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Polycarbonate vs. fiberglass and stainless steel

Wed, 11/13/2013 - 2:02pm
Jim McWilliams, president of Integra Enclosures

Poly wins ... best all-around material for electronics enclosures

When choosing an enclosure to protect sensitive electrical and electronic components, remember this: Not all enclosure materials are equal to the task.

Some materials surpass the performance of others in keeping out moisture, dust and other foreign matter, resisting corrosion and the sun’s harsh ultraviolet rays, and standing up to the impact of natural and manmade forces.

Traditionally, stainless steel and fiberglass—or fiber-reinforced polyester (FRP)—have been considered the primary options for enclosures. But polycarbonate, a high-performance thermoplastic resin processed by injection molding or sheet extrusion, has been rising as a popular alternative due to several performance advantages.

“Many people have had misconceptions about polycarbonate. It is one of the most misunderstood materials,” says Melissa Roesch, marketing coordinator for Integra Enclosures. “Because polycarbonate is a plastic, many at first glance question its suitability for protecting electrical and electronic equipment. But it’s exceptionally strong and nearly unbreakable.”

In fact, polycarbonate, a polymer that is created through the chemical reaction of bisphenol A (BPA) and phosgene (COCl2), is used in making bulletproof windows—among many other uses. Strength is just one of several desirable qualities of the material, which was discovered in 1953 by Dr. H. Schnell at Bayer AG, in Germany, and by D. W. Fox at General Electric Company in the U.S.

In the late ‘50s, polycarbonate was adopted for commercial applications and started being used for enclosures in the ‘70s.

Following is a look at how polycarbonate measures up to stainless steel and fiberglass in several key performance areas:

Durability, impact resistance
Electronic enclosures end up in a wide range of environments—in many cases remote outdoor locations where they continually encounter the elements: rain, humidity, saltwater, dust and sun. Maybe even the occasional bullet. They stand up to harsh conditions in oil and gas drilling operations, irrigation systems out in cornfields, high up on wind turbines, on ocean-going vessels and in ports—to name a few examples.

In these kinds of environments, enclosures are vulnerable to wear, tear and abuse. Polycarbonate enclosures have what it takes to withstand this constant stress and protect the electronic equipment they contain, more so than fiberglass or stainless steel enclosures.

Polycarbonate has more than four times the impact resistance of fiberglass, exhibiting tensile strength of 900 pounds per square inch, compared to fiberglass’s 220 pounds per square inch.

While stainless steel is strong, it dents on impact. Polycarbonate has a greater capability for resisting deformation from impact.

Impact resistance of polycarbonate pays dividends even before enclosures arrive for installation. Because of their significantly lower resistance to impact, fiberglass enclosures are more likely than polycarbonate enclosures to arrive damaged and unusable from mishandling in transit.

UV resistance
Besides taking obvious physical impact from machinery, storms and other sources, enclosures in outdoor applications stand in the way of a constant barrage of the sun’s ultraviolet rays. Day by day, UV radiation breaks down and weakens the fibrous structure of fiberglass. A coating of UV protection added to fiberglass enclosures eventually wears off, opening the enclosures to attack and failure.  

“In contrast,” says Roesch of Integra, “we add a UV inhibitor to the polycarbonate formulation, which protects our enclosures through and through—not just on the surface. They’re made to withstand the sun for the long haul.”

Stainless steel also resists UV, but it comes at a much higher price than polycarbonate.

Ease of modification
Polycarbonate’s resistant and resilient nature translates into another advantage: It’s easy to modify to the requirements of specific applications. Drills and other cutting tools go through polycarbonate as smooth as butter, leaving clean edges.

“That’s critical, because most enclosures have to be cut out in some way, either at the factory or on an installation site, to accommodate wires and other features,” Roesch explains.

In contrast to polycarbonate, fiberglass and stainless steel are difficult to machine. And fiberglass is more than just hard to work with. When cut, it chips and splinters, leaves rough edges, and releases a fine dust that irritates skin and harms the lungs when breathed in.

This is another case where polycarbonate has the advantage.

Ease of installation
Once modifications are made, it’s time to install. And here’s where the weight of enclosures matters—at least to installers and the people who pay them. Polycarbonate weighs about 40 percent less than fiberglass and is about six times lighter than stainless steel.  That’s significant, particularly when it comes to installing enclosures up on communication towers and high-rise buildings. Units enclosed in polycarbonate are typically light enough for one-person installation, while stainless steel and fiberglass enclosures often require two installers.

Lightweight polycarbonate also reduces shipping costs.

Relative cost
If it’s not enough that polycarbonate is more impact and UV resistant, is easier to modify and is less of a strain on installers, another factor worth considering may be polycarbonate’s relative price tag. Here again, the advantage goes to polycarbonate. Stainless steel is the most expensive of the alternatives – 3:1 over polycarbonate. And fiberglass is slightly higher in cost than polycarbonate.

Recyclability
Polycarbonate also wins out in earth-friendliness. Unlike fiberglass, polycarbonate can be recycled and processed for reuse at the end of an enclosure’s life. Fiberglass, however, can’t be recycled. Worn out fiberglass enclosures end up in landfills, as do those damaged in shipping or during installation.

Other positive qualities
Polycarbonate has additional advantages as well:

· High NEMA/IP protection ratings for dust and moisture protection

· Non-conductivity for electrical components

·                   · Extended temperature range (-31 ̊F to 180 ̊F)

·                   · Naturally clear, accommodating fabrication of see-through covers that allow visual inspection of enclosed electronic equipment

·                   · Non-corrosive, making polycarbonate enclosures ideal for marine applications, particularly when made with non-metallic hinges and without screws or other fasteners

And due to their superior durability, polycarbonate enclosures typically outlast the lifetime of the equipment they protect.

So, the scorecard shows polycarbonate as the clear winner, even for applications in the harshest of environments. Polycarbonate enclosures deliver long-lasting, reliable service; resist impact, UV radiation and corrosion; machine and install easily; and treat the earth well. All that, while making a smaller impact on the budget.

Author bio
Jim McWilliams is the president of Integra Enclosures, a manufacturer of engineered thermoplastic enclosures designed for use in construction, water treatment, utility, telecommunication, instrumentation, remote monitoring, energy and other applications. Integra enclosures are non-corrosive, non-conductive easy to install/modify and competitively priced. To learn more, visit www.integraenclosures.com. You may contact Jim at jmcwilliams@mumindustries.com.

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