As a major producer of general-purpose and specialty adhesives, LORD Corporation has been at the forefront of many industry trends. This is especially true for the solar power industry, which was just coming into play when LORD became involved with supplying adhesives for the first solar-electric generating plant (Solar One) in California in the early 80s. Not only was the solar power installation innovative for its time, so were the adhesives used to assemble the solar generating equipment. Since then, LORD has pioneered adhesive technology advancements and is now one the foremost suppliers of adhesive solutions to the solar power marketplace.

In this interview, Dennis Howard, a retired synthetic polymer chemist, discusses the development of polymeric adhesives at LORD and their use in the burgeoning solar industry in the 1980s. Dave Pugne, manager of Structural Adhesives Technology at LORD, brings us up-to-date on the advances LORD has made in adhesive technology for the solar power industry.

What developments in materials were taking place 30 years ago that warranted similar innovations in adhesives?
Dennis Howard: Back then, more and more manufactured assemblies were using new plastic materials that were emerging at the time. Many of these assemblies required the bonding of plastics to metals, and we were working on developing adhesives that could bond dissimilar materials, besides adhering metals-to-metals and plastics-to-plastics. The adhesive had to be so versatile that it could bond a metallic material to a plastic material.

Describe the development of these new polymeric adhesives at LORD.
Howard: At the time, these adhesives were very innovative. We were at the forefront of new polymer development. In our R&D labs, we were not just buying stock components and mixing them together; we were involved in creating new polymeric materials to formulate these adhesives. It is more difficult to develop an adhesive that sticks to plastic on one surface and metal on another surface—but our line of Versilok® adhesives was able to do that—while also bonding metal-to-metal and plastic-to-plastic.

LORD Versilok 204 and 506 structural adhesives were used to fabricate portions of Solar One, the first solar-electric generating plant in the United States.

The solar industry was also just beginning to develop at that time. What was the solar industry looking for in an adhesive?
Howard: Solar panels are often made of dissimilar materials—metal components and plastic components. Solar assemblies need to withstand harsh environmental conditions (rain, wind, sand) and excessive temperature ranges (panels get cold at night, extremely hot during the day, and cold again at night). The solar industry was looking for an adhesive that could meet these criteria—and Versilok adhesives seemed to be a natural application for the solar market.

So, at LORD, you were developing adhesives that were a perfect fit for the solar industry.
Howard: Yes, we were creating new polymer materials that could be used in formulating adhesives that were also very stable against degradation due to water and moisture. This new class of polymeric materials remained flexible at low temperatures but did not decompose at high temperatures and therefore, would be useful over a very wide temperature range. In developing Versilok adhesives, proprietary components enabled the formulation to provide extremely good adhesion to metal and plastic.

How have structural adhesives evolved since the 80s?
Dave Pugne: Most of the racking systems used in today’s solar installations are made of aluminum and are either bonded or mechanically fastened to other substrates to build an assembly. The solar industry is looking for methods to help them decrease maintenance costs, while improving durability and increasing product life expectancy. A new generation of acrylic adhesives, Maxlok™ adhesives, replaces welding, brazing, riveting and other mechanical fastening methods and can be used in a wide range of temperature environments subject to high impact or high peel loads. They are designed to bond a wide variety of unprepared metals and dissimilar substrates, with minimal preparation.

Did the new polymeric adhesives find applications in other industries?
Howard: LORD embarked on developing a new class of adhesives because manufacturers were not happy with what was currently available. Versilok adhesives found acceptance in many industries, including the automotive market and personal recreational vehicles such as watercraft, snowmobiles and jet skis. It then became apparent that these adhesives would be useful for the manufacture and installation of solar equipment, considering their ability to withstand harsh environments.

Did the Versilok adhesives gain wide acceptance in the solar industry?
Howard: The adhesives became very popular in the solar industry, especially because of their versatility. They could be used in the manufacture of solar equipment and in the field to assemble the equipment for installation. Because many of the solar assemblies are large and flat, portions of them are fabricated in the shop, but the actual installation required some assembly of the various components in the field. The adhesives are very easy to use in the manufacturing environment to produce components and are easy to apply at the job site. Not only could you use Versilok to fabricate the sub-assembly, but you could take that same adhesive and do the final assembly in the field.

How did adhesives keep weight down and lower production costs in solar manufacturing?
Howard: Adhesives are an ideal substitute for mechanical fasteners or welding. With these other production methods, you still need a sealant or gasket to seal joints and prevent contaminants, such as dirt, sand and oils, from entering the solar assembly. Adhesives “took off the table” the requirement for any type of sealant or gasket because the adhesive became its own sealant or gasket.

