Alternative accelerated and short-term methods for evaluating slow crack growth in polyethylene resins with high crack resistance

Robledo, Nuria; Domı́nguez, Carlos; García-Muñoz, Rafael A.

doi:10.1016/j.polymertesting.2017.07.022

Cited by 19 publications

(12 citation statements)

References 29 publications

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“…As a result, the resistance to SCG is related to the molecular weight (MW), its distribution (MWD), and short-chain branches (SCB), which govern the characteristics of the final product. 12,13 There are diverse publications concerning the effect of different parameters on the resistance to SCG. 1,[14][15][16][17][18][19] Deveci et al studied the effects of different molecular structure parameters on the SCG resistance of ethylene/1-butene and ethylene/1-hexene resins.…”

Section: Introductionmentioning

confidence: 99%

Effects of polymerization parameters on the slow crack growth resistance and rheological properties of bimodal polyethylene resins

Jandaghian

Maddah

Sepahi³

et al. 2021

J of Applied Polymer Sci

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In this paper, using a comprehensive study, we have investigated the effect of various polymerization parameters during the synthesis of bimodal polyethylene resins on their rheological and mechanical properties. Bimodal polyethylene resins were synthesized in two subsequent stages in a lab-scale reactor by manipulating a set of parameters such as C 2 /H 2 ratios in the first and second stages, the split value, and the comonomer type. The results showed that the comonomer type and C 2 /H 2 ratio of the second stage of the polymerization are the most critical parameters that control the final resins' slow crack growth resistance properties. On the other hand, the shear-thinning behavior of the resins is mainly controlled by the first-stage polymers. Although the C 2 /H 2 ratio of the first stage results in a moderate effect on the rheological properties of the final resins, its split value governs the flow characteristics of the final molten polymers under high shear rates.

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Section: Introductionmentioning

confidence: 99%

Effects of polymerization parameters on the slow crack growth resistance and rheological properties of bimodal polyethylene resins

Jandaghian

Maddah

Sepahi³

et al. 2021

J of Applied Polymer Sci

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“…SH is an accelerated test for SCG resistance determination. [ 32 ] Polyethylene resins with 1‐hexene as comonomer have higher SH values, especially in high resistance to failure resins. According to Dominguez et al., [ 29 ] for PE100RC grade, SH values of 53 MPa are achieved in the case of 1‐butene, while values of 59 MPa are obtained in the case of 1‐hexene comonomer‐based resins.…”

Section: Resultsmentioning

confidence: 99%

Evaluation of Bimodal Polyethylene from Chromium Oxide/Metallocene Hybrid Catalysts for High Resistance Applications

Paredes

Moreno

Carrero

et al. 2020

Macro Reaction Engineering

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impregnation with MAO/metallocene species but they will be able for polymerization as the fragmentation process takes place. These facts cannot be achieved by a commercial support such as silica. [5] As known, some grades of bimodal polyethylene, such as PE100, are especially interesting for several commercial applications because they combine the strength and stiffness of high-density poly ethylene (HDPE) with the high-stress crack resistance and processability of unimodal medium density grades. [8] One of the most employed technology for the production of bimodal polyethylene at industrial scale is a two-stage cascade polymerization process by using a Ziegler-Natta catalyst. [9] The possibility of designing an alternative based on a single reactor pathway is undoubtedly attractive because of numerous reasons: lower investment costs, simpler process control, and greater mixture of chains with low and high molecular weight (they would be simultaneously generated on the same catalyst), among others. [7,10] In this context, previous results obtained with the binary Met-Cr-AlSBA-15 catalyst showed that it is a promising production route that should be more deeply explored. According to aforementioned data, the use of hydrogen is necessary to get a bimodal molecular weight distribution because it has a strong influence on metallocene sites, leading to a considerable reduction of their chains length [11,12] in comparison with those coming from chromium, which maintain their contribution to the high molecular weight fraction. [6,13] Likewise, adding a comonomer during the polymerization carried out on the binary mesostructured catalyst leads to interesting short chain branching (SCB) distribution across the molecular weight curves of the polymers, providing in some cases flat or even growing comonomer distributions. [7] This is a very interesting fact since numerous branches located into de shortest polymer chains are not desirable for most polyethylene properties, especially for mechanical ones. [14,15] So, these growing profiles could involve significant enhancements of some mechanical properties of the polymers such as stress crack resistance or impact strength, leading to novel and improved polyethylene grades. However, investigations focused on evaluating the mechanical properties of these new bimodal resins coming from the Met-Cr-AlSBA-15 catalyst have not been developed yet. This work aims to study in deep the mechanical features of polyethylenes produced by the binary Met-Cr-AlSBA-15 catalyst in only-one step polymerization process, as well as An interesting alternative to the industrial two-stage cascade process for the production of bimodal polyethylene, used for high resistance applications such as pressure pipes, has been developed. The key point is a binary catalytic system with chromium and metallocene sites incorporated together on AlSBA-15 mesostructured material. This hybrid catalyst is able to produce bimodal polyethylene in a single reactor. In the present work, it is shown that, in the presence of h...

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“…The types of specimens used in such experiments are usually the cracked round bars or circular notched specimens. Other types of experiments include specimens for the Pennsylvania notched test (Brown, 2007; Nezbedov a et al, 2013; Robledo, Dom ınguez, & Garc ıa-Muñoz, 2017) and the strain hardening test (Deveci & Fang, 2017;Robledo et al, 2017).…”

Section: Linear Elastic Fracture Mechanicsmentioning

confidence: 99%

A review on the durability of PVC sewer pipes: research vs. practice

Makris

Langeveld

Clemens

2019

Structure and Infrastructure Engineering

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Polyvinyl chloride (PVC) has become one of the dominant construction materials for sewer systems over the past decades, as a result of its reputed merits. However, since PVC sewer pipes have operated for decades in a hostile environment, concern over their longevity has been lately raised by sewer managers in the Netherlands. Towards that direction, the main factors and mechanisms that affect a PVC pipe's lifetime are discussed in this article, along with the current lifetime prediction methods and their limitations. The review of relevant case studies indicates that material degradation, if any, occurs slowly. However, inspection (CCTV) data of three Dutch municipalities reveals that severe defects have already surfaced and degradation evolves at an unexpected fast rate. A main reason of this gap between literature and practice is the fact that comprehensive material testing of PVC sewer pipes is rarely found in the literature although it proves to be essential in order to trustfully assess the level of degradation and its origins.

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Alternative accelerated and short-term methods for evaluating slow crack growth in polyethylene resins with high crack resistance

Cited by 19 publications

References 29 publications

Effects of polymerization parameters on the slow crack growth resistance and rheological properties of bimodal polyethylene resins

Effects of polymerization parameters on the slow crack growth resistance and rheological properties of bimodal polyethylene resins

Evaluation of Bimodal Polyethylene from Chromium Oxide/Metallocene Hybrid Catalysts for High Resistance Applications

A review on the durability of PVC sewer pipes: research vs. practice

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