用高分子附聚法制备大粒径聚丁二烯胶乳

采用高分子胶乳附聚法对小粒径聚丁二烯胶乳（ＰＢＬ）进行附聚,制备大粒径ＰＢＬ。研究了合成附聚剂时的加料方式和不饱和酸用量、附聚剂用量、体系ｐＨ值、附聚温度及其他附聚工艺条件对附聚效果的影响,并对比了附聚前后ＰＢＬ的形态。结果表明,当在合成附聚剂的初期加入丙烯酸乙酯的质量分数为其总量的２０％ ～４０％、不饱和酸的质量分数为１０％以及附聚剂质量分数为１．５％、体系ｐＨ值为９～１０、附聚温度为４０℃和附聚时间为１ｈ时,附聚的效果最好。     

乳胶粒子用附聚剂的制备及应用

采用丙烯酸(AA)、丙烯酸丁酯(BA)混合单体通过乳液聚合方法合成附聚剂,用于聚丁二烯胶乳(PBL)的附聚.研究了附聚时间、附聚剂组成、附聚剂加入量、附聚剂的粒子尺寸等因素对聚丁二烯(PB)胶乳粒径大小的影响.结果表明:附聚时间为40～60 min时,附聚过程基本完成;当BA/AA质量比为80/20时,附聚效果最好;附聚剂在PBL中加入量占PBL总质量的8.3％时,附聚效果明显;PBL平均粒径由原来的96nm附聚到了240～260 nm,粒径得到了明显的增长,合成的附聚剂有良好的附聚效果.     

高分子附聚剂增大聚丁二烯胶乳粒径的研究

用丙烯酸正丁酯(BA)和甲基丙烯酸(MAA)合成了高分子附聚剂,并制备了大粒径聚丁二烯胶乳(PBL)。研究了PBL含量(在规定条件下烘干后剩余部分占总量的质量分数)、附聚剂用量和附聚剂中MAA含量对附聚效果的影响。结果表明：当PBL质量分数为30.0%、附聚剂质量分数为2.5%～3.0%、附聚剂中MAA质量分数为15.0%时,可制得粒径大于300 nm、粒径分布为单峰的稳定PBL。     

附聚法制备大粒径聚丙烯酸丁酯胶乳的研究

以非离子和阴离子表面活性剂为复配乳化剂,制备了丙烯酸丁酯/丙烯酸共聚胶乳,以其为附聚剂制备了大粒径的PBA胶乳,采用红外光谱仪、Zeta纳米粒度仪、Zeta电位仪和透射电镜表征了附聚剂的结构特征、附聚前后PBA胶乳粒子的粒径、电位和形态变化。结果表明:当附聚剂胶乳与PBA胶乳质量比为1/20~1/5时,可使PBA胶乳粒径尺寸扩增4倍以上,附聚后胶乳的表面电位值有所下降。     

高分子附聚法制备超大粒径聚丁二烯胶乳

以自制丙烯酸胶乳为高分子附聚剂,以粒径300nm聚丁二烯胶乳(PBL-0700)为起始胶乳,采用高分子附聚法制备了500～600nm超大粒径聚丁二烯胶乳(目标胶乳),考察了附聚剂加入量、放置时间、后稳定剂的加入、附聚温度等因素对目标胶乳粒径的影响,确定了高分子附聚法超大粒径聚丁二烯胶乳制备工艺。     

醋酸附聚制备大粒径PB胶乳影响因素的研究

以醋酸为化学附聚剂,对小粒径PB胶乳进行化学附聚,研究醋酸浓度、醋酸加入量、附聚温度、附聚时间对附聚效果的影响,评估醋酸附聚制备的大粒径PB胶乳性能。     

有机附聚剂用于砂金矿选别的研究

文章介绍了用有机附聚剂选别砂金矿的实验研究，详细叙述了附聚剂的选别原理及各组份的性能和作用。实验结果，人工配料选金的回收率可达９０％。稳定性和重现性都较好。附聚剂无毒，无害，配制容易，价廉，为工业型实验提供了依据。     

