Samuel Brunner

Characterization of materials released into water from paint containing nano-SiO2.

In order to assess the possible risks of applications containing engineered nanomaterials, it is essential to generate more data about their release and exposure, so far largely overlooked areas of research. The aim of this work was to study the characterization of the materials released from paint containing nano-SiO2 during weathering and exposure to water. Panels coated with nano-SiO2 containing paint and a nano-free reference paint were exposed to accelerated weathering cycles in a climate chamber. The total release of 89 six-hour cycles of UV-illumination and precipitation was 2.3% of the total SiO2 contained in the paint. Additional tests with powdered and aged paint showed that the majority of the released Si was present in dissolved form and that only a small percentage was present in particulate and nano-particulate form. TEM imaging of the leachates indicated that the majority of the particulate Si was contained in composites together with Ca, representing the paint matrix, and only few single dispersed SiO2-NPs were detected. The results suggest that toxicological and ecotoxicological studies need to consider that the released particles may have been transformed or are embedded in a matrix.

Service life prediction for aircraft coatings

A model with three stress types, the temperature, UV and aerosol, for estimating the service life of organic coatings under service conditions has been proposed. The model has been applied to the estimation of the service life for aircraft coatings concerning loss of gloss. The results obtained from a unique natural exposure programme for a reference polyurethane coating have been compared with the results from the specially designed accelerated ageing tests, which were performed with a new designed and constructed weathering device. As a special point of interest, the influence of sulphuric aerosol, which has simulated the stratosphere conditions after a big volcano eruption, on the service life of the reference coating has been investigated.

Analysis of the environmental parameters for aircraft coatings

Temperature, UV radiation and pollutants play a major role in the degradation of aircraft coatings. The UV radiation at flying altitude is more intense than at ground level. An analysis of the radiation spectrum was used to choose the appropriate lamp type for artificial weathering in the laboratory. For the pollutants we examined the fact that the service life of aircraft coatings was considerably reduced in the years following the eruption of the volcano Pinatubo. It is shown that sulphuric-acid-aerosol droplets dispersed in the stratosphere were the main cause for that damage.