Interview: “Digital transformation affects weathering”
What are the trends in weathering testing equipment for coatings?
Florian Feil: The influence of heat on photo-degradation reactions is currently a hot topic in laboratory and outdoor weathering. It is important to measure and control the surface temperature for correlation studies of artificial and natural weathering exposures, for estimation of theoretical acceleration factors using kinetic models (Arrhenius activation energy) and, in the end, for service-life prediction. Therefore, the latest instrument generation can be equipped with a contactless thermometer, which allows measurement of the surface temperature of individual specimen in an operating instrument. Weathering stresses do not act independently. Coating surface temperature also has a major impact on moisture content, which can affect hydrolysis, as well as hydrodynamic volume changes and accompanying mechanical stress.
What innovative test methods could lead to improved testing procedures?
Feil: The measurement and control of the stress parameters becomes continuously better and will improve test methods and standards in a foreseeable future, like the above mentioned contactless measurement of the surface temperature. Also, an improved spectral match to terrestrial solar radiation of modern optical filters in Xenon-arc weathering instruments, in particular in the UV cut-on wavelength range, can have a major impact on correlation. Despite the known correlation problems for some coatings chemistries, the spectral requirements of most standards have been slow to adopt these developments.
Also there is room for improvement in accelerated outdoor weathering. Fresnel-mirror devices, which concentrate solar radiation are an established technology, however often limited by heat effects. Atlas developed a new solar concentrator technology utilizing “cool mirrors.” These mirrors only reflect UV and short wavelength visible radiation. This does not only allow reduction of the specimen temperature, but also increases the number of mirrors. Devices with 20 “cool mirrors” provide approximately 10-12 years of equivalent radiation exposure, as would be received in South Florida in a single year, but still at a realistic temperature level.
How much does digital transformation influence the development of novel testing and measuring technology?
Feil: Digital transformation is, like weathering, a continuous long-term process. It affects weathering testing on many levels, such as test specimen organization, parameter and cycle control, handling of service and calibration, keeping track on spare parts and consumables and many other levels. Remote weathering instrument monitoring over the web has helped to improve the consistency of test exposures by alerting the user to any anomalies and, thus, to decrease instrument downtime. However, many things in weathering testing, like sample handling and evaluation, still require a lot of manpower at the instrument/human interface. The technical testing effort per sample and the test duration are relatively high and the sample turnover relatively limited. Therefore, weathering testing and measuring technology might stay a little behind in this regard compared to other test methods.