The UK's changeable temperature necessitates this test. The plate's shape and size must remain the same when subjected to heat and cold.
The thermal change test is designed to replicate UK climatic conditions over time.
It is one of the most challenging tests to pass due to both 5 cycles of 24 hours of temperature change, plus a long list of failure criteria.
How are plates tested:
A plate is placed vertically (+/- 10°) into a support stand.
The plate is exposed to a thermal change cycle making up 24 hours. This 24 hour cycle is repeated 5 times, totalling 120 hours (5 days).
The exposed plate is compared to an unexposed sample for signs of failure.
What makes a fail:
The plate changes appearance:
- Blistering (bubbles appear in the plate)
- Delamination (where a plate’s components separate)
- Faded print
- Loss of colour
- Loss of retroreflectivity
The plate changes shape:
- Shrinking (part or all of the plate)
- Distortion (bending out of shape)