Atomistic simulations of cavitation in a model polyethylene network

Morozinis, Athanasios K.; Tzoumanekas, Christos; Anogiannakis, Stefanos D.; Theodorou, Doros N.

doi:10.1134/s1811238213050020

Cited by 11 publications

(15 citation statements)

References 28 publications

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“…Different from amorphous polymers, the cavitation observed in semi‐crystalline polymers is much more complicated which is always associated with lamellar slippage, crystal transition, and so on. The cavitation in amorphous polymers has already been well understood that the entanglement density is regarded as one of the most pivotal factors governing the occurrence of cavitation in amorphous materials . Generally, the cavitation stress is proportional to the entanglement density of the polymers.…”

Section: Discussionmentioning

confidence: 99%

“…The cavitation in amorphous polymers has already been well understood that the entanglement density is regarded as one of the most pivotal factors governing the occurrence of cavitation in amorphous materials. [186,187] Generally, the cavitation stress is proportional to the entanglement density of the polymers. If the amorphous polymer is born with a lower entanglement density, it normally shows a brittle behavior and easier cavitation.…”

Section: Discussionmentioning

confidence: 99%

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Cavitation‐Induced Stress Whitening in Semi‐Crystalline Polymers

Men

2018

Macro Materials & Eng

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Cavitation‐induced stress whitening in semi‐crystalline polymers during stretching significantly influences the physical properties of the materials. This review summarizes studies focusing on two different cavitation processes triggered at small and large strain regimes. The corresponding mechanisms of these two cavitation processes are discussed. For cavitation activated at small strain, there are two basic but distinctly different models with the initiation of cavities either in the amorphous phase or in the crystalline skeleton. For the cavitation triggered at a large strain regime, there are also two different arguments being either due to the defects located in the ends of micro‐fibrils or as a consequence of the fragmentation of load‐bearing inter‐fibril/micro‐fibril tie chains in highly oriented amorphous networks. A unified understanding of the cavitation processes during stretching semi‐crystalline polymers based on interpenetrated network model is proposed. Finally, this review outlooks future research topics for better understanding the cavitation mechanism to meet the industrial need.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Cavitation‐Induced Stress Whitening in Semi‐Crystalline Polymers

Men

2018

Macro Materials & Eng

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“…Its M e was estimated 61 from the Kuhn segment of the PPs, and is about half that of the PE melt. The large entanglement density of the rubber is also reflected 104 in a comparatively high, entanglement-dominated, shear modulus for an elastomer, of 5.9 MPa. As is discussed in Appendix I, it is due to the short length of the precursor chains and the artificial preparation conditions of the network.…”

Section: Systems Studiedmentioning

confidence: 99%

“…Details about the dynamics and the equilibration of the systems will appear elsewhere. 104,105 Both systems share, approximately, the same density, 106,107 ρ 0.78 g/cm 3 , and characteristic ratio, C ∞ . The latter is 8.5 for the rubber and 8 for the (C500) melt.…”

Section: Systems Studiedmentioning

confidence: 99%

Microscopic Description of Entanglements in Polyethylene Networks and Melts: Strong, Weak, Pairwise, and Collective Attributes

2012

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Abstract:We present atomistic molecular dynamics simulations of two Polyethylene systems where all entanglements are trapped: a perfect network, and a melt with grafted chain ends. We examine microscopically at what level topological constraints can be considered as a collective entanglement effect, as in tube model theories, or as certain pairwise uncrossability interactions, as in slip-link models.A pairwise parameter, which varies between these limiting cases, shows that, for the systems studied, the character of the entanglement environment is more pairwise than collective. We employ a novel methodology, which analyzes entanglement constraints into a complete set of pairwise interactions, similar to slip links. Entanglement confinement is assembled by a plethora of links, with a spectrum of confinement strengths, from strong to weak. The strength of interactions is quantified through a link 'persistence', which is the fraction of time for which the links are active. By weighting links according to their strength, we show that confinement is imposed mainly by the strong ones, and that the weak, trapped, uncrossability interactions cannot contribute to the low frequency modulus of an elastomer, or the plateau modulus of a melt. A selfconsistent scheme for mapping topological constraints to specific, strong binary links, according to a given entanglement density, is proposed and validated. Our results demonstrate that slip links can be viewed as the strongest pairwise interactions of a collective entanglement environment. The methodology developed provides a basis for bridging the gap between atomistic simulations and mesoscopic slip link models.

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“…The concepts of slip links and slip springs have been successfully introduced in multi-chain mesoscopic simulations of crosslinked polymer networks [35,36,48], which differ from the corresponding multi-chain simulations of polymer melts in the existence of permanent links that do not allow the connecting neighboring chains to slide through them. At more detailed levels of description, crosslinked polymer networks have also been modeled through atomistic simulations; time and length scales are rather limited in such approaches [15,69,70,71,72,73], however. Another approach to molecular simulation of elastomeric materials is coarse-grained molecular dynamics, in which the network is made up of coarser entities than atoms and consequently longer time and length scales are covered in comparison with those of the atomistic models [74,75].…”

Section: Introductionmentioning

confidence: 99%

Slip Spring-Based Mesoscopic Simulations of Polymer Networks: Methodology and the Corresponding Computational Code

et al. 2018

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In previous work by the authors, a new methodology was developed for Brownian dynamics/kinetic Monte Carlo (BD/kMC) simulations of polymer melts. In this study, this methodology is extended for dynamical simulations of crosslinked polymer networks in a coarse-grained representation, wherein chains are modeled as sequences of beads, each bead encompassing a few Kuhn segments. In addition, the C++ code embodying these simulations, entitled Engine for Mesoscopic Simulations for Polymer Networks (EMSIPON) is described in detail. A crosslinked network of cis-1,4-polyisoprene is chosen as a test system. From the thermodynamic point of view, the system is fully described by a Helmholtz energy consisting of three explicit contributions: entropic springs, slip springs and non-bonded interactions. Entanglements between subchains in the network are represented by slip springs. The ends of the slip springs undergo thermally activated hops between adjacent beads along the chain backbones, which are tracked by kinetic Monte Carlo simulation. In addition, creation/destruction processes are included for the slip springs at dangling subchain ends. The Helmholtz energy of non-bonded interactions is derived from the Sanchez–Lacombe equation of state. The isothermal compressibility of the polymer network is predicted from equilibrium density fluctuations in very good agreement with the underlying equation of state and with experiment. Moreover, the methodology and the corresponding C++ code are applied to simulate elongational deformations of polymer rubbers. The shear stress relaxation modulus is predicted from equilibrium simulations of several microseconds of physical time in the undeformed state, as well as from stress-strain curves of the crosslinked polymer networks under deformation.

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Atomistic simulations of cavitation in a model polyethylene network

Cited by 11 publications

References 28 publications

Cavitation‐Induced Stress Whitening in Semi‐Crystalline Polymers

Cavitation‐Induced Stress Whitening in Semi‐Crystalline Polymers

Microscopic Description of Entanglements in Polyethylene Networks and Melts: Strong, Weak, Pairwise, and Collective Attributes

Slip Spring-Based Mesoscopic Simulations of Polymer Networks: Methodology and the Corresponding Computational Code

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