Investigation of the Influence of Sorting on the Property Profile of Colored Polyethylene Recyclates
Sprache des Vortragstitels:
38th International Conference of the Polymer Processing Society (PPS-38)
Sprache des Tagungstitel:
Plastics recycling is crucial for the transition into a sustainable circular economy in the plastics industry. Proper sorting is one of the essential tools to enable the production of high-quality recyclates. However, the sorting process entails several challenges that may hinder the development of plastics circularity. The aim of this study is to understand the influence of sorting on certain properties of recycled polyethylene. A high-density polyethylene (PE-HD) dominated post-consumer feedstock was used in this study. Amongst other pretreatment steps, the feedstock was color-sorted into five different colors, namely, two achromatic (incl. white and black) and three chromatic colors (incl. green, blue, and red). Afterwards, to produce recyclates with the specified colors, the color-sorted feedstock in form of flakes were re-granulated using an industrial recycling extruder with filtration and degassing systems. To characterize the property profile of the resulting recyclates, several measurements including melt flow rate (MFR); Charpy impact tests; and tensile tests were performed. A significant variation in the MFR values as well as the mechanical properties of the materials was observed. Moreover, to further investigate the influence of sorting, mixtures of the colored recyclates with various ratios were produced. The mixtures were compounded using a twin-screw compounder to generate new blends, which to a certain extent can simulate possible recyclates that could result from an unsorted feedstock. Thereafter, the same characterization methods were performed on the different blends to determine the changes in the material properties if the feedstock were unsorted. Additionally, as an attempt to test the applicability of existing mathematical mixing rules, the material properties of the color sorted recyclates were used to calculate the property profile of the mixed fraction.