Plastics for outdoor use: UV-resistant, weatherproof and durable

In the garden, on the roof or on façades – plastics have long since established themselves outdoors as a versatile alternative to metal, wood or glass. They are light, malleable, durable and offer a wide range of design options. But not every plastic withstands sun, rain and frost equally well. This article shows which materials are suitable – and what to look out for when selecting them.

What must plastics deliver outdoors?

Outdoors, materials are exposed to extreme conditions: UV radiation, moisture, freeze-thaw cycles, heat, wind and mechanical loads often act simultaneously. Plastics must therefore be particularly weather-resistant, dimensionally stable and durable to count as a permanent solution. The decisive factors are above all:

• UV resistance: protection against embrittlement, yellowing and structural breakdown
• Water and moisture resistance: no swelling, no cracking
• Temperature stability: dimensionally true from winter frost to summer heat
• Mechanical robustness: under wind, impacts, snow load or vandalism

Not every engineering plastic is suitable for outdoor use. Many materials that prove themselves indoors fail under solar radiation or the influence of weather.

UV resistance: why it is decisive

UV radiation decomposes plastic molecules over time. This leads to:

• Embrittlement and material fracture
• Yellowing or fading of colours
• Loss of impact strength
• Microcracks or stress cracks on the surface

This is particularly critical in transparent applications (e.g. sheets, glazing), but also in coloured or load-bearing plastic components.

A UV-resistant plastic must either be stable by nature (e.g. PMMA, PC) or be equipped with additives such as UV stabilisers, carbon black or coextrusion layers. Depending on the application, the long-term exposure should be taken into account: 1–2 years on the terrace are not the same as 10 years on the roof.

How can UV protection be improved?

Long-term resistance to UV radiation can be increased by the following measures:

• UV stabilisers (additives): chemical additives that absorb UV energy
• Carbon black or titanium dioxide pigments: absorb UV rays effectively, especially in black or white plastics
• Coextrusion: an additional top layer with high UV protection on the surface
• Surface treatments: e.g. paints, stains or special UV-resistant films

Manufacturers usually state whether UV stabilisation is present – if in doubt, it is advisable to ask or have the material tested to a standard (e.g. ISO 4892).

These plastics are suitable for outdoor use

Polycarbonate (PC)

PC is a particularly impact-resistant plastic with high transparency. It is ideal for multiwall sheets, roof glazing or machine covers outdoors. Thanks to a UV-protective coating (on one or both sides), polycarbonate can withstand the weather for many years without yellowing or cracking.

Acrylic glass (PMMA)

PMMA – also known as acrylic glass or "Plexiglas" – is very UV-resistant by nature. It does not yellow, remains dimensionally stable and offers a high-quality glass look. However, it is more brittle than PC and less impact-resistant. Perfect for advertising signs, windows, glazing and design elements outdoors.

PVC-U (rigid)

Rigid PVC is cost-effective, chemical-resistant and largely UV-stable. It is used in particular for window profiles, sheets and cable ducts. Thanks to additives, it achieves good long-term weather resistance. The colour may fade slightly under intense UV radiation, but mechanically PVC remains very robust.

PE-HD / PE 1000

Polyethylene is chemically very resistant by nature and extremely impact-resistant, even in the cold. PE-HD is often used outdoors, e.g. for slide rails, playground walls or cladding. However, without additives PE is not UV-stable. Only UV-stabilised PE types (with carbon black or additives) are permanently suitable for outdoor use.

POM, PA & Co. – only suitable to a limited extent?

Many engineering plastics such as POM, PA or ABS are only conditionally weather-resistant. PA absorbs water, POM becomes brittle under UV radiation, ABS quickly loses its surface hardness. For occasional outdoor contact (e.g. in machines) this may be sufficient – for permanent outdoor solutions it is not.

Comparison of weather-resistant plastics (table)

Plastic	UV resistance	Impact strength	Transparency	Temperature resistance	Outdoor application
PC	very good (coated)	very high	high	approx. -40 to +120 °C	roof, glazing
PMMA	excellent	medium	very high	approx. -20 to +70 °C	windows, signs
PVC-U	good (with additives)	good	medium	approx. -10 to +60 °C	profiles, sheets
PE-HD (UV-stabilised)	good	very high	low	approx. -50 to +80 °C	playgrounds, covers
POM / PA	poor	good	low	up to 100 °C	only sheltered

Typical areas of use outdoors

• Roof glazing and terrace canopies → polycarbonate (impact-resistant + UV-protected)
• Advertising technology, illuminated signs, façades → acrylic glass / PMMA (crystal clear + UV-resistant)
• Cladding, protective sheets, outdoor furniture → PE-HD UV-stabilised
• Engineering profiles, window frames → PVC-U
• Machine covers with occasional outdoor contact → POM or PA with protection

Sustainability & recycling

Weather-resistant plastics usually have a long service life – this reduces replacement cycles and saves resources. Nevertheless, the recycling process poses a challenge: UV-stabilised materials often contain additives that make mechanical recycling more difficult. However, single-grade PE-HD types can be recovered well, especially in black or natural-coloured versions.

Anyone wanting to build more sustainably should rely on long-lasting, repairable plastic solutions and favour single-grade materials that can be materially recovered at the end of their use.

What to look out for when selecting the material

• Check UV resistance: look for specified additives or coextrusion. Natural colours yellow faster than black or through-coloured variants.
• Match mechanical requirements: for impact loads, PC or PE-HD are better than PMMA.
• Observe the temperature range: not every plastic is frost-resistant – and high temperatures (e.g. under roof glazing) can also lead to deformation.
• Have long-term stability documented: manufacturers should provide service life tests, weather ageing data or UV tests to ISO 4892 or comparable standards.

With the right choice of material, long-lasting, attractive and economical solutions for outdoor use can be realised. We will gladly support you in selecting the optimum plastic.

Frequently asked questions (FAQ)

Which plastic lasts longest outdoors? Acrylic glass (PMMA) is extremely UV-resistant by nature. Polycarbonate with a UV coating also lasts a very long time and is mechanically more robust.

Are there transparent plastics that are UV-stable? Yes. PMMA and coated polycarbonate are both transparent materials with good weather resistance.

How do I recognise UV-stable plastics? Best of all from the information in data sheets or type designations (e.g. "UV-stabilised", "outdoor", "UV-resistant"). Alternatively, ask the manufacturer about tests to ISO 4892.

Are black plastic sheets always UV-resistant? Not automatically. Carbon black pigment does offer protection, but long-term stability is only guaranteed in combination with suitable base materials and additives.