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Cited by 23Polymer crystallization and propertiesRheology and Fluid Dynamics StudiesPolymer composites and self-healing

Erosion of the molecular network in the amorphous layers of polyethylene upon high-strain deformation

Open access
Bartczak, Zbigniew, Grala, Magdalena, Richaud, Emmanuel, Gadzinowska, Krystyna·2016·Polymer
DOI 10.1016/j.polymer.2016.07.068
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Written from the paper’s full text.

TL;DR

This study deformed neat and electron-beam-crosslinked linear HDPE by plane-strain compression to true strains above 2 and tracked long-term recovery to probe damage to the amorphous molecular network. It concludes that neat HDPE develops a permanent residual strain above a true strain of about 1, caused mainly by chain disentanglement, whereas crosslinked HDPE recovers fully after crystal melting.

Key findings

  • In neat HDPE, room-temperature recovery increased up to a true strain of about 1.0 and then declined; after melting at 145 °C, the truly irreversible residual strain rose from 0 at e = 1.0 to approximately 0.36 at e = 2.1. Crosslinked samples showed essentially no permanent strain after melting (e_res < 0.02).
  • Crosslinked networks survived heavy deformation: after e = 1.75, gel content and crosslink density were nearly unchanged (e.g., H-50 gel 59.1% to 58.5%, N_x 0.82 to 0.89 × 10^26 m^-3; H-200 gel 76.6% to 75.8%, N_x 2.63 to 2.84 × 10^26 m^-3), with changes within experimental error.
  • Chain scission was minor: GPC showed no significant change in molecular weight or distribution, and FTIR carbonyl concentration remained low (0.12–0.20 mmol/kg), corresponding to less than one chain scission per 1000 chains and calculated M_n/M_n0 = 0.998 and M_w/M_w0 = 0.993 at e = 2.1.
  • Lamellar fragmentation occurred at similar strains regardless of crosslinking: kinking appeared around e = 0.6 and fragmentation at e ≥ 1. At e = 1.75, crystallinity decreased in all samples (e.g., H-0 from 71.5% to 67.8%; H-200 from 69.2% to 63.9%), suggesting crystal damage competed with network damage in crosslinked materials.

Methods

  • Linear HDPE (density 0.962 g/cm³, M_w = 169,300 g/mol, M_w/M_n = 5.9) was compression molded; some plates were crosslinked by 6 MeV electron-beam irradiation at 50, 100, or 200 kGy.
  • Plane-strain compression was performed in a deep channel-die at room temperature and a constant true strain rate of 0.001 s⁻¹, up to fracture or the load limit. Recovery was monitored for up to 6 months at room temperature and after annealing at 110, 123, and 145 °C.
  • Characterization included DSC, 2-D SAXS, gel content and equilibrium swelling, FTIR spectroscopy, and high-temperature GPC.

Limitations

  • The authors state that all results apply to plane-strain compression; other deformation modes, especially tension with cavitation, may produce more chain scission and earlier network damage.
  • The authors note that the H-200 specimen deformed to e = 1.9 was partially fractured, making its carbonyl concentration less reliable, and that a constant polymer–solvent interaction parameter was used despite possible dependence on crosslink density.
  • Evident from the text: the study uses one HDPE grade of moderate molecular weight, and crosslinked samples could not be analyzed by GPC because they were insoluble, so network changes in those samples were inferred from extraction and swelling data.

Model-written summary. Check it against the paper before relying on it.

Integrity signals

Registry

Crossref · 10.1016/j.polymer.2016.07.068

Cites

63 of 63 references verified0 citation errors · 0 not checkable

Statistics

Nothing to recompute.

Claims the paper makes

2 of 56 cited sources checked · 0 supported · 0 flagged · accuracy not yet measured

  • Interpretationcitation

    The experimental findings concerning the activity of chain disentanglement with strain agree quite well with the predictions of the VENU model calculations by Billon et al.

    “Our experimental findings concerning various activity of chain disentanglement with strain agree quite well with the predictions of recent model calculations performed by Billon et al. [34,35]”
    Quote in the paperNot a substantial claim1 of 2 sources checked
    • cites [34] Maurel-Pantel, 2015, A thermo-mechanical large deformation constitutive model for polymers based on material network description: application to a semi-crystalline polyamide 66, Int. J. Plasticity source

      The evolution-equation section (p. 28) models chain disentanglement under loading, and the Conclusions (p. 41) report good agreement between model responses and experimental mechanical and temperature measurements. The paper does not report a direct comparison between experimentally observed disentanglement activity as a function of strain and model predictions; a search for “VENU” also found no such model name in our copy. (LLM, conf=0.86)

      Experimental — accuracy not yet measured
    • cites [35] Billon, 2016, Time dependent mechanical modeling for polymers based on network theory, AIP Conf. Proc. source
  • Findingreasoning

    In the strain hardening stage, samples tested in tension did not show as strong strain hardening as observed in plane-strain compression.

