Weathering technology will continue to evolve with better environmental controls

Where does R&D in weathering testing focus on at the moment?

Sean Fowler: The big picture challenges do not change much over time. The goal is to obtain results that anticipate real-world performance over years or even decades, in as short a time in the lab as possible. Today, companies are pursuing two approaches. The first is to increase the concurrent stresses of sunlight, heat, and moisture as much as possible to screen out some lower performing products, then assume those that pass will perform acceptably in the field. The second is to make lab testing replicate the real-world stressors as accurately as possible, and then develop evaluation techniques that detect degradation processes before they visibly affect the material’s performance. Balancing the stressors in a way that achieves realistic results is often the biggest challenge.

What do you see as the remaining challenges?

Fowler: A hybrid approach to the above is to investigate, on a case-by-case basis, how the most realistic weathering cycles can be accelerated by increasing a single stressor, such as the intensity of the simulated sunlight, to achieve results faster with minimal loss of accuracy. This is more difficult than it first appears. When one has developed a lab test cycle that provides a realistic simulation of the natural weathering environment, that cycle, in theory, should be applicable over a wide range of products or materials. However, when one stressor is accelerated, such as testing at higher UV-irradiance or temperature, the simulation is thrown off-balance. Not only that, but the way it has shifted off-balance is material dependent. What works well for one material probably won’t work as well for other materials, and the adjusted test parameters could completely ruin the simulated test’s accuracy.

Obtaining outdoor weathering data is critical

How do you think the sector will develop in the upcoming years?

Fowler: Weathering chamber technology will continue to evolve with better environmental controls and improvements to their ability to simulate natural weathering. Weathering standards committees are already working on this. In addition to that, microscopic evaluation techniques give researchers tools to find early signs of degradation that differentiate performance levels. What can take thousands of hours to see with typical weathering evaluation techniques — gloss loss, colour change, tensile strength degradation, etc. — may be detected by microscopic techniques much earlier. I hope another focus is on revisiting outdoor weathering. Obtaining outdoor weathering data is critical for validating any new developments in lab weathering; but all too often, developments in the lab are hindered by a lack of the outdoor data. The solution to this problem is to maintain a regular schedule of outdoor weathering to anticipate future needs. Microscopic evaluation techniques should be applied to outdoor weathering more than they currently are, in my opinion. Finally, there are ways to increase the intensity of natural exposures, such as with sunlight concentrators and tracking weathering boxes. These tests are surprisingly underutilized by industry.