Studies on petroleum sulphonates: Correlation between their chemical structure and the oil—Water emulsion stability characteristics

The average molecular weight distribution, emulsion stability of oil—water emulsion, the chemical structure of the hydrocarbon portions of petroleum sulphonates, and surface active properties have been determined with a view to establishing a correlation between the chemical structure of petroleum sulphonates and their emulsion stability characteristics. It has been found that the emulsion stability of oil—water emulsions imparted by sodium petroleum sulphonates depends on: (i) average molecular weight of sodium petroleum sulphonates; (ii) their molecular weight distribution; (iii) oil—water interfacial tension; (iv) hydrophile—lipophile balance values. The structural parameters which predominantly effect the emulsion stability are the ratio of the percentage distribution of carbon atoms in paraffin side chains to the percentage distribution of carbon atoms, the aromatic rings (C_P/C_A), the relative proportions of long chain mono-aromatics and the orientation of the sulphonate group relative to the paraffin alkyl chains in the molecules.     

Some studies on the swelling behavior of polyethylene

When polymers are extruded from a capillary, the amount of extrudate swelling is generally found to be a function of shear rate and capillary dimensions. Experiments with polyethylene now show that when shear rate is replaced by an average transit time in the capillary, postextrusion swell becomes a function of transit time only. Plots of swell versus transit time are independent of the applied stress and reduce to a single line for capillaries of different dimensions. The swell was found to be dependent upon the average molecular weight and the molecular weight distribution. Little correlation, however, was found with the amount of high molecular weight fractions.     

Eigenschaftskennfunktionen thermisch hergestellter polystyrole unterschiedlichen molekulargewichts und unterschiedlicher molekulargewichtsverteilung

Mechanical properties and melt flow behaviour have been measured on thermal polystyrenes in order to study the effect of different molecular weight and different molecular weight distribution. The mechanical properties (impact strength, tensile strength and flexural strength) were found to depend upon a critical molecular weight M_w = 1.5 × 10⁵, where the polystyrenes reached ultimate strength. An influence of molecular weight distribution only can be observed when the average molecular weight is near the critical molecular weight limit. The broader the distribution, the poorer are mechanical properties. Injection molded specimens with different molecular weight distribution but equal average molecular weight showed different molecular orientation and different anisotropic mechanical properties. On the basis of equal orientation the narrow distributed specimens showed higher mechanical strength in direction of orientation. The broader the distribution, the higher the elastic properties of melt. An optimum of physical properties and ease of fabrication will be obtained with narrow molecular weight distributed polystyrenes with an average molecular weight slightly above the critical molecular weight limit.     

Zur nachkondensation von polyamiden im teilkristallinen zustand

The molecular weight of polyamides can be changed by postcondensation in the solid state. The equilibrium molecular weight distribution in the partially crystalline polyamide can be calculated using reasonable assumptions. Under equal post-condensation conditions the calculation yields a higher molecular weight average for the partially crystalline material as compared with the amorphous one, while the type of the distribution function (SCHULZ-FLORY) remains nearly unchanged.     

基于聚合物分子量分布的乙烯淤浆聚合工艺优化

分子量及分布是聚合物生产过程中极其重要的质量指标,但目前的技术水平并不能实现分子量及其分布的实时测量,基于反应机理的动态建模是实现其软测量的重要方法。以乙烯淤浆聚合工艺为研究对象,基于聚合机理,分别以聚合物的平均分子量和分子量分布为目标,以循环气中氢气乙烯比为决定变量,采用稳态优化方法求取聚合物生产的工艺条件。结果表明:以平均分子量为优化目标所得的结果与分析值的偏差较大,虽然聚合物的平均分子量符合要求,但聚合物的分子量分布曲线与所需产品的分子量分布曲线之间的最大误差可达0.092;而以分子量分布曲线为目标所得的最大误差只有0.069。因此,以分子量分布曲线作为目标的优化方法明显比常规的以平均分子量为目标的优化方法优越。     

煤制烯烃基长链烷基二甲苯合成研究

采用无水三氯化铝与多卤代烷组成的络合物催化体系，研究了以煤制烯烃某一馏分段和混合二甲苯为原料合成煤制烯烃基长链烷基二甲苯。采用条件实验法得出的较佳工艺参数是：起始反应温度为室温，混合二甲苯/煤制烯烃的质量比为2∶3，相当于物质的量之比2.2～2.5∶1，催化剂用量为反应液总量的1/110(质量分数)，反应时间为60 min，得到的长链烷基二甲苯的含量在80%以上；计算得到其平均分子量约为302.5，相当于十四烷基二甲苯的平均分子量，具有一定的分子量分布，是更好的生产烷基芳基磺酸盐的原料，并在30 L反应器中进行了放大实验。     

Calibration procedures in gel permeation chromatography

Procedures for the determination of the log molecular weight vs. elution volume calibration relation are reviewed for linear homopolymers. The calibration curve is readily established with narrow molecular weight distribution fractions. For broad molecular weight distribution fractions the peak molecular weight at the peak elution volume of a fraction's gel permeation chromatogram has to be calculated from average molecular weights. When well-characterised fractions of the polymer requiring analysis are unavailable, a calibration curve can be established by procedures which assume that the hydrodynamic volume of a polymer molecule in solution controls fractionation in gel permeation chromatography. These universal calibration procedures require information on Mark-Houwink viscosity constants or polymer unperturbed dimensions. The validity of hydrodynamic volume as the universal calibration parameter is discussed with special reference to the goodness of the solvent for a polymer and polymer polarity. Examples are given of the various calibration procedures which are employed in the determination of molecular weight distribution and average molecular weights for poly(methylmethacrylate), polyethylene and polyisoprene.     

