Cables in the sun - UV resistance in sheath materials
Date Posted:30 May 2017
It’s a well known fact that Australia’s UV levels are much higher than other parts of the world such as Europe and North America.
For electrical equipment such as cables this means UV resistance is an important factor. But what does UV stabilisation actually mean? And how can you ensure your cable installations will stand up to a lifetime of UV exposure?
The most common sheath material used in cables is PVC. This is one of the most inherently UV resistant polymers available. It is regarded as “Very Good” in resistance to UV (not “Excellent”).
In the presence of UV, PVC forms a visible brown residue that is typically a result of the plasticiser separating from the compound in the outer layer. This affects the impact strength of the compound, meaning that the cable becomes brittle, less flexible and prone to cracking. This effect occurs within the first two years of exposure to UV.
Whilst the use of non-stabilised low voltage non-aerial cables is not prohibited by any Australian standard, the dangers caused by cables that are gradually but surely degrading should cause concern.
The method employed to reduce the effects of UV (or stabilise) on cables are the addition of stabilisers to the PVC compound. The most common of these are:
- Carbon Black; this absorbs the UV rays to prevent damage to the polymer structure. A cable is regarded as fully UV stable when it contains 2% carbon black, although in practice 0.5% is sufficient to effectively protect the cable sheath. The addition of carbon black at these levels renders the cable black in colour. This regarded as the best method of UV stabilisation in PVC.
- Titanium Dioxide (Ti02); this is a white pigment that can be added to a variety of materials. Typically, 1.5% content of titanium dioxide will cause a PVC compound to be UV stable.
So what’s the best way of making sure the cable you install is UV stable? The simplest way is to purchase black PVC sheathed cable. PVC cables have a “V” in their material designations – such as V-90HT or 4V-75. If the cable does not have a black outer sheath, check with the manufacturer that it is UV stable.
Amplex supplies UV stable cables such as: