Selected Problems of Reverse Logistics in the Multiple Processing of Polymer Recyclates

The article presents a solution introduced in an industrial enterprise to recover low-density polyethylene from production waste and reintroduce it as a secondary raw material into a separate production cycle, thus obtaining a closed cycle: primary plastic – production – waste – secondary plastic – production. The production assortment consisted of bags, with primary raw material being used to make bags for contact with food (e.g. for freezing), while secondary raw material was used to make garbage bags. The applied technology of extrusion with free blowing, enabled the production of multi-layer film in which primary raw material, secondary raw material obtained from own production waste and secondary raw material from external suppliers, were used. The mutual proportions of raw materials allowed the production of three-layer film with a wide range of performance properties, with a significant group of products constituting a film containing at least 55% of waste polyethylene. The conducted experimental tests were carried out under industrial conditions. The tubular film made from three-layer polyethylene were subjected to testing based on several dozen formulations defining the raw material composition, which relates to the total content of polyethylene regranulate. The results of the studies on selected properties of the secondary raw material and the selected mechanical properties of the three-layer film, which was subsequently used to produce garbage bags in the next stage of the production process, are presented. Based on the results obtained, the effectiveness of the qualification system adopted for polyethylene regranulates was assessed in relation to the formulation scheme developed, ensuring efficient production of three-layer film with appropriate user properties, regardless of random changes in the properties of secondary raw materials recovered internally or sourced externally.