Identification of an Unknown Polymer Sample Using TGA-GC/MS - METTLER TOLEDO

Identification of an Unknown Polymer Sample Using TGA-GC/MS

The TGA-GC/MS system can be used to investigate the composition of unknown samples. This is done by installing the IST16 storage interface between the TGA and the GC/MS. The interface allows up to 16 evolved gas samples to be stored at different furnace temperatures during the TGA measurement. The gas samples are analyzed and identified by GC/MS when the TGA analysis is finished. This article describes how a black polymer granule was characterized using this technique.

 

Introduction

Unfortunately, TGA measurements do not provide any specific information about the nature of decomposition products. For this reason, TGA instruments are often coupled to instruments that allow decomposition products to be identified.

This includes coupling a TGA instrument to an FTIR or MS spectrometer. Both techniques have the disadvantage that products simultaneously released can only be distinguished from one another and identified with considerable difficulty. This is often the case with the pyrolysis of polymers.

The problem can be solved by separating the decomposition products before the identification step. This is possible using a TGA-GC/MS combination [1, 2].

In this example, the IST16 heated storage interface (Figures 1 and 2) was used. This storage unit allows up to 16 gas samples to be collected and stored at specific TGA furnace temperatures during the TGA analysis. The samples are then injected into a gas chromatograph and identified using a mass spectrometer. The sample investigated by TGA-GC/MS in this article was an unknown black polymer.

Conclusions

An unknown polymer sample was investigated by TGA-GC/MS. The main decomposition products of the sample were clearly identified.

For example, cyclopentanone, which is specific for PA 6.6, and caprolactam, a constituent of PA 6, were detected. From this information, we conclude that the sample consists mainly of PA 6/PA 6.6.

The detection of a number of alkanes and alkenes at low concentration indicates that polyethylene could also be present at low concentration.

Identification of an Unknown Polymer Sample Using TGA-GC/MS | Thermal Analysis Application No. UC 433 | Application published in METTLER TOLEDO Thermal Analysis UserCom 43