|
 2. Automobile tire
Figure
32 shows an FTIR-PAS spectrum of a typical automobile tire with
a high carbon black concentration. Tire samples are among the
most difficult materials from which to obtain infrared spectra.
The spectrum of Fig. 32 was obtained on a slab of tire cut out
with a razor blade. Twenty-thousand FTIR scans were co-added
for sample and reference spectra at an OPD mirror velocity of
0.5 cm/s and 8 cm-1 resolution.
Fig. 32. FTIR-PAS spectra of an automobile tier.
The lower
spectrum is the ratio of a single beam tire spectrum to a single
beam glassy carbon spectrum. The upper spectrum is the result
of baseline flattening, subtraction of CO2
bands and blanking of another gas feature between 2000 and 2100
cm-1, and a 19 point smoothing.
F.
Polymer Films
1.
Elimination of interference fringes by FTIR-PAS
Interference
fringe bands are often observed in infrared transmission spectra
of polymer films. These bands interfere with and obscure important
small features in spectra associated with various types of additives.
FTIR-PAS spectra are free of interference artifacts due to the
differences in signal generation between an absorption versus
transmission based measurement.
Figure
33 shows spectra measured by the conventional transmission method
and by FTIR-PAS of the same polyethylene film. The spectra were
measured directly on the film material after punching out a disk
of the film with a cork borer. The FTIR-PAS spectrum |
