This paper describes the effect of individual additives that are present in typical masterbatch formulations; the role they play in modifying physical properties and processability of blends based on RPET. Additives such as titanium dioxide, carbon black, linear low-density polyethylene and polyethylene wax are often incorporated into the composition of masterbatch. Blends based on these additives have been analysed for shifts in thermal transition points, levels of crystallinity and physical properties such as tensile and impact strength. The results show that, at the addition rates used, some additives had significant effects on processability and crystallinity, negligible effects on physical properties and antagonistic effects were noted when additives were combined.