Mechanochemical modification of crosslinked low‐density polyethylene: Effect of solid‐state shear pulverization on crosslinks, branches, and chain lengths

Zack, Spencer J.; Herrold, Nathan T.; Wakabayashi, Katsuyuki

doi:10.1002/pls2.10077

Cited by 7 publications

(8 citation statements)

References 59 publications

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“…In the present investigation, the recycled HDPE (rHDPE/CaCO 3 , designated as ENB‐00 in Table 1) obtained from post‐consumer plastic bags showed an average tensile of 12.4 MPa, modulus of 967 MPa, and strain‐at‐failure of 6% strength after melt reprocessing and compression molding. This value of tensile strength of rHDPE is low compared to virgin HDPE but similar to that of low‐density polyethylene 9,28–30 . The relatively low tensile properties of the rHDPE resin sourced from post‐consumer streams are likely due to various factors, including an inferior‐grade recycled HDPE resin reprocessed multiple times.…”

Section: Resultsmentioning

confidence: 90%

Nitrile rubber/peroxide treatment transformed recycled polyethylene into mechanically improved materials

Ghosh

Kannan

2023

SPE Polymers

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The recycled high-density polyethylene (rHDPE) feedstock containing calcium carbonate (CaCO 3 ) mineral was obtained from post-consumer single-use grocery bags. This feedstock is transformed into new composite materials with improved mechanical properties using a high-shear compounding process. The rHDPE/CaCO 3 feedstock is injected into the high-shear polymer mixer and blended with acrylonitrile-butadiene copolymer or nitrile rubber (up to 10 wt %) and crosslinked with dicumyl peroxide. The resultant materials exhibit high mechanical performance, with a maximum tensile strength of 20.3 MPa, stiffness of 1262 MPa, and impact strength of 63 kJ/m 2 . These mechanical properties are profoundly higher than those of neat rHDPE feedstock. Notably, the post-consumer plastic bags contain a high amount of CaCO 3 mineral of approximately 30 wt% (13 vol%), impacting the materials' mechanical properties with additives such as nitrile rubber. In addition, the materials' meltrheology, viscoelastic, and phase morphology are analyzed. The meltrheological characteristics indicate that the materials' complex viscosity and storage modulus are frequency-dependent, demonstrating the thermoplastic nature of the composite materials and the possibility of thermomechanical recyclability of the materials. However, treating rHDPE/nitrile rubber blends with peroxide creates resistance to the melt-flow of the materials.

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Section: Resultsmentioning

confidence: 90%

Nitrile rubber/peroxide treatment transformed recycled polyethylene into mechanically improved materials

Ghosh

Kannan

2023

SPE Polymers

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“…[ 4,5 ] However, the permanent covalent bonds lead to inferior processability which makes recycling and reusing of XLPE more difficult compared to PE. [ 3,6,7 ]…”

Section: Introductionmentioning

confidence: 99%

Effect of cross‐linking on the mechanical properties, degree of crystallinity and thermal stability of polyethylene vitrimers

Montoya-Ospina

Verhoogt

Ordner

et al. 2022

Polymer Engineering & Sci

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Maleic anhydride‐grafted‐polyethylene was dynamically cross‐linked via reactive melt blending with 4,4′‐dithiodianiline. Thermal and mechanical properties of polyethylene vitrimers with different cross‐linking density were investigated. The results indicate that the degree of crystallinity decreased with increasing cross‐linking density. This behavior was directly related to short‐term and long‐term mechanical properties: vitrimers showed a decrease in yield strength and creep performance. The yield strength of PE vitrimers decreased linearly in relation to the degree of crystallinity. Polarized optical microscopy revealed that the cross‐links inhibit the growth of spherulites structure in polyethylene vitrimers. Thermogravimetric analysis indicated an increase in the onset degradation temperature and decomposition rate for vitrimers with increased cross‐linking density. The stiffness of the vitrimers decreased with increasing cross‐linking density which led to higher damping properties. Finally, it was demonstrated that reprocessing of polyethylene vitrimer was possible without significant impact in mechanical properties.

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“…[ 31–34 ] Both virgin and recycled homopolymers were effectively processed with SSSP to modify the macromolecular chains in ways that enhance crystallinity and crystallization rate, mechanical properties, and melt‐processability. [ 35–38,41 ]…”

Section: Introductionmentioning

confidence: 99%

“…Solid-state shear pulverization (SSSP) is an alternative technique to the industry standard twin screw extrusion (TSE), [25,26] processing polymers through shear and compressive mechanochemistry at temperatures below their melting and vitrification temperatures. [12,[27][28][29][30][31][32][33][34][35][36][37][38][39][40][41] SSSP is a continuous and industrially scalable process that does not use monomers, solvents, or processing aids and therefore is logistically simple and environmentally benign. Previous reports have shown that SSSP can prepare materials with improved properties through favorable nano-and micron-scale morphology development.…”

Section: Introductionmentioning

confidence: 99%

“…[31][32][33][34] Both virgin and recycled homopolymers were effectively processed with SSSP to modify the macromolecular chains in ways that enhance crystallinity and crystallization rate, mechanical properties, and melt-processability. [35][36][37][38]41] The present study applies the SSSP technique for the mechanical recycling of post-industrial UHMWPE, in collaboration with a local snowboard manufacturer. The base board material trimmings from the production facility are subjected to a systematic investigation of the SSSP processing conditions.…”

Section: Introductionmentioning

confidence: 99%

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Solid‐state shear pulverization of post‐industrial ultra‐high molecular weight polyethylene: Particle morphology and molecular structure modifications toward conventional mechanical recycling

Johnson

Scopelliti

Herrold

et al. 2022

Polymer Engineering & Sci

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Ultra-high molecular weight polyethylene (UHMWPE) is one of the most prominent high-performance thermoplastics for biomedical, leisure, and coating applications. Large-scale recycling of UHMWPE is extremely difficult due to the high melt viscosity of the material as well as its exceptional chemical resistance and impact strength. There is a need for a commercially scalable methodology that can process the waste feedstock for mechanical recycling while sustaining the outstanding physical properties of the material. Solid-state shear pulverization (SSSP) is a continuous, twin-screw extruder-based processing technique in which the low-temperature application of shear and compressive forces impart changes in structure at different length scales to overcome the challenges of difficult-torecycle polymers. This paper investigates the use of SSSP in mechanically recycling post-industrial scrap UHMWPE (rUHMWPE) material from a local ski and snowboard manufacturer. The SSSP-processed particles are flat, micron-scale flakes with enhanced surface area, which can sinter very quickly when compression molded. The molded rUHMWPE samples in turn exhibit enhanced ductility and toughness compared to the as-received scrap material, based on the tunable mechanochemical modification of the ethylene chains.

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Mechanochemical modification of crosslinked low‐density polyethylene: Effect of solid‐state shear pulverization on crosslinks, branches, and chain lengths

Cited by 7 publications

References 59 publications

Nitrile rubber/peroxide treatment transformed recycled polyethylene into mechanically improved materials

Nitrile rubber/peroxide treatment transformed recycled polyethylene into mechanically improved materials

Effect of cross‐linking on the mechanical properties, degree of crystallinity and thermal stability of polyethylene vitrimers

Solid‐state shear pulverization of post‐industrial ultra‐high molecular weight polyethylene: Particle morphology and molecular structure modifications toward conventional mechanical recycling

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