Preparation and Characterization of Metalized JP‐10 Gel Propellants with Excellent Thixotropic Performance

The preparation and characterization of a series of D‐gluconic acetal supramolecular organic gelators (Gn) which can form gel with high‐energy density hydrocarbon fuel JP‐10 are reported. Rheological measurements show G8 gel exhibits strong mechanical strength at a concentration of 2 wt %, while G18 gel has a remarkable yield stress. What's more, JP‐10 gels show thixotropy with high viscosity, especially for the G8‐based gel, which has an instantaneous recovery ratio. The CGC (critical gelator concentration) of G8 is less than 0.1 wt %, known as a super gelator. More interestingly, G18 can gel JP‐10 at room temperature, which is the first example of room temperature gel propellant formed by a supramolecular gelator. Nano accelerants (Al, B) are dispersed into the gel propellant system, which can be stable for months. The presence of 50 nm Al powder in G8‐based gel can significantly increase its mechanical strength, yield stress and viscosity, as well as thixotropy.     

流变学在牙膏配方研制中的应用

本文通过对牙膏膏体流变性能的研究，证明了用已知的流变学数据指导牙膏配方研制的可行性，为制定牙膏配方提供了理论依据。     

新型陶瓷原料--绢英岩在生产中的作用机理

绢英岩作为一种新原料上世纪八十年代在国内部分地区开始使用，它属于花岗变斑岩型，原矿呈泛青的白灰色致密块状，有滑腻感。由于绢英岩成分稳定，有害杂质含量低，以及烧结范围宽、烧后白度高等优点，决定了它在陶瓷工业上具有广泛用途。本文从绢英岩的矿物组成、结构特征出发，探讨其在陶瓷生产中的作用机理，以对该原料的广泛使用奠定一定的理论基础。     

pH值和无机盐对阴离子型微乳液流变性的影响

由正十六烷、油酸钾、正已醇和水组成的微乳液，在水油比为１时产生异常流变性，本文研究ｐＨ值和盐类物质对微乳液异常流变性的影响，对产生异常流变性的微乳液微观结构有了进一步的理解。     

Modeling the viscoelasto-plastic behavior of waxy crude

Waxy crude oil exhibits complex rheological behavior below the pour point temperature, such as viscoelasticity, yield stress, and thixotropy, owing to the formation of a three-dimensional spongelike interlock network structure. This viscoelasto-thixotropic behavior is an important rheological behavior of waxy crude oils, determining the flow recovery and safe restart of crude oil pipelines. Up to now, the thixotropic models for waxy crude have been all viscoplastic models, without considering the viscoelastic part before the yield point. In this work, based on analyzing the variation of the elastic stress and viscous stress in the Mujumbar model, a new viscoelasto-plastic model is proposed, whose shear stress is separated into an elastic component and a viscous component. The elastic stress is the product of the shear modulus and elastic strain; the shear modulus is proportional to the structural parameter. For the elastic strain, we followed the line of Zhu and his coauthors and assumed that it may be expressed by an algebraic equation. The model is validated by stepwise shear rate tests and hysteresis loop tests on Daqing and Zhongyuan waxy crude. The results show that the model’s fitting and predictive capability is satisfactory.     

Evaluation of some vanillin-modified polyoxyethylene surfactants as additives for water based mud

Water-based drilling fluids are increasingly being used for oil and gas exploration and are generally considered to be more environmentally acceptable than oil-based or synthetic-based fluids. In this study, new types of vanillin-modified polyoxyethylene surfactants were evaluated as additives in water-based mud. Their rheological properties in water-based mud were investigated which included the apparent viscosity, the plastic viscosity, the yield point, the gel strength, the thixotropy as well as the filtration properties. Also, the effect of high temperature on the rheology of the formulated water based mud was studied. The tested ethoxylated non-ionic surfactants showed good results when utilized in the formulation of water-based mud.     

