Infrared Spectroscopy - Material Assessment

Infrared spectrometer with attenuated total reflection sampling accessory installed

Comparison of polymer spectra

Infrared spectroscopy is a technique that can be used mainly qualitatively but occasionally quantitatively for identification of organic (and sometimes inorganic) substances.

Each organic compound whether it be a simple compound, polymer or adhesive produces a characteristic spectrum when a beam of radiation from the infrared region of the electromagnetic spectrum is passed through it. As the light source changes in wave number, certain molecular vibrations give rise to absorptions or peaks at definite values of wave number. It is the position and pattern of these peaks that produce a characteristic spectrum.

As part of a continuing programme of investment, Sandberg has acquired a spectrometer with attenuated total reflectance sample handling. This allows a direct spectrum to be obtained on dense samples with black or coloured fillers. In the simplest form, the sample might be a piece of plastic, rubber or sealant which can be placed in the sampling device. The sampling device can look at very small amounts of material down to 2mm across without further preparation.

In some cases however the compound of interest must be separated from a substrate such as concrete, plaster or stone and converted to a suitable form for presentation to the instrument.

The technique together with state of the art computer software allows identification of subtle product variations from the same or different manufacturers' products of the generic substance types such as polysulphides or silicones.

The technique has been successfully used on small quantities of extracts to identify additives and bonding agents in construction materials, for example pva bonding agents at render interfaces.