Temperature dependence of X-ray diffractograms of amorphous lignins and polystyrenes

Temperature dependencies of X-ray diffractograms of lignins and polystyrene derivatives were investigated. Bulky side groups, such as methoxyl functionalities were found to expand intermolecular distance, while hydroxyl groups reduce its mean value. Intermolecular distance expands discontinuously at the temperature corresponding to the glass transition temperature.     

Upper and lower critical solution temperatures for polystyrene in methyl cyclopentane and in dimethyl cyclohexane

The demixing of polystyrene in methyl cyclopentane, and in dimethyl cyclohexane has been investigated, and the upper and lower critical solution temperatures established for several polymer molecular weights. In the former solvent both upper and lower θ temperatures can be defined, but not in the latter where cloud point curves for the upper and lower critical temperatures coalesce for high molecular weights. The Patterson theory of polymer solutions has been applied to the data, and the characteristic free volume and exchange energy parameters have been evaluated. The lower critical solution temperatures are nearly the same in cyclopentane and methyl cyclopentane due to a compensation between the free volume and contact interaction terms. Solvent size effects are considered in order to explain the differences in the interaction of solvent with polymer.     

The second virial coefficient of polydisperse polymer samples in a good solvent

Summary In this paper we present analytical expressions for the osmotic and light-scattering second virial coefficients of polydisperse polymer samples in a good solvent. They are derived using the Schulz and the Lognormal molecular weight distribution respectively. The effect of interpenetrating coils is taken into account. Comparison is made with expressions already derived by Casassa using a hard sphere model. The reduction of the obtained expressions to simple scaling laws is discussed.     

Effects of pH,salt type,and ionic strength on the second virial coefficients of aqueous bovine serum albumin solutions

The osmotic pressures of aqueous bovine serum albumin (BSA) solutions were measured at different pH (3.6, 4.6, 5.6, and 7.6) in combination with different concentrations (0.01 M, 0.1 M, 1 M, and 3 M) of salts (sodium, pottasium, and lithum) by using a Wescor colloid membrane osmometer. The osmotic second virial coefficients for BSA were determined from the experimental osmotic pressure. Predominant forces between protein molecules were measured at the various pH, ionic strength, and type of salt. These experimental data were utilized to determine the depth of square-well potential, which accounts for specific interactions between protein molecules at various conditions. This article is dedicated to Professor Chul Soo Lee in commemoration of his retirement from Department of Chemical and Biological Engineering of Korea University.     

干熄炉环形风道内环墙破损的原因及处理

宣钢焦化厂干熄焦装置环形风道内墙出现破损坍塌现象,分析表明,墙砖的自身缺陷、耐火泥强度的降低以及风道内长期的变温和变压环境,是造成内墙破损的主要原因。为防止内墙的整体坍塌,及时对其进行了修补砌筑并在环部严重凸起处浇筑支撑柱。修补后干熄炉总体运行良好。     

Selective solvation of polystyrene in tetralin/cyclohexane mixtures

Refractive index increments and density increments have been measured at 307.6K for polystyrene in binary solvents of 1,2,3,4-tetrahydronaphthalene (tetralin, TET) and cyclohexane over the whole range of solvent composition. Comparison of these increments with the corresponding values obtained at dialysis equilibrium (i.e. at constant chemical potential of low molecular weight species) yielded the coefficients of selective adsorption (γ₁) of TET by the polymer. Positive values of γ₁ were exhibited at solvent compositions up to 78% (v/v) of the thermodynamically better solvent, TET. Theoretical curves of γ₁ vs. composition were calculated on the basis of, firstly, relevant interaction parameters and, secondly, interaction parameters in conjunction with solubility parameters. Both procedures afforded self-consistent results, which were, however, uniformly lower than the experimental values of γ₁.     

An unexpected ring carboxylation in the electrocarboxylation of aromatic ketones

The electrocarboxylation of various aromatic ketones, carried out in N-methyl-2-pyrrolidone (NMP) in a diaphragmless cell equipped with a carbon cathode and an aluminium sacrificial anode, yielded, among the products, the target hydroxy acids, the corresponding alcohols and pinacols and, quite surprisingly, detectable amounts of substituted benzoic acids and cycloexene carboxylic acids. These compounds arise from a never reported before electrocarboxylation on the aromatic ring, respectively, for substitution of an aromatic hydrogen and from an addition reaction. For example, the electrocarboxylation of acetophenone gave rise to the substituted benzoic acids in ortho, para and meta positions, while for 2,2-dimethylpropiophenone the substituted benzoic acid in meta position and the cyclohex-5en-1,3-dicarboxylic acid derivative were detected among the products.     