Star oligomers for low VOC polyurethane coatings

Conclusion  Hydroxyl functional star oligomers prepared by ring-opening polycondensation have a narrow molecular weight and composition distribution. Such oligomers give a solids/viscosity advantage over linear structures at the same molecular weight and can be used in low VOC two component polyurethane coatings. The solids/viscosity advantage is a combination of the highly branched structure and the narrow molecular weight distribution. Acrylic polyols formulated at the same molecular weight/polarity/average functionality and hydroxyl value give poorer drying properties. This difference can be explained by the fact that the free radical polymerisation technique leads to polymer compositions having a broad molecular weight and functionality distribution and high fractions of polymer with a low functionality. The potlife of acrylic polyols based formulations is adversely affected by the higher fractions of high molecular weight material and with a high average functionality. In low VOC polyurethane formulations star oligomers need to be formulated within a narrow range of compositions (TG, polarity), functionality and molecular weight to get an optimum balance of drying properties and potlife.     

改性腐植酸钾对钻井液动电性质影响的研究

腐植酸钾与某些单体共聚后，生成了改性腐植酸钾，改变了其分子的结构和平均分子量的分布，从测定的实验数据可以得到，改性腐植酸钾的动电性质发生了改变，其原因与其分子结构和平均分子量分布有关。     

Molecular weight distribution of phenol-formaldehyde resols by high performance gel permeation chromatography

Resol resins are particularly difficult to characterize with respect to molecular weight because of the large amounts of caustic soda (10–20% w/w) which they contain. A method is described for solubilizing these materials using trichloroacetic acid, such that molecular weight distribution can be measured using a normal gel permeation chromatography system with μ-Styragel columns and tetrahydrofuran as solvent.     

Low-angle laser light scattering–aqueous size exclusion chromatography of polysaccharides: Molecular weight distribution and polymer branching determination

A low-angle laser light scattering detector (LALLS) used with size exclusion chromatography (SEC/LALLS) has been applied for the determination of molecular weight, molecular weight distribution (MWD), and degree of branching of polysaccharides in 0.5N NaOH aqueous solution. Data from both detectors [differential refractive index (DRI) and LALLS] are used to calculate the absolute molecular weight at each point in a sample chromatogram. The correct average molecular weight and MWD can be obtained without calibration methods used in conventional SEC. As a consequence of this technique, Mark—Houwink coefficients can be predicted from a single broad-distribution, homopolymer without recourse to time-consuming fractionation methods. Moreover, the hydrodynamic volume separation mechanism of SEC can be exploited with the SEC/LALLS method to gain information about polymer branching. In the studies described in this paper, SEC/LALLS has been employed to obtain data about the branching parameters g_v and g_M for samples of amylose, amylopectin, starch, and glycogen. For three homopolymers (amylose, amylopectin, and glycogen), branching frequency (as measured by chemical means), and the branching parameters (g_v and g_M) are inversely related. This trend is consistent with theoretical predictions. For starch, a nonhomogeneous branching distribution is observed as a function of molecular weight.     

Molecular weight and polydispersity measurements of polystyrene by quasielastic light scattering

The molecular weight and polydispersity of a polydisperse polystyrene sample was measured by quasielastic light scattering. The molecular weight distribution of the polymer was represented by the Schultz distribution. The weight average molecular weight and polydispersity of distribution was adjusted until the quasielastic light scattering spectra calculated for the distribution agreed with the measured spectra. The calculation was repeated using the logarithmic normal distribution for the polymer. The calculated value of the weight average molecular weight is accurate and insensitive to the assumed molecular distribution function. However, the calculated values of the polydispersity are only of fair accuracy. Thus quasielastic light scattering gives values of the weight average molecular weight at least as accurate as elastic light scattering and gives a crude estimate of the polydispersity of the polymer.     

