Some observations on the long‐term behavior of stabilized polyethylene

Howard, John B.; Gilroy, H. M.

doi:10.1002/pen.760150406

Cited by 44 publications

(11 citation statements)

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“…11), for stabilized HDPE straight line Arrhenius plots are reported too [103].However, deviations from Arrhenius behaviour are found for LDPE, especially when temperatures at which the polymer is molten are also taken into account [103]. Degradation of PP during processing leads to chain scission, resulting in a decrease of the molecular weight and a reduction of the polydispersity [69,104].…”

Section: -Degradation During Processingmentioning

confidence: 99%

“…Peroxide concentrations as calculated according to the above-mentioned equations (lines) and determined by an iodometric method (points) during a peroxide decomposition experiment at 70 °C with polypropylene pre-oxidized for several times at 70°C [108] Reprinted from Polymer Degradation and Stability, Vol 51, P. Gijsman, J. Hennekens and J. Vincent, The mechanism of the low-temperature oxidation of polypropylene, [95][96][97][98][99][100][101][102][103][104][105]1993, , with permission from Elsevier This decay could not be described with first or second order decomposition kinetics. Assuming that the titrated concentration of peroxides consists of two fractions (both decomposing according to first order kinetics), the calculated data could be fitted with the experimental values (see Fig.…”

Section: Fig 12mentioning

confidence: 99%

“…Also shown are the measured peroxide concentration (∆) and the calculated concentration of rapidly decomposing peroxides (+) after the above mentioned decomposition times. Reprinted from Polymer Degradation and Stability, Vol 51, P. Gijsman, J. Hennekens and J. Vincent, The mechanism of the low-temperature oxidation of polypropylene, [95][96][97][98][99][100][101][102][103][104][105]1993, with permission from Elsevier.…”

Section: Fig 12mentioning

confidence: 99%

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Review on the thermo-oxidative degradation of polymers during processing and in service

Gijsman

2008

E-Polymers

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Section: -Degradation During Processingmentioning

confidence: 99%

Section: Fig 12mentioning

confidence: 99%

Section: Fig 12mentioning

confidence: 99%

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Review on the thermo-oxidative degradation of polymers during processing and in service

Gijsman

2008

E-Polymers

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“…This would typically result in a drop in activation energy, resulting in lifetimes that are greatly reduced from the linear, Arrhenius predictions. Work done at Bell Laboratories many years ago [29] com%rned that significant drops in the effective degradation activation energies can occur at low temperatures for oxidation of stabilized polyolefin materials, causing low-temperature predictions, based on linear extrapolations of high temperature results, to be overly optimistic by orders of magnitude. For stabilized low-density polyethylene materials, typical activation energies of 120 kJ/mol and greater at higher temperatures were found to be reduced to around 80 kJ/mol at 80°C [29] and still further to -60 kJ/mol at 45°C [30].…”

Section: Ultrasensitive Oxygen Consumption Measurements To Test Extramentioning

confidence: 99%

Methods for Predicting More Confident Lifetimes of Seals in Air Environments

Gillen

Celina

Keenan

2000

Rubber Chemistry and Technology

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We have been working for many years to develop improved methods for predicting the lifetimes of polymers exposed to air environments and have recently turned our attention to seal materials. This paper describes an extensive study on a butyl material using elevated temperature compression stress-relaxation (CSR) techniques in combination with conventional oven aging exposures. The results initially indicated important synergistic effects when mechanical strain is combined with oven aging, as well as complex, non-Arrhenius behavior of the CSR results. By combining modeling and experiments, we show that diffusion-limited oxidation (DLO) anomalies dominate traditional CSR experiments. A new CSR approach allows us to eliminate DLO effects and recover Arrhenius behavior. Furthermore, the resulting CSR activation energy (EJ from 125°C to 70"C is identical to the activation energies for the tensile elongation and for the oxygen consumption rate of unstrained material over similar temperature ranges. This strongly suggests that the same underlying oxidation reactions determine both the unstrained and strained degradation rates. We therefore utilize our ultrasensitive oxygen consumption rate approach down to 23°C to show that the CSR E~likely remains unchanged when extrapolated below 70°C, allowing very confident room temperature lifetime predictions for the butyl seal.

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“…As noted earlier, substantial evidence for non-Arrhenius behavior has now been shown for numerous polymeric materials 3,[5][6][7]19,[23][24][25][26][27][28][29] . The most compelling evidence comes from the monitoring of the same material property over an extended temperature range that is broad enough to confirm the non-Arrhenius character directly.…”

Section: Chloroprene (Neoprene) Cable Jacketing Materialsmentioning

confidence: 99%

Review of nuclear power plant safety cable aging studies with recommendations for improved approaches and for future work.

Gillen¹,

Bernstein²

2010

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Many U. S. nuclear power plants are approaching 40 years of age and there is a desire to extend their life for up to 100 total years. Safety-related cables were originally qualified for nuclear power plant applications based on IEEE Standards that were published in 1974. The qualifications involved procedures to simulate 40 years of life under ambient power plant aging conditions followed by simulated loss of coolant accident (LOCA). Over the past 35 years or so, substantial efforts were devoted to determining whether the aging assumptions allowed by the original IEEE Standards could be improved upon. These studies led to better accelerated aging methods so that more confident 40-year lifetime predictions became available.Since there is now a desire to potentially extend the life of nuclear power plants way beyond the original 40 year life, there is an interest in reviewing and critiquing the current state-of-the-art in simulating cable aging. These are two of the goals of this report where the discussion is concentrated on the progress made over the past 15 years or so and highlights the most thorough and careful published studies. An additional goal of the report is to suggest work that might prove helpful in answering some of the questions and dealing with some of the issues that still remain with respect to simulating the aging and predicting the lifetimes of safety-related cable materials. EXECUTIVE SUMMARYMany U. S. nuclear power plants are approaching 40 years of age and there is a desire to extend their life for up to 100 total years. Safety-related cables were originally qualified for nuclear power plant applications based on IEEE Standards that were published in 1974. The qualifications involved procedures to simulate 40 years of life under ambient power plant aging conditions followed by simulated loss of coolant accident (LOCA). Over the past 35 years or so, substantial efforts were devoted to determining whether the aging assumptions allowed by the original IEEE Standards could be improved upon. These studies led to better accelerated aging methods so that more confident 40-year lifetime predictions became available.In particular, three of the aging assumptions used were found to be overly simplistic. Thermal aging was typically carried out at a few high temperatures, then they were modeled with an Arrhenius function to derive an Arrhenius activation energy E a and finally the results were extrapolated to ambient conditions assuming no change in E a . Recent studies show that E a often drops at low temperatures, reducing the extrapolated lifetime. For radiation aging, an equal damage, equal dose assumption (e.g., no dose rate effects) was used. Careful studies have now shown that dose rate effects that reduce extrapolated material lifetime are both common and expected and come from several different mechanisms. Finally, for simulating combined radiation plus thermal environments, sequential aging (usually thermal aging followed by room temperature radiation aging) was allowed whereas rece...

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Some observations on the long‐term behavior of stabilized polyethylene

Cited by 44 publications

References 4 publications

Review on the thermo-oxidative degradation of polymers during processing and in service

Review on the thermo-oxidative degradation of polymers during processing and in service

Methods for Predicting More Confident Lifetimes of Seals in Air Environments

Review of nuclear power plant safety cable aging studies with recommendations for improved approaches and for future work.

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