Hiroshi Sakami

Preparation of delaminated clay having a narrow micropore distribution in the presence of hydroxyaluminum cations and polyvinyl alcohol

The pillaring of Na-montmorillonite with cationic oligomers of hydroxyaluminum (COHA) in the presence of an aqueous solution of polyvinyl alcohol resulted in the formation of a clay having a large surface area and pore volume. The pore-size distribution determined from a N2 adsorption/desorption hysteresis was narrow and centered at about 25 Å. The peak width at half height in the distribution curve was < 5 Å. As a result of delamination, the layer structure of the prepared clay was found from X-ray powder diffraction measurements to be lost. Short-range ordering, however, still existed in this delaminated clay, because exchangeable cations in the montmorillonite completely exchanged with Al3+, a requisite step for pillaring.The order of adding the starting materials (Na-montmorillonite, polyvinyl alcohol, and COHA) greatly affected the surface area and the pore volume of the delaminated clay. Two orders of addition (Namontmorillonite, then COHA, then polyvinyl alcohol; and COHA, then Na-montmorillonite, then polyvinyl alcohol) gave no measurable surface area and pore volume. Two other orders of addition (polyvinyl alcohol, then COHA, then Na-montmorillonite; and polyvinyl alcohol, then Na-montmorillonite, then COHA) gave surface areas of 107 and 160 m2/g and pore volumes of 0.13 and 0.29 cm3/g, respectively. The amounts of the COHA solution and polyvinyl alcohol added greatly influenced the surface area and pore volume of the delaminated clay. Both properties increased monotonically with increasing amount of added polyvinyl alcohol, and increased to a maximum and then decreased with increasing amount of added COHA solution. The maximum surface area of the prepared delaminated clay was 330 m2/g.

Studies on controlled pores of polyethylene pore materials. V. Control of layer-like pores of polyethylene and paraffin mixtures intercalated with two guest particles.

高結晶性ポリエチレン (PE) 及び液体パラフィン (Pa) 混合物に少量のポリオキシエチレンステアリルエーテル (POS) あるいはステアリン酸カルシウム (SCa) を加えて種々の倍率に圧延し, Paを有機溶剤により抽出し, PE層間に微細孔を形成させた. その多孔体の微細孔構造を見掛けの比容, 小角X線及び窒素ガス吸着後の脱離による表面積測定により検討した. この多孔フィルムはPaとの混合比 (C) が0.50～1.00, 圧延温度115℃の条件で3から15倍に圧延すると, 圧延方向に層状の空孔が形成した. そのうちCが0.67と1.00で圧延倍率が7～12倍の条件では167～212m2/gの大きい表面積が得られた. POS及びSCaはPa中で異なった大きさのミセル粒子 (ゲスト) を作り, それがPE配向層 (ホスト) にインターカレーションして支柱を形成すると推察された. 最も微細な層状の多孔体では65Åのホストと45Åのゲストが多量に積み重なった構造であった.

Unique pore structure formed in montmorillonite in the presence of polyvinyl alcohol and aluminium chlorohydroxide

Porous montmorillonite, having a sharp pore size distribution (most abundant pore size ca. 30 A), was prepared by the ion exchange of Na–montmorillonite with aluminium chlorohydroxy oligomers in the presence of polyvinyl alcohol.

X-ray diffraction and DSC measurements of frozen sodium-montmorillonite. Amount of the unfrozen water and its location.

未焼成および種々の温度で焼成したナトリウム-モンモリロナイト(Na-Mt)について含水量の異なる試料を-73℃ で凍結させて,X線小角散乱法により底面間隔(d(001))を測定した。焼成温度が600℃ 以下ではNa-Mtは水により膨潤するが,700℃ 以上の温度で焼成するともはや膨潤し得なかった。これらの試料について示差走査熱量計(DSC)により融解熱を測定したところ,膨潤可能なNa-Mt中には0.459-Water/g-Clayの未凍結水が認められた。膨潤能を失なったNa-Mt中にはこのような未凍結水は存在しないので,未凍結水はNa-Mt粒子群が構成する粒子間隙に存在するのではなく,層内空間に存在することが結論された。未凍結水量と層内空間容積から凍結モンモリロナイト中の未凍結水の密度(2.0g/cm3)が推算された。

Tensile Properties and Stress Relaxation of Ultradrawn Polyethylene

The tensile properties and stress relaxation of ultradrawn high density polyethylene were investigated in terms of the deformation process of microfibril. As for microfibril, composed of crystal blocks and amorphous regions, it was discussed whether the molecular chains in crystal blocks were pulled out or not by the tension which was applied to tie chains, connecting crystal blocks. The pulling stress was calculated thermodynamically in relation to melting occurred upon pulling out of chains. The calculated stress was comparable to the observed tensile stress at 20-120°C. The pulling out of chains was conclued to be a cheif process during the stretch of ultradrawn materials.The stress decreased and reached a constant residual value after a sufficient progress of of relaxation. The comparison of the observed stress with the thermodynamically calculated pulling stress indicated that the folded chains and the extended chains in crystal blocks were pulled out during the process of stress relaxation and finally the stress relaxation was completed when the stress was reduced to a value required for pulling out a folded chain.