Reactive Degradation and Upgrading of Recycled Polypropylene Using Nexamite Additives: Effects on Rheological, Thermal and Mechanical Properties

To reduce the environmental impact associated with fossil-based materials, mechanical recycling represents a key strategy, although it inevitably leads to a decline in rheological, thermal, and mechanical properties due to polymer chain degradation. This study investigated the effect of controlled degradation and subsequent reprocessing of polypropylene (PP) using reactive additives from the Nexamite family. Degradation was induced by adding Nexamite R202 at concentrations of 0.5%, 1%, and 2%, while reprocessing was carried out using Nexamite R203 combined with an antioxidant package. The results show that peroxide addition promotes progressive chain scission, leading to reduced thermal stability and mechanical performance. A moderate peroxide content (1%) provided the best balance between improved processability and mechanical performance, showing high ductility and impact toughness. Subsequent reprocessing with Nexamite R203 enabled a significant recovery of the degraded material's properties. Formulation PP REC 8.2 exhibited increased melt viscosity, slight thermal stabilization, and a marked improvement in elongation at break while maintaining stress values comparable to the starting degraded material. Overall, the results demonstrate that a strategy based on controlled degradation followed by targeted reprocessing can effectively tune processability and partially restore the performance of recycled polypropylene, offering promising opportunities for the upgrading of recycled PP for higher-value applications.