Plastics in a Changing Climate: Are We Testing for the Right Conditions?

Summer 2026 has provisionally become the UK’s hottest summer on record. According to the Met Office, the UK’s average mean temperature across June, July and August reached 16.5°C, surpassing the previous record set only last year. The season was also exceptionally sunny in many areas and unusually dry across large parts of the country.

For manufacturers, that is more than a weather headline. It raises an important question: are the assumptions we make about how plastic products will perform outdoors still realistic?

Weather exposure is a material performance issue

Plastics used outdoors are rarely exposed to just one environmental stress. Sunlight brings ultraviolet radiation, high temperatures can accelerate physical and chemical changes, and moisture and humidity introduce further stresses.

Over time, these conditions can contribute to fading, discolouration, loss of gloss, cracking, embrittlement and changes in mechanical performance.

The challenge is that these effects are not always obvious when a product leaves the factory. A component may meet its specification on day one, yet behave very differently after months or years outdoors.

With record temperatures becoming increasingly relevant to real-world operating conditions, long-term durability deserves consideration earlier in product development.

Are existing weathering tests still relevant?

Yes, but the key question is how they are being used.

Established weathering standards provide repeatable methods for comparing materials and evaluating durability. Standards such as ISO 4892 expose plastics to controlled laboratory light sources, heat and moisture so that potential degradation can be assessed under reproducible conditions.

The bigger issue is whether the chosen testing programme reflects the conditions the finished product is actually expected to face.

An indoor component has very different requirements from an exterior automotive part or a product expected to spend years in direct sunlight. Products sold across different markets may also encounter very different combinations of temperature, UV exposure and moisture.

As climatic conditions change, manufacturers may therefore need to revisit the assumptions behind their durability requirements, rather than simply asking whether a material has “passed a weathering test”.

Testing the product, not just the polymer

Material selection is only part of the picture.

Pigments, stabilisers, fillers, coatings and other additives can influence weathering behaviour. Colour can affect surface temperature, while manufacturing processes and product geometry can also influence how a finished component responds to environmental exposure.

Changes made for sustainability or cost reasons introduce further variables. Switching polymer grade, increasing recycled content or adjusting a formulation may deliver one benefit while changing long-term durability.

After weathering, samples can be assessed for visible changes such as colour, gloss or cracking. Mechanical testing can also determine whether properties such as strength or impact resistance have changed.

This gives manufacturers a clearer picture of what environmental ageing has actually done to the product, rather than relying on appearance alone.

Accelerating years of exposure

Waiting several years to discover whether a new product survives outdoors is rarely practical.

Accelerated weathering chambers expose samples to controlled combinations of light, temperature, moisture and spray, allowing manufacturers to investigate degradation over a much shorter development timescale.

At Impact Solutions, our accelerated weathering laboratory includes Q-SUN Xenon Arc chambers and QUV weathering testers, with testing available across a range of industry standards. Testing programmes can be selected according to the material, product and environment being investigated.

The aim is not to reproduce every future summer perfectly. No laboratory test can do that. Instead, accelerated weathering provides controlled evidence that can help compare materials, identify potential weaknesses and support better decisions about durability.

Designing for the conditions ahead

The UK’s record-breaking summer does not mean every manufacturer should immediately change its test specification.

It should, however, prompt a useful conversation.

What environment was your current durability requirement based on? Has the material, formulation or supplier changed since it was established? Is your product now being used in hotter, sunnier or more geographically diverse conditions than originally expected?

Testing should reflect the conditions a product needs to survive, not simply the conditions it has survived before.

If you are reviewing the outdoor durability of a plastic product or material, Impact Solutions can help develop an accelerated weathering programme suited to your application and testing requirements.

Get in touch with our technical team for more information on our accelerated weathering capabilities.

Frequently Asked Questions

What does accelerated weathering testing measure?

Accelerated weathering investigates how a material or product responds to controlled stresses such as UV or simulated sunlight, heat, moisture and water spray. Samples can then be assessed for changes in appearance, physical properties and mechanical performance.

What is the difference between QUV and Xenon Arc testing?

QUV uses fluorescent UV lamps and is commonly used to investigate the effects of UV exposure and moisture. Xenon Arc provides a broader light spectrum intended to reproduce sunlight more closely and can incorporate heat, humidity and water spray. The appropriate method depends on the product, material and relevant testing standard.

Can accelerated weathering predict exactly how long a plastic will last outdoors?

Not exactly. Real-world exposure varies according to location, orientation, season and use. Accelerated weathering is most valuable for comparing materials, investigating degradation and assessing performance under defined conditions, rather than providing an exact outdoor lifespan.