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Sealing Solutions and Material Compatibility

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Doug Sharpe

President of Elasto Proxy

How safe are the sidewalks in your city? If you’re concerned about cracked cement at your feet, you may want to look skyward instead. No, don’t look at the clouds. Instead, examine the windows on the high-rise office buildings. In mid-town Manhattan recently, three pedestrians were injured when a glass window fell from the side of a 34-story structure. During interior renovations, a construction worker accidentally struck the window with a piece of equipment, causing the glass to dislodge.

Material scientists know a lot about glass, but you don’t have to be an expert to know that it can crack and break. Just ask the tourists who stepped onto The Ledge, a glass observation deck high above Chicago. When a thin layer of “sacrificial glass” cracked, the surface resembled a car’s windshield after an accident. Experts debate whether the tourists were really at risk, but that’s small consolation to the Jaguar owner whose car “melted” because of reflected sunlight from a London office building.

Rubber, Glass, and Metal

Glass may be the most commonly used urban building material, but it’s hardly the only one. Rubber seals help hold glass in place. They also keep out wind and weather. When the sun’s rays strike, it’s not just the window glass that expands. As I explained in Seal Selection and Thermal Expansion, changes in temperature cause changes in an elastomer’s length, area, and volume. Several years ago, I saw this firsthand when high heat caused a rubber seal to expand so much that it lifted a large steel cover.

Rubber and glass aren’t the only materials affected by service temperature, and cold weather can also cause part failure. Here in Canada, it’s not uncommon for hockey players to stuff beer in a snowbank while enjoying an outdoor game on a frozen lake or pond. The snow cools the beer, but the aluminum cans aren’t as hearty as a Stanley Cup winner. The beer is made mostly of water, and water expands when frozen. So if the beer gets too cold, the cans explode – and there’s no post-game celebration.

Thermal Expansion and Extreme Conditions

For the pedestrians in Manhattan who were injured by falling glass, the stakes were much higher than a hockey game. The tourists in Chicago and the Jaguar owner in London all stayed safe, but they saw what can happen when environmental conditions cause materials to fail. For the rubber and plastics industry, the incident in Manhattan is especially instructive. Whether with plastic parts or rubber seals, suppliers and buyers alike must consider whether a polymer is compatible with adjacent materials.

In office buildings, homes, and vehicles, window glass is typically part of a “system” that includes metal parts and rubber seals. Evaluating the thermal expansion of each componen tin sealing solutions is important, but factors such as maintenance must also be considered. Today, curtain walls often use EPDM and silicones because these materials provide excellent heat and weather resistance. If a different type of caulking is using during maintenance, however, air leaks and water damage can occur.

Plastic parts can also cause rubber components to fail. Years ago, a supplier packaged a foam rubber armrest against a piece of plastic. During the time the armrest was in storage, the plastic caused the rubber to look like it had been exposed to a hot iron. Today, suppliers must also consider a whole host of conditions. In the case of skyscraper windows, how will rubber parts withstand extreme weather conditions and earthquakes?

How Can We Help You?

For 25 years, Elasto Proxy has been solving sealing and insulation challenges in industries such as building and construction, automotive, and mobile specialty vehicles. By listening to your needs and analyzing all of your requirements, we can recommend solutions that balance the need for safety against cost concerns.

For example, by fully understanding your application’s material compatibility requirements and temperature conditions, we can recommend rubbers with the right material properties. Moreover, we’ll take the time to understand how these rubber products resist aging. The Brooklyn Bridge was built to last, but the Golden Gate requires a special coat of paint ever year. How does your application compare to these structures in terms of service life and maintenance?

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