The effect of γ‐irradiation on thermal strain of high strength polyethylene fiber at low temperature

Yamanaka, Akihiro; Izumi, Yoshinobu; Kitagawa, Tooru; Terada, Toru; Hirahata, Hiroshi; Ema, Kimiko; Fujishiro, Hiroyuki; Nishijima, Shigehiro

doi:10.1002/app.23550

Cited by 10 publications

(7 citation statements)

References 34 publications

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“…Second, the radiation cross-linking of the UHMWPE fiber restricts the mobility of molecular chains of polyethylene, and causes nonuniformity of stress in the fiber. 10,11 Additionally, the decrease in strength after γ-irradiation was found to be dependent on the absorbed dose. The higher the radiation dose, the greater the impairment to the mechanical properties of the fibers, which influences the lifetime and recyclability of the adsorbent.…”

Section: Introductionmentioning

confidence: 99%

Effects of Protective Shell Enclosures on Uranium Adsorbing Polymers

Haji

González

Drysdale

et al. 2018

Ind. Eng. Chem. Res.

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This study aims to evaluate the impact of shell enclosures on the uranium uptake of amidoxime-based polymeric adsorbents they contain. Researchers have observed that the tensile strength of the adsorbent's polyethylene backbone is degraded after γ-irradiation to induce grafting of the amidoxime ligand. A two-part system was developed to decouple the mechanical and chemical requirements of the adsorbent by encapsulating them in a hard, permeable shell. The water flow in six shell designs and an unenclosed adsorbent for control in a recirculating flume was analyzed via a novel method developed using the measurement of radium extracted onto MnO 2 impregnated acrylic fibers. Although the water flow was found to vary with enclosure design, orientation to the flow, and placement within the flume, little to no difference was observed in the uranium adsorption rate between all enclosures. The results of this study will be used to design a large-scale ocean deployment of a uranium harvesting system.

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Section: Introductionmentioning

confidence: 99%

Effects of Protective Shell Enclosures on Uranium Adsorbing Polymers

Haji

González

Drysdale

et al. 2018

Ind. Eng. Chem. Res.

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“…To improve properties such as thermal conductivity [1], low temperature thermal strain [2], and creep resistance of ultra-high molar mass polyethylene (UHMMPE) fibers, many researchers have undertaken efforts to crosslink these fibers using radiation [1,3,4,5,6,7,8,9,10,11]. Exposure to ionizing radiation produces alkyl free radicals (Figure 1) in both the crystalline and amorphous regions of the polyethylene, however subsequent reactions of these moieties occur in the amorphous phase.…”

Section: Introductionmentioning

confidence: 99%

Effect of Irradiation and Detection of Long-Lived Polyenyl Radicals in Highly Crystalline Ultra-High Molar Mass Polyethylene (UHMMPE) Fibers

2019

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To improve properties such as thermal conductivity, low temperature thermal strain, and creep resistance of ultra-high molar mass polyethylene (UHMMPE) fibers, several researchers have previously undertaken efforts to crosslink these fibers using radiation. Ionizing radiation is commonly used to crosslink bulk UHMMPE in other applications, such as artificial joints. However, UHMMPE fibers differ from bulk UHMMPE in that they have a higher crystallinity (approximately 85% to 90%) and are very highly oriented during manufacturing in which the fibers are stretched 50 to 100 times their original length. Thus, the amorphous fraction of the UHMMPE fibers is also highly ordered. Several experiments were conducted to crosslink the UHMMPE fibers using both low dose rate (gamma) and high dose rate (electron beam) irradiation, all in the absence of oxygen. In all cases, the tensile strength of the fiber was greatly reduced by the irradiation. The oxidation index was also measured for the irradiated samples, and oxidation was not found to play a major role in the reduction of tensile strength in the fibers after irradiation. While this work did not achieve the desired result of improving the mechanical properties of the UHMMPE fiber, a significant result was found. The electron paramagnetic resonance (EPR) spectrum of the UHMMPE fibers was measured shortly after irradiation, and a mixture of allyl and alkyl radicals were detected. The irradiated samples were stored in dark ambient conditions for at least six years, then reexamined using EPR for free radical characterization. Surprisingly, the gamma-irradiated samples showed clear evidence of long-lived polyenyl radicals present in the material. Free radicals are very reactive species that will typically migrate to the surface of the crystalline domain and decay in a relatively short time through various reactions in the amorphous regions. It is hypothesized herein that due to the high crystallinity and large anisotropy of the highly drawn UHMMPE fiber, the polyenyl radicals were trapped in the crystal phase and were unable to migrate and decay. An experiment was performed to test this hypothesis, by which samples of the irradiated fibers were heated to temperatures above first the alpha relaxation and then melting point of polyethylene, and EPR measurements were taken. Results showed that the polyenyl radical signal persisted below the Tm, but was rapidly eliminated upon melting of the crystals. These experiments support the hypothesis that the long-lived polyenyl radicals are trapped in the crystalline region of the polyethylene fibers.

