Accelerated Weathering Test Development With Fluorescent UV-Condensation Devices

Quality and durability have become very important aspects in the development of automotive components. Consumer expectations and competitive pressures require reliable and rapid testing to determine end use performance. One of the most important areas of test development is in exterior durability predictions for polymeric materials.

Spearman's rank correlation coefficients were used to determine the ability of several accelerated testing devices to predict the weathering performance of flexible polymer films used in exterior automotive graphic design. Commonly used cycles in carbon arc and fluorescent uv-condensation test equipment exhibited generally unacceptable correlation levels for these materials. Three causes for this poor correlation have been identified:

1. 1.
   Test device variability can be a significant problem and certain precautions have been taken to insure uniform environmental stress application to all test specimens.
2. 2.
   Similar predetermined exposure periods for all samples have proven to be misleading. There is an optimum exposure period for best correlation for each material and each cycle.
3. 3.
   For maximum correlation, the stresses induced by the accelerated testing device should be characteristic of the natural environment. The effect on correlation by varying these stresses (uv spectral distribution and condensation cycle duration) can be significant.