Pugne: Bonding solar panels to the racking system eliminates the need for numerous fasteners. Adhesives also reduce stress points by evenly distributing weight across the entire frame. For example, the bolts in the panels will eventually, over time, begin to work themselves loose due to extreme outdoor conditions such as wind and rain. Adhesives eliminate this problem. You no longer need to have maintenance personnel go into the field for regular check-ups, or to replace or tighten fasteners. Mechanical fasteners are also prone to rusting, while the adhesives are formulated to withstand wind, rain, dirt, sand and salt spray. Installation and construction time is a lot quicker too, compared to labor-intensive operations such as welding. The weight of the racking system is reduced when mechanical fasteners are eliminated. All of these advantages translate into cost savings whether it’s inventory costs, labor costs or production costs.

Were there other advantages to using Versilok adhesives?
Howard: One important aspect of Versilok adhesives was that it did not take a lot of adhesive to form a very strong bond. Only a very thin layer of adhesive is needed to impart a watertight seal. The fact that you need less adhesive to provide a durable bond is a definitely a cost-saving consideration. And the watertight seal goes beyond just “being watertight”—water will not degrade the adhesive either. Even to this day, those polymeric materials have stood the test of time and are still useful in creating new adhesive products.

For the Solar One installation, LORD Versilok adhesives provided a strong bond that was able to withstand harsh, hot environments.

How is the new generation of adhesives different from earlier formulations?
Pugne: The LORD line of metal-bonding adhesives are now formulated to provide the end user with higher degrees of impact and peel strength, increased shelf life, low tack surfaces, and re-mate-ability properties. These new adhesives feature glass-bead technology to insure exact bond-line thickness. Tiny glass beads (only 0.01 in. in diameter), imbedded throughout the adhesive formulation, guarantee that optimum bond-line thickness is achieved when two parts are mated together. The glass beads act like spacers in the bond line to keep the bond-line thickness from varying.

Other areas where these adhesives excel are in application and cure times. The adhesives are easily dispensed, in the manufacturing plant or out in the field, from side-by-side cartridges with a mix ratio of 4:1. A variety of cure times allows the user to choose the adhesive that meets their applications needs. There are formulations that cure very quickly in 3 or 6 minutes to those that are “open” a bit longer, up to 18 minutes.

What is the connection between LORD and Hughson Chemicals, the supplier of adhesives to the Solar One installation?
Howard: LORD Corporation began as LORD Manufacturing back in the 1920s. At that time, the company made mostly rubber-to-metal bonded assemblies such as motor mounts and vibration control equipment. The company was not happy with the adhesives they were getting from their supplier, and were looking for better performing products. LORD embarked on developing a new class of adhesives, and created a new company, Hughson Chemicals, in the late 1950s. The new adhesives were sold under the Hughson Chemicals name until the two divisions were merged in the 1990s.

How did LORD (Hughson Chemicals) become involved with the solar-electric generating plant in the early 80s?
Howard: A major subcontractor for the Solar One installation was awarded a contract to provide 1,800 heliostats for the first solar-electric generating plant in the United States near Barstow, California. They were looking for ways to make solar power cost competitive with fossil-fuel plants and to find the types of materials that would meet the demands of solar energy technology. The company knew that adhesives would be a cost-effective solution, but they needed a formulation that could withstand the ultraviolet effects from the sun. Versilok acrylic structural adhesives were able to not only provide the ultraviolet resistance they required, they also kept weight down, decreased production costs, provided a watertight seal, and imparted structural strength.

Which adhesives were used in the assembly of the solar power equipment?
Howard: For the heliostat mirror modules, Versilok 204 was used to bond the corner clips, the channels and the module support doublers. Versilok 506 was used to bond the special ABS plastic housings to the acrylic Fresnel lenses in the photovoltaic assemblies. Both these applications required an adhesive that could not only deliver a strong bond, but could also act as a sealant and withstand harsh, hot environments.

When the installation was dismantled 30-years later, what did the contractor discover?
Pugne: In 2009, the government decommissioned the Solar One installation and the solar panels had to be replaced. In dismantling the heliostat, the adhesives were found to be intact after almost 30-years of installation. The adhesive bonds had not been compromised, standing up to ultraviolet rays and providing a watertight seal that prevented corrosion for the life of the equipment.

What is the growth potential for structural adhesives in the solar industry?
Pugne: Adhesives will gain more market acceptance, as solar panel manufacturers begin to understand the benefits of replacing mechanical fasteners with adhesives and become more confident with using a chemical method of joining, especially for aluminum racking systems.

How will new types of structural adhesives meet the needs of the solar industry as it continues to develop?
Pugne: Within the thin-film market, adhesives will provide protection against moisture and oxygen. Other opportunities exist in the attachment of thin-film materials to various substrates with no loss of durability or additional hardware required. With more than 60 years of experience designing and developing adhesives to satisfy a wide variety of applications, LORD will continue to develop innovative adhesives to meet the ever-changing requirements of the solar industry.