We’re all well aware of the dangers of ultraviolet (UV) light. Too much of it burns and damages skin, especially in people with lighter skin. Too much skin damage in a lifetime, and we run a high risk of getting skin cancer. UV light even attacks our eyes, causing cataracts – or worse, macular degeneration (a growing blindspot right in the centre of your vision).
The UK isn’t exactly known for its sunny climate – but even so, sensible people make sure they wear lots of sun cream and pop on their sunglasses for those rare sunny days. These wearable UV blockers protect our most sensitive organs from the invisible, harmful radiation that the sun has been blasting out every second for the last 4.6 billion years.
But did you know that UV light attacks polythene, too? With prolonged exposure, polythene can be transformed from an ultra-strong, super flexible wonder material – into a brittle, stained, weak pile of uselessness.
Why does this happen, and what can we do to stop it?
What does UV light do to polythene?
Extended exposure to sunlight and UV light results in molecular breakdown. The result is discoloured and brittle polythene. So, for example, if you had plain, additive-free heavy duty polythene bags filled with aggregate, and they were left out in the sun over the course of a project, you could find that they just fall apart when you go to lift or move them – spilling their contents all over the place.
This happens thanks to a process called photodegradation.
Polythene is an example of a polymer – a material made from long chains of one molecule. UV radiation, in the presence of air, causes the polymer chains to break into smaller and smaller pieces. Eventually, the polythene is broken down so much that the material fails – but the rate at which this happens is unpredictable.
So why doesn’t your polythene shopping bag spontaneously turn to dust as you carry it home?
It takes time for sunlight and ultraviolet radiation to act on the material, and a short trip from A to B isn’t going to do much damage. Most polythene products remain indoors, and don’t get prolonged exposure to the sun. However, some applications of polythene are always exposed to the elements, and need proper protection from UV light.
This is where the importance of ultraviolet inhibitor (UVI) polythene additives comes in.
When to use UVI additives
In farming, polythene bags are often used as grow bags. Naturally, these spend all their time outdoors or in grow rooms lit with special UV lighting. This means the polythene is in near constant exposure to UV light, and prone to breaking down.
The same goes for polythene use in construction, particularly when used to cure concrete. Sheeting can break down over time, leading to excessive waste and poor site management practice. But by applying an ultraviolet inhibitor (UVI) additive, polythene can become highly resistant to UV light.
Read more – What Are Polythene Additives?
UVIs are basically antioxidants, which disrupt the breakdown of the polymer chain because they don’t allow the UV light to initiate the bonds between the molecules in the polythene and the air. There are many different antioxidant additives that have a range of efficacy.
Polythene colour plays an important role, too. Black polythene sheeting absorbs much more UV light, and white polythene reflects more.
There’s no way to shield polythene perfectly from UV light – but UVIs can add far more time to the material’s lifespan.