    “The significant difference between tensile and compression curves can be, however, observed in the strain hardening stage: the samples tested in tension did not show such a strong strain hardening as observed in the plane-strain compression.”
    Quote in the paperSubstantial claim
  • Findingcitation

    The effective network densities (chemical crosslinks and entanglements) estimated by fitting a model amorphous phase to experimental residual stress vs. strain data appeared only slightly higher than the lower-bound estimates.

    “The effective network densities appeared only slightly higher than lower-bound estimates discussed above.”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites [10] Bartczak, 2012, Effect of the molecular network on high-strain compression of cross-linked polyethylene, Eur. Polym. J. source
  • Findingown data

    The deformation of neat, non-crosslinked HDPE is completely reversible above the melting point of the crystalline phase, provided that the applied true strain does not exceed e=1.0 (λ=2.7).

    “Structural studies of deformed samples and investigation of long-term strain recovery demonstrated that the deformation of the neat, non-crosslinked HDPE is completely reversible above the melting point of the crystalline phase, provided that the applied true strain does not exceed e ¼ 1.0 (l ¼ 2.7).”
    Quote in the paperSubstantial claim
  • Findingcitation

    The curve of virgin PE agrees quite well with true stress-true strain curves obtained in tensile deformation mode for polyethylene of similar molecular characteristics.

    “Moreover, the curve of virgin PE agrees quite well with the true stress-true strain curves obtained in tensile deformation mode for polyethylene of similar molecular characteristics [4,45].”
    Quote in the paperNot a substantial claim0 of 2 sources checked
    • cites [4] Hiss, 1999, Network stretching, slip processes, and fragmentation of crystallites during uniaxial drawing of polyethylene and related copolymers. A comparative study, Macromolecules source
    • cites [45] G'Sell, 1992, Video-controlled tensile testing of polymers and metals beyond the necking point, J. Mater. Sci. source
  • May combine two claims. 50
  • Classified as probably not a substantial claim. 11
  • The quote only partly states this claim. 3

  • May combine two claims.

    Premisecitation

    The VENU model accounts for solid crosslinks and entanglements and their evolution as a function of strain energy: weak entanglements are initially not mechanically active and act as crosslinks at low stress/strain, then gain mobility as a function of strain energy, inducing visco-elasticity, and finally gain more mobility, corresponding to disentanglement and visco-plasticity.

    “The model accounts for solid crosslinks as well as entanglements and their evolution as a function of strain energy: weak entanglements are initially not mechanically active and act as crosslinks at low stress/strain, then gain a certain level of mobility as a function of strain energy, which induces visco-elasticity and finally, with further increase of strain energy, entanglements gain even more”
    Quote in the paperSubstantial claim1 of 3 sources checked
    • cites [34] Maurel-Pantel, 2015, A thermo-mechanical large deformation constitutive model for polymers based on material network description: application to a semi-crystalline polyamide 66, Int. J. Plasticity source

      Split into 2 atoms — 1 confirmed, 1 partially supported, 0 disputed, 0 misattributed, 0 unverifiable. Expand the claim to see per-atom verdicts.

      Experimental — accuracy not yet measured
    • cites [35] Billon, 2016, Time dependent mechanical modeling for polymers based on network theory, AIP Conf. Proc. source
    • cites [57] Edwards, 1986, The effect of entanglements in rubber elasticity, Polymer source

  • May combine two claims.

    Findingown data

    Both the insoluble gel content and the network density increase with increasing irradiation dose.

    “It can be seen that both the insoluble gel content and the network density increase with increasing irradiation dose.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Findingown data

    The melting temperature of PE crystals and the long period are both practically independent of irradiation.

    “Data presented in Table 1 confirm that view, revealing the melting temperature of PE crystals and the long period both practically independent on irradiation.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingcitation

    The estimated crosslink network density values Nx are consistent with previously published data and demonstrate a linear dependence on the irradiation dose.

    “The estimated crosslink network density values, N x are consistent with previously published data [43] and demonstrate a linear dependence on the irradiation dose.”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [43] Fu, 2011, Wear resistant UHMWPE with high toughness by high temperature melting and subsequent radiation cross-linking, Polymer source
    • The authors state this as an assumption: The solvent interaction parameter χ for polyethylene and p-xylene is constant and independent of crosslink density.

  • May combine two claims.

    Findingown data

    Above e=1, crosslinked samples were still able to recover fully (residual strain e_res<0.02, below experimental error), while in sample H-0, containing only entangled chains, a fraction of the strain appeared irreversible.

    “Above e ¼ 1 the crosslinked samples were still able to recover fully (the observed residual strain e res < 0.02 is well below the limit of experimental error) while in the sample H-0, containing only entangled chains, a fraction of the strain appeared irreversible.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    There is no significant difference in molecular weight and its distribution between initial and all deformed non-crosslinked samples, therefore no influence of strain history on the length of chains.

    “Both figures demonstrate clearly that there is no significant difference in molecular weight and its distribution between initial and all deformed samples, therefore no influence of the strain history on the length of chains.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    In the carbonyl region 1750-1690 cm−1, all bands developed in crosslinked material much higher compared to neat HDPE, with the acid band at 1714 cm−1 becoming the strongest.

