Reference beam infrared spectroscopy

Miller and Willis" obtained infrared spectra of antioxidants from polymer films. They compensated with additive free polymer in the reference beam. Infrared spectroscopy is more specific than ultraviolet spectroscopy, but some workers find that the antioxidant level in polymers is too low to give suitable spectra. In-situ spectroscopic techniques are not likely to be of value then, in the analysis of samples of unknown composition. 

There is supporting evidence in the literature for the validity of this method two cases in particular substantiate it. In one, tests were made on plastics heated in the pressure of air. Differential infrared spectroscopy was used to determine the chemical changes at three temperatures, in the functional groups of a TP acrylonitrile, and a variety of TS phenolic plastics. The technique uses a film of un-aged plastic in the reference beam and the aged sample in the sample beam. Thus, the difference between the reference and the aged sample is a measure of the chemical changes. 

I suggest the use of infrared spectroscopy for the laboratory tests. Samples of the him can be mounted in the path of the infrared light beam in an infrared spectrometer and the resulting infrared transmission spectra recorded. If your staff is not familiar with infrared spectroscopy or the interpretation of infrared transmission spectra, you might allow them some time to read some basic reference material on this technique. I can provide that for you. The transmission spectrum recorded by the spectrometer is like a fingerprint of the material in the path of the light. It is a pattern that is observed each time that material is tested. 

The use of infrared spectroscopy for the characterization of polymer blends is extensive (Olabisi et al. 1979 Coleman and Painter 1984 Utracki 1989 He et al. 2004 and references therein Coleman et al. 1991, 2006). The applicability, fundamental aspects, as well as principles of experimentation using infrared dispersive double-beam spectrophotometer (IR) or computerized Fourier transform interferometers (FTIR) were well described (e.g., Klopffer 1984). 

All measurements were made in the gas phase. The methods used are abbreviated as follows. UV ultraviolet (including visible) spectroscopy IR infrared spectroscopy R Raman spectroscopy MW microwave spectroscopy ED electron diffraction NMR nuclear magnetic resonance LMR laser magnetic resonance EPR electron paramagnetic resonance MBE molecular beam electric resonance. If two methods were used jointly for structure determination, they are listed together, as (ED, MW). If the numerical values listed refer to the equilibrium values, they are specified by and 6. In other cases the listed values represent various average values in vibrational states it is frequently the case that they represent the Tj structure derived from several isotopic species for MW or the r structure (i.e., the average internuclear distances at thermal equilibrium) for ED. These internuclear distances for the same atom pair with different definitions may sometimes differ as much... 

A review covering instrumentation—sources of infrared radiation, slit system, dispersing elements, detectors, amplification and recording, single and double-beam and fast-scanning spectrometers, preparation and examination of samples, applications of infrared spectroscopy, and infrared spectroscopy and coal structure. 232 references. 

Mirabella and Koberstein have previously shown the benefit of DSC/FT-IR for polymer characterization (3,4). In this work, the same epoxy system described above in the uncured state was analyzed by DSC/FT-IR. Thin films of uncured amine-activated epoxies were placed in the sample pan of the FP84 and heated from 25 to 280 °C at 10 C per minute. Changes in the structure of the epoxy as a fimction of temperature were recorded simultaneously by infrared spectroscopy. The sample was relatively transmissive to infirared radiation. The beam transmitted down through the sample, reflected off the aluminum cup, and passed back up through the material. This type of analysis is called reflection/absorption spectroscopy. A "well behaved" absorbance spectrum was generated directly without any need for correction. To produce a sufficient signal on the DSC, the bulk of the sample had to be placed on the reference side. 

The Michelson interferometer does not measure the infrared spectrum directly. Rather, an interfero-gram is measured, and converted to a single-beam spectrum via Fourier transformation. Because of the critical role of this transformation, the method is generally referred to as Fourier-transform infrared spectroscopy, or FT-IR . Instruments using this... 

Pierre [60] has reported a study of the characterisation of the surface of oil slicks by infrared reflective spectroscopy. A double-beam spectrophotometer was modified for studying the reflectance spectra (at angles of incidence 45°, 60°, 70°) of oil layers (20-30 xm thick) on the surface of water using pure water as reference. 

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