As the global demand for high-quality plastic recyclates grows, advanced analytical methods are becoming essential. This trend is influenced by standards such as DIN SPEC 91446, which defines quality benchmarks for recyclates used in technical applications, and regulatory pressures such as the EU Packaging and Packaging Waste Directive.
 |
NETZSCH, in cooperation with the Institute for Polymer and Production Technologies (IPT) in Wismar, Germany, demonstrates how thermal analysis, specifically Differential Scanning Calorimetry (DSC) and Thermogravimetric Analysis (TGA), provides critical insight into complex polymer mixtures, helping the recycling industry meet these stringent standards.
Thermal Analysis Methods: DSC and TGA
Traditional methods like Near-Infrared Spectroscopy (NIR) and Fourier-Transform Infrared Spectroscopy (FT-IR) are fast for identifying simple polymers. However, they struggle with complex, colored, or highly pigmented compounds. Thermal analysis provides deeper insight. For example, DSC measures phase transitions (The term phase transition (or phase change) is most commonly used to describe transitions between the solid, liquid and gaseous states.phase transitions), allowing identification and quantification of polymer components in recyclates. TGA tracks weight changes, revealing material composition and thermal stability (A material is thermally stable if it does not decompose under the influence of temperature. One way to determine the thermal stability of a substance is to use a thermogravimetric analyzer). Together, these methods provide a powerful toolkit for analyzing recyclates, especially mixtures with unknown or overlapping polymer signals.
Application Example: Beverage Carton Recyclates
In a recent study, NETZSCH and IPT analyzed recyclates from beverage cartons. Using Differential Scanning Calorimetry (NETZSCH DSC 300 Caliris®), they identified overlapping peaks for LDPE, HDPE, LLDPE and PP in the blend and calculated precise weight ratios of each component. Thermogravimetric Analysis (NETZSCH TG 309 Libra®) added further insight by identifying decomposition temperatures (A decomposition reaction is a thermally induced reaction of a chemical compound forming solid and/or gaseous products), which helped distinguish between organic materials such as cellulose and inorganic components such as aluminum.
Benefits for the Recycling Industry
The combined use of DSC and TGA proves invaluable for accurately identifying the composition of recycled materials. Unlike optical methods, the color of polymers does not play a role in thermoanalytical methods. They provide critical data that NIR and FT-IR cannot offer. This approach not only enhances recyclate quality but also maximizes yield, contributing to a sustainable circular economy.
Outlook
The continuous improvement of thermal analysis techniques promises faster, more accurate methods for recyclate characterization, meeting the evolving demands for high-quality recycled materials. NETZSCH's goal is to support the industry's transition to a circular economy.
By Aileen Sammler