    “In the carbonyl region, 1750-1690 cm À1 , all bands developed in crosslinked material much higher comparing to neat HDPE, with the acid band at 1714 cm À1 becoming the strongest one.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Findingown data

    The slow recovery component shows a maximum around an applied strain of e=1.0; at the maximum it is apparently larger than the fast recovery component, then diminishes slowly with increasing strain and almost disappears at strains above e=1.75.

    “The slow recovery component (illustrated by the recovered strain estimated for lapsed times between 24 h and 6 months after unloading) shows in turn a maximum around an applied strain of e ¼ 1.0; at the maximum this component is apparently larger than the fast recovery component, yet diminishes slowly with an increase of strain and finally almost disappears at the strains above of e ¼ 1.75.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    During recovery, sample dimension along LD increased while that along FD decreased.

    “On the other hand, sample dimension along LD increased while that along FD decreased during the recovery period.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Findingreasoning

    The most characteristic difference between neat and crosslinked samples is the amount of recovery above e=1.0: H-0 shows a noticeable decrease of recovered strain Δe with applied strain, while all irradiated samples demonstrate stabilization of recovery and only a slight decrease of Δe with applied strain increasing from e=1.0 to 2.0.

    “The most characteristic difference between the neat (network of entangled chains) and crosslinked samples is an amount of recovery above e ¼ 1.0: while below the melting point H-0 shows a noticeable decrease of the recovered strain De with applied strain, all irradiated samples demonstrate stabilization of recovery and only a slight decrease of De with applied strain increasing from e ¼ 1.0 to 2.0”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    Deformation of the crystalline phase proceeded similarly in all samples, irrespective of crosslinking degree, with the same crystallographic mechanisms engaged.

    “Deformation of the crystalline phase proceeded similarly in all samples, irrespective of crosslinking degree, with the same crystallographic mechanisms engaged.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingcitation

    With increasing irradiation dose, strain hardening sets in earlier and the stress reaches very high ultimate values, above 400 MPa, at considerably lower strain.

    “strain hardening sets in earlier and the stress reaches very high ultimate values, above 400 MPa, at considerably lower strain in samples of higher irradiation dose, i.e. exactly as expected for samples of increasing network density [3].”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites [3] Bartczak, 2005, Influence of molecular parameters on high-strain deformation of polyethylene in the plane-strain compression. Part I. stress-strain behaviour, Polymer source

  • May combine two claims.

    Findingown data

    The onset temperature of melting increases in all samples after deformation, while the peak temperature increases in neat H-0 and decreases in irradiated H-50-H-200 samples.

    “Concurrently, the onset temperature of melting increases in all samples, while the peak temperature increases in neat H-0 and decreases in irradiated H-50 -H-200 samples after their deformation.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    High-strain deformation (e=1.75) of crosslinked samples practically does not lead to any change of network properties: both insoluble gel content and crosslink density remain nearly unaltered after deformation.

    “They demonstrate that a high-strain deformation (e ¼ 1.75) of crosslinked samples practically does not lead to any change of the network properties: both the insoluble gel content and crosslink density remain nearly unaltered after deformation (a small reduction of gel content as well as small increase of the crosslink density are actually within the limit of experimental error).”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    The fast recovery component initially increases with increasing applied strain, then stabilizes around e=0.5 and remains practically constant up to approximately e=1.5.

    “Fig. 5b shows that the fast recovery component, represented by the recovered strains measured in samples immediately after unloading, initially increases with an increasing applied strain, then stabilizes around e ¼ 0.5 and remains practically constant in a broad range of intermediary strain, up to approximately e ¼ 1.5.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    In the studied HDPE samples, permanent deformation after high-strain deformation was observed only in entangled (non-crosslinked) samples, while the crosslinked network response remained purely elastic up to the highest strain reached.

    “a permanent deformation was observed only in entangled samples, while the response of the crosslinked network remained purely elastic up to the highest strain reached”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    Strain recovery revealed two components: a fast process with short and very short relaxation times, observed immediately after unloading and saturating in a few minutes, and a slow process, relatively intense within the first few hours, then slowing down and ceasing in months.

    “Observations of the strain recovery revealed two components of the recovering strain: the fast process, characterized by short and very short relaxation times, observed immediately after unloading and saturating quickly after (in few minutes), and the slow process, relatively intense within first few hours of the recovery period, then slowing down and ceasing in months.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    The concentration of all analyzed carbonyl groups at low and moderate strain, up to true strain e=1, remains practically constant, and then, for e>1, begins to rise slowly with advancing strain.

    “It can be seen that the concentration of all analyzed carbonyl groups at low and moderate strain, up to the true strain of e ¼ 1, remains practically constant, and then, for e > 1, become to rise slowly with an advancing strain.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    The dependence of residual strain on applied strain at elevated temperatures is similar to that at room temperature, and the amount of recovered strain Δe increases from Δe max ~0.4 at room temperature to ~0.6-0.7 at 110 C and ~0.7-0.8 at 123 C.

