FTIR spectroscopy may characterize many chemical substances provided that they have structures interacting with light in the infrared region i.e. wavelengths between 400-4000 cm-1 (or 2,5-25 micrometers). Most polymers have a specific spectrum, like a "fingerprint" for the material.
By FTIR spectroscopy an unknown sample may be determined by comparing the sample spectrum with a reference spectrum from a database. Sometimes it is difficult to interpret spectra from plastics since they often contain additives affecting the spectra. Therefore we often combine FTIR-analyses with DSC (Differential Scanning Calorimetry) to measure the melting point, since polymers have specific melting points.
FTIR-technique can also be used to follow chemical reactions, for example oxygen containing degradation products with a characteristic absorption band increasing with time. In polymerisation reactions the absorption band from the reactants disappear.
The instruments we use are equipped with microscope where the IR beam may be focused on small regions in a sample. This allow analyzes of contaminants in a sample. Cross sections of 5 micrometers may be analysed.
In IR spectroscopy we use the interactions between molecular vibrations and the IR light, which absorb or transmit the the light at specific so called resonance frequencies. The resonance frequencies are specific for different chemical bonds.
The technique may be used for solid samples as well as liquids or gas samples. Usually we analyse solid samples. Plastic samples may be compression moulded to thin films wich are illuminated by the IR light. An ATR (Attenuated Total Reflection) device allow analysis on the sample surface and no sample preparation is needed. IR light is reflected on the ATR device and "bounce" on the sample surface and a spectra from the sample surface, with a penetration depth of only 1-2 micrometer is achieved.
Results are reported in a report containing the interpreted spectra.
FTIR-spectroscopy for polymer, plastics, textile and rubber analysis
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Within two weeks from sample arrivaI, but usually earlier if no sample preparation is needed.