The recyclability of two commercial nylon 66/PPO [poly(phenylene oxide)] alloys has been investigated by examining the effects of multiple and abusive melt processes upon the impact strength. The loss of performance associated with these exposures has been correlated, in one instance, with the thermal degradation of polybutadiene-based impact modifier. The degradation of the rubber has been quantified using an indirect measurement of rubber mobility obtained from the NMR free induction decay of mobile and rigid protons in the material. Substitution of the unsaturated rubber modifier with a saturated hydrocarbon resulted in improved recyclability. Both formulations provide evidence of changes In morphology related to instability of the dispersed PPO phase. The coalescence of PPO particles, evident in later stages of prolonged thermal exposure, appears to cause further loss of impact strength. Currently the chemical and/or physical changes responsible for the increase in average PPO particle size are not known. It is probable that the thermal stability of the compatibilizer, formed during the reactive extrusion manufacturing process, may be insufficient to provide a durable morphology for repeated recycling of these alloys.