Effects of Fluorescent Tracer Additives on PET During Material Recycling

ABSTRACT The material properties and stable chemical structure of PET make it a frequently used polymer, for example, for packaging applications, and allow multiple recycling processes. Fluorescent tracer additives in polymer waste management may enhance the sorting quality of packaging waste streams by using the fluorescent signal of tracer additives introduced into the polymer matrix. Prior to field application of tracer additives, it is necessary to investigate tracer influence on the polymer matrix in general and, more specifically, in multiple recycling cycles. Therefore, PET with mineral tracer concentrations of 0, 10, 100, and 1000 ppm was extruded up to six times. To investigate changes in material properties, differential scanning calorimetry, intrinsic viscosity, spectroscopic analysis, tensile testing, and color measurements were performed. In parallel, the up‐conversion photoluminescence of the tracer was quantified. Polymer degradation is generally induced by mechanical and thermal degradation during multiple processing cycles, leading to chain shortening, reduction of molecular weight, and the formation of new functional groups, as previously published in the literature. The results of the experiments indicate that tracer additives do not further affect the thermal, rheological, chemical, and optical polymer properties. Moreover, photoluminescent tracer properties are not affected by multiple polymer processing cycles.