Role of the Amorphous Morphology in Physical Properties of Ultra High Molecular Weight Polyethylene

Zhi, Li; Zhang, Wei; Feng, Lingying; Shen, Xianting; Mai, Yongyi

doi:10.1080/03602559.2014.891236

Cited by 10 publications

(14 citation statements)

References 25 publications

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“…Figure shows that the calculated crystallinity goes down from 0.66 to 0.46 with the weight fraction of long chains at the end of isothermal treatment because long chains make it more difficult for the polymer chains to crystallize from the entangled melts. This is consistent with Li et al who reported that the crystallization enthalpy (Δ H c ) would decrease with the increased molecular weight. Krumme et al have also drawn a conclusion that the fully achieved crystallinity decreases linearly with the molecular average weight in their experimental study of bimodal MWD PE.…”

Section: Resultsmentioning

confidence: 93%

Crystallization and Molecular Topology of Linear Semicrystalline Polymers: Simulation of Uni- and Bimodal Molecular Weight Distribution Systems

et al. 2019

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The crystallization behavior and the molecular topology of bimodal molecular weight distribution (MWD) polymers are studied using a coarse-grained molecular dynamics model with varying weight fraction of short and long chains. Extensive simulations have been performed to prepare polymer melts and obtain semicrystalline polymers by homogeneous isothermal crystallization. The incubation time (the time elapsed before the establishment of steady-state nucleation) is calculated, and the interfacial free energy is obtained using a mean first-passage time analysis. The incubation time first decreases with the weight fraction of long chains, reaches its maximum at 30%, and then increases. This results from the conflicting effects of interfacial free energy and mobility of chain segments. The interfacial free energy decreases with the weight fraction of long chains, which is attributed to the transition from intermolecular to intramolecular nucleation, whereas the chain mobility decreases with increasing long-chain content. Nevertheless, the growth rate of crystals decreases continuously with the weight fraction of long chains, mainly resulting from reduced chain sliding diffusion. We have provided insights into how bimodal MWD polymers promote both nucleation and processability. Moreover, a numerical algorithm has been proposed, tracing each chain going back and forth among crystallites, to access quantitative data of molecular topology (i.e., loop, tie, and cilia segments). It turns out that the concentration of loop and tie segments increases with the increasing weight fraction of long chains. This could be important to understand the mechanical properties of semicrystalline polymers.

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Section: Resultsmentioning

confidence: 93%

Crystallization and Molecular Topology of Linear Semicrystalline Polymers: Simulation of Uni- and Bimodal Molecular Weight Distribution Systems

et al. 2019

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“…This indicates that the catalytic ash presents less influence on the crystallization of UHMWPE since the ash usually has an irregular shape and random distribution caused by the fragmentation of supports . Interestingly, the polymer with the weakly entangled state (PE-POSS-0.8) presents an exceptional impact strength owing to its amorphous microstructure , (see Figure a).…”

Section: Results and Discussionmentioning

confidence: 99%

Reduced Entanglement Density of Ultrahigh-Molecular-Weight Polyethylene Favored by the Isolated Immobilization on the MgCl₂ (110) Plane

Yue

Wang

Cao

et al. 2020

Ind. Eng. Chem. Res.

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The polyhedral oligomeric silsesquioxane (POSS)-modified Ziegler−Natta catalysts with judicious immobilization of TiCl 4 were synthesized for ethylene polymerization. The structure of active sites in this heterogeneous catalyst was investigated by X-ray photoelectron spectroscopy, CO low-temperature adsorption diffusion reflectance infrared Fourier transform (DRIFT) spectra, and density functional theory calculations. The incorporated POSS molecules contribute to the formation of the MgCl 2 (110) plane, creating more positions for hosting the active sites. Simultaneously, POSS induced the crystallization of MgCl 2 molecules, and the latter capture the deactivated TiCl 4 molecules and consume part of the loaded TiCl 4 . This combination dilutes the active sites on the catalytic surface and gives rise to more isolated active species and results in enhanced catalytic activity and decrement of the chain overlap. As a result, the ultrahigh-molecular-weight polyethylene (UHMWPE) with a less entangled state was successfully synthesized at 80 °C, with exceptional activity (6.18 × 10 5 g PE mol Ti −1 h −1 bar −1 ). The synthesized UHMWPE presents less morphological defects after the fusion, thanks to the weakly entangled state, and shows a pronounced improvement of the impact property.

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“…As the π‐stacking distance decreases from 3.8 to 3.5 å, the mobility of the resulting transistor increases from ~10 −4 to 0.4 cm 2 V −1 s −1 . Another way to tune interchain interactions is through heteroatom substitution . With a series of naphthalenediimide‐based copolymers, Zhao et al .…”

Section: Opportunities For Improving Charge Transportmentioning

confidence: 99%

The Polymer Physics of Multiscale Charge Transport in Conjugated Systems

Loo

2019

J Polym Sci B Polym Phys

102

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Conjugated polymers are promising candidates for next‐generation low‐cost flexible electronics. Field‐effect transistors comprising conjugated polymers have witnessed significant improvements in device performance, notably the field‐effect mobility, in the last three decades. However, to truly make these materials commercially competitive, a better understanding of charge‐transport mechanisms in these structurally heterogeneous systems is needed for providing systematic guides for further improvements. This review assesses the key microstructural features of conjugated polymers across multiple length scales that can influence charge transport, with special attention given to the underlying polymer physics. The mechanistic understanding from collective experimental and theoretical studies point to the importance of interconnected ordered domains given the macromolecular nature of the polymeric semiconductors. Based on the criterion, optimization to improve charge transport can be broadly characterized by efforts to (a) promote intrachain transport, (b) establish intercrystallite connectivity, and (c) enhance interchain coupling. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2019, 57, 1559–1571

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Role of the Amorphous Morphology in Physical Properties of Ultra High Molecular Weight Polyethylene

Cited by 10 publications

References 25 publications

Crystallization and Molecular Topology of Linear Semicrystalline Polymers: Simulation of Uni- and Bimodal Molecular Weight Distribution Systems

Crystallization and Molecular Topology of Linear Semicrystalline Polymers: Simulation of Uni- and Bimodal Molecular Weight Distribution Systems

Reduced Entanglement Density of Ultrahigh-Molecular-Weight Polyethylene Favored by the Isolated Immobilization on the MgCl₂ (110) Plane

The Polymer Physics of Multiscale Charge Transport in Conjugated Systems

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Role of the Amorphous Morphology in Physical Properties of Ultra High Molecular Weight Polyethylene

Cited by 10 publications

References 25 publications

Crystallization and Molecular Topology of Linear Semicrystalline Polymers: Simulation of Uni- and Bimodal Molecular Weight Distribution Systems

Crystallization and Molecular Topology of Linear Semicrystalline Polymers: Simulation of Uni- and Bimodal Molecular Weight Distribution Systems

Reduced Entanglement Density of Ultrahigh-Molecular-Weight Polyethylene Favored by the Isolated Immobilization on the MgCl2 (110) Plane

The Polymer Physics of Multiscale Charge Transport in Conjugated Systems

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Product

Resources

About

Reduced Entanglement Density of Ultrahigh-Molecular-Weight Polyethylene Favored by the Isolated Immobilization on the MgCl₂ (110) Plane