EFFECTS OF LIQUID VISCOSITY ON RHEOLOGY OF CONCENTRATED SUSPENSIONS

This paper presents the experimental results on the effects of liquid viscosity on the rheology of concentrated suspensions of solid particles in Newtonian liquids. Specifically, the relative viscosity of a pseudoplastic suspension decreases as the viscosity of the suspending liquid increases, indicating excess energy dissipation in a less viscous liquid. In contrast, the relative viscosity of a Newtonian suspension is only slightly affected by the liquid viscosity. It is in excellent agreement with the value predicted from the rigid sphere model which neglects nonhydrodynamic interactions, and assumes zero particle-to-liquid relative velocity. The flow behavior indices of both concentrated suspensions are independent of the liquid viscosity.     

分散粒子粒度及其分布对聚醚多元醇流变行为的影响

考察了聚醚多元醇中分散粒子的粒径及分布、固含量、剪切速率和温度对其粘度的影响，指出了降低聚醚多元醇粘度的途径。     

CHARACTERISATION OF THE STRUCTURE OF CONCENTRATED, FLOCCULATED SUSPENSIONS

The structure and properties or concentrated, flocculated suspensions are of widespread importance with respect to separation, handling and related processes in the chemical and allied industries. To improve understanding of such systems it is essential that these materials be studied using methods which directly probe structure and structure-dependent characteristics. In this paper we describe investigations of floc structure using techniques which are suitable for examining morphology in concentrated dispersions, avoiding dilution, or other gross perturbation of the system, before or during measurement. From studies or electrolyte-coagulated and, in particular, polymer-flocculated suspensions a number of general principles are mapped out concerning the influence of basic parameters on the structure and properties of aggregated dispersions.     

CHARACTERISATION OF THE STRUCTURE OF CONCENTRATED,FLOCCULATED SUSPENSIONS

ABSTRACT

The structure and properties or concentrated, flocculated suspensions are of widespread importance with respect to separation, handling and related processes in the chemical and allied industries. To improve understanding of such systems it is essential that these materials be studied using methods which directly probe structure and structure-dependent characteristics. In this paper we describe investigations of floc structure using techniques which are suitable for examining morphology in concentrated dispersions, avoiding dilution, or other gross perturbation of the system, before or during measurement. From studies or electrolyte-coagulated and, in particular, polymer-flocculated suspensions a number of general principles are mapped out concerning the influence of basic parameters on the structure and properties of aggregated dispersions.     

MOLECULAR WEIGHT EFFECTS OF OLIGOMERIC DISPERSANTS ON AQUEOUS ALUMINA SUSPENSIONS

The objectives of this study are to synthesize an oligomer (75% acrylic acid, 15% acrylamide, and 10% methyl acrylate) with different molecular weights and determine the effects of molecular weight on the dispersing ability of the oligomers. Molecular weights were calculated using Proton NMR spectroscopy for end-group analysis. Rheology and adsorption measurements of aqueous alumina slurries at various polymer dosages were acquired at pH 9.5. Based on the results of these studies, it was concluded that the molecular weight of an oligomer does have a significant effect on alumina suspensions. Moreover, there is an optimum molecular weight at which suspension viscosity is the lowest due to the amount of oligomer adsorbed onto alumina particles. In this study, oligomer C (1970 g/mol) with 2 mg/g of alumina dosage in 0.50 volume fraction alumina suspensions yielded the lowest viscosity and highest adsorption. Viscosity and adsorption values increased above and below 1970 g/mol molecular weight. In summary, efficiency of a dispersant is essentially related to the conditions under which it is used. Therefore, it is important to optimize all conditions, molecular weight and charge interactions being most fundamental.     

集中缺陷对蜂窝材料面内动力学性能的影响

利用显式动力有限元ANSYS/LS-DYNA数值研究了三角形和四边形蜂窝材料中集中缺陷对其面内冲击性能的影响.研究结果表明,对于集中缺陷,除了缺陷率,缺陷集中区域的位置也是材料设计中需要考虑的重要指标.随着缺陷率的增加,蜂窝材料的平台应力和能量吸收能力迅速降低,但随着冲击速度的增加,缺陷的影响逐渐减弱.缺陷集中区域的位...     

