Environmental stress cracking of high-density polyethylene under plane stress conditions

Contino, Marco; Andena, Luca; Rink, M.

doi:10.1016/j.engfracmech.2020.107422

Cited by 17 publications

(9 citation statements)

References 60 publications

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“…From the bulk perspective, the key difference between HD 8660.29 and LL 8460.29 was that LL 8460.29 contains less crystallinity content (due to its short branches content 40 ) but this is a minor difference in content and unlikely the primary reason for such a dramatic difference in surfactant absorption, especially since greater amorphous content should aid fluid penetration, rather than hinder. Considering the crystalline morphology of the two polymers, HDPE has a crystalline morphology based on a row nucleated crystal structure consisting of neatly stacked, thick lamellas 49–54 whereas, LLDPE contains thinner, wider lamellas 49,51,55,56 and any spherulitic structures of LLDPE tend to be less ordered and more varied in size compared to HDPE 46 . We believe the greater tortuous path created by LLDPE lies in how its crystals are interconnected.…”

Section: Resultsmentioning

confidence: 95%

“…Internally, this swelling stretches the tie molecules between crystalline regions, thus causing internal stresses to now rise (seen via acoustic spectroscopy 7 ). Once the acceleration time occurs for bending stresses, tie molecules should have disentangled and become stretched with rising internal stresses 44,46 (and a corresponding acceleration in stress intensity factor K is seen). Correspondingly, a steady amount of lamellar stack rotation occurs in crystalline structures now experiencing stresses no longer bore by the amorphous phase alone, which allowed steady conversion of orthorhombic crystals into monoclinic crystals 41 .…”

Section: Resultsmentioning

confidence: 99%

“…Considering the crystalline morphology of the two polymers, HDPE has a crystalline morphology based on a row nucleated crystal structure consisting of neatly stacked, thick lamellas [49][50][51][52][53][54] whereas, LLDPE contains thinner, wider lamellas 49,51,55,56 and any spherulitic structures of LLDPE tend to be less ordered and more varied in size compared to HDPE. 46 We believe the greater tortuous path created by LLDPE lies in how its crystals are interconnected. As IGEPAL CO-630 absorbed into the amorphous contents of either polyethylene, the swollen amorphous regions increased interlamellar shear and promoted increased crystal slippage.…”

Section: Proposed Additions To the Esc Mechanismmentioning

confidence: 99%

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Understanding environmental stress cracking in the Bell Test at the notch region

Gritsichine,

Vlachopoulos,

Thompson

2023

Polymer Engineering & Sci

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The Bell Test (ASTM‐D1693) is commonly used to accelerate part failure in order to evaluate resin selection for applications like piping and tanks where environmental stress cracking is possible, even though the method tends to offer less than desirable repeatability. The working hypothesis for this new study with polyethylenes was that the variability seen in failure times may be attributed to a higher sensitivity of the phase morphology primarily at or near the surfaces of a notch than more commonly referenced bulk descriptors of a polymer, affecting stresses and the localized absorption of the preferred stress cracking agent. Using an organic dye tracer to monitor penetration of stress cracking agent into the polymer along with image analysis for the notch dimensions and a load cell, the local aspects of the mechanism were evaluated for up to four grades of polyethylene of varying crystallinity. By this detailed analysis, it was revealed that for failure to occur by ESC, influences in the polymer by absorption of the stress cracking agent preceded the changes in stresses in the specimen, contrary to original expectation. There was an imminent rate increase in both stresses and notch expansion once absorption of the surfactant reached a critical concentration. This critical nature was shown to be dependent on the crystallinity of the polymer under observation, considering the size/arrangement of crystals present and entanglements formed through the amorphous contents to dictate the rate by which IGEPAL can be absorbed into a polyethylene specimen. The results of this study validate the need for greater focus on polymer properties at the notch rather than the bulk of the specimen, though more techniques for providing analysis of these properties at the notch surfaces are needed for future improvements to the mechanism.Highlights Bromocresol dye acts as a novel visualization aid in tracking IGEPAL CO‐630 sorption Crystallinity was related to a plasticization threshold for absorption of IGEPAL Accelerated increase in internal stresses follow absorption. Variability of the Bell Test was related to crystalline properties at the notch

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Section: Resultsmentioning

confidence: 95%

Section: Resultsmentioning

confidence: 99%

Section: Proposed Additions To the Esc Mechanismmentioning

confidence: 99%

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Understanding environmental stress cracking in the Bell Test at the notch region

Gritsichine,

Vlachopoulos,

Thompson

2023

Polymer Engineering & Sci

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“…To overcome this issue, two different strategies were adopted in the present work. The dependency of the yield stress on the strain rate is addressed by the well-known Eyring equation [47]:…”

Section: Strain Rate Dependencementioning

confidence: 99%

Scratch hardness as a quasi-intrinsic parameter to measure the scratch resistance of polymers

Andena

Chiarot

2023

Wear

Self Cite

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“…Polymers, and thus also PE-HD, are visco-elastic, time-dependent materials which cannot be described by a static Young's modulus only (Equation ( 4)). This visco-elastic behavior requires minor modifications and changes to the analysis, as demonstrated by Rink et al [43] as well as Andena et al [44] and approved recently for SCG and ESC by Contino et al [45][46][47][48] and Kamaludin et al [49][50][51] applying LEFM. This is especially relevant in the case of indirect crack length determination using compliance analyses, representing the relationship between the monitored ∆COD and the resulting crack length.…”

Section: Relation Between Crack Length and Crack Opening Displacementmentioning

confidence: 99%

Environmental Stress Cracking of High-Density Polyethylene Applying Linear Elastic Fracture Mechanics

et al. 2022

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The crack propagation rate of environmental stress cracking was studied on high-density polyethylene compact tension specimens under static loading. Selected environmental liquids are distilled water, 2 wt% aqueous Arkopal N100 solution, and two model liquid mixtures, one based on solvents and one on detergents, representing stress cracking test liquids for commercial crop protection products. The different surface tensions and solubilities, which affect the energetic facilitation of void nucleation and craze development, are studied. Crack growth in surface-active media is strongly accelerated as the solvents induce plasticization, followed by strong blunting significantly retarding both crack initiation and crack propagation. The crack propagation rate for static load as a function of the stress intensity factor within all environments is found to follow the Paris–Erdogan law. Scanning electron micrographs of the fracture surface highlight more pronounced structures with both extensive degrees of plasticization and reduced crack propagation rate, addressing the distinct creep behavior of fibrils. Additionally, the limitations of linear elastic fracture mechanisms for visco-elastic polymers exposed to environmental liquids are discussed.

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Environmental stress cracking of high-density polyethylene under plane stress conditions

Cited by 17 publications

References 60 publications

Understanding environmental stress cracking in the Bell Test at the notch region

Understanding environmental stress cracking in the Bell Test at the notch region

Scratch hardness as a quasi-intrinsic parameter to measure the scratch resistance of polymers

Environmental Stress Cracking of High-Density Polyethylene Applying Linear Elastic Fracture Mechanics

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