can occur. CH2-CH2-CH2-CH2-CH2-CH2-CH2’→ CH2-CH2-CH=CH2 + CH3-CH2-CH2’ or CH2’+CH2=CH-CH2-CH2-CH2-CH3 As polymers approach their ceiling temperature scission starts to take place randomly on the backbone. Oxidation of the polymer Although thermal degradation is defined as an oxygen free process it is difficult in practise to completely exclude oxygen. Where this is the case thermal oxidation is to be expected, leading to the formation of free radicals by way of hydroperoxides. These may then participate in thermal degradation reactions, accelerating the rate of breakdown. Analytic Methods TGA (Thermogravimetric analysis) (TGA) refers to the techniques where a sample is heated in a controlled atmosphere at a defined heating rate whilst the sample's mass is measured. When a polymer sample degrades, its mass decreases due to the production of gaseous products like carbon monoxide, water vapour and carbon dioxide. === DTA and DSC === (Differential thermal analysis) (DTA) and (differential scanning calorimetry) (DSC): Analyzing the heating effect of polymer during the physical changes in terms of glass transition, melting, and so on. These techniques measure the heat flow associated with oxidation. See also Autoxidation Photo-oxidation of polymers Weather testing of polymers Environmental stress cracking References Polymer chemistry Corrosion Forensic phenomena Materials degradation