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Cited by 322Microplastics and Plastic PollutionPolymer crystallization and propertiesPolymer Science and PVC

The DOI matches its Crossref record; its reference list is not available; none of the 18 sources its claims cite is checked for support yet.

From macroplastics to microplastics: Role of water in the fragmentation of polyethylene

Open access
Julienne, Fanon, Delorme, Nicolas, Lagarde, Fabienne·2019·Chemosphere
DOI 10.1016/j.chemosphere.2019.124409
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Abstract

In this work, the artificial photodegradation of polyethylene films was studied in laboratory to compare the fragmentation pathways of this polymer at air and in water. Oxidation, surface mechanical properties, crystallinity and crack propagation were monitored to investigate their influence on fragmentation. Without any external stress, fragmentation only occurred in water despite a higher level of oxidation for films weathered at air. The cracking of the films did not appear correlated with the oxidation level and the presence of water appeared as a promoter of cracking propagation. The results also showed that the mechanical properties at the surface play a major role in the fragmentation pathway whereas the fabrication process may influence the propagation direction of the cracks. Consequently, the distribution in size of plastic fragments in the aquatic environment may be linked to the nature of the polymer but also to its manufacturing process. In this study, after 25 weeks of weathering in water, 90% of the fragments were >1 mm with very similar shapes showing that micrometric fragments were not yet abundant. These results suggest that long times of weathering in water and many steps of fragmentation appear necessary from macroplastics to reach sizes <1 mm in the aquatic environment. These results constitute a first attempt to understand the pathways leading from macroplastics to microplastics in water. They have to be confirmed for other polymers and the long-term behavior of the fragments needs to be studied to predict their decrease in size among time.

Overview

AI snapshot

Written from the paper’s full text.

TL;DR

This laboratory study compared artificial weathering of low-density polyethylene films in air versus water and found that fragmentation occurred only in water after 25 weeks, even though air-exposed films oxidized more. Water appeared to promote crack propagation, while surface mechanical properties and the extrusion process shaped fragment size and orientation.

Key findings

  • After 25 weeks of accelerated weathering without applied mechanical stress, water-exposed LDPE films fragmented, whereas air-exposed films did not fragment and instead curled along the extrusion direction.
  • Water-weathered fragments were anisotropic and bent, with lengths from 0.4 to 7 mm; on average 62% fell below 5 mm, and 90% remained larger than 1 mm, leaving only about 10% below 1 mm.
  • Air-weathered films showed higher oxidation and a much larger surface elastic modulus increase (from 0.17 GPa pristine to 4.86 GPa, about 30×), while water-weathered films increased less (to 0.71 GPa, about 4×).
  • Macrocracks appeared only on water-weathered films and ran perpendicular to the extrusion direction; microcracks below 10 µm also appeared in water, with surface roughness between microcracks increasing to 63 nm versus 26 nm. Cracking did not track oxidation level.

Methods

  • Blown-extruded LDPE films (2×2 cm, thickness 24(3) µm, roughness 25(5) nm, melting point 112°C, crystallinity 32%, no additives) were weathered in a xenon-lamp chamber under ISO 4892-3:2013 conditions at about 60 W/m², total solar radiation 9×10⁹ J/m², and 32–44°C.
  • Two environments were compared: empty quartz beakers for air and Milli-Q water without stirring for water; films floated in water. Two replicates per condition were left unmanipulated until fragmentation.
  • Characterization used µFT-IR for oxidation indexes, confocal Raman for surface crystallinity, AFM topography and force-volume nanoindentation for elastic modulus, and polarized-light imaging with Gwyddion processing for fragment size distribution after 25 weeks.

Limitations

  • The paper states that this is a model study on PE under abiotic photodegradation in water, with strongly accelerated degradation compared with environmental conditions; lower UV, lower temperature, and biofilm in the field are expected to slow degradation. It also states that results need confirmation for other polymers and that the long-term behavior of the generated fragments remains to be studied.
  • Stated methodological limits include that polarized-light imaging cannot resolve objects below 50 µm, so no conclusion could be drawn below that size; DSC could not be used on fragmented samples; and Raman crystallinity data are qualitative rather than quantitative.
  • Evident from the text: the experiment used only LDPE, two replicates per condition, no stirring or external mechanical stress, and a single accelerated weathering setup, so generalization to other polymers, real aquatic conditions, and mechanical forcing is limited.

