FTIR determination of carbonyl structures in oxidized polyethylenes

8 FTIR determination of carbonyl structures in oxidized polyethylenes 

The development of the absorbance of carbonyl groups in IR is proportional to the film thickness of irradiated polyethylene samples. However, an appreciable part of the total oxidation is restricted to the surface layers [854]. 

By assuming the additivity of integral carbonyl absorptions, it is possible to use an IR method for the simultaneous determination of carbonyl, ketone and ester groups in oxidized polyethylenes, but this method neglects aldehydes and a, / -unsaturated ketones and it can not differentiate between ester and lactone structures [589]. 

The IR band-shapes of carbonyl (CO) groups in oxidized polyolefins are of Lorentzian type (Fig. 10.65) however, with an increasing network density a Gaussian broadening of spectra can be observed. 

The band-shape parameters and extinction coefficients of carbonyl groups in polyolefins, from band shape analysis of low molecular weight standards, are listed in Table 10.16. 

---