Post-consumer bottles exposed to ultraviolet (UV) rays impact the physical properties and visual attributes of recycled PET (rPET) bottles, according to a study by Plastic Technologies.
Research undertaken by the the PET technology firm has found that intrinsic viscosity, yellowing and haze are some of the issues that come to the fore while fusing rPET with virgin material.
During the study, the bottles were placed in such a way that sunlight passes through several layers of sidewalls and penetrates to the bottom of the open crate.
PET turns yellow with every melting process. Adhesive label residues, residual label material, inks and coatings account for such color that can ultimately bleed to the PET flake.
This apart, additives that cannot be removed by the washing also contribute to the yellowish hue.
Plastic Technologies vice-president Dr Frank Schloss said: "What the average effect might be on an entire bale of bottles compared to what was seen in this study is a matter of debate. However, one should consider all the potential causes of yellowing that can limit the percentage of recycled PET that can be used.
"Exposure to UV radiation, whether it is from outside bale storage or possibly even exposure to fluorescent lighting in retail stores, should be considered as another contributor to rPET quality degradation."
