The research of rheology and thermodynamics of organic-inorganic hybrid membrane during the membrane formation

To clarify the mechanism of organic-inorganic hybrid membrane formation by phase-inversion method, the thermodynamical and theological properties of PSF/TiO2 casting solution were investigated by the viscosity measurement and the triangle phase diagram, respectively. TiO2 introduction decreased the non-solvent tolerance of casting solution with non-solvent 20% ethanol aqueous solution, which caused thermodynamic enhancement of phase separation, and also resulted in the change of theological properties from Newtonian fluid to non-Newtonian fluid and the viscosity increase of casting solution, which induced rheological hindrance in demixing process

Rheology, morphology and mechanical properties of compatibilized poly(vinylidene fluoride) (PVDF)/thermoplastic polyurethane (TPU) blends

Compatibilized blends of poly(vinylidene fluoride) (PVDF) and thermoplastic polyurethane (TPU) were developed using maleated PVDF (PVDF-g-MA). Excellent compatibilization between PVDF and TPU was demonstrated by theological, morphological, and mechanical measurements. The introduction of PVDF-g-MA into the PVDF/TPU blends caused an increase in viscosity and storage modulus. Much finer morphology was clearly observed by SEM. The tensile tests showed that the tensile strength and ultimate elongation achieved a significant improvement with addition of PVDF-g-MA.

Rheology, morphology and mechanical properties of LLDPE/PS blends catalyzed by combined Lewis acids

The rheological, morphological and mechanical properties of LLDPE/PS blends with a combined catalyst, Me3SiCl and InCl3 center dot 4H(2)O, were studied in this work. The higher complex viscosity and storage modulus at low frequency were ascribed to the presence of graft copolymers, which were in situ formed during the mixing process. From the rheological experiments, the complex viscosity and storage modulus of reactive blends were higher than the physical blends. The dispersion of LLDPE particles of reactive blending becomes finer than that of physical blends, consistent with the rheological results. As a result of increased compatibility between LLDPE/PS, the mechanical properties of reactive blends show much higher tensile and Izod impact strength than those of physical blends.

Morphology and melt rheology of nylon 11/clay nanocomposites

Nylon 11 (PA11)/clay nanocomposites have been prepared by melt-blending, followed by melt-extrusion through a capillary. Transmission electron n-Licroscopy shows that the exfoliated clay morphology is dominant for low nanofiller content, while the intercalated one is prevailing for high filler loading. Melt rheological properties of PA11 nanocomposites have been studied in both linear and nonlinear viscoelastic response regions. In the linear regime, the nanocomposites exhibit much higher storage modulus (G') and loss modulus (G") values than neat PAIL The values of G' and G" increase steadily with clay loading at low concentrations, while the G' and G" for the sample with 5 wt % clay show an inverse dependence and lie between the modulus values of the samples with 1 and 2 wt % of clay. This is attributed to the alignment/orientation of nanoclay platelets in the intercalated nanocomposite induced by capillary extrusion. In the nonlinear regime, the nanocomposites show increased shear viscosities when compared with the neat resin. The dependence of the shear viscosity on clay loading has analogous trend to that of G' and G".

Rheology and morphology of reactively compatibilized PP/PA6 blends

This work aims to use the Palierne emulsion type model to describe the relationship between the rheological response to small amplitude oscillatory deformation and morphology of polypropylene/polyamide 6 (PP/PA6) blends compatibilized with maleic anhydride grafted polypropylene (PP-g-MAH). It was found that the Palierne emulsion type model could describe very well the linear viscoelastic responses of binary uncompatibilized PP/PA6 blends and failed to describe the ternary compatibilized PP/PP-g-MAH/PA6 blends. These features could be attributed to the fact that the morphology of the ternary blends was not of the emulsion type with the PA6 particles dispersed in the PP matrix but of an emulsion-in-emulsion type, i.e., PA6 particles dispersed in the PP matrix themselves contained PP or PP-g-MAH inclusions. By consideration of PP-in-PA6 particles as pure PA6 particles, where the volume fraction of the PA6 phase was increased accordingly, the Palierne emulsion type model could work very well for a ternary blending system. Preshear at low frequencies modified the morphology of both binary and ternary blends. The particles of the dispersed phase (PA6) became more uniform. These results suggested that the Palierne emulsion type model could be used to extract information on rheological properties and interfacial tension of polymer blends from known morphology and vice versa.

Mud mass transport due to waves based on an empirical rheology model featured by hysteresis loop

A vertical 2-D water-mud numerical model is developed for estimating the rate of mud mass transport under wave action. A nonlinear semi-empirical rheology model featured by remarkable hysteresis loops in the relationships of the shear stress versus both the shear strain and the rate of shear strain of mud is applied to this water mud model. A logarithmic grid in the vertical direction is employed for numerical treatment, which increases the resolution of the flow in the neighborhood of both sides of the interface. Model verifications are given through comparisons between the calculated and the measured mud mass transport velocities as well as wave height changes. (C) 2006 Elsevier Ltd. All rights reserved.

