Photoacoustic FTIR spectroscopy polymers

The use of photoacoustic FTIR spectroscopy in quantitative analysis of polymers was investigated with reference to determination of vinyl acetate in EVA, acrylonitrile in NBR, ethylene in EPDM, styrene in SBR and vinyl-butadiene in SBR. The results obtained indicated that, despite the theoretical complexities of photoacoustic FTIR spectroscopy, simple quantitative relationships could be found for many of these polymer analyses. 24 refs. 

New York City, 2nd-6th May 1999, p.2424-8. 012 MOLECULAR ANALYSIS OF POLYMERS BY FTIR PHOTOACOUSTIC SPECTROSCOPY McClelland J F Jones R Bajic S MTEC Photoacoustics Inc. Iowa State University (SPE)... 

FTIR photoacoustic spectroscopy (PAS) has advantages relative to conventional IR techniques (transmission, reflection and emission) because it is non-destructive, does not involve sample preparation and can probe samples with compositional gradients and layers. The theory, instrumentation, methods and applications of FTIR-PAS are discussed and results are presented on several polymer analyses based on FTIR-PAS. 4 refs. USA... 

Some new developments of two-dimensional spectroscopy are discussed. As a specific example, two-dimensional correlation analysis of a polymer laminate film using several different spectroscopic techniques is presented. The versatility of this technique was developed using depth-profiling photoacoustic spectroscopy, mid-and near-IR dynamic rheooptical developments, and spectroscopic imaging microscopy. Spatial and temporal variations of near-IR spectra are effectively analysed by the two-dimensional correlation technique. Step-scanning FTIR spectrometers provide an opportunity to obtain desired spectral information often difficult to obtain by the conventional rapid-scanning technique. 12 refs. 

Impurity inclusions and surface defects are a cause of many difficulties to the polymer producer and user. Equipment used for studying these phenomena discussed in Chapter 4 include electron microprobe x-ray emission/spectroscopy, NMR micro-imaging, various forms of surface infrared spectroscopy, e.g., diffusion reflection FTIR, ATR, also photoacoustic spectroscopy and x-ray diffraction - infrared microscopy of individual polymer fibres. Newer techniques such as scanning electron microscopy (SECM), transmission electron microscopy, time of flight secondary ion mass spectrometry (TOFSIMS), laser induced photoelectron ionisation with laser desorption, atomic force microscopy and microthermal analysis are discussed. 

Kinetic processes can be monitored by a technique known as time-resolved spectroscopy which involves FTIR. This method has been applied to analysis of complex materials such as polymer film stretching which can be carried out in milliseconds and chemical transformations involving, for example, coal pyrolysis it also permits on line analysis of products subject to chromatographic separation methods such as GC and LC. During the past five years GC-IR and GC-FTIR involved separating of mixtures and analysis of the individual compounds by IR spectroscopy. The sensitivity limitation of IR detectors with respect to GC and the time difference between the elution of a GC peak (measured in seconds) and the time scan were two of the problems encountered. GC-FTIR allows an IR spectrum taken from a 5-/u,g GC peak of isobutylmethacrylate by repeatedly scanning with spectral accumulation and enhancement (Fig. 8). FTIR measurements may be carried out by one of the following techniques (a) KBr pellets, (b) photoacoustic, and (c) diffuse reflectance methods. 

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