    “The dependence of residual strain on applied strain at elevated temperatures is similar to that observed at room temperature and only an amount of the recovered strain De ¼ eÀ e r increases: from De max ~0.4 at room temperature to De max ~0.6e0.7 at 110 C and De max ~0.7e0.8 at 123 C.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingnone given

    At true strain increasing to e=1.0, the strain component recovered after unloading at room temperature also increases and approaches 0.5, irrespective of degree of crosslinking of the amorphous phase, and then tends to decrease with further strain increase above 1.0.

    “At the true strain increasing to e ¼ 1.0 the strain component recovered after unloading at room temperature also increases and approaches the value of 0.5, irrespective of degree of crosslinking of the amorphous phase, and then tends to decrease with further strain increase above 1.0.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingreasoning

    A significant part of the residual strain appears truly permanent as it does not recover even after melting of the crystalline component, which releases all previous constraints imposed on the amorphous phase.

    “A significant part of the residual strain appears truly permanent as it does not recover even after melting of the crystalline component, which releases all previous constraints imposed on amorphous phase.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    In crosslinked H-200 samples, concentration of carbonyl groups keeps approximately constant up to e=1.5 and then seems to increase in the sample deformed to e=1.9.

    “concentration of carbonyl groups keeps approximately constant up to e ¼ 1.5 and then seems to increase in sample deformed to e ¼ 1.9”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Premisecitation

    Previous studies supported Strobl's view on the deformation sequence and confirmed a direct correlation between concentration of entanglements and deformation behavior, especially at high strains in the strain hardening range.

    “Our previous studies supported the Strobl's view on the deformation sequence and confirmed a direct correlation between concentration of entanglements and the deformation behavior, especially at high strains, in the strain hardening range, [3,10,15,19,20].”
    Quote in the paperSubstantial claim0 of 5 sources checked
    • cites [3] Bartczak, 2005, Influence of molecular parameters on high-strain deformation of polyethylene in the plane-strain compression. Part I. stress-strain behaviour, Polymer source
    • cites [10] Bartczak, 2012, Effect of the molecular network on high-strain compression of cross-linked polyethylene, Eur. Polym. J. source
    • cites [15] Bartczak, 2005, Influence of molecular parameters on high-strain deformation of polyethylene in the plane-strain compression. Part II. Strain recovery, Polymer source
    • cites [19] Bartczak, 2005, Effect of chain entanglements on plastic deformation behavior of linear polyethylene, Macromolecules source
    • cites [20] Bartczak, 2010, Effect of chain entanglements on plastic deformation behavior of ultra-high molecular weight polyethylene, J. Polym. Sci. Part B Polym. Phys. source

  • May combine two claims.

    Premisecitation

    The rubber-like network stress increases substantially at high strains above true strain e=1.0 and is evidently the main source of strong strain hardening.

    “Model calculations [7] as well as experimental studies of the post-deformation relaxation behavior of compressed polyethylene [10] indicated that the rubber-like network stress, a sub-component of the observed elastic part of the stress, increases substantially at high strains, above the true strain of e ¼ 1.0, and is evidently the main source of the strong strain hardening of the sample.”
    Quote in the paperSubstantial claim0 of 2 sources checked
    • cites [7] Lee, 1993, Simulation of large-strain plastic-deformation and texture evolution in high-density polyethylene, Polymer source
    • cites [10] Bartczak, 2012, Effect of the molecular network on high-strain compression of cross-linked polyethylene, Eur. Polym. J. source

  • May combine two claims.

    Interpretationreasoning

    In a solid sample, the amorphous phase can demonstrate a network denser than estimated from Nx + Ne, because all chemical crosslinks are created in the amorphous part and a significant fraction of entanglements pre-existing in the molten sample was rejected out of growing crystallites and concentrated in the amorphous layers rather than being resolved.

    “In a solid sample however, the amorphous phase can demonstrate a network denser than estimated above since all chemical crosslinks have been created in amorphous part and a significant fraction of entanglements pre-existing in the molten sample was rejected out of growing crystallites and concentrated in the amorphous layers rather than being resolved by”
    Quote in the paperSubstantial claim

  • Classified as probably not a substantial claim.

    Premisecitation

    The transition at point D was postulated to result from intensified crystal fragmentation and presumably chain disentanglement beginning in the amorphous phase, leading to partial disintegration of the molecular network.

    “This transition was postulated to be a result of intensified crystal fragmentation and presumably chain disentanglement beginning in amorphous phase that should lead to a partial disintegration of the molecular network [4].”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites [4] Hiss, 1999, Network stretching, slip processes, and fragmentation of crystallites during uniaxial drawing of polyethylene and related copolymers. A comparative study, Macromolecules source

  • May combine two claims.

    Study design and conductown data

    HDPE contains stabilizers that prevent the generation of chain scissions and unstable oxidation species during polymer processing, as checked by oxidation induction time measurements (OIT>30 min).

    “It was checked by measurements of oxidation induction time (OIT>30min.)that HDPE contains stabilizers, which prevent the generation of chain scissions and unstable oxidation species during polymer processing.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Premisecitation

    At high strains, the interlamellar shear of the amorphous component takes control over further deformation, and deformation of crystals accommodates to strain increment of the amorphous phase.