Prediction of the molecular‐weight dependence of mutual diffusion coefficients in polymer‐solvent systems

The ability of a proposed theory to describe the molecular weight dependence of mutual diffusion coefficients for polymer–solvent systems is examined by comparison with experimental measurements. Good agreement between experiment and theory was observed for two very different polymer molecular weights. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 2778–2779, 2003     

Thermodynamic parameters of poly(lactic acid) solutions in dialkyl phthalate

Some of thermodynamic parameters for poly(lactic acid) (PLA)/dialkyl phthalate systems have been investigated. Both poly(dl-lactic acid) (PDLLA) and poly(l-lactic acid) (PLLA), which are stereoisomers of PLA, were used and a series of 1,2-dialkyl phthalates with different alkyl chain, from methyl to hexyl, was adopted as a solvent. Theta temperatures of PLA/dialkyl phthalate system were determined and subsequently the second virial coefficient and the interaction parameter were evaluated. Theta temperature was determined by the extrapolation of the highest liquid-liquid phase separation temperatures and Zimm plots were constructed by static light scattering to obtain second virial coefficient and z-average radius of gyration. Second virial coefficient and z-average radius of gyration was examined quantitatively as a function of temperature and solvent. Thermodynamic parameters that could not be obtained experimentally were calculated based on the Flory-Huggins theory.     

The Influence of a Phase Transition in Poly(oxyethylene)/Poly(oxypropylene)/Poly(oxyethylene) Block Copolymer Surfactants on the Properties of Material Adsorbed from Dilute Aqueous Solution

In this study the adsorption of poloxamer block copolymer surfactants to polystyrene latex has been studied at a range of temperatures. It has been noted previously that the adsorption first falls, then rises and falls again as the temperature is increased, due to the existence of a phase transition in aqueous solutions of these surfactants at specific temperatures, which may be a critical micelle temperature. The present study shows that the hydrophobicity of the surface changes in a manner related to the amount of poloxamer adsorbed (i.e. is greatly influenced by the temperature of adsorption in relation to the transition temperature). The coating layer thickness, however, is essentially unchanged by the temperature of adsorption (i.e. not related to the amount adsorbed), but is influenced by the temperature at which the sizing was undertaken. This is due to dehydration of the poly (oxyethylene) with increasing temperature. The data presented here provide a possible explanation for the changes in biological distribution of poloxamer coated particles which occur when they are injected into animals.     

宝钢活性石灰回转窑结圈机理研究

为了揭示宝钢石灰回转窑结圈机理,通过湿化学分析、X-射线衍射分析和扫描电子显微镜观察等手段分析了窑皮的化学组成、相组成和显微结构.高温模拟实验揭示:结圈形成条件是低熔物作为黏结相,煤燃烧后的灰分与氧化钙反应生成低熔点氧化物,这些低熔点氧化物黏结氧化钙,随着该过程进行,结圈物变厚.煤中灰分在高温下形成液相是燃煤石灰回转窑结圈的关键.     

The Influence of a Phase Transition in Poly(oxyethylene)/Poly(oxypropylene)/Poly(oxyethylene) Block Copolymer Surfactants on the Properties of Material Adsorbed from Dilute Aqueous Solution

In this study the adsorption of poloxamer block copolymer surfactants to polystyrene latex has been studied at a range of temperatures. It has been noted previously that the adsorption first falls, then rises and falls again as the temperature is increased, due to the existence of a phase transition in aqueous solutions of these surfactants at specific temperatures, which may be a critical micelle temperature. The present study shows that the hydrophobicity of the surface changes in a manner related to the amount of poloxamer adsorbed (i.e. is greatly influenced by the temperature of adsorption in relation to the transition temperature). The coating layer thickness, however, is essentially unchanged by the temperature of adsorption (i.e. not related to the amount adsorbed), but is influenced by the temperature at which the sizing was undertaken. This is due to dehydration of the poly (oxyethylene) with increasing temperature. The data presented here provide a possible explanation for the changes in biological distribution of poloxamer coated particles which occur when they are injected into animals.     

大型冶炼厂环集烟气镁法脱硫装置的设计特点

介绍了氧化镁脱硫技术在大型冶炼环集烟气治理上的实践应用,重点描述了脱硫系统的主要设备和设计要点,为相似工程提供参考。     

The influence of zeolite acidity for the coupled hydrogenation and ring opening of 1-methylnaphthalene on Pt/USY catalysts