聚苯胺悬浮液的电流变效应

以掺杂态的聚苯胺为悬浮颗粒，以硅油为分散介质，制得悬浮液，研究了它的电流变效应及其影响因素，如电场强度，剪切速率，悬浮液浓度，颗粒介电常数等。还研究了该体系的漏电流密度及其影响因素。实验表明，随着电场强度等的增大，悬浮液的电流变效应增大，同时漏电流密度也增大；而随剪切速率的提高，电流变效应及漏电流密度均减弱。     

铝熔体泡沫形成过程中粘度对孔结构影响

采用简便有效的测量搅拌电机功率的方法控制铝熔体泡沫化过程的粘度，研究了粘度、温度与孔结构的关系，随熔体表观粘度提高泡沫孔径变小。合适的表观粘度有利于提高泡沫孔径分布的均匀性、获得高的孔隙率、泡沫孔径随温度提高而增大。     

PES与热致液晶高分子共混物的流变性能

研究了ＰＥＳ与热致液晶聚合物（ＬＣＰ）ＨＢＡ／ＰＥＴ（６０／４０）共混物的转矩流变和剪切流变性能。加入２％～５％ＨＢＡ／ＰＥＴ（６０／４０）可使ＰＥＳ熔体在低剪切速率下的表观粘度下降２～４倍。共混物的粘流活化能也低于纯ＰＥＳ的活化能。加入少量ＬＣＰ（５％以下）可望大大改善ＰＥＳ的加工性能。     

SBS浓溶液流动行为与粘度模型的研究

研究了诸因素对丁二烯－苯乙烯嵌段共聚物（SBS1401）的环已烷浓溶液和甲苯浓溶液粘度的影响，上述溶液的质量百分数范围为2％－25％，温度范围为25℃-50℃。结果表明，溶液的粘度随浓度的增大而增加，随剪切力和剪切速率的增大而减上；溶液的流动曲线符合幂律定律，并根据所测定的数据，利用回归方法对实验数据进行了处理，获得了在一定温度下，描述本体系溶液粘度特性的两变量的半经验关联式。     

69.8m高冷却塔定向爆破拆除

介绍了一座双曲线钢筋混凝土筒式结构冷却塔的定向爆破拆除。阐述了冷却塔结构特点、爆破难点、总体拆除方案、设计参数的选择及飞石防护措施等。爆破取得预期效果,可为同类工程提供参考。     

集中药包和分集药包爆破效果的试验研究

在现场进行了集中药包与分集药包硐室爆破的大量模拟试验。文中对两种药包产生的爆破漏斗和抛掷堆积效果进行了分析 ,并就两种药包产生的爆破漏斗的上、下破裂线和深度以及最远抛距等参数的试验值与计算值进行了对比。同时 ,对分集药包最佳间距进行了研究。试验得出的结论是 :在定向爆破筑坝中 ,可以采用分集药包改善抛掷堆积效果 ;在按经验公式计算的药量不变的前提下 ,存在一个有利于抛掷堆积的分集药包“最佳间距”。     

聚砜/热致液晶共混体系的流变性

用流变仪对聚砜与一种半芳族聚酯液晶聚合物（ Ｔ Ｌ Ｃ Ｐ）共混体系的流变特性进行了研究。研究发现,共混体系的表观粘度均低于纯聚砜体系的粘度。表观粘度的大小与所添加的液晶聚合物的量有关,也与温度的高低及剪切速率的大小有关。 Ｔ Ｌ Ｃ Ｐ的加入可明显改善聚砜的加工性能。     