RHEOLOGICAL PROPERTIES AND FLOW OF CONCENTRATED DISPERSE MEDIA I - MODELLING OF STEADY AND UNSTEADY BEHAVIOR

Abstract

A steady viscosity model, including both volume fraction and shear rate variables, is shown to be applicable to a large class of complex liquids which can be considered as highly concentrated disperse media. The effect of yield stress is taken into account. For unsteady measurements, this model, which includes thixotropy, can be simply extended to viscoelastic behaviour. Some examples of application will be given, specially to heavy crude oil emulsions.     

Designing and transforming yield-stress fluids

We review progress in designing and transforming multi-functional yield-stress fluids and give a perspective on the current state of knowledge that supports each step in the design process. We focus mainly on the rheological properties that make yield-stress fluids so useful and the trade-offs which need to be considered when working with these materials. Thinking in terms of “design with” and “design of” yield-stress fluids motivates how we can organize our scientific understanding of this field. “Design with” involves identification of rheological property requirements independent of the chemical formulation, e.g. for 3D direct-write printing which needs to accommodate a wide range of chemistry and material structures. “Design of” includes microstructural considerations: conceptual models relating formulation to properties, quantitative models of formulation-structure-property relations, and chemical transformation strategies for converting effective yield-stress fluids to be more useful solid engineering materials. Future research directions are suggested at the intersection of chemistry, soft-matter physics, and material science in the context of our desire to design useful rheologically-complex functional materials.     

Influences of pH and electrolyte on the rheological properties of aqueous solution of exopolysaccharide secreted by a deep-sea mesophilic bacterium

The effects of pH and electrolytes (NaCl and CaCl₂) on the viscosity, dynamic modulus (storage modulus G′ and loss modulus G″) and thixotropy of aqueous solution of new exopolysaccharide (SM-A87 EPS) secreted by a deep-sea mesophilic bacterium Wangia profunda SM-A87 were investigated. It was found that at pH 3–12 and the electrolyte concentration of 0.1–80 g/L, the SM-A87 EPS solution showed very weakly pH-dependent and salt-dependent rheological properties and dominant elastic behavior. These properties were considered to arise from the hyper-branched structure of the SM-A87 EPS molecules through the comparison of rheological properties of SM-A87 EPS solutions with those of partially hydrolyzed polyacrylamide ones at different electrolyte concentrations. Such good pH stability and salt resistance of the SM-A87 EPS solution indicate that SM-A87 EPS has great potential for application as food additive, thickener, stabilizer and enhanced oil recovery system. In the studied conditions, 2 g/L SM-A87 EPS solution showed positive thixotropy. The relative thixotropic recovery decreased with pH increasing and the electrolyte concentration decreasing.     

The effects of fluid viscoelasticity on the settling behaviour of horizontally aligned spheres

A study on the interaction of particles settling in non-Newtonian fluids of shear-thinning, thixotropic and viscoelastic characteristics has been conducted. Key aspects of the rheological characteristics of the fluids that influence the interaction of the particles were examined by analysing the trajectories of two particles that are initially placed side-by-side in the fluid medium.The interaction of the particles was found to be highly dependent on the separation distance that is initially set between them. If the initial distance is smaller than a critical value, the spheres would tend to attract and converge. In cases where the initial distance is greater than this critical value, the two spheres would tend to diverge, resulting in a slight (∼20%) increase in their separation distance over their course of settling. This tendency to diverge was found to diminish as the initial distance is increased further from the critical value.The magnitude of the critical separation distance was found to be primarily dependent on the normal stresses of the fluids. A correlation was thus proposed based on this observation. In cases where the two spheres do attract and converge, it was found that the spheres tend to follow a non-symmetrical trajectory, where one of the spheres possesses a slightly lower settling velocity than the other. As a result, the spheres appear to re-arrange themselves into a vertically aligned configuration. Once aligned, the shear-thinning and thixotropic characteristics of the fluid causes the lagging sphere to accelerate and collide with the leading sphere.