Abstract:
This paper studies the characteristics of polyethylene terephthalate (PET) used for
commercial drinking bottles of different brands and colours after the photodegradation
process under three different ultraviolet (UV) sources: sunlight, UV lamp with
wavelength of 365 run and UV lamp with wavelength of 254 run. The tests that were
carried out were tensile tests, Fourier Transform Infrared (FTIR) Spectroscopy and
Scanning Electron Microscopy (SEM). After 250 hours of exposure to sunlight, the
force at break and Young's Modulus were found to decrease up to 36.5% and 47.9%
respectively. For samples exposed to 365 run UV light radiation, the force at break
and Young's Modulus were also found to decrease up to 52.7% and 54.9%
respectively, which is higher than the effect of sunlight radiation. Meanwhile after 250
hours of exposure to 254 run UV light, the force at break decreased up to 34.7% and
the Young's Modulus decreased up to 17.5%. FTIR spectroscopy shows that the
absorbance for samples exposed to the three UV sources decreases with increasing
exposure time especially at peak 1720 cm-
1
, which signifies the carbonyl, C=O bond.
This decrease in absorbance values shows that photodegradation of PET causes C=O
bonds to break, where the longer the exposure time towards the UV source, the ability
to absorb infrared by these bonds decreases. SEM images were obtained after the
tensile tests and the difference between the topography of exposed and unexposed
samples were shown.
