Hiromi Yamakita

Tungsten disulfide prepared from ammonium tetrathiotungstate as a catalyst with high performance for the selective hydrogenation of CO2 to CO

For the hydrogenation of CO2 to CO, tungsten disulfide prepared by decomposing ammonium tetrathiotungstate, was found to exhibit high activity and good selectivity (>99.9%). Large surface area, viz., 64 m2g−1, is primarily responsible for the high activity, while the lack of activity in CO methanation for the good selectivity.

THERMAL OXIDATIVE AGING OF ORGANIC LATENT-HEAT THERMAL STORAGE MATERIALS

ABSTRACT In order to estimate the extent of thermal oxidative aging of organic latent-heat thermal storage materials, the thermal deterioration of paraffin and stearic acid derivatives was investigated by applying the following heating-cooling cycles in air, which simulated the daily temperature fluctuation by insolation, over 6 months: 8-hour holding at 150° as the highest temperature in a day followed by 5-hour holding at 30° as the lowest temperature. The resultant decrease in heat of fusion or crystallization, that in weight, and so forth were discussed in relation with the progress of oxidation. The thermal stability of those materials differed markedly with their substituents. The addition of radical scavengers brought the remarkable suppression on the progress of thermal deterioration of those materials in open atmosphere.

Radiation resistivity of polyacenaphthylene-grafted polyethylene

Abstract Thin poly (ethylene-g-acenaphthylene) films prepared by the vapor-phase grafting method were subjected to the γ-irradiation in air, and various changes in tensile and structural properties of the film were investigated by comparing with those of the untreated or crosslinked polyethylene film. Polyethylene got to lose its inherent necking property by oxidative degradation and to be brittle-fractured by the irradiation dose less than 100 Mrad in air. The polyacenaphthylene-grafted polyethylenes (extent of grafting, ∼ 54 by 100( P-P ° ) P ° ), however, kept their ductility up to 200 Mrad or more, and the rate of increase in elastic modulus as well as yield strength with the increasing irradiation dose was considerably lower than that of untreated or crosslinked polyethylene. The effect of the grafting extent, and that of the irradiation dose-rate on the fracture energy were also examined. The weight increase of polyethylene due to the oxygen consumption and the resulting formation of carbonyl group which proceeded proportionally with the irradiation dose were remarkably suppressed by the grafting, whereas the double bond formation seemed to be unaffected by it. The grafted film held the original content of gel fraction unchanged during the irradiation in air, but the average molecular weight of the sol fraction decreased gradually. Meanwhile, the gel fraction of the crosslinked polyethylene was degenerated by a small dose of irradiation. The analysis of gaseous products revealed the formation of water, methanol, acetaldehyde and so forth from the irradiated grafted film. The grafting procedure and the subsequent irradiation of the grafted film did not affect the degree of crystallinity of the backbone polyethylene. The role played by the grafted polyacenaphthylene for endowing the radiation resistivity to polyethylene and its inherent limitation in effect were discussed from the structural point of view of the grafted film.

Radiation graft polymerization of solid monomers by vapor-phase method

Abstract Radiation graft polymerization proceeding in the sublimation vapors of solid monomers exhibits a peculiar feature differed from that of the ordinary liquid-phase graft polymerization, and also from that of the vapor-phase graft polymerization utilizing gaseous monomers or vapors of liquid monomers. In this experiment, polyethylene and poly(ethylene-co-vinyl acetate) films were irradiated with the γ-rays in the atmosphere of α,β-disubstituted ethylenic solid monomer such as maleimide, maleic anhydride, or acenaphthylene, or in that of the binary solid comonomers. Graft polymerization was characterized by little occluded homopolymer formation and high efficiency of grafting. When the monomer vapor was not sorbed into the polymer film, the reaction took place on the surface of film with the formation of fine granules of the grafted polymer. The oxygen gas coexisting with the monomer vapor did not inhibit the grafting reaction, but merely retarded it to the same extent as nitrogen. Thus the graft polymerization of unsorbed polar monomer as maleimide or maleic anhydride onto polyethylene was considered to proceed on the surface by a solid-state polymerization mechanism. When the monomer was sorbed and dispersed monomolecularly into the backbone polymer film, the grafting reaction seemed to proceed mainly in the inner part of the film. Grafting of copolymer took place when a film was exposed under γ-rays to a combined vapor of binary solid monomers chosen as an electron donor-acceptor combination, and in some cases nearly-alternating copolymer grafting was achieved even if one of the binary comonomers could not be sorbed into the film. The effects of the affinity of film to monomers on the rate of grafting and on the composition of grafted copolymer were also investigated by adopting poly(ethylene-co-vinyl acetate) films of various compositions and their surface-modified ones.

RADIATION-INDUCED SOLUTION POLYMERIZATION OF BIS (

The γ-ray-induced solution polymerization of bis(β-chloroethyl) vinylphosphonate (CEVP) in several kinds of organic solvents was carried out, and the reaction mechanism was studied. Polymerization ...

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ABSTRACT Novel immobilized photosensitizers were prepared and the effect of them on the photoisomerization of norbornadiene(NBD) to quadricyclene(QC) was studied in the heterogeneous phase. Chloromethylstyrene(ClMeST) was graft-polymerized by γ-ray irradiation onto polyethylene(PE) powders or crosslinked PE sponges which had been prepared so as to possess large surface areas. Then aromatic ketocarboxylic acids were combined on the grafted PE by ester linkage. The resultant insoluble photosensitizers were very effective for photoisomerization of NBD. When immobilized photosensitizers were used, the dependency of quantum yield for QC formation and byproduct formation on the wavelength was comparable to that obtained by low molecular weight aromatic ketones as homogeneous photosensitizers. The effect of the quantity of immobilized photosensitizers, the agitation technique, etc. on the quantum yield were also investigated.

-CHLOROETHYL) VINYLPHOSPHONATE.

N-フェニルマレイミド-アセナフチレン, N-ラウリルマレイミド-アセナフチレンおよび N-ラウリルマレイミド-アセナフテンの3種の2成分系における固相重合の研究を行なった。これらの2成分系について差動熱量計により測定した結果, それぞれの系において, 共融混合物を生成することがわかった。N-フェニルマレイミド-アセナフチレン系においては, 生成ポリマーの元素分析, X線回折, 濁り度滴定の結果より, この固相重合はほとんど各成分の単独重合から成ると推定された。一方 N-ラウリルマレイミドーアセナフチレン系においては,重合速度は共融組成において極大に達し,また生成物の濁り度滴定曲線はホモポリマーのどちらとも異なることが示された。X線回折の結果によれば, ラウリルマレイミド・ホモポリマーは結晶性であるのに対し, 共融組成において生成したポリマーはほとんど無定形であった。これらの結果および生成ポリマーの組成の結果より, この系においてはホモポリマーとともに, 長いブロック連鎖をもたないコポリマーが生成し, また共重合はモノマー分子の動き易い状態で進行すると結論した。N-ラウリルマレイミド-アセナフテン系においては, 非重合性のアセナフテンが重合に及ぼす効果について検討した。