Kimiko Ema

Radiolytic degradation of a crown ether for extractability of strontium

ABSTRACT Dicyclohexano- 18-crown-6 (DC18C6), dissolved in chloroform, 1-octanol, toluene or cyclohexane, was irradiated by 60Co γ-rays. Radiolytic destruction of DC18C6, measured by gas chromatography, decreased in the order: chloroform > cyclohexane > 1-octanol > toluene. Distribution coefficients in the solvent extraction of strontium from nitric acid solution were measured. These distribution coefficients were minimally affected by γ-irradiation in toluene solution, but decreased with the absorbed dose in chloroform solution. It was suggested that the distribution coefficient for the liquid-liquid extraction system was influenced by radiolytic products. The effect of radiolytic products on the distribution coefficients was evaluated by considering DC18C6 remaining in the organic phase after irradiation. The distribution coefficient measured for the organic phase with radiolytic products was larger than that without radiolytic products. The radiolytic products were thus shown to contribute to the increa...

Thermal Expansion Coefficient of Unidirectional High-Strength Polyethylene Fiber Reinforced Plastics at Low Temperature

High-strength polyethylene fiber (Dyneema®, DF) has a negative linear thermal expansion coefficient in the direction of the fiber. Thermal expansion coefficients of fiber-reinforced plastics are of important applications in cryogenic use. The purpose of this study is to construct the engineering technology for the thermal strain of DF reinforced plastics (DFRP) for cryogenic engineering. In this study, we investigate the thermal expansion coefficient of unidirectional high-strength DF reinforced plastics (UD-DFRP) in which DFs with different tensile moduli (15–134 GPa) and thermal expansion coefficients are used. Furthermore, using the thermal expansion coefficient and tensile modulus of each DF fiber and the matrix resin, the thermal expansion coefficients of the DFRPs are estimated by the rule of mixtures and are compared with the measured values. The results indicate that the thermal expansion coefficient of UD-DFRP behaves in a similar way to that expected from calculations based on the rule of mixtures. In addition, relationships concerning the difference between the calculated and measured values, the difference in the thermal expansion coefficient of the fiber and the resin, and the surface treatment of the fiber (adhesivity), as well as the diameter of the fiber (the area of the interfacial bonding) are studied. The results show that all of these influence the thermal expansion coefficient of UD-DFRP. The design of negative thermal expansion coefficient of UD-DFRP is established.

Effect of molecular orientation on the radiolysis of polyethylene in the presence of oxygen

Abstract Gas evolution, oxygen consumption, and change of mechanical property induced by the γ-irradiation of ultra-high molecular weight polyethylene (UHMW-PE) fiber were studied, and compared with those of high density PE (HDPE). Samples were irradiated in oxygen under pressure from 0 to 60 kPa by 60Co γ-ray up to 1.0 MGy at room temperature. For irradiation under vacuum, G(H2) is 2.4 and G(CH4) is 2.0 × 10-3. In the presence of oxygen, G(H2) was about the same, and the G-values for other hydrocarbons were more than 20 times those under vacuum. The tensile strength of the fiber was decreased greatly by irradiation in oxygen.

Solvent Effect in Isotope Exchange Reaction of Strontium by Liquid Chromatography using a Cryptand (2B,2,2) Polymer

Abstract Strontium isotopes were fractionated using liquid chromatography with a cryptand (2B,2,2) polymer as a stationary phase. In this study, we observed that the single stage isotope enrichment factor of 84Sr shows the following order, water[6.4×10−3]>MeOH[4.9×10−3]>DMF[1.1×10−3]. The enrichment factors observed in this study did not show a mass‐dependent profile, indicating that the mass‐independent isotope effect affects isotope enrichment phenomena. The mass‐dependent and the mass‐independent isotope effects that influence the enrichment factor of 84Sr are related to the donor number linearly, implying that the solvation strongly affects the isotope effect.

Effect of Hydrogen Atmosphere on Radiation-Induced Gas Evolution from Polyisoprene

Polyisoprene was irradiated in hydrogen atmosphere by 60Co γ-rays. The evolved gases were methane, ethane, ethylene, propane, propylene and butane. With respect to saturated hydrocarbons, the yields increased with increasing pressure of hydrogen. On the contrary, the yields of unsaturated hydrocarbons decreased. The G-value of methane in hydrogen of 1 MPa was about four times larger than that in vacuum for irradiation of cis-polyisoprene (Cis) at 160 kGy. The gas evolution from trans-isomer (Trans) was about the same as that from Cis. The yields of gases from gloves made of natural rubber were smaller than those from Cis or Trans.

Radiation Grafting of Thermo-Responsive Gel onto Poly (vinyl chloride)

温度応答性ハイドロゲル材料であるN-イソプロピルアクリルアミド (NIPAAm) の温度応答の機能性を損なうことなく力学的強度を向上させるために, 同時照射放射線重合法による汎用材料との複合化を試みた。NIPAAmは水溶液中で効率良く放射線重合し, ポリ塩化ビニル (PVC) フィルム表面に結合した。得られたグラフトフィルムを洗浄してもPVCに結合したNIPAAm部位は除去されず, PVCに温度応答変形作用が付与できることがわかった。

Interaction of Tritium with Polyethylene

ABSTRACT Polyethylene (PE) was exposed to tritium gas at about 1 atm pressure. Low density polyethylene (LDPE) was more labeled than high density polyethylene (HDPE) was. Tritium labeling was enhanced at higher temperature. The rate of specific activity of HDPE was 2.5×108 Bq/g atm hr. n-Eicosane was molded to a small spherical shape, and the activity depended on the surface area and the averaged specific activity was 7×107 Bq/g atm hr.

Effect of atmospheric hydrogen on the radiation-induced gas evolution from polybutadiene

Abstract The evolution of lighter hydrocarbon molecules induced by the γ-irradiation of polybutadiene was studied. Samples were irradiated in hydrogen atmosphere from 0 to 1 MPa by 60 Co γ-ray up to 160 kGy at room temperature. With respect to saturated hydrocarbons, the yields increased with increasing hydrogen pressure. On the contrary, the yield of unsaturated hydrocarbon decreased. The mechanism of the radiolysis of polybutadiene in the presence of hydrogen was discussed.