A series of polypropylene filaments containing a number of recycled polyolefins in varying concentrations are extruded in the absence and presence of a thermal stabilizer package. The physical and chemical properties of these filaments are then characterized to identify the effects of adding the recyclate. While the added recyclate affects the overall properties, there is a tolerance level up to which the changes may be accepted, and the magnitude of the overall effect depends on the physical and chemical properties of the recyclate.