Examining differences in the uptake of corrosive gases in polymer films and its dependence on temperature and relative humidity using a novel procedure combining sample weathering and LA-ICP-MS analysis

Abstract

In polymer coating applications for technological products exposed to harsh environmental operating conditions, it is essential to provide and extend the protection capability of the coating material against corrosive gases, such as hydrogen sulfide or sulfur dioxide. Therefore, applied materials are subject to ongoing developments to improve their properties. Such developments aiming to establish improved polymer materials can only be performed accompanied by suitable testing procedures and analysis methods, for which a versatile approach is proposed in the presented work. We developed a testing approach, combining a mixed flowing gas setup (MFG) that allows flexibly adjustable exposure conditions for weathering experiments, and laser ablation – inductively coupled plasma – mass spectrometry (LA-ICP-MS) for subsequent sample analysis, allowing quantitative and spatially resolved determination of the sulfur uptake derived from H₂S or SO₂ weathering with high sensitivity. The testing procedure is demonstrated on four different polymer types – polyimide (PI), polyvinylpyrrolidone (PVP), polystyrene (PS), and polyvinylacetate (PVA). Results from bulk measurements showed a significantly higher uptake of SO₂ compared to H2₂, and that the uptake increases with higher exposure temperatures and relative humidity levels. Further, quantitative sulfur depth profile measurements reveal diffusion profiles into the polymer films. The gas uptake was observed mostly withing the uppermost 1–2 µm of the surface, with quickly decreasing concentrations into the bulk of the materials. However, strong variations of the spatial distribution of sulfur between the different polymer types and between different exposure conditions were determined. The results provided give a good insight into what possibilities the proposed investigation procedure opens up for specifically dedicated research compared to standard methods that are used to determine gas permeation.