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Prevent UV from Degrading Non-Metallic Enclosures in Outdoor Environments by Using Protective Coatings or Alternative Materials Greg Quick, Product Manager Non-metallic materials withstand many conditions that traditional steel enclosures cannot, providing excellent corrosion and chemical resistance, rugged durability and long operational life. Due to these benefits, non-metallic materials have become increasingly popular choices for outdoor applications. Fiberglass Composed of a high-performing, engineered composite resin, fiberglass enclosures are typically formed in one of two ways. The first method, compression molding, utilizes a material known as SMC (sheet molding compound) a long-glass-fiber pigmented polyester resin. These long fibers provide ultimate rigidity and, when formulated with UV inhibitors and aluminum trihydrate, they provide resistance to material degradation and achieve the UL 94 5V flame rating, the highest performance requirement for a UL 508 enclosure. These precision-designed molds result in extremely high part uniformity and material consistency. The second method, the hand lay-up or spray-up process, also utilizes molds that provide part uniformity and material consistency. This material also achieves the UL 94 5V rating. The heavy, unfilled pigmented outer gel coat layer delivers exceptional protection and is available in numerous colors. Injection compression, pultrusion and resin transfer molding (RTM) are other fiberglass molding processes. Injection compression is used for molding components such as hinges, latches or handles, while the pultrusion process is used to produce structural components, including wireway. The RTM process is utilized when a Class A gel finish is required on both the interior and exterior of a component. The inside and outside of the component is encapsulated in a gel coat, which provides exceptional protection against UV and moisture and has an extremely high resistance to acids, alkyds and organic solvents. While fiberglass enclosures provide many benefits, UV, in combination with wind, dirt and rain, will eventually erode an enclosure’s surface regardless of the forming process that was utilized. This phenomenon occurs throughout nature and cannot be prevented. Exposure to these elements causes the surface of fiberglass to become rough and porous. As the resin-rich surface is worn, glass fibers are exposed. This effect is referred to as fiberbloom. While fiberbloom does not impact an enclosure’s functionality or its ability to protect components, it does negatively affect aesthetics, which can be a cause for concern, especially for applications located in highly visible areas. However, protective coatings such as the RTM process previously described, or the addition of painting or gel-coating applied to the fiberglass minimizes this effect. Another option is to select an enclosure constructed of unfilled materials, such as polyester or polycarbonate, to help combat the effects of UV degradation. Benefits of applying a glossy, light colored paint or gel-coating to the fiberglass surface include increased surface reflectivity and reduced surface roughness resulting in decreased UV absorption. Applying paint to resin-rich fiberglass surfaces before they begin to degrade provides additional protection to the surface. Four mils of primer and paint applied over 4 mils of surface resin will extend performance and aesthetics of the enclosure surface. Selecting a white paint further reduces the solar heat load absorption, since white absorbs less UV than other colors. While more expensive than painting, applying a 12 to 15 mil white gel coat provides the optimum level of protection by making fiberglass enclosures more resistant to UV. Gel coating also provides protection against corrosion, delivering an ideal solution for many wet environments. Fiberglass is a thermoset material, which means the composition cannot be changed. Once a fiberglass object has fulfilled its purpose, it ends up in a landfill. Polyester (Hybrid Polycarbonate/Polyester Blends) Other benefits of polyester include excellent impact resistance, less susceptibility to scratches and abrasion than fiberglass and performs well in extreme temperatures. Since polyester is flame retardant, it will not ignite, even when in contact with flame. It delivers excellent corrosion and chemical resistance, withstanding a wide range of solvents, alkalis and acids. Polyester can be easily drilled and punched for holes and cutouts in the field as it contains no glass and produces little dust. Polyester exhibits less wear on tools and doesn’t cause skin irritation associated with loose glass particles. Polyester is a thermal-molded material. This means it can be changed and reused, it is recyclable. Further, it takes less energy to recycle polyester than many alternative materials, making it an eco-friendly enclosure material that is accepted worldwide. Polycarbonate Most polycarbonate enclosures offer corrosion protection at a low to moderate price. Similar to hybrid PBT/PC (polyester polycarbonate blends), polycarbonate does discolor and experiences low levels of surface deterioration with no fiberbloom, because it does not contain glass, with the exception of the glass fiber-reinforced grades. Many enclosure materials are available to protect electrical and electronic components from harsh outdoor environments, chemicals, and corrosive agents. Non-metallic options provide different performance attributes, cost points and aesthetic qualities. Care should be exercised when selecting the best material suited to an application’s specific requirements. Pentair Technical Products is a provider of worldwide product and service solutions for enclosing, protecting and cooling electrical and electronic systems. Its brands, Hoffman, Schroff, McLean Cooling Technology, Calmark, Birtcher, Aspen Motion Technologies and Taunus provide a broad variety of solutions to numerous markets. For more information visit www.hoffmanonline.com.
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