Characterization of adhesive content in post-consumer poly(ethylene terephthalate) bottles and assessment of its impact on poly(ethylene terephthalate) recyclability

Although the consequences of adhesive residues from post-consumer Poly(ethylene terephthalate) (PET) beverage bottles on the performance of recycled products are known, the quantitative effects of these adhesives are not well-stablished in the literature. Therefore, these residues were determined by gravimetry, and the adhesive content range from 200 to 2800 ppm in post-consumer PET bottles, depending on the drink filled. Through FTIR analysis, it was determined that the adhesives for bottles labelling are composed by poly(ethylene-co-vinyl acetate) (EVA). Based on these results, recycled PET with 0, 200, 700, 1500 and 3000 ppm of hot melt EVA were processed in an internal mixer connected to a torque rheometer at 265 degrees C for 10 min. Tensile tests indicate that 200 ppm of adhesive reduced PET tensile strength by 15%. Furthermore, when about 1500 ppm of adhesive is present, PET mechanical properties are reduced by 50%. Therefore, it is of utmost importance to warn the PET bottle production chain to reduce adhesive content used in labelling so that it should not exceed 200 ppm, if a high quality recycled PET is desirable.

Automated summary

Although the effects of adhesive residues from post-consumer PET bottles on recycled products are known, the quantitative effects of these adhesives are not well-established. The adhesive content in post-consumer PET bottles ranges from 200 to 2800 ppm, depending on the drink filled. The presence of adhesive, primarily composed of EVA, significantly reduces PET mechanical properties, with 200 ppm reducing tensile strength by 15% and about 1500 ppm reducing mechanical properties by 50%. It is crucial to limit adhesive content in PET bottle production to no more than 200 ppm for high quality recycled PET.