Chapter 8. Calorimetry and thermal analysis for the study of polymer properties
Résumé
Nowadays, the production and intensive use of plastics having remarkable
properties, such as transparency, lightness, resistance to water, solvents and corrosive
agents, insulating character, and thermal stability, lead to the study of their physical
and chemical properties and in particular to those that are strongly dependent on
temperature. Among these properties, one can mention glass transition (Tg), enthalpy
of melting and crystallization, decomposition temperature, thermal stability, and dimensional
changes (such as softening, expansion, and shrinkage).
This chapter shows how polymers can be fully and very accurately characterized
by using thermal analysis and calorimetry. Various examples are given in order to
illustrate the potential of thermal analysis and calorimetry for measuring their physical
properties, different types of transitions, aging, thermal stability, oxidation, degradation
mechanism, effect of plasticizers, influence of synthesis, or shaping conditions.
These examples will be presented using the following techniques: differential scanning
calorimetry (DSC), pressurized-DSC, Calvet calorimetry, thermogravimetric analysis
(TGA), thermomechanical analysis (TMA), TGA coupled to mass spectrometry
(TGA-MS), TGA coupled to Fourier-transform infrared spectroscopy (TGA-FTIR), and
TGA coupled to gas chromatography and mass spectrometry (TGA-GC-MS). The development
of all these techniques and couplings between different instruments has
greatly contributed to the understanding of the physical and chemical phenomena
that occur within materials when they are synthesized, shaped, heated, burned, or degraded.
These techniques are nowadays increasingly used in the field of plastic recyclability.
They undeniably allow a better understanding of the mechanisms involved
in the new recycling processes explored in research and development laboratories.