Characterization of fluoroelastomers compounds by ATR-FTIR

Abstract

Fluoroelastomers (FKM) are used to manufacture seals and other rubber devices that can withstand harsh operating conditions, including aggressive media and extreme low and high temperatures. Even though nuclear magnetic resonance, Fourier-transform infrared spectroscopy (FTIR), and chromatographic techniques have been extensively used in the characterization of raw FKM molecules, the identification of cured compounds entails a characterization method that is able to overcome the complexity related to this kind of structure. In this sense, attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy can outperform other characterization techniques because it does not require solubilization or any special preparation of the sample. In this study, 10 FKM compounds were produced in this study utilizing four commercial types of FKM and the fillers carbon black, barium sulfate, and iron oxide. All unfilled-FKM (as received) and their compounds were analyzed by ATR-FTIR with germanium crystal. Between 15 and 25 analyses were performed for all each FKM type sample and their respective compounds. All spectra were analyzed, and the bands were assigned. Findings regarding the interference of the fillers in the spectra were also reported. From relationships between the height of the spectral zones and the bands at 1397 and 1428 cm−1, it was possible to distinguish all sample compositions of FKM types 1, 2, 3, and 5. This study demonstrates that ATR-FTIR has the potential to be utilized as a technique to detect the type of FKM compounds, an important rubber used in harsh industrial applications. Replacing carbon with BaSO4 reduces the tensile at 50% strain of FKM types 1 and 2 composites. FKM types 3 and 5 composites filled with 30 phr of carbon black have a higher tensile at 50% strain than those of FKM type 1.