QUV is an accelerated aging instrument which creates an artificial environment in a 12-hour cycle. These cycles are designed to stimulate UV exposure on surface finishes, coatings, and polymers. Testing consists of 8 hours UVA-340 at 60 degrees, then 4 hours of darkness and condensation (mimicking dew) at 50 degrees.
Photo- degradation occurs because UV light has a shorter wavelength than visible light and can penetrate polymers deeper. As the adhesive starts to break down from UV light, the first three changes are noticeable to the human eye:
- Change in colour
- Loss of gloss
- Chalking (white precipitate starts to migrate towards the surface of the polymer).
After prolonged exposure, further visible changes are:
- Embrittlement (the adhesive can no longer withstand its original shape or form; can turn entirely into chalk)
There are some colours which are more susceptible to UV degradation than others. For example, red, orange and blue pigments contain an aromatic ring structure which increases said susceptibility. This is because structures like aromatic rings absorb UV rays more readily, causing a breakdown.
There are several tests that can be done under QUV requirements dependant on what the consumer is looking to achieve:
Practice for exposing non-metallic materials in accelerated test devices that use laboratory light sources.
Standard test method for accelerated weathering of solvent-release-type sealants.
Standard specification for nonvulcanized (uncured) rubber sheets used for roof flashing
Standard guide for testing coating powders and powder coatings
Standard test method for accelerated weathering of solvent-release-type sealants
If you have any questions about testing methods, or are unsure what to do next, feel free to contact our team for some non-biased advice.
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