For polyethylene, the area of the peaks at 1780 and 1700
cm-1 was used for the oxidized components (carbonyl
forming bands) and the area of the peak at 1465 cm-1
was used to represent the natural component of PE. For
polypropylene, the same area of 1780 and 1700 cm-1 was
used for the oxidized components, whereas the area belonging
to the peak at 2720 cm-1 was used to represent
the natural component of PP.