PVDF under the effects of weather

PVDF is a plastic that is highly UV resistant. However, what does “high” mean? How does the material change when it is exposed to the effects of weather over a prolonged period? An important question, especially regarding use in solar plants. We have been searching for an answer.

Solar energy in particular is benefiting from the changeover to alternative energy sources. Groups of solar panels are combined to form modules and trackers (15 x 7 m), for which the piping is implemented with PTFE hoses and PVDF unions. The hoses and unions are exposed to direct sunlight whilst the solar plants themselves are set up in very dry regions with a great deal of sunlight that also have wide-ranging fluctuations in temperature.

SERTO has been delivering these pre-assembled lines to the full satisfaction of customers for over 5 years. We have now asked customers to provide us with a few of these 5-year old PTFE hoses and PVDF unions for tests. We wanted to submit these components to intensive tests in the in-house SERTO testing and experimental workshop.

In these internal tests, the seal and pressure resistance of the system was checked. The result was clear and showed no technical defects after an intensive period of 10,000 hours exposure to light. No air leakage could be detected and the bursting pressure was still more than three times the rated pressure. However, there was visible yellowing as a result of UV radiation.

At the same time, we also investigated PVDF films in an independent laboratory and assessed the ageing of the material with regard to mechanical properties. The measurements show slight brittleness. Even after 9 years of exposure to the weather, the mechanical properties of the investigated PVDF films are rated as good.

Summary

The results from the test laboratory and in practice agree and show that our PVDF unions have great resistance to the effects of weather. Long-term tests have shown that large temperature fluctuations and intense UV only change the mechanical properties of PVDF unions to a negligible extent.
 

Excerpt from Uptodate 44