Fracture Surface Analysis in HDPE Pipe Material Fatigued at Different Temperatures and Loading Frequencies

Khan, Zulfiqar Ahmad

doi:10.1007/s11665-011-0024-z

Cited by 6 publications

(5 citation statements)

References 22 publications

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“…The results show that fatigue life decreases as the diameter of the pores became larger, and increases as their aspect ratio increases, which is the ratio of the maximal and minimal diameter of the pores. The presence of nanoparticles, such as CaCO 3 in high-density polyethylene, has been observed by Khan [26]. It was noted that particles act as stress concentrators, helping in the void formation, which indicates that crack growth occurs through a fully developed crazing process.…”

Section: Introductionmentioning

confidence: 79%

“…The fatigue life and its limits strongly depend on process condition, chemical structure, morphology, crystallization, density and porosity, as well as the presence of nanoparticles [19,[24][25][26]. It was shown by Sauer and Richardson [20] on polystyrene that as molecular weight increases, the S-N (stress-fatigue life) curves shift to higher stress values and a higher number of cycles, increasing the fatigue limit.…”

Section: Introductionmentioning

confidence: 99%

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Evaluation of Fatigue Life of Recycled Opaque PET from Household Milk Bottle Wastes

et al. 2022

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Polyethylene terephthalate (PET) is among the most used thermoplastic polymers in large scale manufacturing. Opaque PET is increasingly used in milk bottles to save weight and to bring a glossy white aspect due to TiO2 nanoparticles. The recyclability of opaque PET is an issue: whereas the recycling channels are well established for transparent PET, the presence of opaque PET in household wastes weakens those channels: opaque bottles cannot be mixed with transparent ones because the resulting blend is not transparent anymore. Many research efforts focus on the possibility to turn opaque PET into resources, as one key to a more circular economy. A recent study has demonstrated the improvement of the mechanical properties of recycled PET through reactive extrusion. In the present work, the lifespan of recycled opaque PET has been evaluated throughout tensile–tensile fatigue loading cycles at various steps of the recycling process: The specimens are obtained from flakes after grinding PET wastes (F-r-OPET), from a subsequent homogenization step (r-OPET-hom) and after reactive extrusion (Rex-r-OPET). Virgin PET is also considered as a comparison. First, tensile tests monitored by digital image correlation have been carried out to obtain the elastic modulus and ultimate tensile stress of each type of PET. The fatigue properties of reactive REx-r-OPET increase, probably associated with the rise of cross-linking and branching rates. The fatigue lifespan increases with the macromolecular weight. The fracture surface analysis of specimens brings new insight regarding the factors governing the fatigue behavior and the damaging mode of recycled PET. TiO2 nanoparticles act as stress concentrators, contributing to void formation at multiple sites and thus promoting the fracture process. Finally, the fatigue life of REx-r-OPET is comparable to those of virgin PET. Upcycling opaque PET by reactive extrusion may be a relevant new route to absorb some of the growing amounts of PET worldwide.

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Section: Introductionmentioning

confidence: 79%

Section: Introductionmentioning

confidence: 99%

Evaluation of Fatigue Life of Recycled Opaque PET from Household Milk Bottle Wastes

et al. 2022

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“…In addition, nanoparticles are presumed to restrict the motion of polymer chains, influencing stress transfer at the nanoscale, which increases the creep stability of the material [22,23]. Unfortunately, these small particles sometimes accelerate material rupture, especially if the nature and distribution of these particles cannot be sufficiently controlled [14]. For instance, SEM images have revealed the presence of small filler particles at the bottom of these microvoids.…”

Section: Discussionmentioning

confidence: 99%

“…During service, the materials are subjected to cyclic load fluctuations so it is important to analyze their resistance to crack growth under cyclic loading. It should be stressed here that the effects of test frequency and the temperature on fatigue crack growth rate is complex [13,14]. For practical reasons, the present comparative study used fixed parameters: a temperature of 26 C, an R-ratio (defined as the ratio of the minimum stress to the maximum stress in the fatigue loading cycle) of 0.1 with constant maximum load intensities of 700, 760, 840, and 900 N, and a loading frequency of 2 Hz.…”

