Why Does Polycarbonate Sheet Turn Yellow in South Africa?

Polycarbonate Sheet is a transparent material that is prone to yellowing when exposed to sunlight in South Africa.

Polycarbonate sheets are strong, clear and light but they do have one thing in common. When exposed to the extreme outdoor conditions in South Africa, polycarbonate sheets yellow, become brittle and lose clarity. This is known as UV degradation, and is the most frequent cause of early failure in outdoor applications of polycarbonate sheets in South Africa.

Fortunately, yellowing can be avoided. Properly specified for South African outdoor conditions, the right grade of polycarbonate sheet will not yellow for 10 years or more. If the grade is wrong, it will begin to turn yellow after 12 to 24 months.

At Allrich Trading, we have a wide selection of quality polycarbonate sheets for sale to companies, contractors and buyers in Johannesburg, Durban and Cape Town. This guide will tell you all about the reasons why polycarbonate sheets turn yellow in South Africa — and how to avoid it.

Why does Polycarbonate Sheet turn Yellow?

Why does polycarbonate sheet get yellow with age?

Polycarbonate sheet will yellow due to UV radiation. The polycarbonate polymer is degraded by ultraviolet radiation from the sun (photo-oxidation). As these bonds deteriorate, it becomes less optically clear, yellow or amber, and brittle and cracky.

Not caused by a manufacturing fault. This is a natural chemical change that can occur to any polycarbonate (and any clear plastic material!) if left unprotected in the sun. The issue isn't if, but when.

UV degradation occurs much more rapidly in South Africa than in cooler, less sunny climates. The sun's UV Index is often high (11-12) in South Africa during summer. This is a much greater level of UV exposure than is used in most of the technical data for polycarbonate that has been originally tested in Europe or the UK.

How fast Polycarbonate Sheet Yellows in South Africa?

What is the rate of yellowing of polycarbonate sheet in South Africa's outdoor environment?

The rate of yellowing is dependent on two factors: whether the polycarbonate is coated with UV protection, and the amount of direct sunlight the material is exposed to.

Unprotected polycarbonate sheet will begin to visibly yellow in 12 to 24 months when installed outside in South African conditions. In year 3 to 4, the sheet becomes very discoloured, brittle and crazes on the surface. It has totally failed by year 5 and must be replaced.

Co-extruded UV protection: Quality polycarbonate sheet with a co-extruded UV-protective layer, will retain its clarity and optical properties for 10 - 15 years in South African outdoor conditions. The UV coating will absorb and scatter the UV radiation before it reaches and damages the polycarbonate.

The difference between 2 years and 15 years of outdoor life is one specification choice: Is the sheet co-extruded with a UV layer or not?

The distinction between UV protected and regular polycarbonate sheet is that the former is designed to block out harmful UV rays, while the latter contains no such filtering properties.

What is the meaning of UV protection in polycarbonate sheet?

There are two types of UV protection, which are used in the production of polycarbonates:

Co-extruded UV layer — the right specification for South Africa: A thin layer of UV absorber is fused on to the surface of the polycarbonate sheet during the manufacturing process. It's a part of the sheet itself, not something added later. This is the only long term outdoor protection in South Africa that is provided with UV. The co-extruded UV layers absorb the UV radiation before it reaches the polycarbonate core thus precluding photo-oxidation.

For outdoor use in South Africa, Allrich Trading's quality polycarbonate sheet is guaranteed to be UV protected by standard.

UV-stabilised additives – less effective: UV stabilising additives are incorporated into the polycarbonate compound itself rather than as a surface layer. These additives are able to reduce the rate of UV degradation but not quite as effectively as a co-extruded surface layer would. The UV-stabilised sheets generally do not last as long outdoors in South Africa as co-extruded UV sheets.

Standard polycarbonate sheet which is not UV protected — sometimes sold at reduced prices — should never be used outdoors in South Africa. Will turn yellow quickly, and die too early. The early replacement costs immediately cancel out the cost savings on the material.

Does All Polycarbonate Sheet Yellow?

Why do some polycarbonate sheets turn yellow quicker than others?

No — there are three factors that affect the rate of yellowing:

2. UV protection specification: As explained above — co-extruded UV layer perform much better than UV-stabilised additives which perform much better than no UV protection. This is the largest variable.

2. Sheet thickness: Thicker the polycarbonate sheet, the more material mass that exists between the surface and center. UV degradation begins at the surface — even with a UV layer, thicker sheets will not show visible yellowing until later. This, however, is no replacement for UV protection, it just puts it off.

