Thermogravimetry is often used to study polymer degradation. Most often the information obtained may have some practical application
but is of limited value for the determination of fundamental processes which may be occurring. A kinetic expression or activation
parameters for a complex process which may involve consecutive or parallel reactions provides almost no information about
any of the reactions that might be occurring. However, for single, well-defined processes, thermogravimetry, in conjugation
with other analytical methods, can be effectively utilized in the determination of reaction mechanism. The thermal degradation
of vinylidene chloride barrier polymers corresponds to the elimination of hydrogen chloride initiated at an allylic dichloromethylene
unit in the mainchain. This process is uncomplicated by competing reactions.
Thermogravimetry may be utilized to obtain meaningful rate constants and activation parameters for the degradation. This in
conjunction with mass spectral analysis of evolved gas, characterization of both the polymer and degradation residue by ultraviolet,
infrared and 1H and 13C NMR spectroscopy, and the study of model compounds has permitted a detailed description of the degradation process. General
purpose poly(styrene) is a commodity polymer widely used in the food packaging industry as well as many others. If processed
at excessively high temperature, it undergoes thermal degradation to expel styrene monomer which can impart negative flavor
and aroma characteristics to packaged food items. The degradation reaction has been fully detailed using thermogravimetry
in conjugation with evolved gas analysis, size exclusion chromatography and NMR spectroscopy.