What Is Weathering?
Weathering testing is a test group that assesses a material's ageing under the combined effects of sun, heat, humidity and pollutants. It is conducted naturally (outdoor) or in accelerated form (laboratory).
Purpose of Weathering
The purpose is to determine how long a material intended for outdoor use retains its appearance and mechanical properties.
Which Products Is Weathering Applied To?
- Building profiles and facade elements
- Automotive exterior parts
- Paint and coating systems
- Garden furniture and outdoor plastics
- Membranes and roofing
In Which Sectors Is Weathering Used?
Standards Related to Weathering
- ISO 877
- ASTM G7
- ASTM G24
- ISO 4892-2
- ISO 4892-3
- ASTM G155Accelerated aging with xenon arc test
- ASTM G154fluorescent UV accelerated aging test
Weathering Conditions
- Method
- Natural outdoor exposure or laboratory accelerated aging
- natural exposure
- Panel angle, orientation and climate zone are defined in the standard
- Accelerated
- Xenon arc or fluorescent UV cycles
- Time
- Years of natural exposure; Hundreds to thousands of hours in time-lapse
Equipment for Weathering
- Outdoor exposure racks (natural method)
- Xenon arc or fluorescent UV chamber
- Colour, gloss and mechanical measurement instruments
- Meteorological data logging (natural method)
Sample Requirements for Weathering
- Initial colour, gloss and mechanical values must be measured
- A reference sample must be kept in the dark
- Panel angle and orientation must be recorded for natural exposure
- Generally at least three specimens
Duration of Weathering
One to five years for natural exposure; weeks to months for accelerated methods, depending on the specification.
Weathering Procedure
- 1Initial measurements are taken and a reference sample is kept.
- 2A method is selected: natural exposure or accelerated cycling.
- 3Samples are placed at the defined angle and location.
- 4Interim measurements are taken at defined intervals.
- 5At the end of the exposure, colour difference, gloss and mechanical properties are compared.
Weathering Acceptance Criteria
The acceptance criterion is given in the specification as maximum colour difference, maximum gloss loss, or minimum retained mechanical property.
Evaluation of Results
Accelerated results do not translate directly to natural exposure; correlation can only be established with coefficients validated for the same material class. The method must therefore always be stated in the report.
Weathering Report
- Standard and method applied
- Exposure conditions or cycle programme
- Total duration or irradiance
- Colour, gloss and mechanical results
- Reference sample comparison
Accreditation
EUROLAB holds internationally recognised accreditation obtained from accreditation bodies party to the IAF and ILAC multilateral recognition arrangements, under ISO/IEC 17025 for laboratory testing, ISO/IEC 17020 for inspection and surveillance, and ISO/IEC 17021-1 and ISO/IEC 17065 for system and product certification. This chain ensures the reports and certificates issued are accepted worldwide.
Whether this test can be offered within accredited scope depends on your product and the standard applied; since accreditation is method-based, the scope is confirmed in writing at the quotation stage.
Scope and authorisationsRelated Regulations
- Construction and automotive material specifications
Plastics Testing — What Does This Testing Field Cover?
The section below describes the field that the Weathering test belongs to; the conditions and acceptance criteria of this particular test are given in the sections above. The scope specific to your product is confirmed in writing at the quotation stage.
Plastics testing determines the mechanical, thermal and burning behaviour of a polymer material. Unlike metals, plastics are VISCOELASTIC: their behaviour depends on loading rate, temperature and moisture. The same material therefore gives different results under different conditions, and the test conditions are an inseparable part of the result.
The practical consequence of viscoelasticity is this: a plastic part continues to deform over time under a constant load (creep) and the stress it carries at constant deformation falls over time (stress relaxation). A screwed joint loosens, a clamp loses its clamping force, a shelf sags over time. A short-term tensile test does not show this behaviour; a long-term test or an accelerated model is needed.
Thermal behaviour is the second main axis. Melt flow rate indicates the processability of the material and lot-to-lot consistency; heat deflection temperature and the Vicat softening point give a rough limit for service temperature. Thermal analysis (DSC, TGA, DMA) reveals the identity of the material: glass transition temperature, melting behaviour, crystallinity, filler content and decomposition temperature.
Burning behaviour is the third axis and ties directly into product standards. The UL 94 class and the limiting oxygen index are written into the material data sheet; a particular class is required for the housing of an electrical appliance, while a different classification system applies to a construction product.
Ageing is the most frequently skipped part of the field. Plastics degrade under UV, heat, moisture and oxygen: colour changes, the surface cracks, impact strength falls. For a part intended for outdoor use, what matters is not its values on day one but its values after ageing. Xenon arc and fluorescent UV equipment accelerate this degradation and allow comparison.
The output of this family is usually written into the material data sheet, and product standards refer to that sheet. But there can be a difference between the data sheet value and the behaviour of the actual part: orientation formed during moulding, weld lines and internal stresses make the part behave differently from the specimen.
The use of recycled content has added a new question to the field. Recycled resin varies from lot to lot; mechanical properties, colour and burning behaviour can shift between batches. For a manufacturer using recycled material, incoming material control is therefore not a choice but a necessity.
Method groups in this field
Mechanical
Tension, compression, bending, Charpy and Izod impact, hardness (Shore), creep and environmental stress cracking.
Thermal
Melt flow index (MFI), heat deflection temperature (HDT), Vicat softening temperature, linear thermal expansion.
Thermal analysis
Transition temperatures and crystallinity by DSC, composition and decomposition by TGA, dynamic mechanical behaviour by DMA.
Burning
UL 94 classification, limiting oxygen index (LOI), glow wire and needle flame tests.
Ageing
Accelerated ageing by xenon arc and fluorescent UV, hot air ageing, humidity and condensation.
Physical
Density, water absorption, ash content, gas and water vapour permeability of films and sheets.
Commonly confused in this field
- A plastics result without a stated test rate and temperature cannot be interpreted; viscoelastic behaviour depends on these parameters.
- A specimen result does not transfer directly to the actual part; moulding orientation and weld lines are decisive.
- HDT and Vicat values are NOT service temperatures; they are a rough indication of an upper limit and do not apply under load.
- The UL 94 class depends on thickness; a different wall thickness requires re-verification.
- For moisture-absorbing polymers (such as polyamide), results are misleading unless conditioning is carried out.
- ASTM D638 and ISO 527 results are not directly equivalent; the specimen geometries and rate definitions differ.
Which decisions these results support
- Material selection and supplier approval
- Meeting the flammability and thermal requirements of the product standard
- Verifying the use of recycled content and lot control
- Moulding process control and lot consistency
- Demonstrating ageing resistance for outdoor use
Related Tests
Frequently Asked Questions About Weathering
How many years of natural exposure does an accelerated test correspond to?
There is no universal conversion factor. Correlation depends on the material class, degradation mechanism and climate zone. Specifications therefore usually define test duration or total irradiance directly.