April 22, 2025 – In the realm of recycled plastics, the yellowing of recycled PET bottle flakes has long been a major obstacle hindering their high-value utilization. As one of the most widely used recycled plastic varieties globally, the color stability of PET bottle flakes plays a decisive role in their expansion into fields such as food packaging and high-end textiles. A thorough investigation reveals that the factors causing the yellowing of these flakes are complex and diverse, each with its own underlying mechanism.
PET bottles are highly susceptible to aging when exposed to sunlight and high temperatures over an extended period. Under the combined effects of light and heat, the molecular chains of PET gradually break down and degrade. This not only significantly impairs the physical properties of the material but also leads to a series of issues after recycling and processing, including yellowing of color and a decrease in strength. During the recycling and cleaning process, fluorescent detergents added to enhance the appearance of PET bottles are also a major contributor to yellowing. These detergents tend to undergo chemical reactions under high temperatures, producing yellow by-products that mar the original luster of the bottle flakes.
Moreover, to extend the shelf life of products, some PET bottles are incorporated with barrier materials such as UV stabilizers and antioxidants. According to AsiaMB, these barrier agents are prone to chemical changes during the high-temperature recycling process, resulting in significant yellowing of the bottle flakes. The presence of barrier agents has far-reaching implications for the quality of recycled materials. Yellowed bottle flakes cause uneven coloration in recycled pellets, which is particularly noticeable in transparent or light-colored products. To improve the appearance, companies are compelled to add extra color masterbatch, increasing both raw material and processing costs. Material degradation also weakens the toughness, strength, and durability of recycled plastics, leading to a higher defective rate. More severely, due to these appearance and performance flaws, recycled materials struggle to enter the high-end market and are confined to the low-end sector, severely limiting profit margins and product competitiveness.