A small change in rubber molecular analysis means a large change in results

Konstantin Tartakovsky, Fuel and Chemistry Department, Israeli Air Force, Depot 22, Materials Division, Israeli Air Force, Depot 22, Materials Division, Israel (kosta002@gmail.com)
Bruno J. Beccard, Thermo Fisher Scientific, Paris , France
Michael S. Bradley, Thermo Fisher Scientific, Madison , Usa
Moshe Rabaev, Fuel And Chemistry Department, Israeli Air Force, Depot 22, Materials Division, Israeli Air Force, Depot 22, Materials Division, Israel

Black rubber is made up of a large number of materials, including a polymer, carbon black and inorganic fillers. The presence of carbon black in rubber makes the identification of the polymer via FTIR - a simple and available method for polymer identification - rather difficult.


To identify black rubber in FTIR, ATR may be used with a germanium crystal, leading to a very shallow penetration of the IR beam into the material, thus leading to a smaller interference of the carbon black within the spectrum. This analysis may allow for some identification of the rubber material, but the spectrum that is gotten this way is usually not very informative because of the interference of other fillers with FTIR-rich spectra. The usual analysis, therefore, is pyrolysis of the rubber onto a crystalline IR-transparent substrate, like KCl, KBr or NaCl, and then these substrates are tested using a transmittance method. Standards ISO 4650 and ASTM D3677 describe this test method well.


However, the problem with this method is that all these substrates are very hygroscopic, allowing the absorbance of water molecules to obscure a large part of the spectrum of the pyrolyzate.


As of late, many laboratories turn to complex, combined techniques, like PYR-GCMS or FTIR-TGA. Of course, these combined techniques have many advantages, but our laboratory had found a way to improve the pyrolysis FTIR analysis, thus reducing the usage of costly and time-consuming techniques.


The improvement is rather simple – instead of an ionic salt crystalline substrate, we found that by using a glass slide as the substrate, then transferring the pyrolyzate vapors upon the slide to be tested using an ATR method with a diamond crystal, we were able to get a very detailed, much better spectrum, clean of water vapor absorbance.

Short Biography of Presenting Author

Konstantin Tartakovsky is the Head of Analytical Laboratory in the Israeli Air Force. He has a BSc in Chemistry and an MSc in Medical Science, both from Tel Aviv University. His lab provides chemical and analytical support for aviation failure investigations. They design and develop reliable analytical methods including quantitative and qualitative identification of different contaminants in oils, fuels and cooling fluids. In addition, they research the aging and degradation of materials; material compatibility and their stability in different environments, and perform extensive quality control research of air quality inside jet cockpits.

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