Infrared Photoacoustic Spectroscopy of Carbon Black Filled Rubber: Concentration Limits for Samples and Background

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Abstract
Infrared spectroscopy studies of the cure chemistry, state of cure, and surface bloom on rubber materials have always been limited by the presence of carbon black in samples. One of the modern methods for recording infrared spectra of solid samples is photoacoustic detection Fourier transform spectroscopy. It has been demonstrated in the past that surface-segregated species can be identified with this technique, but the results are complicated by the presence of carbon black, which limits the optical depth. As for the study of bulk chemistry, photoacoustic detection does not require that the sample be infrared transparent, and the method can be used with samples containing as much as a 15 wt % carbon. At loadings higher than 30 wt %, the material becomes a total absorber and can be used to record an instrument background spectrum.