There are many transparent plastics which are difficult to distinguish from one another at the time of purchase. However, their chemical composition differs considerably – and with it, so do their properties.
This becomes very apparent in exterior applications: Within just a few years, sunlight, wind and weather can cause dramatic changes to many plastics. They can no longer withstand the impact of the weather and they begin to turn yellow, become brittle and can break. But not PLEXIGLAS®!
Why plastics weather
The number of different types of plastic available today is virtually endless. However, all of them have one thing in common: They are made from molecular chains. The way in which the molecular chains are structured – how long they are, the atoms they consist of, etc. – determines the appearance, quality and mechanical properties of the plastics. Among other things, the composition determines just how stable the connections created by the molecules are. When UV light and other weather conditions impact the plastics, the molecule chains can – greatly simplified – be damaged. This results in the material properties changing. It can, for example, turn yellow, become coarse or brittle – effects which can be compared to when metals begin to rust.
On the one hand, the extent to which the plastics change under weather influences depends on the intensity thereof, for example UV radiation and moisture. This impact is affected by the geographical location, weather, place of installation, light wavelength and similar factors. On the other hand, in addition to the weather influences, the internal composition of the plastics is decisive; in other words, how stable are the molecular connections.
