Characteristics Study of Polyethylene Terephthalate (PET) Used For Commercial Drinking Bottles Under Ultraviolet (UV) Radiation

The characteristics of polyethylene terephthalate (PET), used for commercial drinking bottles of different brands and colours after photodegradation process under three different ultraviolet (UV) sources: sunlight, UV lamp with wavelength of 365 nm and UV lamp with wavelength of 254 nm, were studied. The tests that were carried out included 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 nm 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. After 250 hours of exposure to 254 nm UV light, the force at break decreased up to 34.7% and the Young’s Modulus decreased up to 17.5%. FTIR spectroscopy showed that the absorbance for samples exposed to the three UV sources decreased with increasing exposure time, especially at peak 1716.42 cm-1, which signifies the carbonyl, C=O group with the highest decrease in absorbance is 62.33%. The decrease in absorbance values showed that photodegradation of PET caused the C=O bonds to break. The longer the exposure time towards the UV source, the ability to absorb infrared by these bonds decreases. SEM images obtained after tensile tests showed the fractured surfaces having suction cups.