Due to insufficient sorting and recycling, macroscopic contaminations remain in post-consumer polyolefin recyclates. It is known that these contaminations affect the mechanical properties of the recyclates, as they constitute defects and thus crack initiators. However, the influences of different types and amounts of macroscopic contaminants have not yet been analyzed systematically. In this study, to close this knowledge gap, virgin polypropylene (PP) was systematically contaminated with paper, aluminum, sand, wood, in-mold labels, jute fibers and long glass-fibers. Additionally, three commercially available post-consumer PP recyclates were investigated. In a two-stage process, all materials were injection-molded into plates and subsequently milled to specimens. The specimens underwent (i) tensile tests at 50 mm/min, (ii) intermediate-rate tensile tests at 2000 mm/min, and (iii) tensile impact tests. Further, optical microscopy was used to measure the dimensions of the defects on the fracture surfaces. First, the influences of various types and quantities of contamination were evaluated. No significant effects were detected, as the matrix material was very brittle. Compared to the virgin reference grade, most samples showed lower strain-at-break values, except for those with labels and long glass-fibers, for which strain values increased. All PP post-consumer recyclates exhibited a more pronounced ductile behavior, although the contaminations incorporated gave rise to relatively high standard deviations. Second, in a comparison of various testing speeds, a greater influence of contaminants was detected in test (iii). Samples taken from a position close to the sprue had better mechanical properties than samples taken from the opposite side of the plate, as contaminants tend to flow to the end of the produced part. Finally, a non-linear relationship between the energy needed for fracture in testing methods (ii) and (iii) and the dimensions of the contamination on the fracture surface was found.
The use of fossil resources and their negative environmental impacts has awakened the awareness of the petrochemical industry. Hereby, we are presenting some upstream industrial scalable and commercial solutions to process sustainable feedstocks, either biogenic or recycled, to produce drop-in hydrocarbons that can be converted into light olefins using the same assets and infrastructure currently established in the petrochemical industry (e.g. steam crackers), reducing the environmental impact of large-volume chemicals such as ethylene, propylene and benzene, which are the most demanded building blocks in the petrochemical value chain. Mass balanced certified co-processing of biogenic and recycled waste plastics as raw materials, are the key for the de-fossilisation of the petrochemical industry. Production of polypropylene (PP) using renewable feedstock can reduce the GHG above 80% or 3.8 kg CO2eq/kg in comparison with the fossil-based. For making a higher impact in the plastic industry, a full integration of the value chain is needed to guarantee allocation of the sustainable credits to targeted products. As a showcase, a collaboration project between partners in different parts of the value chain to produce biobased PP thermoformed plastic cups, is presented. As a result from this collaboration, PP cups with final properties identical in range to the traditional fossil were obtained and the renewable hydrocarbons could be identified in the product using C14. Drop-in solutions using renewable or recycled feedstock is paving the way in the petrochemical industry to obtaining sustainable products with low impact in the current downstream infrastructure. 2b1af7f3a8