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“…First, γ-irradiation causes the degradation of the UHMWPE molecular chain, thereby leading to a decrease in the molecular weight of polyethylene. Second, the radiation cross-linking of the UHMWPE fiber restricts the mobility of molecular chains of polyethylene, and causes nonuniformity of stress in the fiber (Yamanaka et al, 2006;Zhao et al, 2010).…”

Section: Motivationmentioning

confidence: 99%

Extraction of uranium from seawater : design and testing of a symbiotic system

Haji¹

2017

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Seawater is estimated to contain 4.5 billion tonnes of uranium, approximately 1000 times that available in conventional terrestrial resources. Finding a sustainable way to harvest uranium from seawater will provide a source of nuclear fuel for generations to come, while also giving all countries with ocean access a stable supply. This will also eliminate the need to store spent fuel for potential future reprocessing, thereby addressing nuclear proliferation issues as well. While extraction of uranium from seawater has been researched for decades, no economical, robust, ocean-deployable method of uranium collection has been presented to date. This thesis presents a symbiotic approach to ocean harvesting of uranium where a common structure supports a wind turbine and a device to harvest uranium from seawater. The Symbiotic Machine for Ocean uRanium Extraction (SMORE) created and tested decouples the function of absorbing uranium from the function of deploying the absorbent which enables a more efficient absorbent to be developed by chemists.The initial SMORE concept involves an adsorbent device that is cycled through the seawater beneath the turbine and through an elution plant located on a platform above the sea surface. This design allows for more frequent harvesting, reduced downtime, and a reduction in the recovery costs of the adsorbent. Specifically, the design decouples the mechanical and chemical requirements of the device through a hard, permeable outer shell containing uranium adsorbing fibers. This system is designed to be used with the 5-MW NREL OC3-Hywind floating spar wind turbine.To optimize the decoupling of the chemical and mechanical requirements using the shell enclosures for the uranium adsorbing fibers, an initial design analysis of the enclosures is presented. Moreover, a flume experiment using filtered, temperaturecontrolled seawater was developed to determine the effect that the shells have on the uptake of the uranium by the fibers they enclose. For this experiment, the AI8 amidoxime-based adsorbent fiber developed by Oak Ridge National Laboratory was used, which is a hollow-gear-shaped, high surface area polyethylene fiber prepared by radiation-induced graft polymerization of the amidoxime ligand and a vinylphosphonic acid comonomer.The results of the flume experiment were then used to inform the design and fabrication of two 1/10th physical scale SMORE prototypes for ocean testing. The 3 AI8 adsorbent fibers were tested in two shell designs on both a stationary and a moving system during a nine-week ocean trial, with the latter allowing the effect of additional water flow on the adsorbents uranium uptake to be investigated. A novel method using the measurement of radium extracted onto MnO 2 impregnated acrylic fibers to quantify the volume of water passing through the shells of the two systems was utilized.The effect of a full-scale uranium harvesting system on the hydrodynamics of an offshore wind turbine were then investigated using a 1/150th Froude scale wave tank test. These ...

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The effect of γ‐irradiation on thermal strain of high strength polyethylene fiber at low temperature

Cited by 10 publications

References 34 publications

Effects of Protective Shell Enclosures on Uranium Adsorbing Polymers

Effects of Protective Shell Enclosures on Uranium Adsorbing Polymers

Effect of Irradiation and Detection of Long-Lived Polyenyl Radicals in Highly Crystalline Ultra-High Molar Mass Polyethylene (UHMMPE) Fibers

Extraction of uranium from seawater : design and testing of a symbiotic system

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