高分子附聚法450nm聚丁二烯胶乳的制备研究

高分子附聚方法是一项独特的技术。特别是在制备超大粒径胶乳方面,可以在较短的时间内制备稳定的胶乳,从而改善产品质量,提高生产效率。作者对制备粒径450nm聚丁二烯胶乳的附聚工艺进行了深入研究,考察了附聚剂胶乳用量、附聚后静置时间、乳化剂用量和搅拌强度等附聚工艺对聚丁二烯胶乳粒径及稳定性的影响,确定了制备450nm聚丁二烯胶乳较为优化的附聚工艺,制备的聚丁二烯胶乳稳定,可用于高性能ABS的制备。     

静态混合附聚胶乳制备丙烯腈-丁二烯-苯乙烯树脂

以丙烯酸酯类共聚物乳液作为聚合物乳液附聚剂,采用在线静态混合器对粒径为100.5 nm的小粒径聚丁二烯胶乳(PBL)进行附聚,并与采用传统附聚器间歇附聚法PBL进行了对比,对用2种方法获得的丙烯腈-丁二烯-苯乙烯(ABS)树脂的性能进行了比较。结果表明,采用静态混合器在线附聚法,可得到粒径呈双峰分布、有效粒径为298.3 nm、多分散性指数为0.316的大粒径PBL;而在同样条件下采用附聚器间歇附聚法,所得PBL粒径也呈双峰分布,有效粒径为268.4 nm,多分散性指数为0.359,可见静态混合器在线附聚效果好于附聚器间歇附聚法。采用静态混合器在线附聚法获得的ABS树脂,其抗冲击性能优于附聚器间歇附聚法ABS树脂。     

玉米加工蒸煮液等添加剂对炭黑粘着强度和电性能的影响

本文考察了玉米加工业蒸煮液（Nejayote，玉米饼加工业产生的废水，俗称黄浆水）及其它添加剂（水、木素磺酸钾、糠醇）对炭黑附聚体的粘着强度和电性能的影响。炭黑附聚体的热稳定性与木素磺酸钾、糠醇和该蒸煮液相似。蒸煮液和木素磺酸钾对炭黑附聚体的粘着强度的影响也相似，然而对电性能的影响不同。含蒸煮液的炭黑附聚体具有较低的导电率。水对炭黑附聚体粘着强度的影响不严重，但对其导电性却至关重要。蒸煮液是玉米加工业的一种无用的副产品，在炭黑造粒过程中可作为有潜力的促聚剂。     

Mathematical modelling of the MCFC cathode

Different models for the NiO cathode have been compared with respect to their abilities to predict polarization curves and the influence of the amount of electrolyte on the electrode performance. It has been shown that the agglomerate model for the MCFC cathode gives more reasonable results when the exterior agglomerate surface area is specifically taken into account. In the cathode only the outermost layer of nickel oxide particles in the agglomerate is utilized for the electrochemical reaction. The pseudohomogeneous approach is questionable for these agglomerates since the individual particles constituting the agglomerate are of the same size as the reaction zone thickness. A thin-film model with a roughness factor for the electrode surface appears to be as good a model as the agglomerate model. A model based on a chain of spherical agglomerates and the partially drowned agglomerate model are physically more realistic models than the homogeneous agglomerate model for the prediction of the influence of electrolyte fill on the electrochemical performance.     

Numerical simulations of diametrical compression tests on agglomerates

The paper reports discrete element simulations of the diametrical compression test applied to two spherical agglomerates: one a dense agglomerate and the other a loosely packed agglomerate. The results obtained for the dense agglomerate show that the agglomerate fractures along a slightly inclined, approximately diametrical plane. Outwardly, the agglomerate shows all the characteristics of brittle fracture but half of the final number of broken bonds was progressively broken during loading. In the simulation on the loose agglomerate, significant flattening occurred at the platens and the agglomerate failed by crushing.     