Section: Mechanical Propertiesmentioning

confidence: 99%

Mechanical properties and molecular structures of virgin and recycled HDPE polymers used in gravity sewer systems

et al. 2015

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a b s t r a c tThe widespread use of plastics in the conditioning, packaging and building material sectors generates an enormous amount of industrial waste which could be recycled for wastewater pipes and fittings. Nevertheless, current manufacturing standards in the piping industry recommend against the use of post-consumer recycled materialsda policy based on inadequate understanding of the properties and long-term mechanical performance of recycled materials. The present study compared the material characteristics of virgin and recycled high-density polyethylene (HDPE) plastics commonly found in the piping industry. Mechanical testing, oxidative induction time (OIT), melt flow index (MFI) and thermal analysis were used in conjunction with X-ray fluorescence (m-XRF), size exclusion chromatography and 13 C solid-state NMR to evaluate mechanical behavior and molecular structure as well as contaminant or filler contents. This study provides evidence for the degradation processes impact that can occur when post-industrial and post-consumer polymers are recycled. However, the study identified two measures to improve the material qualities of post-consumer recycled HDPE: 1) reducing the amount of contaminants or, alternatively, improving their compatibility with HDPE resins, and 2) improving current sorting and recycling processes to increase the amount of tie molecules in HDPE materials.

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“… SEM analysis showed cracks and pores in the HDPE basal resin and the absorption effect by EDX. 2011 Fracture Surface Analysis in HDPE Pipe Material Fatigued at Different Temperatures and Loading Frequencies [ 123 ] Fatigue The material exhibited fatigue failure due to cyclic loading at different temperatures. Crack growth was dominant at the higher temperature (40 °C) while at 0 °C, only a limited amount of shear yielding occurred.…”

Section: Table A1mentioning

confidence: 99%

Permeation Damage of Polymer Liner in Oil and Gas Pipelines: A Review

2020

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Non-metallic pipe (NMP) materials are used as an internal lining and standalone pipes in the oil and gas industry, constituting an emerging corrosion strategy. The NMP materials are inherently susceptible to gradual damage due to creep, fatigue, permeation, processing defects, and installation blunder. In the presence of acid gases (CO2, H2S), and hydrocarbons under high pressure and temperature, the main damage is due to permeation. The monitoring of possible damage due to permeation is not well defined, which leads to uncertainty in asset integrity management. Assessment of permeation damage is currently performed through mechanical, thermal, chemical, and structural properties, employing Tensile Test, Differential Scanning Calorimetry (DSC), Fourier-transform Infrared Spectroscopy (FTIR), and Scanning Electron Microscopy (SEM)/Transmission Electron Microscopy (TEM), to evaluate the change in tensile strength, elongation, weight loss or gain, crystallinity, chemical properties, and molecular structure. Coupons are commonly used to analyze the degradation of polymers. They are point sensors and did not give real-time information. Polymers are dielectric materials, and this dielectric property can be studied using Impedance Analyzer and Dielectric Spectroscopy. This review presents a brief status report on the failure of polymer liners in pipelines due to the exposure of acid gases, hydrocarbons, and other contaminants. Permeation, liner failures, the importance of monitoring, and new exclusive (dielectric) property are briefly discussed. An inclusive perspective is provided, showing the challenges associated with the monitoring of the polymer liner material in the pipeline as it relates to the life-time prediction requirement.

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Fracture Surface Analysis in HDPE Pipe Material Fatigued at Different Temperatures and Loading Frequencies

Cited by 6 publications

References 22 publications

Evaluation of Fatigue Life of Recycled Opaque PET from Household Milk Bottle Wastes

Evaluation of Fatigue Life of Recycled Opaque PET from Household Milk Bottle Wastes

Mechanical properties and molecular structures of virgin and recycled HDPE polymers used in gravity sewer systems

Permeation Damage of Polymer Liner in Oil and Gas Pipelines: A Review

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