We use a premium grade UV protecting polymer additive designed to absorb the sun's harmful rays and prevent any colour fade. After 17,500 hours in a laboratory weathering test, there was no visible change in either the physical appearance of the material, including colouration, or the brittleness of the polymer.
What is PE?
Polyurethane (PE), or the base material that we use for most artificial plants or screening, is renowned for its high tensile strength, elasticity and its ability to resist grease, solvents, chemicals and physical abrasion. These traits make it both economical to use in manufacturing and ideal for use in the garden where materials are likely to encounter all of these challenges. Aromatic TPUs, which make up the majority of polymers used in our products, stand up particularly well to these, as well as showing a high resistance to weathering caused by rain.
Where’s the problem then?
PE does have a tendency to discolour and become brittle when exposed to ultraviolet light for long periods of time. This can be a major drawback when designing products for the garden, especially for those to be used in direct sunlight. You may have noticed garden products that have faded from green to a blueish colour. Or perhaps you have seen your products slowly begin to perish, becoming brittle and broken around the edges. This is especially true if you have ever left an indoor product outside for too long, as they often contain none of the chemicals needed to strengthen plastics. As the treatment of plastics is expensive and somewhat complicated, there are companies that do not invest the time or money into ensuring your outdoor products are strong enough to last. The result is, you get a product that appears good quality when you get it, but 6 months down the line it is already showing signs of deterioration.
Tell me more about the chemistry
Urethanes are susceptible to free radical pathways induced by ultraviolet light. Without delving into the organic chemistry too deeply, the energy from the UV light splits Chlorine [CL2] molecules, leaving two chlorine “free radicals”, with an electron deficiency, raring to bind to the nearest molecule it can find. Within polymers, the weak bonds of the hydrocarbon chain make an easy target. The chlorine radical pulls it apart, snatches a hydrogen atom, and disappears into the distance in a cloud of hydrochloric acid, leaving behind a broken home of a hydrocarbon chain: Polarized, weakened and susceptible to further degradation.
In plastics, this leads to the breakdown of the pigments that give it colour. And reds and greens are particularly affected, which is why you often see fade in these colours. Yellows do very well - you may notice if you go to a hot country like spain, along with white plastics, they use yellow a lot in their awnings and umbrellas etc. to prevent this fade.
How we solve the problem
We add UV stabilizing chemicals to our PE - approximately 3% of the material is made up by this stabiliser. The stabilizer acts to absorb the energy from the UV light, so preventing it from radicalizing the molecules within the plastic. This is very effective at preventing the deterioration caused by light and after extensive testing, we found 3% to be an optimal level to increase the longevity of our products. There is now no fade of colour, even greens, after the equivalent of two years weathering carried out in a specialist weathering facility. There was also no degradation of the mechanical properties of the material, with no increase in brittleness or decrease in pre tensile strength. We believe this provides us with a material superior to most on the market, enabling you to enjoy your products for longer.