Alumina Agglomerate Effects on Toughness-Curve Behavior of Alumina–Mullite Composites

Toughness-curve ( T -curve) behavior of composites of spherical, polycrystalline, coarse-grained, alumina agglomerates dispersed throughout a constant-toughness, fine-grained, 50–50 vol% alumina–mullite matrix has been evaluated as a function of agglomerate content for the range 15 to 45 vol%. T -curve behavior was evaluated using the indentation-strength method. Increasing alumina agglomerate content resulted in a progressive increase of large indentation load strengths with negligible change of plateau strength levels at small indentation loads. This behavior is consistent with underlying T -curves that rise to greater values and are shifted toward longer crack lengths with increasing agglomerate content, suggesting that both bridge spacing and bridge potency increase with increasing agglomerate content over the range tested. The proposed relationships between bridge spacing and agglomerate content, and bridge potency and agglomerate content, are rationalized in terms of residual stress considerations. The indentation-strength data also demonstrated that the composite containing the greatest alumina agglomerate content, 45 vol%, exhibited the greatest flaw tolerance.     

Agglomerate Sizes of Binary Nanoparticle Mixtures in a Vibro‐Fluidized Bed

Agglomerate size is one of the key factors influencing the fluidization behavior of nanoparticles. The effect of fluidization time, superficial gas velocity, and vibration frequency on agglomerate sizes for different binary mixtures of nanoparticles at the top of the bed was investigated in a vibrated fluidized bed (VFB). The agglomerate sizes decreased and fluidization quality was significantly enhanced owing to introduction of vibration energy. The Richardson‐Zaki equation combined with Stokes' law permitted the prediction of mean agglomerate sizes. Experimental and estimated results indicated that vibration led to a smaller agglomerate size. The mean predicted agglomerate sizes were in agreement with those determined experimentally in the VFB.     

细颗粒的团聚流态化及其判定

本文在考查了不同细颗粒的流态化过程及物料的气动特性与粘附力关系的基础上，提出了当量流态化的概念；实验发现聚团密度的减小是改善细颗粒流化性能的一种有效途径；根据气动情况下不同的成团结果，把细颗粒的聚团流态化分成了三类：沟流；似A类聚团流态化；似B／D类聚团流态化；同时，结合实验结果，给出了不同细颗粒聚团流态化类型的定量判据     

A Die Pressing Test for the Estimation of Agglomerate Strength

A die pressing test was developed for quick and inexpensive estimation of the agglomerate strength of ceramic powders. The critical nominal pressure ( p _c) at which contact areas between agglomerates start to increase rapidly was found from the relationship between change in sample height and applied pressure in uniaxial single-ended die pressing. A quantitative microscopic method was used for measuring the area fraction (Ψ) of agglomerates which transmits the force through the assembly. A die pressing agglomerate strength, σ_d, is defined as σ_d= 0.7 p _c/Ψ. This strength was compared with the agglomerate tensile strength obtained from single agglomerate diametral compression tests and found to be 50% higher than the latter because of multipoint loading. A suggested guideline is that the mean agglomerate tensile strength is approximately 52% of p _c determined in a die pressing test for spherical agglomerates. In addition to agglomerate tensile strength, the mean agglomerate size, the interior macropore structure of agglomerates, as well as the packing efficiencies between and inside agglomerates can be estimated by the procedure.     

Hydrodynamics of inhomogeneous agglomerates for a fractal dimension of 2.5 at intermediate Reynolds numbers: Effect of agglomerate sizes and Reynolds numbers

In this study, the effect of agglomerate sizes for a fractal dimension (D_f) of 2.5 on the hydrodynamics at intermediate Reynolds numbers (Re) of 1–120 was assessed. The results show that a core behaves like a solid sphere that exists in the central region inside the agglomerate. In addition, increasing the agglomerate diameter represents adding an extra permeable layer outside the agglomerate. For a larger Re or a smaller agglomerate diameter, the fluid can enter and penetrate through the agglomerate more easily, and the hydrodynamic characteristics of agglomerates deviate more from those of solid spheres. The effect of diameters on the velocity and pressure profiles becomes less significant with the increase in the diameter. Based on the simulated results, the drag ratio has an approximately linear relationship with Re, and its intercept has an exponential relationship with the dimensionless agglomerate diameter. Compared with homogeneous porous spheres, the drag ratio of the agglomerate is different. The effect of diameters on the drag ratio decreases as the diameter increases. It should be noted that the effect of radially varying permeability on inhomogeneous agglomerates should not be ignored and that the effect weakens as Re increases.     

