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Mei 11, 2023

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Abraison Resistance Improvement of a High Density Polyethylene by Cross-Linking for Manufacture of Mine Tailings Transportation Pipes

Patricia Perdiz Fernandez, Miguel Angel Molano Niampira, Felipe Salcedo Galán, Felipe Álvarez Torres

Papers # 2014 Chicago

Abrasion resistance is the ability of a material to withstand mechanical action such as rubbing, scraping, or erosion. Such ability helps to maintain the material’s original appearance, structure and mechanical properties. It’s a decisive factor in the selection of materials for their use in mining pipe. Abrasive effect of solid particles in mining slurries can significantly decrease the average service life of a pipeline. The extent of the problem depends on the type, size and concentration of the solid in the slurry, frequency with which the solid is in contact with the pipe, velocity of the flow, and the material type of the pipe among others.

Cross-linking consists of connecting the different polymer chains through carbon-carbon bonds, which directly link adjacent chains; the making of a three-dimensional structure improves the mechanical and thermal performance of the resin.

A two-stage cross-linking process was developed using an initiator to verify if this molecular modification created an improvement in the abrasion resistance of a high density polyethylene resin.

A phenomenon of competition between the three-dimensional structure formed as a result of cross-linking and a decrease in the degree of crystallization of the material was observed with increasing initiator content. This behavior induced property changes in the material, which resulted in an abrasion resistance improvement of up to 58% at low initiator contents when tested at extreme loading and friction conditions¸ using abrading wheels to simulate the wear associated with the collision of solid particles on the surface of the pipe.

source:
https://www.pe100plus.com/PPCA/Abraison-Resistance-Improvement-of-a-High-Density-Polyethylene-by-Cross-Linking-for-Manufacture-of-Mine-Tailings-Transportation-Pipes-p1470.html

Mei 3, 2023

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PE 100+ association leads permeation tests for H2 ready certification

A number of gas utilities and grid owners have approached the PE 100+ association regarding the suitability of PE 100 pipe systems for the transport of hydrogen. In order to answer to these queries, which mainly concerned the permeability of hydrogen through the wall of PE 100 pipes, the association initiated a program with the German DBI Test Institute.

This involved a series of tests to measure the permeability of typical PE 100, PE 100-RC and PE 80 materials, in pipe form, at temperatures of 8, 14 and 20 °C and at a target pressure of 6.3 bar. The report is now published on our website to assist gas utilities and other organisations in undertaking permeation calculations.

In summary, the results show that the determined permeation coefficients of all the tested PE materials lie in a similar range, are in line with the expectations and demonstrate that they are suitable for use in hydrogen distribution networks

source: https://www.pe100plus.com/PE-Pipes/news/PE-100-association-leads-permeation-tests-for-H2-ready-certification-i2498.html

April 17, 2023

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Fatigue crack growth testing in chlorinated water at elevated temperatures – Test equipment and test procedure

Joerg Fischer, Patrick R. Bradler, Reinhold W. Lang

Papers # 2018 Las-Vegas

In the present paper, a novel test system for conducting fatigue crack growth (FCG) experiments under superimposed mechanical-environmental conditions is presented. FCG experiments were performed on a polypropylene (PP) grade and a short-glass fiber reinforced polyamide 66 (PA-GF) grade as model materials. The environmental conditions were air, non-chlorinated water and chlorinated water at elevated temperatures (80°C and 95°C). In terms of ranking, the FCG resistance of PP in the various environments decreased in the order non-chlorinated water, air and chlorinated water. For PA-GF, the FCG resistance in chlorinated water was reduced with increasing chlorine content at least in the range from 1 to 10 mg/l.

