Plastic enclosures survive UV exposure

Edited by the Engineeringtalk editorial team Dec 4, 2007

All Stahlin products are moulded from Spelsberg's patent pending SolarGuard SMC formulation, delivering both strength and extremely high protection from UV degradation.

The benefits of nonmetallic enclosures are well known.

They are generally lighter, more aesthetically pleasing, easier to adapt, and for the most part come with far more built-in features than metal alternatives.

Most metal enclosures are generally larger cabinets where sealing isn't a crucial issue, and cast metal boxes used for high pressure differential applications and explosive environments.

Although materials such as polycarbonate are flame retardant and highly resistant to some chemicals, other plastics used for manufacturing electrical junction boxes and enclosures tend to degrade rapidly outdoors due to UV exposure.

For many outdoor applications such as lighting, wiring junctions, HVAC and housing controls both in fixed positions and on mobile on plant machinery and transport vehicles, pressed steel enclosures do not provide the level of sealing required.

Cast metal enclosures are overkill and other nonmetallic alternatives are either too mechanically fragile or susceptible to UV.

How to achieve the robustness of a metallic enclosure, but retain the sealing and practical flexibility, and avoid the fragility of some nonmetallic materials?.

One answer is to use what is generally regarded as an "old school" material - glass fibre.

Recently introduced into the UK by plastic enclosure specialist Spelsberg, Stahlin brand enclosures are made using a glass-fibre manufacturing process that employs specially developed fibre matting, high pressure moulding machines and the latest polymer technology to create a smart sheet moulding compound (SMC) that produces tough enclosures that can be easily machined and are virtually impervious to UV.

These new generation glass-fibre enclosures have all the flexibility and convenience of plastics, but, offer the same physical protection as pressed steel alternatives that are highly susceptible to corrosion.

One of the key elements in the enclosures construction is protection from UV degradation.

A classic flaw in many glass-fibre derivatives is to leave the resin component without adequate protection from weathering.

In extreme cases exposure can weaken the material structure, raising safety and maintenance issues.

All Stahlin products are moulded from the company's patent pending SolarGuard SMC formulation, delivering both strength and extremely high protection from UV degradation.

The SolarGuard system fights polymer degradation by making it much more difficult for UV light energy to attack the molecular bonds of both primary chains and crosslinks.

Effectively building in sunscreen to the enclosure and ensuring that it retains the original surface gloss and colour after exposure to concentrated UV light over an extended period of time.

A special UV absorber is added to the SolarGuard formulation, which acts to absorb UV energy, then to release it without damaging the polymer chain.

The neo-pentyl glycol (NPG) isopthalic based resin used along with special additives also ensures UL94V5 fire retardancy and provides a much stronger bond of the polymer chain, resulting in significantly improved weathering and corrosion resistance.

As a nonhalogen glass fibre system it beats the effects of outdoor exposure plus provides the chemical and flame resistance required for many extreme environments.

The advanced glass fibre is easy to drill and machine without affecting the structural integrity of the box and thanks to built in seals offers sealing up to IP68 on standard boxes.

Spelsberg offer enclosures ready fitted with DIN-rails and busbars, circuit breakers, colour coded clip-on terminals for rail mounting and a wide selection of cable entry devices from simple push-in protection up to fully clamping IP68 cable glands.