Inelastic mechanical behavior in tension of a recycled polypropylene (rPP and a rPP with addition of 10% of maleic anhydride grafted polypropylene (rPP + MAPP) was characterized and compared. The time-dependent response was decomposed into nonlinear viscoelastic and viscoplastic parts and each of them quantified. It was found that the elastic properties did not degrade during loading. The addition of MAPP did not change the mechanical properties of the rPP. A nonlinear material model was developed and the involved parameters (stress-dependent functions) were identified. The model was then validated in a stress controlled test at a constant stress rate. © The Author(s), 2011.