In the electrical enclosure industry, there are several different materials to choose from. Plastic has become an increasingly popular material for small to medium electronic enclosures because it is lightweight, cost-effective and corrosion resistant. While plastic electrical boxes can offer many benefits over metal or fiberglass enclosures, it’s important to note that not all plastic is the same.
Some of the most widely used thermoplastics for electronic enclosures are Polycarbonate, ABS and PVC. Each of these materials vary greatly in their chemical makeup, strength, and lifespan. So how do you know which material is best for an outdoor electrical enclosure? Let’s explore the benefits and drawbacks of each material and how they can affect the protection level of the enclosure.
Material Properties
First, it is important to distinguish how each of these thermoplastics are made. Polycarbonate is a homogeneous material, meaning it is made of one single type of plastic. Polycarbonate molecules have very strong bonds, contributing to the material’s overall strength and stability.
ABS and PVC are both made by combining other materials. ABS is a combination of acrylonitrile, butadiene, and styrene plastics. PVC is made up of chlorine and carbon.
The next step in choosing the correct material for your application is to look at the features each material offers: tensile strength, impact strength, UV resistance, flame retardancy, and thermal aging.
Tensile Strength
Tensile strength measures the amount of force or pressure a material can withstand before it breaks. This measurement is important for understanding how the material will hold up to external forces – like atmospheric pressure from underwater submersion. Polycarbonate is the clear winner with an ultimate tensile strength of approximately 10,000 psi. This is more than double the tensile strength of ABS (4,500 psi) and considerably greater than that of PVC (6,300 psi).
Impact Strength
Polycarbonate is famously used for safety lenses, automotive headlights and bulletproof glass. So it should be no surprise that it can also withstand greater impacts than ABS and PVC. Polycarbonate has a notched izod impact strength of 12 ft-lb/in. ABS has a notched izod impact strength of 4 ft-lb/in. PVC has a notched izod impact strength of 10 ft-lb/in. This makes polycarbonate enclosures the ideal choice for rugged, outdoor applications and high-traffic environments.
UV Resistance
Polycarbonate and PVC both have relatively good UV resistance, making them suitable for outdoor electrical enclosures. Polycarbonate is rated at UL 746C f1. PVC isn’t measured the same way, but is used in direct sunlight applications (Like windows). ABS is not UV resistant and will quickly discolor and degrade in the sunlight.
Flame Retardancy
Polycarbonate and PVC are both rated UL94 5Va which is the highest level of UL Flame Retardancy. The 5Va standard means that the enclosure will not have a burn through hole, will not drip burning plastic and will self-extinguish if it catches fire. All these qualities should equate to the enclosed electronics being completely protected from the flame. ABS enclosures can be rated 5Va with additional accommodations like thicker plastic and special coatings. However, ABS material is inherently less flame retardant than PVC and Polycarbonate.
Thermal Aging
A Relative Thermal Index measures the maximum temperature a material can withstand over long periods of time without degrading. RTI tests simulate between 5,000 and 20,000 hours at elevated temperatures and measures material properties like impact resistance and electrical insulation.
Polycarbonate has a Relative Temperature Index (RTI) rating of 221° F, making it a much safer choice for high heat environments. PVC has an RTI rating of 185° F and ABS has an RTI rating of 140° F.
Color
Polycarbonate is naturally ‘water clear’. This contributes to the material’s excellent color-ability and allows polycarbonate enclosures to have clear doors, providing visibility to the internal components. Traditionally, visibility into the enclosure could only be accomplished through an installed window. However, windows are more costly due to the added labor and can pose as a possible leak point. Clear doors are a much better alternative, especially when paired with overlay artwork to create a “window” effect for desired areas while concealing others.
PVC can also be formulated to be water clear but is more often seen in white, black or gray. ABS is naturally opaque beige and is typically colored gray or black.
Conclusion
Because of its superior strength (both tensile and impact), outdoor suitability, flame rating, heat tolerance and colorability, Polycarbonate is the ideal (and often necessary) choice for enclosures used in rugged environments. Whether it bakes in the sun day after day, is submerged in seawater, encased in concrete, or on the business end of uninvited target practice… polycarbonate electronics enclosures will stand strong through the most challenging conditions.
Integra’s polycarbonate enclosures are ideal for the construction, telecom, marine, oil and gas, utilities, water treatment, instrumentation, remote monitoring, alternative energy and many other industries that require non-corroding, non-conductive enclosures that are easy to transport, modify and install. For more information about choosing the best polycarbonate enclosure for your application, contact the experts at Integra Enclosures.
*Polycarbonate grades suitable for use in UL50 or IP66 Enclosures/applications used for comparison purposes.
**ABS grades suitable for use in non UL50 or IP66 Enclosures/applications.
***PVC grades suitable for UL50 or IP66 applications.
