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UV Radiation

Everyone is exposed to ultraviolet (UV) radiation from the sun and other artificial sources used in industry, commerce and recreation. Emissions from the sun include light, heat and UV radiation. The sun is the strongest source of UV radiation in our environment. Small amounts of UV radiation are essential for the production of vitamin D in humans. However, over-exposure to it may lead to short and long term adverse effects on the skin, eyes and immune system.


UV radiation is electromagnetic radiation, with wavelengths between 100-400 nm. It is divided into three bands :



As sunlight passes through the atmosphere, all UVS and about 90% of UVB is absorbed by ozone, water vapour, oxygen and carbon dioxide. UVA is not filtered as significantly by the atmosphere. Therefore, the UV radiation reaching the Earth’s surfacee is largely composed of UVA with a smaller amount of UVB component.


UV Radiation levels are influenced by:


The higher the sun in the sky, the higher the UV radiation level. Thus UV radiation levels vary with time of the day and time of year.


The closer to the equator, the UV radiation level is higher. Closer to the equator, the sun’s rays have a shorter distance to travel through the atmosphere and therefore less radiation can be absorbed.


UV radiation levels are highest under cloudless skies. However, light or thin clouds have little effect in reducing exposure and may even enhance UV levels because of scattering.


The higher the altitude, the UV radiation level is higher. There is less atmosphere available in higher altitudes to absorb the radiation. With every 1000m increase in altitude, UV radiation levels increase by around 10%.


Ozone in the stratosphere absorbs some of the UV radiation that would otherwise reach the Earth’s surface. Ozone levels vary over the year and even across the day.


UV radiation is reflected or scattered to varying extents by different surfaces, e.g. fresh snow can reflect as much as 80% of UV radiation, dry beach sand about 15% and sea foam about 25%.



UV Degradation of EPDM Wet-pour

What is ultra violet?

Ultraviolet (“UV”) light is one of the frequencies of light that is given off by the sun. Ultraviolet light is not visible to the human eye; it is an invisible part of the “electromagnetic spectrum”. Ultraviolet radiation, visible light and infrared energy are all given off by the sun. The image below shows the electromagnetic spectrum, which includes ultraviolet, infrared and visible light along with other types of energy.



UV Degradation of EPDM Wet-pour

UV Degradation

Some colors of wet pour surfacing are more prone to higher levels of degradation from UV (ultraviolet) light exposure. This means that certain colors in the manufacturing process of the rubber can fade over time because they have been exposed to ultra violet radiation from the sun. Generally speaking, the brighter colors are more prone to UV Degradation and during this process the sunlight radiation attacks the synthetic polymeric within the EPDM material, leading to a loss of the original vibrant color.






Definition of Pigments

Pigments are generally coloured, organic or inorganic solid powder, and usually are insoluble. They are not affected physically or chemically in the substrate in which they are incorporated. Pigments can give a full range of colours.


Types of pigments

Inorganic Pigments: Those pigments that are made up of mineral compounds are known to be Inorganic Pigments. These minerals are mainly oxides, sulphides of one or more metals.

Organic Pigments: In organic pigments, the molecules are made of carbon atoms along with hydrogen, nitrogen or oxygen atoms. Organic pigments are carbon based and are often made from petroleum compounds


The Differences between Organic and Inorganic Pigments


Inorganic pigments

Organic pigments


Minerals Chemically refined oil


Often dull


Opacity Opaque


Light fastness

Very good Vary from poor to good

Dyeing/Coloring Strength



Cost Moderate

Mostly too expensive




Color is simply defined as the light of different wavelengths and frequencies. Light, however, is just one form of energy that we can actually see that is made up of photons.

Colour comes from light. We can see even main colours of the Visible Spectrum. The retinas in our eyes though have three types of colour receptors in the form of cones, we can actually only detect three of these visible colours – red, blue and green. These colours are called additive primaries. It is these three colours that are mixed in our brain to create all of the other colours we see. The wavelength and frequency of light also influences the colour we see. The seven colours of the spectrum all have varying wavelengths and frequencies. Red is at the lower end of the spectrum and has a higher wavelength but lower frequency than that of violet at the top end of the spectrum which has a lower wavelength and higher frequency. To physically see this, we need a prism. When light from the sun passes through a prism, the light is split into the seven visible colours by refraction. Refraction is caused by the change in speed experienced by a wave of light when it changes medium.


About Wet-pour Rubber Surfacing

Wet pour rubber surfacing is becoming a very popular choice for playground safety surfacing. Its combination of aesthetic appeal, nearly limitless design potential and unmatched non slip characteristics make it a strong candidate for playground surfacing.

Wet pour rubber surfacing is used in a wide variety of applications, from playground safety surfacing, to running tracks, on pool decks and patios and even in water parks and on cruise ship decks. The surface must be able to withstand a tremendous amount of wear and tear from foot traffic, the elements and most of all the sun.

A typical wet pour system consists of a cushion layer composed of recycled tyre rubber that is buffed or ground to specific sizes and a wear course layer made of EPDM (Ethylene Propylene Diene Monomer) granules that come in a variety of colors. The cushion layer and the wear course layers are held together by either an Aromatic or Aliphatic binding agents and typically installed over a crushed stone, asphalt, or concrete sub-base.