Rheological study methods

Rheo-NMR [86] methods have been shown to be well-suited to emulsion rheology studies [28] and could be combined with any of the topics described above. The combination of structural and rheological measurements is a promising area for further research. 

Rheological studies involving Fe oxides appear to be sparse. Most are carried out on acicular crystals, usually maghemite. Details of the method of synthesis or properties of the particles are often lacking. 

Rheological studies on cement pastes and concrete have been reviewed in a book (T42) and several shorter articles (H40,L40,S76). The results in the literature show wide variations, many of which reflect the large effects of seemingly minor differences in experimental technique. Since cement pastes do not show Newtonian behaviour, methods giving only a single parameter are inadequate. Viscometers in which the material is studied in shear between a shallow cone and a plate, or between concentric cylinders, have generally been used. 

Over the past few decades there has been an increase in the research tools for fundamental rheology studies of surfactant solutions and commercial detergent formulations. The coupling of rheometers with other methods has broadened the range of studies that can be completed, leading to a better understanding of solution properties, self-assembled mesophases, multiple-component dispersions, and gels. 

Loglio G, Pandolfini P, Tesei U, and Noskov B (1998b) Measurements of interfacial properties with the axisymmetric bubble-shape analysis technique effects of vibrations. Colloids Surfaces A 143 301-310 Loglio G, Pandolfini P, Miller R, Makievski AV, Ravera F, Ferrari M and Liggieri L (2001) "Drop and Bubble Shape Analysis as Tool for Dilational Rheology Studies of Interfacial Layers", in "Novel Methods to Study Interfacial Layers", Studies in Interface Science, Vol. 11, D. Mobius and R. Miller (Eds.), Elsevier, Amsterdam, pp 439-485... 

A complete rheological study of the polymer component serves to establish knowledge of the flow behavior of the material and thus contributes toward an optimal choice of melt processing methods. 

The present chapter gives also detailed introduction to a large number of experimental methods, suitable for studying dynamic interfacial tensions. The methods are discussed in terms of the available time window. There are methods which complement each other such that a time interval from less than 100 microseconds up to hours and days of adsorption time can be covered (about ten orders of magnitude). The relaxation methods, also suitable for detecting the adsorption mechanism of surfactant s adsorption provide in addition the dilational rheology of interfacial layers. It is discussed that in particular these dilational rheological studies are most informative in respect to adsorption mechanisms, as the data interpretation includes the thermodynamic model as well as the adsorption dynamics. 

Due to the positive influence of these nanofillers in the nanocomposites, an abundance of articles on different methods to quantify the influence of the nanofiller can be found in the literature. Many articles on assessing the clay dispersion in a polymer matrix by morphological and rheological studies have been published. Due to the relatively easy sample preparation and sample loading, rheology is often used to screen or characterize the nanofiller dispersion, or more generally determine the influence of the... 

Loglio, G. Pandolfmi, P Miller, R. Makievski, A. V. Ravera, R Ferrari, M. Lig-gieri, L. Drop and bubble shape analysis as tool for dUational rheology studies of interfacial layers. In Novel Methods to Study Interfacial Layers, Studies in Interface Science. Mobius, D. Miller, R., Eds., 2001 II, 439 84. 

For polymer melts and polymer solutions, numerous excellent reviews [1-5] have provided detailed descriptions of the concepts, test methods and rheological transitions in these systems. The rheological behaviors of thermoplastic blends, including both homopolymers and block copolymers, have also been extensively reviewed [6]. In the case of thermosetting blends, the majority of the information related to rheological studies has been reported in journals. Consequently, after a brief introduction of some of the concepts related to these studies, recent developments in thermosetting blend systems will be reviewed in the following sections. 

Rheological studies show some similarities with chemical relaxation studies. For instance, a rectangular shear rate is applied and the relaxation of the stress is monitored. This directly yields the stress relaxation time(s). One can also apply a sinusoidal deformation or strain of angular frequency 0). The response of the system is a two-component sinusoidal shear stress. The first component is in phase with the strain and corresponds to the elastic (storage) properties of the system. The second component is out of phase with the strain with a phase angle 5, and corresponds to the viscous loss in the system. These quantities give access to the storage (elastic) modulus G (co) and to the loss (viscous) modulus G"(o)), with G" ((o)/G (co) = tg5. As in the case of chemical relaxation methods with harmonic perturbation, the variations of G (w) and G" (co) with co yield the relaxation time(s) of the system. 

Some specific experimental methods have also been recently elaborated and new reliable results have been obtained in rheological studies [49] of commercial thermotropic polymers, such as Titan and Zenith. 

Studies of the relationship of macroscopic properties to internal structure have been at the forefront of polymer science for many years. We are now in a position to use rheological studies as a method of elucidating internal stmcture and internal structural distortion mechanisms. This paper will use this approach to determine the characteristics of transitions above the glass transition temperature, Tg, in amorphous polymers with the objective of understanding the stmcture of these polymers and the mechanisms involved in the transitions. 

Several independent experimental methods were applied that allowed comparison of the properties of these systems [ 18-20]. We present only the principal results of the three foDowing approaches (i) rheological studies of interfacial adsorption layers (lAL) by the rotating suspension method (ii) observation of the compression of two nonpolar droplets in the surfactant aqueous solution, with measurement of the force needed for their coalescence and (iii) evaluation of the free energy of interaction between nonpolar groups of lAL and various nonpolar liquids by measuring the contact rupture force between two methylated (or fluorinated) smooth solid particles in a given liquid. 

The mechanical (rheological) studies of the considered lALs by the rotating suspension method show an essential difference between the liquid-like behavior of such layers for HS/HL and FS/FL systems and the solid-like one (manifestation of the critical shear stress, the strength) in both FS/HL and HS/FL... 

In this chapter, novel method for microencapsulation by coacervation is presented. The method employs polymer-polymer incompatibility taking place in a ternary system composed of sodium carboxymethyl cellulose (NaCMC), hydroxypropylmethyl cellulose (HPMC), and sodium dodecylsulfate (SDS). In the ternary system, various interactions between HPMC-NaCMC, HPMC-SDS and NaCMC-(HPMC-SDS) take place. The interactions were investigated by carrying out detailed conductometric, tensiometric, turbidimetric, viscosimetric, and rheological study. The interactions may result in coacervate formation as a result of incompatibility between NaCMC molecules and HPMC/SDS complex, where the ternary system phase separates in HPMC/SDS complex rich coacervate and NaCMC rich equilibrium solution. By tuning the interactions in the ternary system coacervate of controlled rheological properties was obtained. Thus obtained coacervate was deposited at the surface of dispersed oil droplets in emulsion, and oil-content microcapsules with a coacervate shell of different properties were obtained. Formation mechanism and stability of the coacervate shell, as well as stability of emulsions depend on HPMC-NaCMC-SDS interaction. Emulsions stabilized with coacervate of different properties were spray dried and powder of microcapsules was obtained. Dispersion properties of microcapsules, and microencapsulation efficiency were investigated and found to depend on both properties of deposited coacervate and the encapsulated oil type. 

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