Carbon black absorbance spectra

The difference spectrum shows negative absorbance at 1720 cm"1 which is due to the reaction between -COOH groups on the oxidised carbon black surface and to -NH2+— and Si-OCH3 of silane coupling agent. This is further substantiated from the appearance of a peak at 1635 cm-1 with a shoulder at 1620 cm 1, which is due to formation of -(C=0)—N—(amide) and -Si-0-(C=0)- (silyl ester). 

Carbon blacks are strong absorbers of light over the entire spectrum and are the... 

When neither transmission nor reflection infrared spectra are satisfactory, spectra can generally be obtained by photoacoustic spectroscopy. The IR spectrum that is obtained is ratioed against an IR spectrum of carbon-black. PAS spectra resemble normal IR spectra with the same absorbance peak wavenumber locations as classic transmission spectra. Because the signal-to-noise ratio of PAS is very low, several thousand scans are needed to obtain a spectrum. The nature and interpretation of the spectra are markedly influenced by the thermal and acoustic properties of the sample. 

Because the beam in an FTIR spectrometer is modulated, the signal that the microphone measures is an interferogram, and this can be transformed to give a spectrum. The sample spectrum is usually measured as a ratio against a carbon black spectrum, because this absorbs all of the radiation falling onto it. The result is an absorbance-like spectrum (Fig. 10.76). In addition, because the photoacoustic effect occurs in the surface of the sample, it is possible to obtain depth-related information by altering the interferometer mirror velocity [1487]. 

Figure 6. Transmission spectra of two 30% glass fiber reinforced PA6 compounds. One contains carbon black and absorbs light over the whole spectrum. The second contains selected pigments which render it transparent for IR radiation, while it still appears black in the visible spectrum. Thickness is 3 mm. 

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