Learnings about design from recycling by using post-consumer polypropylene as a core layer in a co-injection molded sandwich structure product

Gall, Markus; Steinbichler, Georg; Lang, Reinhold W.

doi:10.1016/j.matdes.2021.109576

Cited by 27 publications

(31 citation statements)

References 38 publications

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“…Recent studies suggest that the presence of inclusions and defects in post-consumer recyclates have a severe impact on mechanical properties like ultimate strain and toughness [60,70,71]. This is even the case in sandwich structures with virgin material skin layers [41]. There is hence a need to further characterize the role of such inclusions and defects, e.g., by means of fracture mechanical methods [11,12] in order to arrive at adequate assessments of part performance, service life, and reliability/safety.…”

Section: Discussionmentioning

confidence: 99%

“…Analogously, the similar MFR values of the rPPs (on a logarithmic scale) would indicate rather similar average molecular weight and this would fit well to the rather narrow range of Charpy NIS values. However, besides molecular mass and polydispersity, Charpy NIS of PP is also dependent on polymer architecture (co-monomers, tacticity, and chain defects) and micro-structural morphology [16,61,62] as well as (legacy) fillers and stress-concentrating defects [41,60].…”

Section: Technological Characterizationmentioning

confidence: 99%

“…It is increasingly being understood that there is an intrinsic connection between recyclate composition, including minor fractions and contaminants, and the resulting structure-property relationships [37,38]. Recent developments, such as the design-from-recycling concept [39][40][41][42], try to account for these peculiarities of (post-consumer) recyclates. However, it has to be admitted that the classical situation when it comes to using rPE and rPP materials is still such that we have only very rudimentary information regarding their composition and we are still far from being in the position of tailoring structure-property profiles of PO recyclates for challenging applications.…”

Section: Introductionmentioning

confidence: 99%

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Characterization of Composition and Structure–Property Relationships of Commercial Post-Consumer Polyethylene and Polypropylene Recyclates

et al. 2021

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The current efforts in moving closer towards a circular plastics economy puts massive pressure on recycled plastics, especially recycled polyethylene (rPE) and recycled polypropylene (rPP) to enter new markets. Their market penetration remained low so far, despite PE and PP constituting the largest share of plastic wastes. However, with the current imperative of more circularity comes a new focus on performance of recyclates. Hence, a detailed understanding of composition and structure–property relationships of post-consumer recyclates has to be developed. Five recycling companies from the Austrian and German markets were asked to supply their purest high-quality rPE and rPP grades. These were characterized by differential scanning calorimetry (DSC), thermo-gravimetric analysis (TGA), and Fourier-transform infrared (FTIR) spectroscopy, and micro-imaging. Technological characterization included density measurements, determination of the melt flow rate (MFR), and Charpy impact testing. All recyclates contained diverse contaminants and inclusions ranging from legacy fillers like calcium carbonate to polymeric contaminants like polyamides or polyolefin cross-contamination. The overall amount, size, and distribution of contaminants varied significantly among suppliers. Furthermore, first structure–property relationships for polyolefin recyclates that link inorganic content and polymeric purity with density and impact performance could be derived.

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Section: Discussionmentioning

confidence: 99%

Section: Technological Characterizationmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Characterization of Composition and Structure–Property Relationships of Commercial Post-Consumer Polyethylene and Polypropylene Recyclates

et al. 2021

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“…A promising way of design from recycling without sacrificing visual quality and mechanical stability while using the required amount of plastic recyclates is to produce products with a multilayer structure to encapsulate the recyclates. Recyclates, which often have a grayish or greenish appearance and are therefore not as attractive as transparent, clear white, or brightly colored materials, can be wrapped in pigmented top layers [7]. Furthermore, migration can be weakened by the use of multilayer structures, which could help recyclates to be applicable for food contact products [8].…”

