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991.
992.
The binary lanthanide catalyst for 1,3‐butadiene was invented for 40 years ago. However, it has not been employed in commercial application due to its poor solubility and low activity. Nanosized neodymium chloride (NdCl3) was prepared in tetrahydrofuran (THF) medium through dissolution, chelation, and colloidal formation steps. Anhydrous NdCl3 was dissolved in THF, and ca. 1.5 THF molecules were coordinated. In the colloidal formation step, THF was slowly replaced with the addition of cyclohexane, and pale blue nuclei, nanosize below 200 nm, were formed. The structural studies for NdCl3 · xTHF using X‐ray powder diffraction (XRD) and scanning electron microscope (SEM) indicate that high ordered crystallinity is decreased with reduced particle size from trigonal prismatic to porous sphere structure. Nano NdCl3, obtained as colloidal state in cyclohexane, was activated with Al(iBu)3 and Al(iBu)2H at room temperature and employed for 1,3‐butadiene solution polymerization. The nanosized Nd catalysts showed high activity (1.0 ~ 1.3 × 105 g/Nd mol · h), which is comparable to that of the ternary neodymium catalyst Nd(neodecanoate)3/AlEt2Cl/Al(iBu)3. The microstructures of polybutadiene, cis, trans, and vinyl, are about 96.0, 3.5, and 0.5%, respectively. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 1279–1283, 2005 相似文献
993.
The clouding points and equilibrium concentrations of PEG/dextran/water and PEG /ammonium sulfate/water systems were experimentally
determined for different molecular weights of PEG by titration method and direct determination of concentrations. In phase
diagrams of PEG-water with ammonium sulfate or dextran, the addition of salt or dextran induced the phase separation of PEG-rich
phases near the PEG-lean phases having the different partitioning of PEG. The concentrations of PEG in PEG-rich phases increase
as the amounts of PEG or salt and dextran increase, while the concentrations of PEG in aqueous media decrease in any cases.
The higher the molecular weight of PEG has, the wider the two-phase regions are. In dextran DT10 systems, the partition coefficients
of egg albumin into PEG-lean phases increase with concentrations of dextran and the molecular weight of PEG. In ammonium sulfate
systems, the partitioning coefficients showed a maximum, having lower partitioning at the very high and low concentration
of salts. It is also observed that as the amounts of albumin increase, the partitioning of albumin into PEG-lean phase increases. 相似文献
994.
改性SBS胶粘剂的研制 总被引:14,自引:3,他引:14
以丙烯酸酯类混合单体对SBS热塑性弹性体在混合溶剂中接枝共聚,添加混合型增粘树脂,研制成接枝改性的SBS胶粘剂,具有较高的初粘力和终强度。探讨了单体比例、引发剂用量、反应温度、反应时间、增粘树脂对胶液性能的影响。 相似文献
995.
Yeong-Kyeun Paek Jung-Ho Ahn Gyeung-Ho Kim Suk-Joong L. Kang 《Journal of the American Ceramic Society》2002,85(6):1631-1633
The densification behavior of a 3-mol%-Y2 O3 -doped ZrO2 (3Y-ZrO2 ) has been investigated under N2 and O2 atmospheres. Powder compacts have been sintered at 1550° and 1400°C for various times. The density of the specimen sintered at 1550°C is higher in N2 than in O2 , while the contrary result is obtained in the case of the specimen sintered at 1400°C. Such results can be explained in terms of nitrogen solubility and oxygen vacancy in a ZrO2 matrix. Because nitrogen solubility into the ZrO2 increases with an increase in heat-treatment temperature, leading to the formation of oxygen vacancy, the densification rate becomes higher. The present study thus shows evidence of nitrogen solubility into the ZrO2 and its role on the densification behavior of 3Y-ZrO2 . 相似文献
996.
997.
998.
T. J. Shin H. K. Park S. W. Lee B. Lee W. Oh J.‐S. Kim S. Baek Y.‐T. Hwang H.‐C. Kim M. Ree 《Polymer Engineering and Science》2003,43(6):1232-1240
A series of aromatic polyimides composed of well‐defined conjugation units were synthesized form 5,5′‐bis(4‐aminophenyl)‐2,2′‐bifuryl (PFDA) and 2,2′‐bis(furyl) benzidine (FurylBZ) with various dianhydrides. The synthesized polyimides emit blue to green light with a quantum yield of 7.3–14.9%, depending on the polymer backbone. In particular, PFDA‐based polymers exhibit extremely narrow photo‐luminescence. The structure, thermal stability, refractive index and dielectric properties of the polymer films were also determined. 相似文献
999.
Solid circulation characteristics in an internally circulating fluidized bed with orifice-type draft tube 总被引:1,自引:0,他引:1
Sang Done Kim Yo Han Kim Seon Ah Roh Dong Hyun Lee 《Korean Journal of Chemical Engineering》2002,19(5):911-916
Effects of superficial gas velocities to a draft tube, to an annulus section and particle size on the solid circulation rate
(G,) have been determined in an internally circulating fluidized bed (0.28 m I.D. × 2m high) with an orifice type draft tube.
The solid circulation rate from the draft tube to an annulus section increases with increasing gas velocities to the draft
tube(U
d
) and annulus section (Ua) and consequent increase in pressure drop across the orifice (ΔPor). However, the values ofG
s
decrease by 7–21% with increasing particle size from 86 to 288 μm. The pressure drop across the orifice increases with increasingU
d
andU
a
. However, ΔPor decreases by 5–23% with increasing particle size. To predictG
s
in an internally circulating fluidized bed, a correlation is proposed as a function of ΔPor
This paper is dedicated to Professor Dong Sup Doh on the occasion of his retirement Korea University. 相似文献
1000.
An axial dispersion of gas in a circulating fluidized bed was investigated in a fluidized bed of 4.0 cm I.D. and 279 cm in
height. The axial dispersion coefficient of gas was determined by the stimulus-response method of trace gas of CO2. The employed particles were 0.069 mm and 0.147 mm silica-sand. The results showed that axial dispersion coefficients were
increased with gas velocity and solid circulation rates as well as suspension density. The experimentally determined axial
dispersion coefficients in this study were in the range of 1.0-3.5 m2/s. 相似文献