20-1 Thermal Methods Theory Instrumentation Thermal methods §Physical properties of a substance are evaluated as a function of temperature àMay include reaction products àTemperature is controlled §Methods àThermogravimetry àDifferential thermal analysis àDifferential scanning calorimetry

20-2 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 §N 2, O 2, air, He §Ambient to 1000 °C §Can record the first derivative of the mass loss

20-3 Thermogravimetric MS can be coupled to TGA §On line analysis §Evolution of gas evaluation of the thermal decomposition kinetics of materials §Polymers §Resins §rubbers àprovides 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

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20-5 Analysis of Resin

20-6 Table 10. Phenomenological data on the thermal decomposition of the phenolic resins ResinT 1, ˚CT 2, ˚CWeight loss at 500˚C, % PF CF RF CQF RQF Table 11. Phenomenological data on the thermal decomposition of the metal complexes of phenolic resins Resin complex T 1, ˚CT 2, ˚CT 3, ˚CT 4, ˚CWeight loss at 500˚C, % PF-Eu CF-Eu RF-Eu CQF-Eu RQF-Eu

20-7 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 à emissions of heat (exothermic) àabsorptions 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=-kGm  H àA= peak area, G is geometry factor, k is constant related to thermal conductivity

20-8 New Zealand Halloysite. Premium

20-9 Differential Scanning Calorimetry Differences in heat flow are measured as a function of temperature §Sample and reference àEnergy difference measured Power Compensated DSC §Two furnaces §Heat flow evaluated §Difference in power input montiored àIn watts Useful for glass transition temperatures Purity of drug samples

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20-11 Automated methods Automatic §No feedback Automated §Includes feedback Different methods §Discrete/batch àsample remains isolated throughout §Continuous àsample introduced into stream *Simpler instrumentation *more efficient

20-12 Flow Injection Analysis Samples carried by flow Flow can have chromatographic properties §Good behavior in system

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20-14 Diffusion processes