中日国际流变学学术会议(CJICR’91)

<正> 中日国际流变学学术会议(China-Japan International C onf erence on Rheology)由中国力学学会和中国化学会下属流变学专业委员会同日本流变学会联合发起,在北京清华大学举行.会议由中国湘潭大学袁龙蔚和日本京都大学小谷寿共同主持.

利用损伤力学模型研究地震前兆现象

在地震等灾变破坏发生之前会出现一定的前兆现象，本文通过损伤力学模型，运用数值计算的方法对此进行了研究从计算结果可以看到，在灾变破坏发生之前，由损伤所释放的能量(能量释放)和加卸栽响应比值Y都发生了异常明显的变化，这表明二者具有相同的物理机制，在一定程度上都能够较为定量地刻画出系统的损伤演化过程如果把二者相结合则可能对地震等灾变破坏做出更为准确的预测，本文结合实际震例对此也进行了一定的研究．

“Deborah Numbers”, Coupling Multiple Space and Time Scales and Governing Damage Evolution to Failure

Two different spatial levels are involved concerning damage accumulation to eventual failure. nucleation and growth rates of microdamage nN* and V*. It is found that the trans-scale length ratio c*/L does not directly affect the process. Instead, two independent dimensionless numbers: the trans-scale one * * ( V*)including the * **5 * N c V including mesoscopic parameters only, play the key role in the process of damage accumulation to failure. The above implies that there are three time scales involved in the process: the macroscopic imposed time scale tim = /a and two meso-scopic time scales, nucleation and growth of damage, (* *4) N N t =1 n c and tV=c*/V*. Clearly, the dimensionless number De*=tV/tim refers to the ratio of microdamage growth time scale over the macroscopically imposed time scale. So, analogous to the definition of Deborah number as the ratio of relaxation time over external one in rheology. Let De be the imposed Deborah number while De represents the competition and coupling between the microdamage growth and the macroscopically imposed wave loading. In stress-wave induced tensile failure (spallation) De* < 1, this means that microdamage has enough time to grow during the macroscopic wave loading. Thus, the microdamage growth appears to be the predominate mechanism governing the failure. Moreover, the dimensionless number D* = tV/tN characterizes the ratio of two intrinsic mesoscopic time scales: growth over nucleation. Similarly let D be the “intrinsic Deborah number”. Both time scales are relevant to intrinsic relaxation rather than imposed one. Furthermore, the intrinsic Deborah number D* implies a certain characteristic damage. In particular, it is derived that D* is a proper indicator of macroscopic critical damage to damage localization, like D* ∼ (10–3~10–2) in spallation. More importantly, we found that this small intrinsic Deborah number D* indicates the energy partition of microdamage dissipation over bulk plastic work. This explains why spallation can not be formulated by macroscopic energy criterion and must be treated by multi-scale analysis.

Microfluidic Rheometry

The development and growth of microfluidics has stimulated interest in the behaviour of complex liquids in micro-scale geometries and provided a rich platform for rheometric investigations of non-Newtonian phenomena at small scales. Microfluidic techniques present the rheologist with new opportunities for material property measurement and this review discusses the use of microfluidic devices to measure bulk rheology in both shear and extensional flows. Capillary, stagnation and contraction flows are presented in this context and developments, limitations and future perspectives are examined. (C) 2008 Elsevier Ltd. All rights reserved.

Modelling of submarine landslides and generated water waves

The slide of unstable sedimentary bodies and their hydraulic effects are studied by numerical means. A two-dimensional fluid mechanics model based on Navier-Stokes equations has been developed considering the sediments and water as a mixture. Viscoplastic and diffusion laws for the sediments have been introduced into the model. The numerical model is validated with an analytical solution for a Bingham flow. Laboratory experiments consisting in the slide of gravel mass have been carried out. The results of these experiments have shown the importance of the sediment rheology and the diffusion. The model parameters are adjusted by trial and error to match the observed “sandflow”.

