Identifying key properties of thermoplastics affected by mechanical recycling processes to support material selection for circularity

To support the circular economy in product design, engineers increasingly consider replacing raw materials with recyclates and future recyclability. Mechanical recycling, however, can alter material properties, thus affecting the utilization potential. For enabling closed-loop material flows, these changes must be considered in material selection. This study proposes to consider circularity indices in commonly used material properties for thermoplastics to help engineers in designing products for manufacturing and recycling. Through literature research and empirical data, these indices are established and material properties are derived and analyzed. Results show that various properties change differently across materials during mechanical recycling. The proposed material indices consider these changes, enhancing material selection for circular flows. This research underscores the need to consider the implications of multiple life cycles in material selection to improve sustainability.