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

Integrity signals

Registry

Crossref · 10.1016/j.chemosphere.2019.124409

Cites

Statistics

Nothing to recompute.

Verification

Claims the paper makes

0 of 18 cited sources checked · 0 supported · 0 flagged

  • Findingown data

    The Raman ratio indicated no clear increase in surface crystallinity for weathered samples compared with the pristine film.

    “Figure 5 indicates no clear increase of the surface crystallinity for the weathered samples compared to the pristine film.”
    Quote in the paperNot a substantial claim
  • Findingreasoning

    In water, crack enlargement led to fragmentation of the polymer without any other external stress.

    “The enlargement of cracks lead to the fragmentation of the polymer in water without the necessity of any other external stress.”
    Quote in the paperSubstantial claim
  • Findingown data

    Surface roughness between microcracks increased in the water condition compared with the air condition, with values of 63 nm versus 26 nm.

    “together with an increase of the surface roughness between the microcracks as indicated by the topography analysis (63 nm vs 26 nm).”
    Quote in the paperSubstantial claim
  • Findingown data

    The temperature difference between the air and water conditions in this experiment was low, with 59°C for air and 53°C for water.

    “However, in this experiment the temperature difference is rather low (59°C for air and 53°C for water).”
    Quote in the paperNot a substantial claim
  • Findingown data

    This study confirms that weathering of LDPE films in water or air introduces oxygenated groups, chain scission, and rearrangement on the uppermost surface of the films.

    “This study confirms that the LDPE films weathering, either in water or at air, leads to the introduction of oxygenated groups, chain scission and rearrangement on the uppermost surface of the films.”
    Quote in the paperSubstantial claim
  • It may state two separate claims as one. 18
  • The quote only partly states this claim. 1
  • Probably not a substantial claim. 2

  • It may state two separate claims as one.

    Findingcitation

    Microcracks shorter than 10 μm were visible on water-weathered films between macrocracks and oriented normal to the extrusion direction, while no such defects appeared in the air condition.

    “On the water-weathered films, microcracks (length <10µm) are visible between the macrocracks, normally to the extrusion direction (Deblieck et al. 2011) whereas no such defaults appear for the air condition.”
    Quote in the paperSubstantial claim

  • It may state two separate claims as one.

    Findingown data

    The average surface elastic modulus increased by a factor of 30 for air-weathered films and by a factor of 4 for water-weathered films.

    “The averaged elastic modulus increases by a factor of 30 for the films weathered in air and only by a factor of 4 for the film weathered in water.”
    Quote in the paperSubstantial claim

  • The quote only partly states this claim.

    Findingreasoning

    After 25 weeks of weathering, surface oxidation was lower for films weathered in water than for films weathered in air.

    “The lowest oxidation observed on the films in water may be explained by a light exposure less important due to the light absorption by the water molecules.”
    • Also stated in: § Discussion: From oxidation to fragmentation · plain
      “after a long weathering duration, a difference of surface oxidation was monitored between water and air conditions.”
    Quote in the paperSubstantial claim

  • It may state two separate claims as one.

    Findingown data

    After 25 weeks of accelerated weathering without manipulation, LDPE films in water fragmented, whereas films in air did not fragment.

    “After 25 weeks of accelerated weathering with no manipulation, the replicates in water have fragmented in anisotropic bended fragments with the longer length in a normal direction toward the extrusion direction.”
    • Also stated in: § Fragmentation · plain
      “After the same weathering time in air, the films were not fragmented but appeared coiled upon themselves along the extrusion direction.”
    Quote in the paperSubstantial claim

  • It may state two separate claims as one.

    Findingown data

    After 25 weeks in water, fragment lengths ranged from 0.4 to 7 mm, and on average 62% of fragments were below 5 mm, the microplastic size threshold.

    “The size of the fragments appeared as a large distribution from 0.4 to 7 mm in length with 62 % on average of the fragments which correspond to the definition of microplastics (< 5 mm).”
    Quote in the paperSubstantial claim

  • It may state two separate claims as one.

    Findingown data

    Macrocracks longer than 100 μm were visible only on films weathered in water and were oriented perpendicular to the extrusion direction; air-weathered films had unchanged macroscopic surface structure.

    “Optical microscopy images indicate that macrocracks (defined here as cracks with length > 100µm) are only visible on the films weathered in water and that these cracks are oriented perpendiculary to the extrusion direction.”
    Quote in the paperSubstantial claim

  • It may state two separate claims as one.