    “From this point on, the interlamellar shear of amorphous component takes control over the process of further deformation, and deformation of crystals now only accommodates to strain increment of the amorphous phase.”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites [7] Lee, 1993, Simulation of large-strain plastic-deformation and texture evolution in high-density polyethylene, Polymer source

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Premisecitation

    For plastic deformation prior to fracturing, the chain scission mechanism was excluded as a major contributor to plastic deformation, although some reports indicated its occurrence upon very heavy deformation.

    “For plastic deformation prior to fracturing, the chain scission mechanism was excluded as a major contributor to the plastic deformation [29e31], although some reports indicated its occurrence upon a very heavy deformation [32].”
    Quote in the paperNot a substantial claim0 of 2 sources checked
    • cites [29e31]

      Couldn’t be matched to a paper in Crossref, so it can’t be checked.

    • cites [32] Costa, 1997, Ultra-high molecular weight polyethylene .1. Mechano-oxidative degradation, Polym. Degrad. Stab. source

  • Classified as probably not a substantial claim.

    Study design and conductnone given

    All samples were prepared according to the same protocol to obtain similar supermolecular structure.

    “All samples were prepared according to the same protocol to obtain similar supermolecular structure.”
    Quote in the paperSubstantial claim

  • Classified as probably not a substantial claim.

    Premisecitation

    Strain hardening in amorphous polymers originates from the network structure.

    “It is already well understood that strain hardening in amorphous polymers originates from the network structure [11e13].”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites [11e13]

      Couldn’t be matched to a paper in Crossref, so it can’t be checked.

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Study design and conductreasoning

    The specimens cut from the core parts of the plates, used in all experiments, demonstrated quite uniform structure compared to removed skin layers in which a structure gradient due to fast cooling conditions was observed.

    “The specimens cut from the core parts of the plates, used in all experiments, demonstrated quite uniform structure as compared to removed skin layers in which a structure gradient due to fast cooling conditions was observed.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Interpretationown data

    Radiation-induced crosslinks are preferentially generated in the amorphous phase, while the dense and ordered crystalline phase remains practically free of chemical crosslinks.

    “Radiation induced crosslinks are preferentially generated in amorphous phase while a dense and ordered crystalline phase remains practically free of chemical crosslinks.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Interpretationreasoning

    Such behavior can be read as a mark of competition between network and crystal damage: in crosslinked samples destruction of crystals appears easier than disintegration of the network of crosslinked chains within the amorphous phase, while in entangled samples partial destruction of the molecular network (erosion) seems easier than crystal damage.

    “Such a behavior can be read as a mark of a competition between network and crystal damage e in crosslinked samples destruction of crystals apparently appears easier than disintegration of the network of crosslinked chains within amorphous phase, what is opposite to entangled samples, in which partial destruction of the molecular network erosion seems easier than crystal damage.”
    Quote in the paperSubstantial claim

  • May combine two claims. The quote only partly states this claim.

    Interpretationreasoning

    Consequently, already highly strained lamellar crystals and highly extended amorphous material within interlamellar layers are much more constrained than in tension, and the sample responds to compression with higher stress than to extension at the same strain.

    “interlamellar layers are much more constrained than in tension and the sample responds to compression with higher stress than to extension at the same strain.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Interpretationreasoning

    Another, much more intense mechanism(s) was necessary to cause an erosion of the network, and consequently enable plastic flow and produce the permanent residual strain.

    “It becomes clear that another, much more intense mechanism(s) was necessary to cause an erosion of the network, and consequently enable plastic flow and produce the permanent residual strain.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Interpretationown data

    Networks of crosslinked chains survived deformation even to high strain approaching e=1.5-2 (λ=4.5-7.4) most probably unaltered, while the network of entangled chains had to be partially destroyed, resulting in increasing permanent flow upon deformation and a non-reversible, permanent residual strain left in the material.

    “This behavior confirms suggestions given earlier e networks of crosslinked chains survived the deformation even to high strain approaching e ¼ 1.5e2 (l ¼ 4.5e7.4)most probably unaltered, while the network of entangled chains had to be partially destroyed, which resulted in an increasing permanent flow upon deformation and a non-reversible, permanent residual strain left in the material.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Interpretationreasoning

    Microcavitation, while severe in tension, is completely suppressed in plane-strain compression due to external constraints imposed by the die, resulting in a significant compressive stress component.

    “Simultaneously, microcavitation, while severe in tension, is completely suppressed in plane-strain compression due to external constraints imposed by the die, resulting in a significant compressive stress component.”
    Quote in the paperSubstantial claim

  • Classified as probably not a substantial claim.

    Interpretationreasoning

    To change the properties of such a network, breaking of numerous chemical bonds would have to occur.

    “To change the properties of such network breaking of numerous chemical bonds would have to occur.”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim: may not pass S4 (based).

    Interpretationnone given

    Chain entanglements are generally entrapped between chemical crosslinks, therefore cannot be resolved easily during deformation.