The influence of framework and extraframework composition of USY zeolite on the catalytic performance of bifunctional Pt/USY (1 wt.% Pt) catalysts for the coupled hydrogenation and ring opening of 1-methylnaphthalene (1-MN) has been studied on a continuous fixed bed high pressure reactor. All Pt/USY catalysts showed very high methylnaphthalene (MN) conversions under the reaction conditions studied (T=300–375 °C, P=4.0 MPa, WHSV=2 h⁻¹, H₂/1-MN=30 mol/mol). Product yields and selectivities were mainly determined by the zeolite composition (i.e. acidity). Selectivity to products with the same number of carbon atoms than the feed (C11) increased, at constant temperature, with decreasing the Brönsted acidity of the USY zeolite, that is, with decreasing the concentration of framework Al (FAL) and increasing extraframework Al (EFAL). Selectivity to high cetane ring opening products (ROP=C11-alkylbenzenes (C11AB) and C11-alkylcycloalkanes) within the C11 fraction was higher for the less acidic catalysts. A maximum yield of ROP of ca. 15 wt.% at a C11 yield of ca. 73 wt.% was obtained at 350 °C (P=4.0 MPa, WHSV=2 h⁻¹, H₂/1-MN=30 mol/mol) for a USY zeolite with an intermediate degree of dealumination (a₀=24.33 Å) and containing all the EFAL (bulk Si/Al ratio of 2.6). For this catalyst, a slight increase in ROP yield (ca. 17 wt.%) at similar C11 yield (ca. 74 wt.%) was obtained by working at lower temperature (300 °C) and lower space velocity. Increasing the reaction pressure above 4.0 MPa had only a marginal influence on product yields and selectivities.     

苯乙烯在MCM-41介孔材料中聚合的研究

The polymerization of styrene in the media of MCM-41 is carried out by means of host-guest polymerization of styrene in MCM-41 mesoporous material with the aim to investigate the effects of interface and confinement of MCM-41 on host-guest interactions. Detailed physical properties of the mesoporous MCM-41 material containing polystyrene is characterized by XRD(X-ray diffraction), FT-IR(Fourier transform infrared), TGA(thermal gravimetric analysis), and nitrogen adsorption-desorption isotherms. We also find a great increase in the glass transition temperature of guest polystyrene influenced by the confined geometry of the host by differential scanning calorimetry(DSC).     

A Comparison of the Phase Behaviour of Polystyrene in Cycloalkanes and n-Alkanes

Cloud point curves for several narrow fractions of polystyrene dissolved in cycloheptane, in cyclooctane and in cyclodecane have been established, and the critical solution temperatures extrapolated to give the respective temperatures. All three cycloalkanes are good solvents for the polymer. A comparison is made between the phase behaviour of polystyrene dissolved in cyclic alkanes and in n-alkanes using free volume polymer solution theory.     

聚丁二烯橡胶改性高抗冲聚苯乙烯的性能研究

介绍了聚丁二烯橡胶的用量、种类和结构以及粒径对高抗冲聚苯乙烯性能的影响     

The use of bagasse in the preparation of fireclay insulating bricks

Acidic insulating refractory bricks were prepared by mixing kaolin and grog with polystyrene (PS) beads up to 1.5% and bagasse up to 5% (by weight). This latter is a fibrous waste residue from the sugar cane industry. The bricks were dried and fired at 1250°C in a cycle lasting for 16 hours. The bricks were tested for water absorption, porosity, bulk density, cold crushing strength and thermal conductivity at three different temperatures (400, 600, and 800°C). It was concluded that bricks containing 1% PS and 3% bagasse abided by ASTM C155-97 for C-30 type insulating refractories with a bulk density of 1.01 g/cm³, a cold crushing strength of 4.08 MPa, and a thermal conductivity of 0.37 W/K/m at 800°C.     

聚苯乙烯在空气中热降解的化学动力学研究

研究了聚苯乙烯在空气中的热降解化学动力学机理。实验结果显示,聚苯乙烯在空气中热降解存在两个失重阶段:第一阶段,温度范围从250.59℃开始至397.41℃,在此范围内,大约有85%的聚苯乙烯发生了分解;第二阶段为397.41～515.29℃,大约有15%的聚苯乙烯发生分解。动力学计算拟合结果表明,聚苯乙烯的主要失重阶段(第一阶段)的热解符合二级化学反应方程,其平均表观活化能Ea值为166.19kJ/mol,lnA值为32.15。     

Study of multiple melting behaviour of syndiotactic polystyrene in β‐crystalline form

A series of syndiotactic polystyrene (SPS) samples in β‐crystalline form were prepared by cooling from the melt at various rates. The effects of cooling rate from the melt, DSC heating rate and annealing on the multiple melting behaviours of β crystals were investigated by differential scanning calorimetry (DSC) and temperature modulated differential scanning calorimetry (TMDSC), from which the nature of the multiple melting behaviour was determined. The two melting endotherms of β‐form crystals were considered to arise from the occurrence of simultaneous melting, recrystallization and remelting processes in the melting region. It is suggested that the lower melting endotherm is due to the melting of imperfect β crystals originally present in the sample, whereas the higher melting endotherm comes from the melting of recrystallized SPS crystals, ie more perfect β crystals that formed during the DSC scanning process. © 2000 Society of Chemical Industry