共查询到10条相似文献,搜索用时 125 毫秒
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Heimei Yuki Koichi Hatada Koji Ota Ikuya Kinoshita Shunsuke Murahashi Katsuhiro Ono Yoshiyuki Ito 《Journal of polymer science. Part A, Polymer chemistry》1969,7(6):1517-1536
Polymerization of benzyl vinyl ether was carried out by BF3·OEt2, and the effects of polymerization conditions on the stereoregularity of the polymer were studied by NMR analysis. The polymerization at ?78°C in toluene gave a highly isotactic polymer. The isotacticity of the polymer was independent of the catalyst concentration but increased with a decrease in the initial monomer concentration and decreased slightly on raising the reaction temperature. When the polymerizations were carried out in toluene—nitroethane mixtures, a gradual decrease in the isotacticity and a rapid decrease in the molecular weight of the polymer were observed with increasing nitroethane in the solvent. The molecular weight of the polymer was almost constant, regardless of the catalyst concentration, and increased with increasing initial monomer concentration and decreasing polymerization temperature. When the polymerization was performed in toluene at ?78°C with a small amount of water or benzyl alcohol, a linear relationship was found between the reciprocal DP of the polymer and water or benzylalcohol concentration. The mechanisms of the initiation reaction and the stereoregulation in the polymerization were also discussed. 相似文献
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Nd—Al双金属活性体对异戊二烯的溶液聚合 总被引:3,自引:0,他引:3
近年来,对于稀土Ziegler-Natta催化剂活性体的研究比较活跃。使用催化剂活性体可以消除剩余烷基铝等因素对聚合反应的影响,比以前所用的多组分混合物的催化体系更客观地反映出聚合过程。我们在以前工作的基础上,从体系中分离出Nd-Al双金属活性体,并用于引发异戊二烯溶液聚合,探讨不同聚合条件下异戊二烯溶液聚合的规律,以利于对稀土催化聚合反应的深入了解。 相似文献
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TiCl4/MgCl2/clay compound catalyst was prepared by chemical reaction.Exfoliated polypropylene(PP)/clay nanocomposites were synthesized by in situ polymerization with this compound catalyst.Effects of polymerization temperature,polymerization time,propylene pressure,solvent consumption and pre-treat time of catalyst on catalyst activity and catalytic stereospecificity were studied.Under optimal conditions,activity of the nano-compound catalyst is about 88.3 kg/(mol Ti·h).Isotacticity of PP obtained in the nanocomposites is in the range of 89%-99%,and its melting temperature is about 159℃.The weight-average molecular weight of PP can reach 6.7×105 - 7.8×105,and the molecular weight distribution is between 7.7 and 7.9. 相似文献
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David P. Mobley 《Journal of polymer science. Part A, Polymer chemistry》1984,22(11):3203-3215
Reaction rate measurements show that a Michaelis-Menten model proposed earlier is inadequate to describe the full course of the polymerization of 2,6-dimethylphenol to poly(2,6-dimethyl-1,4-phenylene oxide). Modification of this model to include the effects of catalyst deactivation during the reaction and difference in reactivity between the monomer and other oligomers resulted in much greater accuracy. The kinetic constants in the modified model were influenced by reaction temperature, system composition, and method of catalyst component addition. 相似文献
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Hisao Yokota Masatsune Kondo Tsutomu Kagiya Kenichi Fukui 《Journal of polymer science. Part A, Polymer chemistry》1968,6(2):435-446
The kinetic behavior on the polymerization of formaldehyde with and without acidic catalyst, in liquid carbon dioxide, in the temperature range of 30 to 50°C. was investigated. In the polymerization without catalyst both the polymer yield and the degree of polymerization increased with reaction time and also with rising temperature. With acidic catalyst, such as acetic acid and dichloroacetic acid, both the polymer yield and the degree of polymerization increased more than that in the polymerization without catalyst. The overall rate of polymerization with and without acidic catalyst was expressed by the first-order rate equation with respect to monomer concentration. From the results it was concluded that the polymerizations belonged to a type of successive polymerization with rapid initiation and no termination. The rate constant and the activation energy of each elementary process of polymerization were estimated on the basis of the results. 相似文献
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《先进技术聚合物》2018,29(6):1870-1874
In this study, we have for the first time demonstrated that palladium chloride (PdCl2) is an efficient catalyst for ring‐opening polymerization of cyclohexene oxide in a solvent‐free condition. The polymerization product was in atactic structure, and reaction conditions, such as reaction temperature, time, and catalyst amount, showed effects on polymerization conversion yield, turnover number, and number‐average molecular weight of the resulting poly(cyclohexene oxide). PdCl2 catalysis follows a cationic ring‐opening mechanism. The polymerization result is highly determined by the chemical structure of the monomers. 相似文献
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A MATLAB program was developed to simulate polyurethane foaming reaction. Key reactions (including isocyanate–polyol and isocyanate–water) and dozens of primary side reactions were taken consideration into the simulation of polymerization. The model tracks reaction rates, component concentration profiles and the temperature profile for the reactions under different conditions respect to different catalyst types, amount of catalyst loading, reaction temperature and the reactivities of the monomers with each other. Tin based catalysts and amine based catalysts were applied into gel and foam recipes separately to evaluate the impact of each catalyst on both gel and blow reactions. The model predicts performances of diverse foam recipes and can be effective for “sensitivity studies” useful in designing form formulations. The simulations have been validated for estimating catalyst loadings, identifying the tradeoff between higher catalyst loadings versus preheating of reagents, and providing insight into fundamental mechanisms/reactions. 相似文献