    Findingown data

    The water-weathered fragments were anisotropic and bent, with their longer dimension oriented normal to the extrusion direction.

    “the replicates in water have fragmented in anisotropic bended fragments with the longer length in a normal direction toward the extrusion direction.”
    Quote in the paperNot a substantial claim

  • It may state two separate claims as one.

    Findingown data

    After 25 weeks of weathering in water, 90% of fragments were larger than 1 mm, and micrometric fragments below 1 mm made up only 10%.

    “In this study, after 25 weeks of weathering in water, 90 % of the fragments were > 1 mm with very similar shapes showing that micrometric fragments were”
    • Also stated in: § Discussion: From oxidation to fragmentation · hedged
      “It appears that fragments with micrometric size (< 1 mm) are not abundant as they represent only 10 % of the fragments.”
    Quote in the paperSubstantial claim

  • It may state two separate claims as one.

    Findingreasoning

    When a weak external stress is imposed on the aged air film, catastrophic crack propagation occurs and appears independent of the extrusion direction.

    “When a weak external stress is then imposed to the aged film, a catastrophic crack propagation is observed, which appears to be independent of the extrusion direction.”
    Quote in the paperSubstantial claim

  • It may state two separate claims as one.

    Findingown data

    After long weathering in air, films had higher surface oxidation and higher surface crystallinity than water-weathered films, resulting in high surface rigidity as shown by AFM.

    “Indeed, after a long weathering duration in the air, the films present a higher oxidation level and a higher crystallinity at their surface compared to water condition resulting in a high surface rigidity as desmonstrated by AFM.”
    Quote in the paperSubstantial claim

  • It may state two separate claims as one.

    Findingreasoning

    In water-weathered films, induced stress is released partly through crack propagation and partly through film wrapping, producing wrapped fragments covered by macro- and micro-cracks.

    “As a consequence, the induced stress can be release partly through crack propagation and partly through film wrapping as observed by the formation of wrapped fragments covered by macro and micro-cracks.”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim.

    Premisecitation

    An external stress is necessary to achieve fragmentation.

    “An external stress is necessary to achieve fragmentation (Kalogerakis et al. 2017).”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites Kalogerakis et al. 2017

  • It may state two separate claims as one.

    Interpretationreasoning

    Weathering-induced oxidation of LDPE increases its hydrophilicity and increases the ability of water to act as a crack promoter.

    “the oxidation of LDPE due to the weathering is going to increase the hydrophilicity of LDPE and increase the ability of water to act as a crack promoter.”
    Quote in the paperNot a substantial claim

  • It may state two separate claims as one.

    Interpretationown data

    The loss of fragments smaller than 1 mm described in the environment may be due to a lack of methodology for sampling and analyzing small microplastics and to the long weathering times and many fragmentation steps needed to reach sizes below 1 mm in water.

    “This loss may be due to the lack of methodology for sampling and analyzing small microplastics but also to the fact that long times of weathering and many steps of fragmentation appear necessary from macroplastics to reach sizes < 1 mm in water.”
    Quote in the paperSubstantial claim

  • It may state two separate claims as one.

    Premisecitation

    Oxidation induces chain splits and formation of low molecular weight free segments, which can rearrange into a crystalline phase, leading to chemi-crystallization.

    “This oxidation process induces chain splits and accordingly low molecular weight free segments are formed.Due to their smaller size, they can rearrange into a crystalline phase leading to the process of chemi-crystallization which can be illustrated by an increase of the crystallization degree after weathering (Ojeda et al. 2011).”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Ojeda et al. 2011

  • It may state two separate claims as one.

    Premisecitation

    Water acts as a plasticizer for PE by penetrating between polymer chains and preventing rearrangements involved in crosslinking.

    “the role of water as a plasticizer (Levine and Slade 1988).Actually, this effect consists in the penetration of small molecules between the polymer chain which prevents the rearrangements of polymer chains involved in crosslinking (Robeson 2013).”
    Quote in the paperSubstantial claim0 of 2 sources checked
    • cites Levine and Slade 1988
    • cites Robeson 2013

  • Probably not a substantial claim. The paper’s conclusions may not depend on it.

    Premisecitation

    According to the Irwin model, the critical stress for crack propagation is given by σcr2 = G E / (π a).