To prevent the spread of waterborne diseases, a sufficient water disinfection is essential for meeting hygiene standards for potable and other tap water worldwide. Chlorine is the most widely utilized and the most affordable water disinfectant. Due to the increasing application of polymeric materials in water supply systems, there is a great need for adequate test methods that are capable of determining the crack growth resistance of polymers under superimposed mechanical loading and exposure to chlorine. Hence, a novel test arrangement was designed and implemented on a conventional electrodynamic test machine that permits for such superimposed mechanical-environmental loading conditions in a cyclic manner. Simultaneously, it allows for the determination of the quasi-automatic determination of the fatigue crack growth kinetics via an optical crack length measurement system. The test arrangement was developed to ensure tests with cracked round bar and compact type specimens. By using sodium hypochlorite in a controlled system under continuous flow, preventing also the faster decrease in reactive chlorine content at elevated temperatures, constant chlorine contents in the range between 0.1 and 10 mg/l over the complete testing time are assured. Fatigue crack growth results for a polypropylene pipe fitting grade and a polyamide pipe push-fitting grade used as model materials and tested at different temperatures and chlorine concentrations are compared and contrasted to highlight the potential of this novel test procedure. As expected, for both materials, the more critical test environment with the lowest crack growth resistances was found to be the liquid environment with the highest chlorine content.

https://www.pe100plus.com/PPCA/Fatigue-crack-growth-testing-in-chlorinated-water-at-elevated-temperatures-Test-equipment-and-test-procedure-p1662.html

April 11, 2023

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Effect of beta-nucleation on aging and crack growth resistance of polypropylene exposed to chlorinated water

Joerg Fischer, Paul J. Freudenthaler, Patrick R. Bradler, Reinhold W. Lang, Susan C. Mantell

Papers # 2018 Las-Vegas

This research addresses the effect of nucleation on the global aging behavior and the fatigue crack growth (FCG) resistance of commercial alpha- and beta-nucleated polypropylene random copolymer pipe grades (PP-R) when exposed to chlorinated water (5 mg/l free chlorine) at an elevated temperature of 60°C. Comparing the two PP-R grades, for the alpha-nucleated PP-R a significantly higher embrittlement due to exposure to hot chlorinated water was obtained in tensile tests with micro-sized specimens. In the FCG experiments with cracked round bar specimens, the beta-nucleated PP-R also outperforms the alpha-nucleated type in non-chlorinated water. Experiments with PP-beta in chlorinated water revealed a significantly reduced FCG resistance, most likely caused by enhanced local crack tip aging.

In many world regions, water is polluted with bacteria, viruses and parasites, and disinfection of contaminated water is required as a prevention of waterborne diseases. Chlorine is the most widely utilized and the most affordable water disinfectant, as it is easy to use and highly efficient against different kinds of waterborne pathogens. In this context, it is well known that polyolefins in general exhibit a significant degree of aging when exposed to water disinfectants. However, for the case of polypropylene (PP), little information is available on how the aging behavior and crack growth resistance in chlorinated water environments is affected by the material morphology. Hence, the aging behavior and crack growth resistance of two commercial PP random copolymer pipe grades was systematically investigated. One of the PP grades was of a conventional alpha-nucleated type (PP-alpha), whereas the other was specifically beta-nucleated (PPbeta). Material exposure and testing was performed at an elevated temperature of 60°C, and under environmental conditions of non-chlorinated and chlorinated water, the latter containing 5 mg/l chlorine. In addition to global aging and fatigue crack growth (FCG) experiments, tensile tests and DSC experiments were conducted. While for the microsized specimens of PP-alpha the exposure to chlorinated water at 60°C resulted in significant embrittlement after 1000 h, beta-nucleated PP-R exhibited a high resistance to chlorinated water exposure. In the FCG experiments, PP-beta turned out to be superior to PP-alpha under non-chlorinated water environment. Furthermore, in chlorinated water crack growth rates for PP-beta were found to be higher than in non-chlorinated water.

https://www.pe100plus.com/PPCA/Effect-of-beta-nucleation-on-aging-and-crack-growth-resistance-of-polypropylene-exposed-to-chlorinated-water-p1669.html

April 4, 2023

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FLOWABLE FILL FOR PLASTIC PIPE

