Characteristic study of polyethylene terephthalate (PET) used for commercial drinking bottles under uv radiation

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.