Analysis of an Unknown Polymer Sample by TGA/DSC-FTIR

The composition of unknown polymer samples can be quickly characterized by means of combined TGA/DSC-FTIR measurements. This article describes a typical example.

Introduction

A TGA/DSC directly coupled to an FTIR spectrometer can be used to investigate the decomposition products of a material while it is heated [1]. This provides information about the composition of the original material. Further information can be obtained from the DSC curve measured simultaneously during the TGA experiment. In this article, we show how the composition of an unknown black polymer sample can be determined from measurements using a TGA/DSC-FTIR instrument combination.

Experimental Details

The experiments were performed using a TGA/DSC 1 equipped with a DTA sensor. The TGA/DSC 1 was coupled to a Thermo Nicolet iS™50 FTIR spectrometer. Both the transfer line and the gas cell in the spectrometer were maintained at 200 °C to prevent condensation of the decomposition products. Our instrument was also equipped with an ATR accessory (attenuated total reflectance), which can be used to measure the infrared spectra of opaque solids.

The measurements were carried out from room temperature at a heating rate of 10 K/min. A purge gas rate of 50 mL/min nitrogen was used up to 700 °C and from then on 50 mL/min air. The IR spectra were recorded at a resolution of 4 cm-1. Eight spectra were averaged to improve the signal-noise ratio. With these settings, a spectrum was obtained every 2 K at the heating rate used. The sample mass was 6 to 9 mg.

Conclusions

The composition an unknown polymer sample can be easily characterized by means of combined TGA/DSC-FTIR measurements. Table 1 summarizes the results obtained from the TGA measurement and the IR spectra for the particular sample investigated. The polymers in the unknown material were identified and their approximate contents determined from the DSC measurement.

_{Analysis of an Unknown Polymer Sample by TGA/DSC-FTIR | Thermal Analysis Application No. UC 467 | Application published in METTLER TOLEDO Thermal Analysis UserCom 46}