The thermal degradation of polymers has very important implications with respect to their suitability for particular end-user applications, particularly in relation to their physical properties and the lifetime over which the manufactured articles retains these properties after which they become unsuitable for purpose.
By the correct selection of polymer type, the method of manufacture and addition of chemicals that slow down the polymer degradation, manufactured articles can be produced that have suitable processing and end-user physical properties such as tensile strength and avoidance of embrittlement.
Particular applications that come to mind are critical applications of polymers to the manufacture of electronic components and the design of polymeric alloys for aircraft fuselage assembly which retain their properties for many years over which the alloy must retain the physical properties at high or low operating temperatures.
A wide and increasing range of types of polymers are being used in these critical applications, and an understanding of thermal degradation processes will be very important in developing new applications in the future.
An object of this review is to discuss our present understanding of the chemical changes of the polymer that accompany degradation, and to discuss analytical methods by which these changes can be ascertained.
The principal techniques used in degradation studies are based on thermal methods such as thermogravimetric analysis which is the subject of this article and differential scanning calorimetry. Other methods are based on pyrolysis of the polymer followed by mass spectrometry or infrared spectrometry or, to a lesser extent, techniques such as nuclear magnetic resonance spectroscopy, electronic spin resonance spectroscopy, chemiluminescence and positron annihilation lifetime mass spectrometry.