Polypropylene from post-consumer waste (PCR-PP) was melt-mixed with a di- and trifunctional molecule and treated with E-Beam radiation, to increase its viscosity and melt strength by long-chain ...branching and partial crosslinking. After adding diallyl- or triallylisocyanurate to polypropylene by melt compounding, the compounds were subjected to e-beam irradiation with doses between 10 and 60 kGy. Two types of polypropylene recyclates were investigated, both differing in the content of polyethylene. The samples were investigated with respect to the formation of microgels (gel content), rheological behaviour, melt flow rate and their mechanical properties. It was found that low irradiation doses in the range from 10 to 30 kGy reduce the melt flow rate significantly, and increase the tensile properties of PCR-PP while the gel content stays low. The results are discussed with respect to the amount of polyethylene impurities, and the processing behaviour of polypropylene, aiming at technically feasible recycling strategies for polyolefin recyclates.
Display omitted
•E-Beam treatment of post-consumer recycled polypropylene.•Melt Flow Rate adjustment of polypropylene.•Importance of post-consumer waste analytics.
Single-use plastic applications have resulted in a staggering amount of plastic waste. The total amount of plastic waste was estimated at 80 million tons in 2015, showing an increasing trend. A ...significant proportion of the total plastic waste is polypropylene (PP). PP offers good mechanical and chemical properties and can be manufactured and molded in a cost- and energy-efficient manner. This amount of plastic waste is forcing society to develop sustainable recycling strategies. For this reason, commercially available PP feedstocks made from post-consumer waste are available for manufacturing. These materials are primarily designed for injection molding or extrusion processes. Additive manufacturing, and in particular material extrusion-based additive manufacturing (ME-AM), has gained significant momentum over the past decade and is already widely used not only for prototyping but also for series production. PP is a material that is typically challenging to process by ME-AM due to its high crystallinity, high shrinkage, and poor adhesion properties. Therefore, this work investigates the use and applicability of PP recyclates in ME-AM. For this purpose, filaments were produced from a commercial grade PP recyclate and tensile specimens were printed with different printing parameters. The mechanical properties were compared to those of injection molded parts and a good relative performance of 64% to 81% was obtained. Although PP seems to be difficult to process with ME-AM, with an optimized print setup and suitable processing parameters, complex parts could be produced.
The study aims to analyze the strength properties obtained from three-point bending tests of epoxy-glass composite samples modified by adding rubber recyclate. A pure epoxy-glass composite is used as ...a comparative variant. The tested materials, which varies in the percentage of rubber recyclate and distribution, are cut through waterjet cutting to minimize the influence of temperature. The results undergo statistical analysis, and the microstructures are examined using scanning electron microscopy. The decreasing bending strength of the composites is observed, as the content of rubber recyclate in the material increased. However, adding rubber recyclate directly into the resin subtly decreases in bending strength compared to adding in the layers between the glass mat layers. Composites with rubber recyclate exhibits lower deflection under load compared to pure composites. The most favorable bending test parameters are obtained for the material containing 5% rubber recyclate distributed in three layers.
Plastics and plastic products have become part of our lives extremely quickly. Although, they make our lives easier in many aspects, at the end of their useful life, especially thanks to the ...thoughtless actions of people, they are becoming a serious environmental problem. Even though the laws and legislation are still forcing limits of using the plastic products and thus prevent waste, the concept of plastic-free living is probably not going to be reached easily and quickly. Using the recycling technology, we can prepare the recycled material, which represents a new raw material resource. With the right choice of physical-chemical parameters of recycled materials and using a suitable reaction condition we can incorporate them into the asphalt mixtures. Since their introduction the polymer-modified asphalt mixtures have gained in importance during the second half of the twentieth century, and they now play a fundamental role in the field of road paving. Moreover, the use of recycled plastic in such a product will contribute to the technical and economic recovery of secondary raw materials. The use of various recycled material in paving industry is a common practice but needs further research work. Thus, this study aims to the incorporation of recycled plastics into asphalt mixture. The main objective of our work was to find a suitable recycled plastic, which with its physico-chemical and technical parameters is suitable for incorporation into the asphalt mixture. In our study the recycled low-density polyethylene granulate was used, taken from films and various packaging materials. Our preliminary laboratory experiments were based on the possibilities to prepare and characterized the asphalt mixtures containing recycled plastic at different percentage, i.e., 4 %, 6 %, 8 % and 10 % by weight of bitumen. The experimental tests performed in the study were bitumen content, intergranularity, maximum bulk density, water sensitivity and resistance to permanent deformations. The results showed that the mix containing 6 % by weight of recycled plastic has ideal properties and meets most of the criteria that have been set for asphalt mixes. A commercially available polymer of similar chemical composition to the recycled material was used as a reference sample.
Yogurt cups with their recognizable design are made from plastics that are approved for food contact. The materials used have an interesting property profile. Therefore, these products represent a ...promising waste fraction for plastics recycling. In this study, yogurt cups were pre-sorted by consumers and further hand-sorted. A 2:1 ratio of polypropylene (PP) cups to polystyrene cups was found. In terms of decorations, cups with printing inks dominated. Two thirds of the PP cups were produced by thermoforming and one third by injection molding. Compositional analysis of the recycled PP showed no significant contamination other than residual dyes. Material characterization exhibited that both processing and application-oriented properties can compete with virgin material. To demonstrate a closed-loop, the recycled PP was used to produce thermoformed cups with exceptional properties. This study shows the positive effect of closed-loop recycling and points out potential waste fractions that can be used in the future.
