Solid-state, mechanochemical polymer processing techniques are explored as an effective and sustainable solution to appearance and performance issues commonly associated with recycled plastic products. Post-consumer high-density polyethylene (HDPE) from milk jugs is processed via conventional twin screw extrusion (TSE), solid-state shear pulverization (SSSP), and solidstate/melt extrusion (SSME), and compared to the as-received and virgin forms regarding output attributes and mechanical properties, as well as morphology. Solid-state processing methods, particularly SSME with a harsh screw configuration, produce samples with consistent appearance and melt flow characteristics. Tensile ductility/toughness and impact toughness are enhanced by up to 11-fold as compared to the as-received sample, to a level near and above those of an equivalent virgin HDPE. Calorimetry, optical microscopy, X-ray scattering, and rheology characterization reveal that the mechanical improvements result from a favorable combination of physical and molecular changes in rHDPE, such as impurity size reduction, spherulite size enlargement, and chain branching.