In recent years numerous research papers have been published on the changes in chemical structure and in physical properties of polymers when they are exposed to heat over a range of temperatures. For example, these changes can occur at any time during the injection moulding of the plastic, in the subsequent processing and in its end-use application when exposed to elevated temperatures. Thermal stability is a very important parameter which must be taken into account when selecting polymers whether for their use as constructional or engineering applications or in the packaging of food at high temperatures. The mechanisms by which such changes occur are many and it is important to know what these are and to be able to measure the rate of change of polymer structure and its dependence on temperature and time. Development of an understanding of the mechanisms of thermal degradation will help the chemist to develop materials with better thermal stability. This is particularly important in newer developments in engineering and aerospace. This book reviews in nine chapters the measurement of these properties in the main types of polymers in use today. Numerous techniques are discussed ranging from thermogravimetric analysis, differential scanning calorimetry, infrared and nuclear magnetic resonance based methods to pyrolytic techniques such as those based on pyrolysis, gas chromatography and mass spectrometry. The book is aimed at those engaged in the manufacture of polymers and the development of end-use applications. It is essential that students of polymer science should have a thorough understanding of polymer stability and an additional aim of the book is to help in the development of such an interest.