Display omitted
This study establishes a valid theoretical model for food and beverage sustainable packaging in Indonesia along with packaged product pre-, during-, post-consumption stages. Food and beverage product ...packaging dominates the total waste composition due to slow recycling rates and low recyclate supply, and packaging tends to be littered in the post-consumption stage. This study aims to address the sustainable packaging attributes and understand which consumption stage needs prioritizing for improvement. A hybrid method is employed. Fuzzy Delphi method is applied to eliminate and validate the attributes. The interrelationships among attributes are examined and visualized using fuzzy decision-making trial and evaluation laboratory. The priority consumption stage is identified by applying Choquet integral method. The results show that post-consumption stage fundamentally aims to address sustainable packaging. This study finds that conservation proficiency, environmental communication, and cost consideration are the driving aspects in improving sustainable packaging. For practices, the top criteria are identified including recylates for packaging, multi-stakeholder interaction, waste disposal infrastructure, waste collection infrastructure and waste disposal management.
•The quality of recyclates can be determined via PE/i-PP model blends.•FT-IR and DSC are suitable methods to estimate recyclate composition.•Source separated and commingled collected PPW have ...comparable quality.•Manual screening of recyclates is beneficial for reproducible mechanical properties.
The global plastics production has increased annually and a substantial part is used for packaging (in Europe 39%). Most plastic packages are discarded after a relatively short service life and the resulting plastic packaging waste is subsequently landfilled, incinerated or recycled. Laws of several European and Asian countries require that plastic packaging waste collected from households has to be sorted, reprocessed, compounded and reused. These recycling schemes typically produce milled goods of poly(ethylene terephthalate) (PET), poly(ethylene) (PE), isotactic poly(propylene) (PP), mixed plastics, and agglomerates from film material. The present study documents the composition and properties of post-consumer polyolefin recyclates originating from both source separation and mechanical recovery from municipal solid refuse waste (MSRW). The overall composition by Fourier transform-infrared (FT-IR) spectroscopy and differential scanning calorimetry (DSC) were determined and compared with the sorting results of the sorted fractions prior to the reprocessing into milled goods. This study shows that the collection method for the plastic packaging waste has hardly any influence on the final quality of the recyclate; however, the sorting and reprocessing steps influence the final quality of the recyclate. Although the mechanical properties of recyclate are clearly different than those of virgin polymers, changes to the sorting and reprocessing steps can improve the quality.
Abstract
Thermoformed products bear great potential for the application of recycled materials when using multilayer structures for incorporating post‐consumer recyclates. For this study, four ...different commercially available polypropylene recyclates are selected as possible core layers for the processing of multilayer thermoformed products with top layers of virgin polypropylene. Tests are performed on material level as well as on product level. At the material level, recyclates exhibit different mechanical property profiles with lower stiffness but higher toughness values due to polyethylene contamination. At the product level, thermoformed cups with core layers of recyclate material show lower shrinkage than cups made from polypropylene virgin material only. Most cups with recycled content achieve lower top load than the control cup. Based on these results, three strategies for improving product performance are defined and tested. Namely, (i) the use of a higher share of top layers, (ii) the blending of the recyclate core layer with a polypropylene virgin material with higher stiffness, and (iii) the increase in overall film thickness. All the strategies to adjust the film structure achieve better results in terms of shrinkage behavior and top load. However, the strategy that focuses on increasing the overall film thickness is not economically feasible.
Plastic recyclates can be contaminated with a variety of impurities due to their previous life, which cannot always be perfectly separated in recycling pretreatment steps. Hence melt filtration is an ...important step in reprocessing plastic recyclates to achieve material of sufficient purity, but it also leads to more stress on the material due to higher pressures and longer processing times. In our study, we investigated the influence of typical particulate impurities as may occur in recyclate on the mechanical and rheological properties of ABS. Even low amounts of contaminations lowered the key properties. Melt filtration of post‐consumer ABS recyclate with different mesh size melt screens showed little improvement of mechanical properties, but longer idle times and loss of material. Damage to the material caused by finer filtration could be shown by thermal measurements.
Highlights
Determination of properties of ABS contaminated with 0.5–2.0 wt.% of selected impurities (wood and rubber particles).
Melt filtration of post‐consumer ABS recyclate with different melt screens.
Investigation of process and properties of filtered ABS recyclate.
Mass pressure increases with filtration time for melt filtered ABS recyclate with screens with a mesh size of 250, 100, 60, and 20 μm. Melt filtration improves different properties of the recyclate, but the lowered throughput and increased loss of material have to be considered.
The use of the polypropylene (PP) recyclates in certain processing methods and applications is still limited by their quality. The high melt flow rate (MFR) and the inconsistent properties of ...recyclates are common obstacles to their use. Therefore, this work aims to identify possible reasons for the low and inconsistent quality of PP recyclates depending on the source material in PP waste bales. The levels of polymeric and non-polymeric contaminants were assessed. As mixing of different PP grades is an issue for the MFR, the proportions of the different processing grades were also investigated and the potential of sorting by processing method to produce lower MFR recyclates was assessed. The analysis showed that the waste bales, although pre-sorted, still contained high amounts of contaminants. Injection moulding was found to be the predominant processing method in the bales, explaining the high MFR of PP recyclates. However, a sufficiently high amount of low MFR products was found in the bales, which seems promising for the production of low MFR recyclates. Seasonal variations in the composition of the waste bales were identified as one of the reasons for the inconsistent qualities of recyclates. These results highlight the importance of proper sorting and treatment of PP waste bales prior to reprocessing in order to obtain high-quality recycled products.
