.2.4.4. Proton nuclear magnetic resonance
1
H NMR spectra were recorded at room temperature with a
VARIAN GEMINI-200 MHz spectrometer in deuterated chloro-form/trifluoro acetic acid at 1/1 V/V solutions, by using glass tubes
with 5 mm of diameter. The chemical shifts were assigned in d
(ppm) and the solvent signal was used as reference.
The number average molecular weight (Mn) of degraded PET
samples was calculated by using the Eq. (1) (Dannoux et al., 2002).
Mn¼ 192
A
E
þ 62 ð 1 Þ
where A and E are the area of
1
H NMR signals of aromatic protons of
terephthalate units (8.2 ppm) and hydroxyl end groups (4.2 ppm),
respectively. 192 is the molecular weight of the PET repeating unit
and 62 is the molecular weight of ethylene glycol terminated
terephthalate oligoesters by supposing a ,x –diol (Dannoux et al.,
2002).