    “Chain entanglements are generally entrapped between chemical crosslinks, therefore cannot be resolved easily during deformation.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Interpretationown data

    The observed changes in crystallinity and melting behavior support the view of deformation-induced destruction of the lamellar structure: fragmentation of lamellae in H-0 as a result of advanced crystallographic slip, occurring preferentially at points of smallest thickness of lamellae.

    “The observed changes in crystallinity and melting behavior support rather the view of deformationinduced destruction of the lamellar structure: fragmentation of lamellae in H-0 as a result of an advanced crystallographic slip, that occurs preferentially at points of the smallest thickness of lamellae [46,47].”
    Quote in the paperSubstantial claim0 of 2 sources checked
    • cites [46] Galeski, 1992, Morphological alterations during texture-producing plastic plane strain compression of high-density polyethylene, Macromolecules source
    • cites [47] Bartczak, 2005, Evolution of lamellar orientation and crystalline texture of various polyethylenes and ethylene-based copolymers in plane- strain compression, Polymer source

  • Probably not a substantial claim: may not pass S4 (based).

    Study design and conductnone given

    The FTiR measurements were performed after a half-year recovery period, which was long enough to complete all reactions possibly triggered by deformation.

    “The FTiR measurements were performed after the half a year recovery period, which was long enough to complete all reactions, possibly triggered by deformation.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Interpretationown data

    An increase of Tons and reduction of Tm observed in irradiated samples suggests that not only the thinnest lamellae (melting at Tons) but also a fraction of thick lamellae (Tm) had to be destroyed in these samples.

    “not only the thinnest (melting at T ons ) but also a fraction of thick lamellae (T m ) had to be destroyed in these samples.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Interpretationreasoning

    These mechanisms of reduction of effective crosslink density seem practically insignificant, since they should be equally active in samples with entangled chains and in those with crosslinked chains, both materials undergoing very similar lamellar fragmentation at the same strain range.

    “These mechanisms of reduction of effective crosslink density seem, however, practically insignificant, since they should be equally active in samples with the network of entangled chains and in those with crosslinked chains, both materials undergoing very similar lamellar fragmentation at the same strain range (cf.Fig. 3).”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Interpretationreasoning

    The other plausible mechanism of network modification can be a partial release of constraints imposed on amorphous layers by adjacent lamellae, induced by their fragmentation.

    “The other plausible mechanism of network modification can be a partial release of constraints imposed on amorphous layers by adjacent lamellae, induced by their fragmentation.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Interpretationown data

    It is the amorphous component that can recover an additional part of the strain, due to activation of a relaxation process and possibly a partial release of constraints imposed on amorphous layers by adjacent crystallites, while plastic deformation of the crystalline phase remains irreversible.

    “All this indicates that it is the amorphous component that can recover additional part of the strain, due to activation of a relaxation process and possibly a partial release of constraints imposed on amorphous layers by adjacent crystallites, while the plastic deformation of crystalline phase remains irreversible.”
    Quote in the paperSubstantial claim

  • May combine two claims. The quote only partly states this claim.

    Interpretationown data

    The maximum in the slow recovery strain component at approximately e=1 coincides with severe destruction of lamellar structure (fragmentation) observed in compression and with point D of Strobl's deformation scheme, ascribed to the beginning of chain disentanglement.

    “the point D of the Strobl's deformation scheme, ascribed to the beginning of chain disentanglement [4].”
    Quote in the paperSubstantial claim0 of 2 sources checked
    • cites [47] Bartczak, 2005, Evolution of lamellar orientation and crystalline texture of various polyethylenes and ethylene-based copolymers in plane- strain compression, Polymer source
    • cites [4] Hiss, 1999, Network stretching, slip processes, and fragmentation of crystallites during uniaxial drawing of polyethylene and related copolymers. A comparative study, Macromolecules source

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    Such FTIR changes are typical for polyethylene crosslinked by irradiation.

    “Such changes are typical for polyethylene crosslinked by irradiation [31,55,56].”
    Quote in the paperNot a substantial claim0 of 3 sources checked
    • cites [31] Czaja, 2011, Studies on electron-beam irradiation and plastic deformation of medical-grade ultra-high molecular weight polyethylene, Radiat. Phys. Chem. source
    • cites [55] Bracco, 2005, Radiation-induced crosslinking of UHMWPE in the presence of co-agents: chemical and mechanical characterisation, Polymer source
    • cites [56] Costa, 2008, Post electron-beam irradiation oxidation of orthopaedic UHMWPE, Polym. Degrad. Stab. source

  • May combine two claims.

    Interpretationreasoning

    That nearly unconstrained transformation is accompanied by strong orientation and flow of neighboring amorphous material that facilitates chain disentanglement and more chain scission, both leading to partial destruction of the molecular network and irreversible flow, which may be even stronger than observed in compression.

    “That nearly unconstrained transformation is accompanied by a strong orientation and flow of neighboring amorphous material that facilitates chain disentanglement and more chain scission, both leading to partial destruction of the molecular network and irreversible flow, which may be even stronger than these observed in compression.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Interpretationreasoning

    Such strain can develop in amorphous layers only after destruction of the initial lamellar structure, which initially constrains strongly amorphous layers and does not allow for high deformation within these layers.

