Qualification of New Polymeric Materials for Solar Thermal Applications
Abstract
Polymers can offer additional degrees of freedom for collector design and access to cost-effective mass-production technologies for solar thermal applications, like collectors for example. But they have to stand harsh operational conditions. They are exposed to high temperatures, humidity and UV- irradiation. We exposed different types of polymeric materials to accelerated ageing tests. Samples were based on commodity plastics like poly-propylene (PP) with different stabilization systems, technical polymers like polyamide (PA) and cyclic olefin copolymers (COC), some with nano-fillers like glass-fiber (GF) or carbon-nano-tubes (CNT). Different compounds of high-performance polymers like polyphenylene sulfide (PPS) have been exposed, too. Some of the materials have been coated with optical selective coatings. The ageing conditions were different levels of high temperatures, high humidity and high UV- irradiation as well as combined tests. Optical, non-destructive methods like FFT-IR spectroscopy and Raman microscopy have been used for the characterization of the samples as well as atomic force microscopy (AFM). The results show a very strong influence of humidity at high temperatures on the degradation while UV exposure didn’t lead to significant changes of the surfaces.