V. Komolprasert et al., Volatile and non-volatile compounds in irradiated semi-rigid crystalline poly(ethylene terephthalate) polymers, FOOD ADDIT, 18(1), 2001, pp. 89-101
In this study two different semi-rigid crystalline and oriented polyethylen
e terephthalate materials were used and were irradiated at 25-kGy dose at r
oom temperature by using a caesium (137) radiator. Volatile and nonvolatile
compounds present in the irradiated materials were identified and quantifi
ed. The qualitative results obtained from HS/GC/TCD/FID analysis at room te
mperature showed volatiles could not be identified. The HS/GC/MSD analysis
performed at 106 degreesC showed that the irradiation generated 668-742 mug
/kg formic acid, 868-922 mug/kg acetic acid, 17-32 mug/kg 1,3-dioxolane, an
d 47-71 mug/kg 2-methyl-1,3-dioxolane based on PET weight. The results obta
ined from the thermal desorption and GC/MSD performed at 200 degreesC showe
d that 10-12 mg/kg acetaldehyde, 479-975 mug/kg 1,3-dioxolane, and 6.6-11.2
mg/kg methyl-1, 3-dioxolane were detected after irradiation. The concentra
tions of the two dioxolanes found from thermal desorption were much higher
than those observed in the HS, although formic and acetic acids were not de
tected. It is possible that the formic and acetic acids produced by irradia
tion underwent further reactions with ethylene glycol during thermal desorp
tion to form the dioxolanes. The soluble solid extracted from various PET s
pecimens before and after irradiation were in a range of 0.67-0.78%. PET cy
clic trimer is the major component and is present at 0.41-0.50%, accounting
for more than 50% of the percent total solid in PET. Statistically, irradi
ation did not increase the soluble solid and cyclic trimer. The overall res
ults suggest that 25-kGy irradiation had a significant effect on increasing
the volatile but not the non-volatile compounds detected in the PET specim
ens.