高分子溶液中物理凝胶化的Monte Carlo模拟和小角中子散射研究

高分子凝胶广泛地存在于自然界以及日常生活中，按其形成作用力不同分为化学凝胶和物理凝胶两大类。由于高分子物理凝胶具有凝胶化的可逆性及其对环境条件强烈的响应性，因此，在近半个世纪的研究与应用中受到极大的关注。高分子溶液中的物理凝胶因其结构及形成机制复杂，在实验方面，除了散射技术及流变技术能够有效地揭示它的部分信息外，其它的实验手段很难用于这个领域的研究；在理论方面，化学凝胶的理论已经比较成熟，而物理凝胶的粘弹性质以及凝胶化是一个远离平衡态的松弛过程，除了一些特征的标度指数外，人们还没有得到适用于高分子物理凝胶的普适规律。当前，由于计算机模拟理论及模拟方法的发展，使得计算机模拟成为除了实验和理论研究方法之外的第三个重要的研究方法。但是，由于物理凝胶化行为的复杂性，用实验和理论获得的信息很难较好地描述凝胶化过程，而计算机模拟的高度透明性及反映信息的完整性，有助于理解这一复杂过程中所涉及的物理本质。因此，利用计算机模拟结合实验及理论方法深入研究高分子物理凝胶的形成机制、结构与性能关系已成为目前最有效的手段之一。 本论文主要运用Monte Carlo模拟方法，并结合小角中子散射（Small-Angle Neutron Scattering, SANS）和流变（Rheology）等实验手段从多个角度探讨了以下几类典型的高分子溶液物理凝胶化行为。 1. 温度对遥爪型三嵌段共聚物在选择性溶剂中的自组装及凝胶化行为影响的研究：采用二维简单方格子Monte Carlo模拟方法，结合逾渗（Percolation）理论，建立了溶胶－凝胶转变相图在统计热力学中的确定方法；甄别了具有特征构象的链，讨论了链及胶束的聚集，明晰了相互作用（体现为约化温度）、构象转变、聚集与凝胶化的一致的关联关系；提出了构象转变模型，进而明确了此体系的凝胶化过程，在微观尺度上表现为桥型链和环型链之间的竞争。 2. 模拟模型改进及其应用到持续长度对稀溶液中高分子链构象影响的研究：考虑到原始八位置键涨落模型效率低，实现复杂且不能应用到复杂的高分子体系，对该模型进行了改进，使其实现简单、效率高，并拓宽了该模型的应用范围。然后，以刚性对均聚物构象的影响为例，发现随着刚性增加，均聚物构象从球形椭球到棒状椭球的转变，并对比了自由连接链（Free Joint Chain, FJC）模型和蠕虫链（Wormlike Chain, WLC）模型在不同刚性范围内对高分子链末端距预测的偏差，首次给出了这两个经典模型的半定量的适用边界。 3. 溶剂尺寸对遥爪型三嵌段共聚物在选择性溶剂中的自组装及凝胶化行为影响的研究：用改进后的八位置键涨落Monte Carlo模型，研究了遥爪型三嵌段共聚物在选择性溶剂条件下的聚集和凝胶化对溶剂尺寸的依赖性，发现溶剂尺寸效应对凝胶化的作用是非单调的。由一个均聚物体系的对比模拟证明这种作用主要是由熵驱动的，并给出了中分子溶剂的半定量定义。在均聚物和嵌段共聚物溶液中，不同尺寸的溶剂分子可以使溶液由于高分子聚集不同而具有不同的微结构，并影响高分子链构象和溶液的性质。从多个角度研究了三嵌段共聚物在不同尺寸溶剂的溶液中所遵循的三种不同的凝胶化机理。 4. 聚氧化乙烯－氧化丙稀－氧化乙烯三嵌段共聚物（poly(ethylene oxide)-poly (propylene oxide)-poly-(ethylene oxide), PEO-PPO-PEO）重水溶液凝胶化的小角中子散射（SANS）和Monte Carlo研究：结合Pluronic F127（EO65PO99EO65）/D2O三嵌段共聚物溶液的特征，对照SANS数据，用改进后的八位置键涨落模型成功地从模拟中获得了F127/D2O的溶胶－凝胶转变相图。详细地考察了体系的微观结构，提出此类高分子溶液中形成的物理凝胶包含高分子逾渗网络的生成，以及被束缚溶剂（Bound Solvent）必须超过离散组分体系逾渗的临界体积分数的机理。着重研究了一定浓度的F127水溶液随温度升高引起的溶胶－凝胶转变以及凝胶－溶胶转变的Reentrant相行为，发现体系在低温区域的溶胶－凝胶转变遵循相同的机理，而在中等温度和较高温度以及不同浓度区域中的凝胶－溶胶转变遵循不同的机理。 5. 极性基团饱和度和溶剂条件对两亲性聚合物在溶液中的聚集行为和凝胶化影响的研究：用改进后的八位置键涨落模型，针对两亲性聚合物在不同溶剂条件的溶液建立了粗粒化模型，以两亲性聚合物中极性基团的饱和度，溶剂条件和高分子浓度为变量，考察了其对链构象、聚集及其凝胶化的影响。 6. 多糖水溶液凝胶化的流变和小角中子散射研究：用流变和SANS考察了两个多糖水溶液中物理凝胶化过程，针对由氢键主导的水基凝胶体系的典型特征进行了讨论，从分子链构象，聚集体结构及其关联以及流变特征等方面对聚强电解质角叉胶（Carrageenan）水溶液和聚弱电解质明胶（Pectin）水溶液进行了详细的讨论。考察了不同多糖的种类（聚合物链的电荷密度），盐的种类和浓度，溶液温度等对凝胶化和凝胶结构的影响，分析了不同多糖溶液的凝胶化机理。