A STUDY OF MULTI-FUNCTIONAL ELECTROLYTIC OLIGOMERS AS DISPERSANTS FOR CONCENTRATED AQUEOUS ALUMINA SUSPENSIONS

ABSTRACT

The effects of dispersant charge density, active binding site density, and hydrophilic/hydrophobic balance on the rheology of concentrated aqueous alumina suspensions have been studied. Twenty-one three- and four-component oligomeric dispersants with varying monomer composition were synthesized by free-radical telomerization of acrylic acid (AA), acrylamide (AAm), methyl acrylate (MA), and sodium acrylamido-2-methyl-propanesulfonate (NaAMPS). The monomer compositions for the dispersants were varied between 40 and 75%, 3 and 50%, 3 and 30%, and 0 and 15% for AA, AAm, MA, and NaAMPS, respectively. Aqueous alumina suspensions of volume fraction 0.50 at pH 9.5 were obtainable with all the dispersants. Rheological measurements of these suspensions revealed that most of these dispersants produced suspensions with similar viscosity with only a few exceptions. Rheological comparison of these suspensions with suspensions produced with poly(acrylic acid) of molecular weight 1800 (PAA-1800) showed that a good number of the multi-component were more effective than the PAA-1800, This material is recognized as being one of the most effective dispersants for alumina suspensions under conditions used in this study, according to the unpublished ERC results. Zeta-potential measurements and adsorption studies gave a good indication that differences between PAA-1800 and the multi-component dispersants may be due to steric forces brought about by differences in dispersant conformation and adsorption behavior.     

取代基对芳脂族规则共聚酯液晶性能的影响EI

利用先合成复合单体,然后进行溶液缩聚的方法制备了含三芳香酯介晶单元组的芳脂族规则共聚酯,介晶单元的中心苯环分别为氯代/甲基取代/苯基取代。用热台偏光显微镜、DSC和X射线衍射研究了所得共聚酯的液晶行为,并重点研究了取代基对相变温度及液晶态稳定性的影响。     

熔体的粘性和弹性对LDPE／PS共混物形态的影响

研究了粘性和弹性对低密度聚乙烯／聚苯乙烯共混物形态的影响。结果表明，不相容聚合物在均匀剪切流动中的分散程度以及分散相的形状与组分的粘度比、相对弹性和体积分数有关。当分散相的粘性和弹性较基相大得多时，随分散相的体积分数增加，球状的液滴形成葡萄串状。若两组分的粘性和弹性相当，在适中的混合比下，分散相产生高度变形。不管组分的粘反比和弹性比大小，若分散相的体积分数非常低，共混物的主要形态皆为分散相的球状液滴分散在基体中。     

PMMA-PET共混体系流变性能

研究了PMMA含量小于7．5％的PMMA—PET共混体系的流变性能．结果表明，共混体系为切力变稀的非牛顿流体，随着共混体系中PMMA组分的增加，非牛顿指数呈减小趋势，粘度有一定下降；在280℃低剪切应力时，ηa随着PMMA组分的增加而上升，在高剪切应力时，则相反；共混体系的粘流活化能基本上都大于纯PET。     

热致性液晶聚合物的种类对环氧树脂共混物的结构和性能的影响

通过静态力学、动态力学实验方法,研究了热致性液晶聚合物(LCP)的种类对环氧树脂共混物在不同温度下的拉伸强度和应力-应变曲线的影响,通过TEM观察了共混物的相形态结构。结果表明,反应型液晶聚合物(LCPU)比其它种类的液晶聚合物对环氧树脂的改性效果更好;在不同温度下,其拉伸强度和应力~应变行为均比其它材料优越;固化物的动态力学结果表明,反应型的液晶聚合物键入了固化网络,出现新的松弛。TEM结果表明,反应型的液晶聚合物在基体材料中形成大小在纳米数量级的液晶聚集微区,没有反应基团的液晶聚合物PHBHT在10%的加入量下,与环氧的共混物结构也有液晶聚集微区产生,但是聚集区大小在微米量级。     

GMT压缩模塑流变行为研究

对GMT／PP圆盘试样在平行平板模间进行了轴对称200℃等温挤压流研究，由Instron试验机自动记录挤压过程中挤压力与合模速度和位移的关系，认为GMT基本上是各向同性的，除紧贴模具的树脂层无滑移外，其中的玻纤层均匀变形，厚度方向速度分布为平推流，获得了挤压流的流变学参数，并用拉伸流模型模拟了挤压力的变化历程，模拟计算值与实验结果在给定的范围内吻合得相当好。     

松香型聚氨酯发泡流变性研究

用自行设计的绝热发流变仪研究了松香型聚氨酯发泡流变性。用流变仪同时测得发泡过程温升、粘度和发泡高度对时间的关系。将温度和反应程度、反应热关联、显示反应动力学与发泡流变性的关系。考察了羟值和催化剂对动力学和流变性的影响。用有机酸封闭步叔胺催化剂，加快发发泡速度同时推迟凝胶时间，可改善泡沫流动性并缩短脱模时间。