Applications of infrared spectroscopy in material characterization

It is of great importance to identify and understand curing reactions for the development and production of tailored and high performance fiber-reinforced polymers. Infrared spectroscopy (IR spectroscopy) and in particular the combination with other characterization methods provides a high potential.
In infrared spectroscopy (IR spectroscopy), molecular vibrations are induced by electromagnetic radiation and afterwards detected. The vibrations are influenced by the mass and the bond strength of the molecules. However, molecules react to IR radiation not only with changes in vibration energy, but also with changes in rotational energy. These rotational transitions are particularly interesting in gas phase. Nowadays, mainly Fourier transform infrared spectrometers (FT-IR spectrometers) are used. They measure an interferogram and calculate the corresponding IR spectrum using a Fourier transformation. FT-IR spectrometers are characterized by short measurement times and a high signal-to-noise ratio.

Last year, three different couplings between FT-IR spectrometers and other characterization methods were installed at Institut für Verbundwerkstoffe GmbH (IVW), allowing the correlation between changes in material properties and molecular changes. Combining light microscopy and IR spectroscopy in the NicoletTM ContinuμmTM infrared microscope makes it possible to detect chemical information at the microscopic level (e.g. differences at interfaces). The combination of rheological data and structural changes of the molecules in a simultaneous FT-IR rheology measurement makes it possible to correlate viscosity changes directly with advancing chemical reactions (e.g. cross-linking reactions). The corresponding measurements are performed by a HAAKE MARS 60 Rheometer and a NicoletTM iSTM 50 FT-IR spectrophotometer, coupled by the Rheonaut. Investigation and detection of escaping gases, e.g. in curing or degradation reactions, can be realized by coupling a thermogravimetric analysis (TGA/DSC 3+) and a NicoletTM iSTM 50 FT-IR spectrophotometer. By characterizing the gas phase, it is possible to identify polymer combinations and obtain additional information about intermediate products during thermal degradation or chemical reactions in addition to the change in mass and heat flow. This provides new possibilities for a better identification of complex materials or thermally induced processes in particular.

Further information:
Maurice Gilberg, Dipl.-Chem.
Tailored Thermosets & Biomaterials
Institut für Verbundwerkstoffe GmbH
Erwin-Schrödinger-Str. 58
67663 Kaiserslautern
Phone: +49 (0) 631/2017-348
E-Mail: maurice.gilberg@ivw.uni-kl.de