Stages of degradation

A few relatively recent published examples of the use of NMR spectroscopy for studying polymer degradation/oxidation processes will now be discussed briefly. At the early stages of degradation, the technique can be used to provide chemical identification and quantification of oxidised species for polyolefins, oxidation sites can be identified by the chemical shifts of -CH2- groups a and ji to carbons bonded to oxygen [85]. Spin-spin relaxation times may be determined by a pulse sequence known as the Hahn spin-echo pulse sequence. 

Oxidation parameters can be used instead of mechanical strength to measure very early stages of degradation by oxidation [14, 15]. 

Figure 9-3. The three stages of degradation (Scott 1995, with kind permission of Kluwer Academic Publishers).

Fig. 8A.1 Wine aroma precursors, their main stages of degradation during the wine biotechnological sequence and general impact on wine aroma of the odorants generated...

Figure 3. Molecular weight distribution (weight fraction) of polypropylene at initial and two subsequent stages of degradation...

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