It is not uncommon to see a 25-30% post-consumer recycled (PCR) content in a carbonated soft drink (CSD) PET bottle on the market. With the growing availability of PCR resin, food and beverage brand owners are pushing for higher recycling content in their packaging. Recent studies have been published showing that high- recycling-content in PET packaging will adversely affect the performance of pressurized bottles when compared to virgin material or low-recycling-content counterparts. However, little has been done to quantify the degradation of the specific material properties that govern pressurized bottle performance. This paper focuses on quantifying changes in the short- and long-term material properties that govern a bottle’s ability to retain its original shape when subjected to sustained carbonation pressurization. This performance attribute is typically characterized as ‘thermal stability,’ which is the ability of the package to retain its shape and molded-in feature definition over time, after pressurization. Two commercially available packages, one molded of 100% recycled PET and another molded of typical PET (30% recycled PET content), are used to extract the test samples. The study indicates that the effect of the high- recycle-content on the CSD PET bottle cannot be over- looked. The results of the tensile tests show that the 100% recycled PET is stiffer and tougher in the axial direction (up to 26%), but softer and weaker in the hoop direction (up to 14%), compared with its typical PET counterpart. Based on the creep test results, the 100% recycled PET also creeps 50% faster. This will have a noticeable effect on the bottle’s thermal stability, which is only 1-2% (height and diameter growth or contraction under carbonation pressure) for most commercial packages on the market. The effect will become more pronounced for non-cylindrical designs or designs with non-cylindrical features. Failure to adequately retain the bottle’s shape (thermal stability) will affect the bottle’s overflow capacity, stacking stability, vending and brand image (feature) retention.
Yuan J.Z., Haynes, C.A. and Harrell P.A., “The Effect of High-Recycle-Content on CSD PET Bottle’s Thermal Stability”, Society of Plastics Engineers, ANTEC 2013 Conference & Tradeshow, April 22, 2013, Cincinnati, Ohio.