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Thermal Methods

Thermal Methods. Theory Instrumentation Thermal methods Physical properties of a substance are evaluated as a function of temperature May include reaction products Temperature is controlled Methods Thermogravimetry Differential thermal analysis Differential scanning calorimetry.

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Thermal Methods

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  1. Thermal Methods • Theory • Instrumentation • Thermal methods • Physical properties of a substance are evaluated as a function of temperature • May include reaction products • Temperature is controlled • Methods • Thermogravimetry • Differential thermal analysis • Differential scanning calorimetry

  2. Thermogravimetric (TGA) • Thermogravimetry is one of the oldest thermal analytical procedures • has been used extensively in the study of polymeric systems • involves monitoring the weight loss of the sample in a given atmosphere as a function of temperature • N2, O2, air, He • Ambient to 1000 °C • Can record the first derivative of the mass loss

  3. Thermogravimetric • MS can be coupled to TGA • On line analysis • Evolution of gas • evaluation of the thermal decomposition kinetics of materials • Polymers • Resins • rubbers • provides information on thermal stability • provide information on the bulk composition of compounds • Oxidation • heat resistance • the amount of water • compositional analysis • measurement of ash content in a sample

  4. Analysis of Resin

  5. Table 10. Phenomenological data on the thermal decomposition of the phenolic resins Table 11. Phenomenological data on the thermal decomposition of the metal complexes of phenolic resins

  6. Differential thermal analysis • temperature difference between a substance and a reference material is measured as a function of temperature • substance and reference material are subjected controlled temperature • emissions of heat (exothermic) • absorptions of heat (endothermic) • comparison with a passive material such as alumina • Can be used to identify samples • Clay materials • Peak areas depend upon sample mass and enthalpy • A=-kGmDH • A= peak area, G is geometry factor, k is constant related to thermal conductivity

  7. Differential Scanning Calorimetry • Differences in heat flow are measured as a function of temperature • Sample and reference • Energy difference measured • Power Compensated DSC • Two furnaces • Heat flow evaluated • Difference in power input montiored • In watts • Useful for glass transition temperatures • Purity of drug samples

  8. Automated methods • Automatic • No feedback • Automated • Includes feedback • Different methods • Discrete/batch • sample remains isolated throughout • Continuous • sample introduced into stream • Simpler instrumentation • more efficient

  9. Flow Injection Analysis • Samples carried by flow • Flow can have chromatographic properties • Good behavior in system

  10. Diffusion processes

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