Orientation effects on poly(ethylene terephthalate) as a packaging material for carbonated soft drinks

Amorphous PET sheets were simultaneously and sequentially stretched with various stretch ratios to examine how orientation (uniaxial and biaxial) affected optical, CO₂ barrier and tensile properties. Haze, transmission, clarity and gas barrier properties were not significantly influenced by stretch ratios employed, while the refractive index, birefringence and tensile properties appeared to be affected by the stretch method. Commercial PET bottles (500 mL and 1 L) filled with carbonated water were stored at selected temperatures from 4 to 30°C to study CO₂ loss over 56 days. The CO ₂ loss increased with increasing temperatures, and rate of CO₂ loss was slower in the 1 L bottle under the same storage condition. Additional PET bottles, partially masked with epoxy to study CO₂ loss through different bottle regions, showed that the wall region had a lower rate of CO₂ loss per unit area than the shoulder and base regions.