The degradation, grafting and crosslinking of polypropylene have been studied with a free modelling system. the squalane. This study used conditions similar to reactive extrusion in terms of temperature and concentration of actives species. The products of reactions were characterized by mass spectrometry and IR spectroscopy. The reaction between peroxide and squalane confirms the importance of the half-life of the peroxide in limiting the degradation of the squalane chain. In presence of monomer we observed simultaneously grafting and beta-scission of squalane. Comparison between methacrylates and acrylates shows that acrylates are much more effective for grafting than methacrylates. With trifunctional monomers, the main reaction is the crosslinking of squalane (or recombination of macroradicals via the monomer). In this case, triacrylates were also more effective.