Supplement: Enclosures UV-stable plastic enclosures OKW explains how to protect your devices from damage caused by sunlight
A
good enclosure must do so much more than simply safeguard your electronics. Its elegant aesthetics must showcase your technology
– underlining its quality, enhancing its desirability, enticing buyers and impressing end users.
But the allure of a beautifully presented enclosure can fade surprisingly quickly if it’s moulded from the wrong plastic…one that discolours if exposed to sunlight for too long. Worse still, those punishing ultraviolet rays can weaken the material, making it fragile and compromising its structural integrity. Compared with other hazards, it’s all too easy to underestimate how much damage sunlight can do to UV-vulnerable plastics (especially when we see so few sunny days in this country).
But the threat from UV rays is all too real, even for enclosures that spend their lives
30 April 2025
indoors on desktops, tabletops or walls. This is why so many enclosures are now moulded from UV-stable plastics as standard. UV-related discolouration and damage – ‘photodegradation’ – occurs when ultraviolet light causes a photochemical reaction within the plastic. UV rays are divided into three types: UVA, UVB and UVC. When plastics are exposed to ultraviolet light, the energy from the UV rays can excite the polymers’ chains, causing them to break down. Additionally, the presence of oxygen can accelerate this process – leading to faster degradation. UVA, UVB, and UVC all have different effects on plastics. UVA (320-400 nm) and UVB (280-320 nm) rays can pass through some types of plastic, causing discolouration and brittleness over time. UVC (100-280 nm) is often blocked by most common plastic materials but when it does penetrate, it can cause significant damage due to its higher energy levels. Even enclosures used
Components in Electronics
predominantly indoors can still be susceptible to sunlight – at least 50 per cent of UVA rays can pass through standard window glass. Photodegradation can give some plastics a yellow or chalky appearance. The breakdown of polymer chains can make the plastic more brittle, causing it to crack or shatter more easily. Also, the surface of the plastic can become rough and less glossy, affecting both its appearance and its functional properties. Some plastics may show signs of degradation within a few months of continuous exposure, while others may take years. The time it takes for UV light to discolour and damage plastics depends on several factors, including the type of plastic and the intensity of exposure to UV light. Environmental conditions can also play a role. Higher temperatures can accelerate the degradation by increasing the rate of chemical reactions within the plastic. This can lead to faster breakdown of polymer chains.
Humidity can introduce moisture into the plastic, reacting with its chemical structure and speeding up the disruption of the polymer chains. Additionally, the presence of moisture can facilitate the formation of free radicals, which are highly reactive and can cause further damage to the plastic.
Acrylonitrile butadiene styrene (ABS) can be prone to UV damage, creating an Achilles heel in what is otherwise a strong and reliable thermoplastic. For many years, ABS was a go- to plastic for many standard enclosures – and it remains a dependable material. But in recent years its vulnerability to sunlight has resulted in it being superseded by other plastics. Acrylonitrile Styrene Acrylate (ASA) was developed as a UV-stable alternative to ABS. ASA copes better with UV rays than ABS due to its composition. ASA replaces the polybutadiene rubber found in ABS with acrylic rubber, which is inherently more UV resistant. This substitution significantly improves ASA’s
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