Thermogravimetric analysis, evaporation

Figure 15. A typical thermogravimetric analysis (TGA) trace of a polymer resist that has been spin-coated and NOT prebaked. The small weight loss at low temperature is due to solvent evaporation and the high temperature weight loss is due to thermal decomposition.

Thermogravimetric analysis (TGA) is a suitable technique for the study of explosive reactions. In TGA the sample is placed on a balance inside an oven and heated at a desired rate and the loss in the weight of the sample is recorded. Such changes in weight can be due to evaporation of moisture, evolution of gases, and chemical decomposition reactions, i.e. oxidation. 

Thermogravimetric analysis (TGA) is used to determine the decomposition temperature of a material. A material is placed in a small pan and then heated under a gaseous environment. When it evaporates, the pan becomes lighter due to the evaporation of the material as it decomposes. The temperature at which this occurs helps determine the quality of a material because weaker bonds break apart and evaporate sooner than more strongly bonded materials. It can be used to determine the quality of crystal materials, and it can be used to determine the mass loss under specific experimental conditions. 

Thermogravimetrical analysis provides information on loss of mass which may be a result of degradation with volatilization of plasticizer component, plasticizer evaporation, or degradation and volatilization of any other component of the tested mixture (most likely polymer and stabilizer because test formulations are usually kept simple). Beeause of these different reasons for mass loss the results are difficult to interpret. In some studies reported here, evaporation loss of plasticizer was distinguished from loss of degradation products by ranning two separate tests one for the pure plasticizer and the other for the entire composition. This may help to better understand reasons for mass loss but it... 

Plasticizer evaporation during thermogravimetric analysis is given by the equation ... 

Heym, F., Etzold, B.J.M., Kern, C., and Jess, A. (2011) Analysis of evaporation and thermal decomposition of ionic liquids by thermogravimetrical analysis at ambient pressure and high vacuum. Green Chem.(accepted). doi 10.1039/C0GC00876A... 

Normally, the analyses mentioned previously are performed on the residual materials. However, there is nothing to prevent measurements being made on the separated fractions or on condensate materials. In the case of samples containing water, be aware that the condensate will be enriched with water. An interesting approach to the controlled evaporation of materials is to use the combined techniques of thermogravimetric analysis and infrared. Although this technique is typically used for the determination of thermal decomposition products, it may also be used for controlled and reproducible selective removal of volatile components, with on-line monitoring of the volatile components. 

Thermogravimetric Analysis - Empty UF microcapsule shows - Figure 8, a weight loss (around 10 %) until 110 °C corresponding to the evaporation of free water in microcapsules, and an important decreasing in weight (around 80 %) starting from 180 °C due to the decomposition of urea-formaldehyde microparticles. Therefore the urea formaldehyde could not be used to self-heal spatial device composites because of polymer decomposition below 300 °C (maximum temperature in space). 

Among the most commonly used thermoanalytical techniques is thermogravimetric analysis (TGA), which provides information about the mass variations resulting from a physical (sublimation, evaporation, condensation) or chemical (degradation, decomposition, oxidation) change as a function of time and/or temperatiue [12]. 

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