    “assuming Irwin model (Yarema 1996), the critical stress for crack propagation can be expressed as:”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Yarema 1996

  • It may state two separate claims as one.

    Interpretationreasoning

    Water probably accelerates crack propagation by penetrating to the craze tip, plasticizing the polymer, and allowing the craze to grow.

    “Moreover, water probably accelerates the propagation of cracks: once the liquid penetrates to the craze tip, it then begins to plasticize the polymer and allows the craze to grow.”
    Quote in the paperSubstantial claim

  • It may state two separate claims as one.

    Premisecitation

    An incompatibility between tensile stress in the upper degraded layer and compressive stress in the unchanged material layer, together with manufacturing stress, causes the film to bend along the extrusion direction.

    “This results in an incompatibility between tensile stress within the upper degraded layer (surface) and the compressive stress in the unchanged material layer.In addition together with manufacturing stress, these stresses cause the bending of the film along the extrusion direction (Choi et al. 2005) as shown in air condition (Figure 1).”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Choi et al. 2005

  • It may state two separate claims as one.

    Interpretationreasoning

    Crack propagation and the manufacturing process appear to be major factors governing the initial shape of the fragments.

    “In this case, the cracking propagation and the manufacturing process appear to be the major factor governing the initial shape of the fragments.”
    Quote in the paperSubstantial claim

  • It may state two separate claims as one.

    Premisecitation

    Polymer films that have undergone photodegradation are first altered at the surface, and no molecular chain scission appears in the core until the molar mass at the surface decreases considerably.

    “Yakimets et al. (2004) demonstrated that polymer films having undergone photodegradation are first altered in surface and no molecular chain scission appear in the core until the molar mass of the sample at the surface decreases considerably.”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites Yakimets et al. 2004
21 of 21

  • The paper relies on this without support.

    In semi-crystalline polymers such as LDPE, oxidation mainly occurs in amorphous regions where oxygen can readily diffuse.

    “In semi-crystalline polymers such as LDPE, oxidation mainly occurs in amorphous regions in which oxygen can readily diffuse.”

  • The authors state this as an assumption.

    The chemical changes caused by oxidation result in an increase in surface rigidity.

    “It can be assumed that these changes result in an increase of the surface rigidity (Craig et al. 2005).”

  • The paper relies on this without support.

    The main mechanism for fracture development in a semi-crystalline polymer begins with the formation of nano-cavities or voids in the amorphous phase.

    “As already described in literature, the main mechanism for the fracture development in a semi-crystalline polymer is initiated through the formation of nano-cavities (voids) in the amorphous phase.”

  • The paper relies on this without support.

    Crack propagation occurs only when the released strain energy exceeds the energy required to create a fracture surface.

    “Crack propagation only occurs when the released strain energy is greater than the energy required to create a fracture surface.”
4 of 4

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References 36 · Cited by 322

Research works printed but not linked: 28

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Metadata

Authors
Julienne, F., Delorme, N., & Lagarde, F.
Affiliations
Centre National de la Recherche Scientifique (FR)
Corresponding author
Lagarde, Fabienne
ORCID
Venue
Chemosphere
Publisher
Elsevier BV
Published
2019-12
Volume
236
Pages
124409
ISSN
0045-6535 (ISSN-L)
DOI
10.1016/j.chemosphere.2019.124409
OpenAlex
W2964173088
Cited by
322
References
36
Citations by year
2026: 38 · 2025: 44 · 2024: 52 · 2023: 57 · 2022: 59 · 2021: 48 · 2020: 22 · 2019: 2
FWCI
9.81
Type
journal article
Language
en
Open access
Licence
Locations
  • Chemosphere (acceptedVersion)
  • PubMed (publishedVersion)
  • HAL (submittedVersion, cc-by-nc)
Funders
Agence Nationale de la Recherche
Topics
  • Physical Sciences › Environmental Science › Pollution › Microplastics and Plastic Pollution
  • Physical Sciences › Materials Science › Polymers and Plastics › Polymer crystallization and properties
  • Physical Sciences › Materials Science › Polymers and Plastics › Polymer Science and PVC
Keywords
polyethylene, microplastics, macroplastics, photodegradation, fragmentation pathways, oxidation, surface mechanical properties, crystallinity, crack propagation
MeSH terms
Microplastics, Environmental Monitoring, Oxidation-Reduction, Plastics, Surface Properties, Water, Water Pollutants, Chemical, Polyethylene, Photochemical Processes

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