Amster Howard

# 2021 Amsterdam

Flowable fill is used for many applications, but mainly for pipe trench embedment and backfill. There are three ways that using flowable fill can be kind to the environment. Because flowable fill is self-leveling and has a strength greater than the native soil, the trench cross section can be minimized. This means less excavation which means less energy used to excavate the trench, handle the spoil pile, and to backfill the trench. In urban areas, pipeline installation can proceed quicker which means reducing traffic delays, traffic detours, truck traffic, business interruptions, and the impact on the community. Secondly, flowable fill can be made using many waste products or recycled materials. Flowable fill is basically a mixture of cementitious material, aggregate, and water. Admixtures can be used for special circumstances, but are not necessary. Typically, flowable fill is thought of as a mixture of Portland cement, concrete sand, and potable water. It is usually batched at a ready-mix plant and transported to the site in transit mixers. However, since low strength is a desirable property of flowable fill, materials not usually considered for concrete can be used. Class C flyash, cement kiln dust, and waste by-products of coal fired electricity plants have been used in place of Portland cement. Recycled concrete, Class F flyash, foundry sand, and aggregate plant by – products have been used as aggregate. Using these recycled products and waste materials in flowable fill keeps them out of the landfills. The third way that flowable fill can be sustainable is to use the native soils excavated from the trench as the aggregate in the flowable fill mix. The flowable fill can be mixed using trench-side mixing equipment or portable batch plants that move along with the pipe installation. Using the soil excavated from the trench reduces spoil pile waste, spoil pile handling, importing aggregate materials, and transit mixer traffic from ready -mix plants Sustainability is achieved through less time for excavation, less handling of soil excavated from trench, less hauling of materials (both to and from construction sites), and reuse and recycling. This all means less energy consumption: In many cases, these reuse and minimizing methods result in flowable fill that can be competitive with compacted earth fill.

article source: https://www.pe100plus.com/PPCA/FLOWABLE-FILL-FOR-PLASTIC-PIPE-p1731.html

Maret 27, 2023

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SLOW CRACK GROWTH IN POLYETHYLENE PIPES: FRACTURE SURFACE EVIDENCE FOR THE SLOW CRACK GROWTH MECHANISM IN ACCELERATED TESTS

Mark Boerakker, Rudy Deblieck, a Harm Caelers, Arno Wilbers, Tine Boonen a DSM, Britta Gerets, Mirko Wenzel

# 2021 Amsterdam

Components made of plastic are facing ever-increasing demands with respect to their production, use and durability. This also holds for gas and drinking water pressure pipes made of high-density polyethylene (PE-HD), where service lifetimes of up to 50 years and in some cases even 100 years are required. One of the most important failure modes determining the lifetime is slow crack growth induced failure. This failure mode needs to be assessed by means of accelerated test methods. Several accelerated methods have been developed recently. Decent correlations between these recent tests and the earlier established (slower) methods have been reported. In the absence of real life examples the validation of the above-mentioned tests is examined in this paper through the use of existing deformation and failure models of craze propagation and craze-crack transition, coupled to crack growth kinetics, the outcome of which can be translated into the molecular network condition via the surface energy. The validity of these deformation and failure models for acceleratedtests will be connected to the analysis of the fracture surface textures found in accelerated Full-Notch Creep Tests (aFNCT) for a set of polyethylene materials and further to the results of the Strain Hardening Test (SHT).

source: https://www.pe100plus.com/PPCA/SLOW-CRACK-GROWTH-IN-POLYETHYLENE-PIPES-FRACTURE-SURFACE-EVIDENCE-FOR-THE-SLOW-CRACK-GROWTH-MECHANISM-IN-ACCELERATED-TESTS-p1745.html

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Abraison Resistance Improvement of a High Density Polyethylene by Cross-Linking for Manufacture of Mine Tailings Transportation Pipes

Patricia Perdiz Fernandez, Miguel Angel Molano Niampira, Felipe Salcedo Galán, Felipe Álvarez Torres

PE 100+ association leads permeation tests for H2 ready certification

Fatigue crack growth testing in chlorinated water at elevated temperatures – Test equipment and test procedure

Effect of beta-nucleation on aging and crack growth resistance of polypropylene exposed to chlorinated water

FLOWABLE FILL FOR PLASTIC PIPE

SLOW CRACK GROWTH IN POLYETHYLENE PIPES: FRACTURE SURFACE EVIDENCE FOR THE SLOW CRACK GROWTH MECHANISM IN ACCELERATED TESTS

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Patricia Perdiz Fernandez, Miguel Angel Molano Niampira, Felipe Salcedo Galán, Felipe Álvarez Torres

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