As the demand of plastics is increasing plastic waste is a constantly growing concern and recycling methods need to be adapted consistently in order to meet new requirements. Thermoplastics account for a large proportion of waste but have the potential to be reintroduced in product cycle. While polyethylene terephthalate as well as polyethylene are reintroduced (more or less) easier polypropylene (PP) is highly prone to thermal oxidation and radical degradation due to its high number of ternary carbon atoms and the abstraction of the hydrogen atom adjacent to the pendant methyl groups. Depending on the certain field of application and processing procedure of PP additives are essential in maintaining physical and mechanical properties during use. Decreasing molar mass, impurities and also heterogeneous composition of stabilizers and additives lead to challenges in reprocessing of post-consumer-PP (pc-PP) waste. [1] For that reason the knowledge about the content of stabilizers (phenolic antioxidants, phosphite-type, hindered amine light stabilizers) and additives remaining as well as their degradation products is essential for chemical or physical modification of post-consumer-PP waste, and as a result of this for new and innovative methods in terms of polypropylene upcycling. Chemical modification of PP is sensitive to certain functional groups such as radical scavenger or peroxide decomposer. In this study a series of reference formula of post-consumer-PP waste is produced. Samples are characterized spectroscopically (FT-IR), thermally (DSC, TGA) and thermo-mechanically (rheology) in order to gain an insight into the resultant composition of specific functional-groups and their product of degradation, thermal stabilization condition, and changes in molar mass respectively. In a last step methods are evaluated on real pc-PP waste and modified samples. [1] P. Brachet, L.T. Hoydal, E.L. Hinrichsen, F. Melum, Waste Manage. 28, 2456 (2008)