Section: Introductionmentioning

confidence: 99%

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

Traxler¹,

Marschik²,

Farthofer

et al. 2022

Polymers

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To enable the use of recyclates in thermoformed polypropylene products with acceptable optical appearance and good mechanical stability, a multilayer structure of virgin and recycled material can be used. When producing multilayer films with more than two layers, the used materials should have similar melt flow properties to prevent processing instabilities. In the case of a three-layer film, post-consumer recyclates are often hidden in the core layer. Due to the inconsistent melt flow properties of post-consumer recyclates, the adjustment of the melt flow properties of the core layer to those of the outer layers has to be realized by blending with virgin materials. In order to understand the effect of mixing with a virgin material with a certain pre-defined melt flow rate (MFR), material mixtures with different mixing partners from various sources were realized in this study. Hence, the pre-defined virgin material was mixed with (i) virgin materials, (ii) artificial recyclates out of a mixture of different virgin materials, and (iii) commercially available recyclates. These blends with mixing partner contents ranging from 0–100% in 10% increments were prepared by compounding and the MFR of each mixture was determined. For a mathematical description of the mixing behavior and furthermore for a proper MFR prediction of the material mix, existing mixing rules were tested on the three pre-defined sample groups. Therefore, this paper shows the applicability of different mixing rules for the prediction of the MFR of material blends. Furthermore, a new mixing rule was developed using symbolic regression based on genetic programming, which proved to be the most accurate predictive model.

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“…[10][11][12] On the other hand, the PP has also constituted a major fraction of post-consumer plastic waste by its widespread use. [13] Although a relatively low processing temperature of PP (~200 C) has attracted many researchers and engineers for polymer-polymer composite recycling, practical recycling of PP blends with high-performance polymers, such as polyamide (PA), has been challenging because PP lacks functional groups resulting in weak interfacial adhesion with the reinforcing material. [14][15][16][17] The lack of specific molecular interactions leads to rough phase structure as well as poor mechanical properties in finished products.…”

Section: Introductionmentioning

confidence: 99%

Tailoring compatibilization potential of maleic anhydride‐grafted polypropylene by sequential rheochemical processing of polypropylene and polyamide 66 blends

Seo

Kearney

Datta

et al. 2022

Polymer Engineering & Sci

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Reactive compatibilization of immiscible polymer blends using a preferred compatibilizer leaves the following question: How much loading of a compatibilizer is good enough and what maximum properties can be achieved? A good understanding of the process can help solve the reutilization of mixed waste plastics. Here, the reactive compatibilization of polypropylene-graftmaleic anhydride (PP-g-MAH) on polypropylene/polyamide 66 (PP/PA66) blends is quantitatively assessed using thermorheological, microoptical, spectroscopic, and x-ray scattering-based characterization tools. The overall compositions of all PP(60%)/PA66(30%)/PP-g-MAH(10%) blends are kept constant while systematically controlling the degree of the chemical reaction by varying the sequential addition of PP-g-MAH to the melt mixture. The first feeding of PP-g-MAH (x%,0 ≤ x ≤ 10) is conducted at 280 C and the second feeding of (10 À x)% is at 200 C. During the first step, a larger amount of chemical activity is observed up to 4%-6% addition of PP-g-MAH. The constant chemical composition allows a systematic comparison of the compatibilizer-dependent thermal, rheological, morphological, and mechanical properties. With an increased degree of interfacial reaction, the size of dispersed PA66 domains decreases to register improved interfacial adhesion with the PP matrix, yielding enhanced Young's modulus and absolute failure strength of the isotropic matrix.

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Learnings about design from recycling by using post-consumer polypropylene as a core layer in a co-injection molded sandwich structure product

Cited by 27 publications

References 38 publications

Characterization of Composition and Structure–Property Relationships of Commercial Post-Consumer Polyethylene and Polypropylene Recyclates

Characterization of Composition and Structure–Property Relationships of Commercial Post-Consumer Polyethylene and Polypropylene Recyclates

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

Tailoring compatibilization potential of maleic anhydride‐grafted polypropylene by sequential rheochemical processing of polypropylene and polyamide 66 blends

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