Mechanical and thermal properties of an alternating methyl methacrylate styrene copolymer

The copolymer resulting from the polymerization of methyl methacrylate and styrene in the aqueous phase was tested for its mechanical and thermal properties. The usual procedure to obtain such a copolymer is by radical polymerization, but it can be done also by an ionic solution polymerization and in most cases the copolymer obtained has a statistical polymer arrangement. As this polymer is made by a complex mechanism in the presence of zinc chloride and water, it has many interesting features. The polymerization itself in the presence of water has a good industrial appeal as it simplifies considerably the operations as well as eliminates the suspension phase solvent cost. Another feature is the molecular weight distribution; we have two definite nearly monodisperse groups of polymers—one of these groups has an average molecular weight of 10⁷. The thermal properties of the polymers were studied as functions of the polymerization conditions and a mathematical expression was derived relating these factors. The mechanical properties of this, polymer compares favorably to available industrial products.     

The influence of molecular weight on the melt rheology of polypropylene

Melt viscosity and melt elasticity data were obtained over a broad range of temperatures and shear rates on a series of four polypropylenes of different molecular weight but approximately the same molecular weight distribution. The superposition technique was used with both temperature and molecular weight to shift flow curves for all four materials at three temperatures each along the shear rate axis to generate a master flow curve at a given temperature and molecular weight. For polypropylenes of this type, and molecular weight distribution shift, factors which can be used to extend the useful range of experimentally obtained flow data were determined. The dependency of apparent viscosity on weight average molecular weight at shear stresses as high as 10⁶ dynes/cm² is shown. The dependency of melt elasticity on molecular weight and temperature is discussed.     

橡改型CPE专用HDPE树脂剖析

通过熔体流动速率仪、梯度密度计、差示扫描量热仪、凝胶渗透色谱仪、物理吸附分析仪、粒度分析仪、扫描电镜等分析了橡改型氯化聚乙烯(CPE)专用高密度聚乙烯(HDPE)树脂的基本物理性能、热性能、结构、表面形貌等。结果表明,橡改型CPE专用HDPE树脂具有低蜡含量、中等重均相对分子质量、较窄相对分子质量分布且呈单峰分布、高熔点、高结晶度等特点;具有较大的比表面积、细粉(粒径小于125μm)和粗颗粒(粒径大于500μm)含量较低,表面呈微孔结构;国产料具有更大的平均粒径、孔容。     

Molecular structure of high melt strength polypropylene and its application to polymer design

We report a numerical technique to investigate the branching process of linear Ziegler-Natta polypropylenes. Using an iterative procedure, linear chains are created based on the molecular weight distribution (MWD) of linear Ziegler-Natta polypropylenes as determined by GPC. By varying one parameter, MWDs of polymers with various levels of branching are simulated, and the simulated MWDs agree very well with experimental GPC data of branched polymers. From the simulation, the average branching parameters as well as the branching distributions of the polymers can be obtained. The branching information is related to the moments of the MWD, and a criterion of the onset of gelation is proposed. The melt flow rate (MFR) is correlated with the weight-average molecular weight. These relationships make it possible to design a polymer having a prescribed MFR.     

苯乙烯连续搅拌釜式本体聚合工业过程模拟

采用了机理分析建模法对苯乙烯工业本体预聚过程进行了模型化研究，并通过对流体在反应器中混合模式的分析，表明预聚釜可视作全混流（CSRT）反应器模型，此外对热聚合机理中的引发级数和终止反应进行了考察，利用预聚釜的工业数据确立了三分子引发，同时考虑偶合和歧化终止以及向溶剂链转移的反应机理模型，并选取了合适的动力学参数，然后利用工业装置采集的数据进行了模拟，从宏观转化率，平均分子量和微观分子量分布两个方面对模型进行了验证，模拟结果和工业数据符合得较好，该模型方程不仅能模拟稳态，非稳态预聚过程，同时也为装置开发新产品，改造扩建，优化操作方案等提供了理论基础。     

Modeling of molecular weight distribution of propylene slurry phase polymerization on supported metallocene catalysts

A mathematical model of the molecular weight distribution (MWD) based on a particle growth model and the kinetic scheme is developed to simulate the MWD of the slurry phase propylene polymerization on a silica-supported metallocene catalyst by means of the equations of moments. The model is used to predict molecular weight distribution, including the number-average molecular weight, the weight-average molecular weight, and the polydispersity index. The results show that the mass transfer has great influence on the polymerization reaction, and it can broaden the MWD especially; moreover, the MWD can be evaluated by simulation; the average molecular weight increases as pressure or temperature, and MWD shifts to long chain lengths as the effective diffusion coefficient increasing thought the influence is not remarkable; furthermore, the MWD's simulation results are calculated, which fit greatly with the experimental data.     

液相法制备BZP族磷酸盐陶瓷粉体分散性研究

用共沉淀法合成了单相的BaZr4(PO4) 6粉体 ,研究了两种不同的分散方法制得的BZP粉体的粒度分布及其烧结体的力学性能。结果表明 :与用有机高分子分散剂PEG改性处理相比较 ,采用低分子有机溶剂分散处理所制得的BZP粉体具有较窄的粒度分布 ,平均粒径 1 6 μm～ 1 8μm ,在同样的烧结条件下 ,烧结体的抗压强度也明显优于前者。另外 ,在液相反应中控制pH =7～ 1 1 ,可有效防止反过程中团聚体的形成