Aluminum Agglomeration on Burning Surface of NEPE Propellants at 3–5 MPa

Aluminum agglomeration and agglomerate sizes of NEPE propellants were studied by cinephotomicrography at pressures of 3 and 5 MPa. Accumulation, aggregation, and agglomeration of aluminum particles similar to that at pressures below 1 MPa were observed. Coalescence of two agglomerates on the burning surface is obtained for the first time. A decrease in the burning rate from 8 to 5 mm s⁻¹ leads to about 20 % increase in the agglomerate diameter. The pressure is found to have no direct influence on the agglomerate diameter when the burning rate is kept constant. The evolution of the agglomerate diameter according to the increase of the virgin aluminum size from 16 to 36 μm is convex in shape and reached its maximum at a particle diameter of 29 μm. Increasing the amount of RDX crystals added in the propellants causes a larger agglomerate diameter. The experimental mass average agglomerate diameters were compared with various agglomeration models. It is found that Hermsen and Salita empirical models have a higher accuracy for NEPE propellants rather than Becksted, Liu, or pocket models.     

Effect of morphology and extent of infiltration on the cohesivity and dispersion mechanisms of particle agglomerates

A unified approach to predict the tendency for dispersion of particle agglomerates, inclusive of a wide range of particle and agglomerate properties, is presented. This framework is applied to analyze the behavior of three prototypical materials (fumed silica, calcium carbonate and titanium dioxide) across a range of agglomerate packing densities. Simulations of dispersion phenomena, which employ our previously developed solution for liquid-bridge interactions for wet interparticle contacts and the Rumpf model for the tensile strength of the dry and wet portions of the agglomerate, have been performed. Various mechanisms of dispersion are predicted for various conditions of agglomerate density and extent of fluid infiltration. These range from an adhesive mechanism at the wet-dry interface for sparse materials to a cohesive mechanism by erosion as agglomerate density increases. The results correspond well with the results of earlier experimental studies involving the same materials.     

Effect of size ratio on the behaviour of agglomerates embedded in a bed of particles subjected to shearing: DEM analysis

This paper presents the results of analysis of the deformation and breakage of spherical agglomerates embedded in a bed of particles and subjected to shearing, a situation commonly encountered in powder granulation. The study is based on three dimensional distinct element method (DEM), in which the inter-particle interactions are governed by theories of contact mechanics. An agglomerate was first generated in a bed of particles having the same size as the primary particles forming the agglomerate. Different size ratios (i.e., the ratio of the diameter of agglomerate to the diameter of surrounding particles) in the range 3-10 were then simulated by varying the size and number of surrounding particles. The agglomerates were subjected to shearing (shear rate and strain of about and 0.3, respectively) and their breakage characteristics were analysed. The agglomerate with the size ratio 10 does not break but undergoes some structural deformation by re-arrangements of contacts. However, the agglomerates with ratio about 7 or smaller suffer breakage. For the size ratio equal or smaller than 5, the agglomerate breaks significantly leading to full disintegration. The results of stress analysis of the agglomerates suggest that the resistance to breakage for the agglomerate with size ratio of 10 is due to the nature of stresses exerted on the agglomerate. For large size ratios the stress on the agglomerate is predominantly hydrostatic. The ratio of deviatoric stress over hydrostatic pressure increases as the size ratio of the agglomerate is reduced. The nature of stresses experienced by agglomerates with smaller size ratios is predominantly deviatoric, thus causing shear deformation and breakage. The results are compared with physical experiments and a satisfactory agreement is obtained.