3. Installation orientation/exposure: Polycarbonate sheets installed at a steep angle (e.g. pitched roof) shed water and dust better, thus minimizing surface contamination that can accelerate UV degradation. Horizontal installations trap more dust, water, and debris, resulting in extra surface damage from dust, water and dirt, as well as UV damage. Abrasion from South Africa's dust and sand in Gauteng and Northern Cape also plays its role in surface deterioration.

Is the yellowed Polycarbonate Sheet Reparable?

Can You Revive Yellowing Of Polycarbonate Sheet?

Partial restoration can be achieved in early stage yellowing, but it is not a cure. Polishing compounds and plastic restoration products will temporarily remove surface oxidation and enhance clarity. After the UV degradation has reached beneath the surface layer, however, there is no way to restore the optical clarity by a polishing treatment.

So, as a South African buyer, it's a truth universally acknowledged that when a polycarbonate sheet is visibly yellowed, the UV degradation is too far gone and replacement is the only viable option. Only restoration will benefit very lightly yellowed sheets where the damage is only surface.

With any restoration, prevention is cheaper than the cost of restoration.

Avoid yellowing of polycarbonate sheet in South Africa.Prevent polycarbonate sheet from becoming yellow in South Africa.

What is the best way to prevent the yellowing of polycarbonate sheet in south Africa?

• Step 1 – Always use co-extruded UV protected polycarbonate sheet for outdoor applications. This is the only prevention with a long-term effect. Avoid using standard or UV-stabilised polycarbonate for outdoor use in South Africa. Co-extruded UV protected polycarbonate sheet is available as standard item from Allrich Trading for all outdoor applications.
• Step 2 — Avoid scratching UV coating while installing. The co-extruded UV layer is on the surface of the sheet — it is what protects everything underneath. When the scratch is made during installation, it eliminates the UV protection from the affected areas, leading to the formation of UV hotspots over time. Carefully remove protective film from all surfaces. Cut with the proper cutting tools. Take care to handle sheets during installation.
• Step 3 — Properly clean polycarbonate sheets. Clean with soft cloth and mild soap and water. Do not use solvents, abrasive cleaners or rough cloths, as these will remove the UV-protective surface layer which will lead to faster degradation. In South African dusty environments – especially Gauteng – regular gentle cleaning will remove abrasive dust, which causes surface wear.
• Before purchasing, review the UV protection warranty (Step 4). A good polycarbonate sheet supplier will designate the warranty on the UV protection of the polycarbonate sheet, usually 10 years for good quality co-extruded polycarbonate sheets used outdoors. Do not use a polycarbonate sheet for outdoor use in South Africa unless the supplier is able to guarantee the UV warranty.

Polycarbonate Sheet Supplies Johannesburg, Durban and Cape Town.

Johannesburg experiences some of the highest UV Index levels in South Africa – highveld altitude makes a big difference to UV radiation exposure than coastal cities. Polycarbonate sheet fitted in Gauteng is more prone to yellowing than in other South African regions, without any co-extruded UV protection. Allrich Trading is a supplier of UV protected polycarbonate sheet for the South African highveld UV rating to customers in Johannesburg.

Durban's subtropical coastal climate is characterized by both high UV and high humidity levels, which can both lead to degradation on the surface of polycarbonate without protection. Whether you are buying polycarbonate sheet for your coastal applications in KwaZulu-Natal, Allrich Trading has the correct polycarbonate sheet specifications for you.

The UV levels in Cape Town are lower than Gauteng but are still much higher than the levels found in Europe, where most polycarbonate is tested. You can get less direct sunlight on installations facing south in Cape Town, but even the north facing and horizontal installations need co-extruded UV protection for long-term outdoor use. Allrich Trading are able to offer Cape Town buyers polycarbonate sheet matched to the unique outdoor environment of the Western Cape.

Your Polycarbonate Sheets Supplies By Allrich Trading.

Avoiding yellowing of polycarbonate sheet in South Africa is possible — if the correct specification is used from the beginning. Allrich Trading's co-extruded UV protected polycarbonate sheet has been rated for South Africa's harsh UV environment and will retain UV clarity and performance over 10 years and more for outdoor use.

Allrich Trading is a supplier of high quality polycarbonate sheets in Johannesburg, Durban & Cape Town with UV protection. Call our team to talk about your project or request a supply quote.