Recycling processes for thermoplastics-based nanocomposites involve grinding the recyclate into small pieces, which are fed back into the process, for example, injection molding or extrusion. During the grinding and recycling of nanocomposites, nanoparticles may be released into the air, causing worker exposure. The potential harm from such releases is an important concern for nanoproduct recycling, also the effect of recycling on nanoproduct properties. Molecular chain breakage during reprocessing may lead to decreased mechanical properties. In the case of CNT filled thermoplastics the repeated high shear of the injection molding process during recycling may improve CNT dispersion and properties. These competing processes may result in differing effects depending on the specific polymer. The effect of grinding and reprocessing on the properties of polypropylene/carbon nanotube (CNT) and polycarbonate (PC)/carbon nanotube (CNT) composites was investigated. Materials were recycled using repeated injection molding/grinding to twenty cycles. Characterization of the chemical, mechanical, thermal, rheological, and morphological properties were investigated for the impact of recycling processes on material properties. It was found that the impact of recycling can be very different for various CNTs filled polymers. Noticeable degradation of mechanical properties (such as strength and toughness) were found for PC/CNTs, but for PP/CNTs, very change in properties was found. This was attributed to the improved secondary nucleation effect induced by CNTs. Nanoparticle release and personal exposures to CNTs and fibers were also quantified during grinding and reprocessing.