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Glass versus Polycarbonate in lighting fixtures

Glass is a natural product that is produced from sand and soda. It consists of crystals and is 100% recyclable. The glass in the TNAML luminaires is hardened safety glass, 4 mm thick and has an impact resistance of 4 joules, tested in accordance with standard IEC 60079-0 and in accordance with standard IEC 62262 an impact test of 20 joules! (IK 10)

For specific applications in the food sector the glass is covered with a foil that prevents glass contamination of processes in the case of breakage. This version meets the HACCP standards and is confirmed by an independent third party laboratory, DEKRA

Polycarbonate is a product that is produced from mineral oil. It is a plastic that contains substances including aromatic bisphenol A. This is a substance that may be detrimental to health and may no longer be used, for example, in eating utensils such as forks, cups, etc.

It is a transparent plastic and is resistant to higher temperatures < 120°C and it also meets the standard IEC 60079-0, with an impact resistance of 4 joules.

It is generally assumed that polycarbonate has a higher impact resistance than the glass used in the TNAML luminaire, but this is not true as also the glass in TNAML meets the same standards.

Polycarbonate is traditionally used in the lighting industry as the transparent part where the light emits through.

There are several disadvantages of polycarbonate:

  1. Discolouration due to the effects of UV; the so-called ‘yellowing’ effect which causes the light output to decrease enormously.
  2. Permeation; As polycarbonate consists of a particular molecule structure, the material is not really 100% sealed, as is the case with glass. This means that water vapour can penetrate the molecule structure of the polycarbonate, which leads to condensation. A solution to prevent this is to have the lighting on permanently (higher energy consumption / extra maintenance and lamp replacement / light pollution) which means having certain extra operational costs.
  3. Static charge; Wind or other air flow can cause a static charge accumulate on lighting fixtures with a polycarbonate cover. These luminaires are labelled with the text – “clean with a damp cloth”- .This static charge attracts dirt and dust that ‘sticks’ to the cover. This reduces the light efficiency and causes extra operational costs.
  4. The surface of the polycarbonate cover becomes craquelé under the influence of UV (it dries out). This creates small cracks in the surface of the cover, and this allows the abovementioned dirt and dust to accumulate in these cracks, having as a result an even further reduction of light efficiency. In order to keep the lighting levels within the required levels this creates again extra operational costs by either installing more luminaires or due to maintenance.

The result of using polycarbonate in comparison with glass, as used in TNAML, are:

  1. More luminaires are needed to compensate for the reduction in light levels.
  2. Extra operational and maintenance costs