Application of Mixing Rules for Adjusting the Flowability of Virgin and Post-Consumer Polypropylene as an Approach for Design from Recycling

Traxler, Ines; Marschik, Christian; Farthofer, Manuel; Laske, Stephan; Fischer, Joerg

doi:10.3390/polym14132699

Cited by 13 publications

(27 citation statements)

References 43 publications

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“…For thermoforming applications, the most requested properties are (1) a melt mass-flow rate (MFR) within the range of the currently used virgin thermoforming materials, (2) a high tensile modulus of above 1500 MPa, and (3) a Charpy notched impact strength of above 3.5 kJ/m 2 . To make blends with the three high MFR rPPs, a virgin blending partner with very low MFR is crucial [ 19 ]. Furthermore, a high tensile modulus and Charpy notched impact strength are also beneficial to achieve high recyclate contents while still fulfilling the requirements.…”

Section: Methodsmentioning

confidence: 99%

Polypropylene Post-Consumer Recyclate Compounds for Thermoforming Packaging Applications

et al. 2023

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Polypropylene (PP) plastic packaging waste consists of a variety of different plastic packaging products with a great span in rheological and mechanical behavior. Therefore, the resulting post-consumer recyclates usually show melt mass-flow rates (MFR) in the region of injection molding grades and intermediate mechanical properties. High-quality packaging applications demand a distinct property profile that is met by tailor-made PP grades and cannot be met by recyclates with intermediate performance. One such application with high market volume is high-stiffness thermoforming trays. The aim of this research was to blend intermediate-performance recyclates with a virgin PP grade to obtain compounds that fulfill the rheological and mechanical demands of this application. Three commercially available PP post-consumer recyclates were acquired and compounded with different blending ratios with a high stiffness, low MFR virgin PP grade. As the pure recyclates show different rheological properties, the blending ratios had to be adapted for each of them to fit into the MFR range of 2–4 g/10 min which is desirable for thermoforming applications. The resulting PP recyclate compounds show a distinct correlation of recyclate content with rheological and mechanical performance. However, the resulting property profile was directly dependent on the performance of the originally used recyclate. The best-performing recyclate could be used in a blending ratio of 65 m% recyclate content while adhering to both property limits, the MFR of 2–4 g/10 min and the lower bound tensile stiffness of 1500 MPa.

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Section: Methodsmentioning

confidence: 99%

Polypropylene Post-Consumer Recyclate Compounds for Thermoforming Packaging Applications

et al. 2023

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“…The pure recyclates are not shown in Figure 1 , as their unproportionally high MFRs of 15.6 g/10 min (rPP-A), 13.3 g/10 min (rPP-B) and 9.1 g/10 min (rPO-C) would distort the graph and render the lower MFRs indistinguishable. The compounds show MFRs in the range of the Arrhenius mixing rule predicted values (see Figure 2 ) with rising MFRs for rising recyclate contents [ 34 ]. Therefore, linear fits within the logarithmic graph show high R 2 values of 0.98 and 0.99.…”

Section: Resultsmentioning

confidence: 99%

Polypropylene Pipe Compounds with Varying Post-Consumer Packaging Recyclate Content

et al. 2022

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The high recycling targets set by the European Commission will create an increased availability of polypropylene (PP) post-consumer recyclates (PCRs). However, no regulations mandate the use of recycled PP (rPP), so the industry is challenged to explore possibilities to utilize such materials. One option, as suggested by the European Commission, is the introduction of rPP in pipe applications. According to existing standards, the use of recyclate is not allowed in pressurized gas and drinking water systems. However, many other pipe and underground applications, such as stormwater systems, open the increased use of PCRs. Additionally, even for less-demanding applications, such as non-pressure sewage systems, highly durable solutions are needed to cover the requested lifetime and request an ambitious property profile to fulfill the application needs that cannot be met by PP packaging materials and even less by PCRs thereof. Hence, this work explores the possible use of commercially available PCRs out of polypropylene from packaging applications in compounds together with virgin PP pipe grades to meet the demands for less-demanding applications. Two different commercially available rPPs and one commercially available recycled polyolefin (rPO) from mixed polyethylene and PP waste were acquired and, together with two predefined virgin PP pipe grades, were blended to compounds in the range of 10 m%, 20 m%, and 30 m% recyclate content. The compounds and three virgin PP pipe grades, acting as benchmarks, were tested in terms of short- and long-term mechanical performance as well as for many other physical properties. All of the compounds showed good results regarding fatigue crack (FCG) resistance with virgin polymer as the reference. The factors influencing FCG resistance, such as melt flow rate and polyolefin cross-contamination, were thoroughly investigated as the used virgin grades and recyclates cover a broad range of these properties.

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“…These products are normally produced by various processing technologies (e.g., injection molding, extrusion, blow molding) and, based on the desired property profile of the end product, proper material selection is required [15]. Melt flow rate (MFR) of the polymer is usually used as an indicator to determine the compatible processing technology for a certain product [11,16,17]. Gall et al [16] carried out a survey of relevant material selection guides and data sheets from several polymer suppliers to investigate the diversity of materials that are used for cap and closure applications in the beverage industry.…”

Section: Life Cycle Of Polyolefin Productsmentioning

confidence: 99%

“…Afterwards, the resulting recyclates might undergo some post-treatment steps (e.g., decontamination, compounding) before being converted into new products [38]. Compounding, with virgin materials and/or additives, is usually used to improve the quality of the recycled plastics to fulfil product requirements [17,51]. Several organizations and initiatives introduced guidelines that include sets of requirements and test protocols to evaluate the reliability of the waste supplier as well as the recyclability of the input materials in the recycling industry [52,53].…”

Section: The Inherent Heterogeneity Of Plastic Wastementioning

confidence: 99%

Sampling Scheme Conception for Pretreated Polyolefin Waste Based on a Review of the Available Standard Procedures

Akhras

Fischer

2022

Polymers

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Given the rapid development of plastics recycling in recent years, the need for guidelines for sampling and material characterization is steadily emerging. However, there still exists a considerable scarcity of methods that enable proper material data acquisition. This paper consists of two parts. The first part provides a critical review of the available sampling techniques that can be utilized in the field of plastics recycling. Several sampling studies were covered in the review alongside the prominent standardization institutions. It was found that neither the literature nor the standards provide a comprehensive practice that considers the distinctive characteristics of plastic waste and applies it to different situations along the value chain. In the second part, a proposal of a sampling plan for pretreated rigid plastic waste is conceptualized based on selected information from the reviewed methods. Two variants of the proposed plan were evaluated based on the flake size distribution and the apparent density of four different pretreated polyolefin (PO) waste materials. The results of the study showed that combining stratified random sampling with composite sampling yields a good sampling technique for rigid PO waste. Moreover, the analysis of a composite sample adequately conveys the true material properties of a sublot or lot.

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Application of Mixing Rules for Adjusting the Flowability of Virgin and Post-Consumer Polypropylene as an Approach for Design from Recycling

Cited by 13 publications

References 43 publications

Polypropylene Post-Consumer Recyclate Compounds for Thermoforming Packaging Applications

Polypropylene Post-Consumer Recyclate Compounds for Thermoforming Packaging Applications

Polypropylene Pipe Compounds with Varying Post-Consumer Packaging Recyclate Content

Sampling Scheme Conception for Pretreated Polyolefin Waste Based on a Review of the Available Standard Procedures

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