Thermal Gravimetric Analysis

Materials and Chemistry Laboratory, Inc. has expanded our analytical capabilities to include Thermal Characterization. This capability is useful in a variety of applications, including analysis of carbon fiber and other complex composites. Our system includes Thermogravimetric Analysis (TGA) coupled with Mass Spectrometry (MS). Thermal analysis combined with compositional analysis is a powerful tool to identify evolved gas during thermal processes.

The Seiko Instruments TG/DTA 6300 Thermogravimetric/Differential Thermal Analysis Module is used to simultaneously perform thermogravimetric and differential thermal analytic measurements on inorganic materials including ceramics, glasses and metals, as well as high polymer organic materials. The ideal sample size for this system is between 20-50mg. Samples may be analyzed in an air or inert gas environment at temperature ranges from ambient temperature to 1000°C.

In essence, TGA utilizes heat and stoichiometric ratios to determine composition and purity.  Changes in sample weight are monitored either isothermally as a function of time or, more commonly, in relation to gradually rising temperatures as components decompose. Weight percentage versus time/temperature is analyzed to find the exact points of inflection which may indicate degradation temperatures, absorbed moisture content of materials, the level of inorganic and organic components in materials, decomposition points of explosives, and solvent residues.

Coupling TGA with MS or FTIR offers structural identification of compounds evolved during thermal processes.

The gas produced during thermal analysis is fed directly into an integrated FTIR in order to identify organic molecules based on absorption of infrared radiation at specific frequencies that are characteristic of their structure. Spectra from a known sample or library database are used to compare spectra profile.The off-gas of the TGA is streamed into a Mass Spectrometer, an analytical instrument in which ions are separated by electromagnetic fields according to their mass-to-charge ratio. The ions are then detected and processed into mass spectra to identify the constituents of the sample. Mass Spectrometry provides information that the FTIR may not provide- e.g. some diatomic molecules that do not have a permanent dipole moment.

TGA-MS and TGA-FTIR offer lab bench top representations of large-scale processes to permit evaluation of chemical pathways for degradation reactions. For example, MCLinc recently utilized this system coupled with a Hydrogen Specific Detector for evolved gas analysis to identify quantitative and qualitative volatile products (including H2) formed during combustion and pyrolysis of a complex composite material.