    “such strain can develop in amorphous layers only after destruction of the initial lamellar structure, which initially constrains strongly amorphous layers and does not allow for high deformation within these layers.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Interpretationreasoning

    Since cavitation starts at early stages of deformation, the accompanying chain scission may result in noticeable deterioration of the molecular network much earlier than in compression due to chain disentanglement, which commences above true strain e=1.

    “since cavitation starts at early stages of deformation, the accompanying chain scission may result in noticeable deterioration of the molecular network much earlier than that taking place in compression due to chain disentanglement, commencing above the true strain of e ¼ 1.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Interpretationreasoning

    This partial destruction of lamellar structure relieves some constraints imposed earlier on amorphous layers by adjacent crystals, which facilitates further deformation of the molecular network, leading eventually to strong strain hardening of the amorphous phase that gradually approaches its extensibility limit.

    “This partial destruction of lamellar structure relieves some of constraints imposed earlier on amorphous layers by adjacent crystals, which facilitates further deformation of the molecular network, leading eventually to a strong strain hardening of amorphous phase that gradually approaches its extensibility limit.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Interpretationreasoning

    Formation of a cavity is a local event of micro-fracture, and it is highly probable that chain scission contributes significantly to the formation of new polymer-cavity interfaces.

    “Formation of a cavity is a local event of micro-fracture and is highly probable that chain scission contributes significantly to the formation of new polymer-cavity interfaces.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Interpretationown data

    Two plausible mechanisms of network erosion-chain scission and elimination of a fraction of physical crosslinks at the crystal-amorphous interface due to partial destruction of the lamellar structure-both demonstrated very limited activity.

    “two plausible mechanisms of network erosion, by (i) chain scission or (ii) elimination of a fraction of physical crosslinks at crystal-amorphous interface due to partial destruction of the lamellar structure, demonstrated both very limited activity”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Interpretationreasoning

    This erosion results in increasing irreversible flow and reduction of the strain recoverable at temperatures below the melting point.

    “This in turn results in increasing irreversible flow and reduction of the strain recoverable at temperatures below the melting point.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Study design and conductreasoning

    All results discussed in this paper refer to polymer response to deformation in plane-strain compression, in which plastic deformation is not accompanied or obscured by side effects such as cavitation, because cavitation is inhibited by compressive stress components.

    “All the results discussed in this paper refer to polymer response to deformation in the plane-strain compression mode, in which the plastic deformation is not accompanied and obscured by any sideeffects, as e.g.cavitation, which is inhibited by compressive stress components generated in the material.”
    • Also stated in: § 4. Conclusions · plain
      “The reported study concerns deformation by plane-strain compression.”
    Quote in the paperSubstantial claim

  • The quote only partly states this claim.

    Interpretationreasoning

    This easier lamellae fragmentation eventually leads to fast completion of transformation of the initial structure into a new micro-fibrillar structure.

    “This eventually leads to fast completion of transformation of the initial structure into a new micro-fibrillar structure.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Interpretationreasoning

    The erosion of the network occurs only when the deformation is well advanced, at high strain above e=1.0, since large local strains are needed for chain disentanglement.

    “The erosion of the network occurs only when the deformation is well advanced -at high strain above e ¼ 1.0, since large local strains are needed for chain disentanglement.”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing), S4 (based). May combine two claims.

    Interpretationreasoning

    An evolution of the molecular network can take place in a different way when a polymer is deformed in other deformation modes facilitating cavitation, such as tension, since chain scission, presumably accompanying cavitation, can contribute to disintegration of the molecular network significantly more than in compression, where it appeared merely a secondary mechanism.

    “an evolution of the molecular network can take place in a different way when a polymer is deformed in other deformation modes, facilitating cavitation, as e.g.tension, since chain scission, presumably accompanying cavitation, can contribute to disintegration of the molecular network significantly more than in compression, where it appeared merely a secondary mechanism.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Study design and conductreasoning

    The H-200 material usually fractured at strains above e=1.5, and the e=1.9 specimen was partially fractured, making its carbonyl concentration less reliable.

    “the H-200 material fractured usually at strains above e ¼ 1.5, and the specimen of e ¼ 1.9 used in this experiment was partially fractured”
    • Also stated in: § 3.4. Changes in molecular network due to deformation · plain
      “the value of carbonyl concentration determined for this particular sample is less reliable than others.”
    Quote in the paperSubstantial claim
60 of 60

  • The paper relies on this without support.

    During swelling in p-xylene at 138 C, all entanglements except those entrapped between chemical crosslink junctions produced by irradiation are resolved and disappear.

    “At such conditions, all entanglements, except of those entrapped between chemical crosslink junctions produced by irradiation, were resolved and disappeared.”

  • The authors state this as an assumption.

    The solvent interaction parameter χ for polyethylene and p-xylene is constant and independent of crosslink density.

