Experimental study on the effect of molecular weight and chemical composition distribution on the mechanical response of high‐density polyethylene

Jani, Farzad; Sepahi, Abdolhannan; Afzali, Seyyed Kamal; Moayed, Saeed Houshmand

doi:10.1002/pen.26196

Cited by 5 publications

(3 citation statements)

References 72 publications

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“…It is not yet clear whether this means local disentanglement in the melt near the crystal surface or simply pushing the entanglements some distance away from the surface [112][113][114]. In the case of a rapidly crystallizing high-molecular-weight polymer, the second option is probably preferred [115,116] Another question that is being answered in studies on the crystallization of disentangled polymers is whether the thickness of the growing crystal depends on the distance between the entanglements, i.e., on the length of the disentangled fragment of the chain capable of crystallization.…”

Section: General Remarksmentioning

confidence: 99%

Crystallization of Polymers with a Reduced Density of Entanglements

Pawlak

2024

Crystals

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Since methods for reducing macromolecule entanglements have been developed, it has become possible to better understand the impact of polymer chain entanglement on the crystallization process. The article presents basic information about the disentangling of macromolecules and the characterization of the degree of entanglement. The basic knowledge of polymer crystallization was also presented. Then, it was discussed how polymers crystallize during their disentangling. Non-isothermal and isothermal crystallization experiments using disentangled polymers, and for comparison using entangled polymers, are described in more detail. The influence of disentangling on both nucleation and crystal growth is highlighted. It is also shown how the crystallization of polymers changes when macromolecules re-entangle.

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Section: General Remarksmentioning

confidence: 99%

Crystallization of Polymers with a Reduced Density of Entanglements

Pawlak

2024

Crystals

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“…Attempts to prepare trimodal HDPE by melt blending with a low percentage of UHMW polyethylene powder have failed since UHMW polyethylene powder does not melt during the short residence time extrusion and leads to nonhomogenous products. 5,6 Furthermore, multisite catalysts still have limited potential for implementation in commercial processes. [7][8][9] Sturzel et al applied three-site catalysts supported on functionalized graphene to achieve self-reinforced polyethylene with trimodal molar mass distributions, so that trimodal product had both great stiffness and high impact strength.…”

Section: Introductionmentioning

confidence: 99%

“…The most popular aforesaid strategies are post‐polymerization melt blending and multisite catalysts. Attempts to prepare trimodal HDPE by melt blending with a low percentage of UHMW polyethylene powder have failed since UHMW polyethylene powder does not melt during the short residence time extrusion and leads to nonhomogenous products 5,6 . Furthermore, multisite catalysts still have limited potential for implementation in commercial processes 7–9 .…”

Section: Introductionmentioning

confidence: 99%

Influence of trimodal polymerization on melt rheology, thermal, and mechanical properties of HDPE resin

Bazgir,

Hosseini,

Sepahi

et al. 2024

Polymer Engineering & Sci

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Trimodal polymerization of polyethylene has become a research interest in recent years due to its excellent potential for altering material properties and overcoming the limitations of the bimodal process. Here, we have comprehensively investigated the effects of manipulating polymerization parameters, such as split value (SV), hydrogen‐to‐ethylene ratio (H2/C2), and stage switching, on the rheological, thermal, and mechanical properties of synthesized trimodal high‐density polyethylene (HDPE). The synthesized samples were obtained through three consecutive stages in a slurry lab‐scale reactor. The results of molten state analysis demonstrate that recipe modification, particularly SV and H2/C2 balancing in the second and third stages, had a dramatic effect on the rheological properties including dynamic moduli, G′‐G″ crossover, and the shear‐thinning behavior. Concurrently, improvements in physio‐mechanical properties, such as sagging behavior and slow crack growth resistance (SCG), were observed compared to the bimodal resin. The thermal characterization indicates that the polymerization adjustments made did not notably impact the thermal properties of HDPE samples (e.g., Tm), throughout the all‐recipe manipulation. However, minor fluctuations in crystallinity and crystallization kinetics were observed which was presumably attributed to the molecular weight of the final resin. Overall, in our trimodal polymerization recipe, the HDPE powder is within the specified range of particle size distribution, which ensures excellent bulk density and flowability.Highlights Influence of polymerization parameters such as split value, H2/C2, and stage switching in properties of trimodal HDPE. HDPE resin received from split value and H2/C2 balancing have superior SCG and sagging resistance. All HDPE samples synthesized by different recipes have similar thermal properties.

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Improving Environmental Stress Cracking Resistance of High‐Density Polyethylene Grades by Comonomer Addition and Nanocomposite Approach

Mansouri,

Ghasemi Hamedani,

Zou

et al. 2024

Chemistry A European J

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The aim is to determine the effect of polymer density, correlated to the comonomer content, and nanosilica addition on the mechanical and Environmental Stress Cracking Resistance (ESCR) characteristics of high‐density polyethylene (HDPE). In this regard, five HDPE samples with similar Melt Flow Index (MFI) and molar mass but various densities were acquired from a petrochemical plant. Two polymerization reactors work in series and differ only in the amount of 1‐buene comonomer fed to the second reactor. To ascertain the microstructure of the studied samples, GPC and SSA (successive self‐nucleation and annealing) analyses were accomplished. All samples resulted having similar characteristics but slightly various SCB/1000C=7.26‐9.74 (SCB=Short Chain Branching). Consequently, meanwhile studied HDPEs reveal similar notched impact and stress at yield values, the tensile modulus, stress‐at‐break, and elongation‐at‐break tend to demonstrate different results with the SCB content. More significantly, ESCR characteristic varied considerably with SCB/1000C extent, so that higher amount of SCB acknowledged advanced ESCR. Notably, blending HDPE sample containing higher amount of SCB/1000C, with 3 wt.% of chemically modified nanosilica enhanced ESCR characteristic by 40%. DFT (Density Functional Theory) calculations unveiled the role of the comonomer, quantitatively by binding energies and qualitatively by Non Covalent Interaction (NCI) plots.

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Experimental study on the effect of molecular weight and chemical composition distribution on the mechanical response of high‐density polyethylene

Cited by 5 publications

References 72 publications

Crystallization of Polymers with a Reduced Density of Entanglements

Crystallization of Polymers with a Reduced Density of Entanglements

Influence of trimodal polymerization on melt rheology, thermal, and mechanical properties of HDPE resin

Improving Environmental Stress Cracking Resistance of High‐Density Polyethylene Grades by Comonomer Addition and Nanocomposite Approach

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