedback, both positive and negative. Using that feedback, the recipe was modified and the process started again. Once the recipe was finalized, the scale up process began as Sika had to prepare a plant trial in the production facility to ensure that the preferred recipe could be produced at a commercial scale.

When asked what the biggest challenge was to overcome in this development, Dr. Yao said, “The true and most difficult challenge is the balancing of all constraints in one product. When one specific product characteristic is addressed, all other essential properties and performance requirements must also be fully met.” Sometimes solving one problem creates another. Through experience, trial and error, and thousands of hours in the lab and at customers’ powder coating operations, Dr. Yao and his team created a product that meets or exceeds all the necessary performance requirements. Sika has now been able to introduce its first product solely intended to support and enhance the powder coating process.

Daniel Henry is the senior market field manager at Sika Corporation.