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Abstract <p>This investigation delves into the degradation mechanisms of high-density polyethylene geomembranes (PE GMXs) under a spectrum of conditions, replicating real-world scenarios within a rigorously controlled laboratory setting. The treatment protocols applied induced a notable increase in the crystallinity of the treated specimens relative to the untreated controls. Small-angle x-ray scattering (SAXS) analysis identified an initial long period (interlamellar distance) of 16.9&#xa0;nm for the untreated polymer, which expanded by 19.5% at a strain of 16.7&#xa0;percent. Conversely, the treated PE GMXs exhibited a more gradual elongation of the long period, with an increase of merely 10.6% at a strain of 23.3&#xa0;percent. At an elevated temperature of 65°C, both samples exhibited pronounced strain hardening, with the treated PE GMXs demonstrating superior stability even at a strain of 150&#xa0;percent. Wide-angle x-ray scattering (WAXS) experiments corroborated these observations, revealing that the diffraction patterns of the untreated PE remained stable up to a strain of 16.7%, whereas those of the treated PE remained distinct up to a strain of 46.1&#xa0;percent. Scanning electron microscopy (SEM) images substantiated the formation of a shish–kebab structure in the treated samples. The study concludes that the geopolymer underwent oxidation and material degradation as a result of the chemical and mechanical treatments, transitioning to a more crystalline state and concomitantly losing its initial elasticity.</p> Impact statement <p>This study offers pivotal insights into the degradation mechanisms of high-density polyethylene geomembranes (PE GMXs) through the application of <i>in situ</i> SAXS/WAXS techniques. As a crucial material in waste containment infrastructures, PE GMXs' durability is paramount. By simulating real-world exposure conditions (encompassing chemical environments and mechanical stress) in a controlled laboratory setting, we elucidate the structural transformations at micro- and nanoscales within the polymer. Our findings reveal that oxidation-induced chain scission markedly enhances the crystallinity of treated PE GMXs, resulting in a more crystalline and less elastic state. The combined use of FTIR, DSC along with SAXS/WAXS, and simultaneous tensile testing corroborates these structural changes, demonstrating the material’s diminished deformation capacity under tensile stress and elevated temperatures. SEM micrographs further illustrate the formation of shish–kebab crystals during high-temperature stretching in chemically and mechanically treated samples, contributing to the increased rigidity of PE GMXs. This comprehensive analysis underscores the critical importance of understanding the chemical and mechanical degradation processes in PE GMXs. The data provided herein are invaluable for improving the durability and performance of geosynthetics in field applications. This innovative approach and detailed findings make a significant contribution to the fields of polymer science and environmental engineering, paving the way for enhanced longevity and reliability of waste containment systems.</p> Graphical abstract <p></p>

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Nanoscale structural evolution and phase transformation of geopolymers: In situ SAXS/WAXS investigation under uniaxial tension at elevated temperatures

  • 期刊论文

  • 发表日期：

    2025年2月13日

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  • S. A. K. V. Miyurudarshi Piyathilake,
  • Ivan Kuzmenko,
  • Luckshitha Suriyasena Liyanage,
  • Christopher Bareither

摘要

Abstract

This investigation delves into the degradation mechanisms of high-density polyethylene geomembranes (PE GMXs) under a spectrum of conditions, replicating real-world scenarios within a rigorously controlled laboratory setting. The treatment protocols applied induced a notable increase in the crystallinity of the treated specimens relative to the untreated controls. Small-angle x-ray scattering (SAXS) analysis identified an initial long period (interlamellar distance) of 16.9 nm for the untreated polymer, which expanded by 19.5% at a strain of 16.7 percent. Conversely, the treated PE GMXs exhibited a more gradual elongation of the long period, with an increase of merely 10.6% at a strain of 23.3 percent. At an elevated temperature of 65°C, both samples exhibited pronounced strain hardening, with the treated PE GMXs demonstrating superior stability even at a strain of 150 percent. Wide-angle x-ray scattering (WAXS) experiments corroborated these observations, revealing that the diffraction patterns of the untreated PE remained stable up to a strain of 16.7%, whereas those of the treated PE remained distinct up to a strain of 46.1 percent. Scanning electron microscopy (SEM) images substantiated the formation of a shish–kebab structure in the treated samples. The study concludes that the geopolymer underwent oxidation and material degradation as a result of the chemical and mechanical treatments, transitioning to a more crystalline state and concomitantly losing its initial elasticity.

Impact statement

This study offers pivotal insights into the degradation mechanisms of high-density polyethylene geomembranes (PE GMXs) through the application of in situ SAXS/WAXS techniques. As a crucial material in waste containment infrastructures, PE GMXs' durability is paramount. By simulating real-world exposure conditions (encompassing chemical environments and mechanical stress) in a controlled laboratory setting, we elucidate the structural transformations at micro- and nanoscales within the polymer. Our findings reveal that oxidation-induced chain scission markedly enhances the crystallinity of treated PE GMXs, resulting in a more crystalline and less elastic state. The combined use of FTIR, DSC along with SAXS/WAXS, and simultaneous tensile testing corroborates these structural changes, demonstrating the material’s diminished deformation capacity under tensile stress and elevated temperatures. SEM micrographs further illustrate the formation of shish–kebab crystals during high-temperature stretching in chemically and mechanically treated samples, contributing to the increased rigidity of PE GMXs. This comprehensive analysis underscores the critical importance of understanding the chemical and mechanical degradation processes in PE GMXs. The data provided herein are invaluable for improving the durability and performance of geosynthetics in field applications. This innovative approach and detailed findings make a significant contribution to the fields of polymer science and environmental engineering, paving the way for enhanced longevity and reliability of waste containment systems.

Graphical abstract