    “A constant value of the solvent interaction parameter c was used despite several authors claim that the solvent interaction parameter can depend on the crosslink density [39].”

  • The authors state this as an assumption.

    Crystallization does not resolve any entanglement; instead all entanglements and all chemical crosslinks are concentrated in amorphous layers constituting about 1/3 of the sample volume.

    “under a severe assumption that crystallization does not resolve any entanglement, but instead all of them have been concentrated in amorphous layers constituting about 1/3 of the sample volume, together with all chemical crosslinks.”

  • The authors state this as an assumption.

    All new carbonyls are related to chain scission products and no crosslinking phenomena occurred.

    “Assuming that all new carbonyls are related to chain scission products and no crosslinking phenomena occurred, the corresponding changes in molecular weight can be calculated with the following equations [54]:”

  • The paper relies on this without support.

    An average chain in the entangled network statistically contributes through about 20 entanglements.

    “Taking into account that an average chain statistically contributes to the molecular network of entangled chains through about 20 entanglements”
5 of 5

Self-check

Percentages, sums and reported differences re-computed from the paper’s own numbers.

Each contradiction between two passages listed here was confirmed by an independent check.

  • Effective network density is below the stated lower bound

    Minor

    The paper defines the lower-bound estimate as chemical crosslink density plus an entanglement density of about 4 × 1026 m−3. For H-200, the tabulated crosslink density of 2.63 gives a lower bound of about 6.63 × 1026 m−3, but its tabulated effective density is 5.7 × 1026 m−3-not slightly higher.

  • Wrong equation cited for the loose-chain-end correction

    Minor

    The cited Eq. (2) defines gel content and contains no M*c term to replace. M*c appears in Eq. (3).

  • Carbonyl increment exceeds the stated per-chain limit

    Minor

    The reported increase of 0.08 mmol/kg corresponds, at the stated number-average mass of 28,900 g/mol, to about 0.00231 new carbonyl groups per average chain. That exceeds 0.002 and corresponds to roughly one group per 433 chains, rather than per more than 500 chains.

3 of 3

Cites

Flagged first, then by citations

3 of the 66 references couldn’t be matched to a known paper.

Research works printed but not linked: 1

  1. Oleinik, 2003, Plasticity of semicrystalline flexible-chain polymers at the microscopic and mesoscopic levels, Polym. Sci. C, 45, 17

Cited by

Sorted by citations

Related

Authors
Bartczak, Z., Grala, M., Richaud, E., & Gadzinowska, K.
Affiliations
  • Centrum Badań Molekularnych i Makromolekularnych Polskiej Akademii Nauk (PL)
  • Centre National de la Recherche Scientifique (FR)
Corresponding author
Bartczak, Zbigniew
ORCID
Venue
Polymer
Publisher
Elsevier BV
Published
2016-09
Volume
99
Pages
552-565
ISSN
0032-3861 (ISSN-L)
DOI
10.1016/j.polymer.2016.07.068
OpenAlex
W2482685110
Semantic Scholar
169503084916ad43dddc4917d11285e42abc3dbf
Cited by
23
References
66
Citations by year
2026: 1 · 2025: 4 · 2024: 3 · 2023: 2 · 2022: 2 · 2021: 3 · 2020: 1 · 2019: 4 · 2018: 3
FWCI
1.57
Type
journal article
Language
en
Open access
Licence
www.elsevier.com/tdm/userlicense/1.0/ (tdm)
Locations
  • Polymer (publishedVersion)
  • HAL (Le Centre pour la Communication Scientifique Directe) (submittedVersion)
  • SAM, the Arts et Métiers ParisTech open access repository (Paris Institute of Technology) (submittedVersion, other-oa)
Funders
  • National Science Centre, Poland (DEC-2014/15/B/ST8/04306)
  • Agilent Technologies (PL-GPC 220)
Topics
  • Physical Sciences › Materials Science › Polymers and Plastics › Polymer crystallization and properties
  • Physical Sciences › Chemical Engineering › Fluid Flow and Transfer Processes › Rheology and Fluid Dynamics Studies
  • Physical Sciences › Materials Science › Polymers and Plastics › Polymer composites and self-healing
Keywords
linear polyethylene, molecular networks, chain disentanglement, chain scission, strain recovery, plane strain compression, high strain deformation, electron beam crosslinking, plastic deformation

About these checks

Registry, retraction, Cites and statistics results are computed, not judged, with one exception: a printed reference that no index lists is read once by a model before it counts as a citation error. Claims are extracted by a model and kept only when their quote appears verbatim in the text; each cited source is then checked, with a model’s help, for whether it says what the claim relies on. Those verdicts can be wrong — read the claim’s quote and the cited source before relying on one.

Claims read by deepseek-v4.1-flash under definition version 3 (extract-v3) on 2026-10-11.

Classified by jev-1.13-20260917 (gold-guideline-v0.2) on 2026-10-11.

Cited sources are checked by gpt-6-sol.

Statistics and arithmetic are recomputed, not judged.

Confidence bands are shown only for fields calibrated on our annotated test set. None is calibrated yet, so no band is shown.

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