Thermogravimetric analysis is a branch of materials science involving the study of material properties as they change with temperature. The science includes many techniques and sub-disciplines including differential scanning calorimetry (DSC), differential thermal analysis (DTA), thermomechanical analysis (TMA), and many more. TGA techniques are important in a wide range of areas including, characterization of pharmaceutical materials, polymer analysis, food safety, semiconductors, and forensics, to name a few.
Differential Scanning Calorimetry
DSC is a thermoanalytical technique in which the difference in magnitude of heat required to change the temperature of a sample is measured against that of a reference. Generally, the temperature is raised linearly as a function of time. The reference material has a well-defined heat capacity and the difference data or DSC curve demonstrates inflections characteristic of the sample under analysis, and useful for calculation of enthalpies of transitions.
A basic premise of DSC is that when a sample undergoes heat-induced phase transition, a greater or lesser amount of input heat is needed to maintain the sample at the same temperature as the reference. This observation provides information on whether the phase transition (chemical change) is endothermic, requiring more heat, or exothermic, requiring less heat, as compared to the reference. Subtle chemical transitions may also be measured, making the technique applicable to wide range of materials and behaviors.
Differential Thermal Analysis
DTA is similar to DSC in that a sample is subjected to temperature change in relation to and inert reference. Any differences in the observed temperatures between these is plotted against time to product a thermogram. Exothermic or endothermic transformations, such as glass transitions, crystallization, melting, sublimation, and others can be tracked and quantitated.
Thermogravimetric Analysis Applications
TGA analysis provides information on thermal stability of materials as no or negligible mass loss results when a substance is thermally stable. TGA can provide the upper use level of a material, or analysis of material components in the cases of fatigue/failure analysis or forensics investigations – such as fraudulent materials or products. Chemical resistance or reactivity, oxidation and combustion, as well as thermal reaction kinetics can all be investigated via TGA.
Simultaneous Thermal Analysis
STA systems include modern technology and instrumentation to incorporate DSC, DTA, and other TGA techniques under one hood, providing temperature, heat flux, and sample loss in a combined analysis – with advanced software and data analysis tools.
Thermal Analysis of Polymers
One very productive area for TGA application is polymer analysis. Most polymers melt or degrade under 200 °C, however, thermally stable polymers may persist at 300 °C to 500 °C and beyond -- offering advantages of TGA for these wide-ranging materials with specific characteristics.
TGA instruments which continuously weigh samples as they are heated up to 2000 °C can be coupled with FTIR or gas chromatography mass spectrometers. The resulting removal of constituents during heat transformations can subsequently be detected and quantitated using these downstream measurement technologies.
State-of-the-art Simultaneous Thermal Analysis Technologies
Advanced instruments make use of high accuracy detectors to measure microgram-level weight changes. Digital signal processing and temperature control features can minimize baseline fluctuations and temperature variations, thereby increasing measurement precision. Improved data analysis software can enable increased analytical power and versatility.
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