Polymeric materials are increasingly used in the construction of machines and devices. As their use increases, so does the proportion of the waste produce in the industry. One of the ways to reduce the waste is the addition of recycled material into the re-production. Although the addition of the return material reduces the proportion of produced waste, it can lead to the modification of mechanical properties of the produced products. The subject of the present article is precisely investigating the mechanical properties modification of the final injection moulding during the plastic injection technology. The tensile strength Rm of the samples taken from the injection volume produced from the material composed of pure and return material in the ration 100/0, 30/70, 50/50, 70/30 and 0/100 is investigated. Considering the possibility of Rm modification in the injection volume, individual samples are taken from four zones depending on the position from the ingate. It is demonstrated that Rm decreases with the increasing ratio of the return material as well as with the increasing distance from the ingate.