Rheology concentrated polymer solutions

IS). Lodge.A.S. Rheological properties of concentrated polymer solutions. I. Growth of pressure fluctuations during prolonged shear flow. Polymer (London) 2,195 201 (1961). 

Hayashi.S. Concentration dependence of rheological properties in concentrated polymer solutions. In Onogi,S. (Ed.) Proceedings of the Fifth International Congress of Rheology, Vd. 4, pp. 179-190. Baltimore University Park Press 1969. 

Despite the large amount of literature on this subject, the rheology of polymer solutions is less completely understood than that of polymer melts. This is because two more parameters are involved the nature and the concentration of the solvent. 

The rheology of concentrated polymer solutions shows a striking correspondence with that of polymer melts, which has been discussed in Chap. 15. The influences of the parameters molecular mass, temperature and shear rate on the viscosity are largely analogous, but the situation is made more complicated by the appearance of a new parameter the concentration of the polymer. 

This section on concentrated suspensions discusses the rheological behavior of sj tems which are colloidally stable and colloidally unstable suspensions. For stable sj tems, the rheology of sterically stabilized and electrostatically stabilized systems wiU be considered. For sterically stabilized suspensions, a hard sphere (or hard particle) model has been successfid. Concentrated suspensions in some cases behave rheologically like concentrated polymer solutions. For this reason, a discussion of the viscosity of concentrated polymer solutions is discussed next before a discussion of concentrated ceramic suspensions. 

They have been developed based on either molecular structure or continuum mechanics where the molecular structure is not considered explicitly and the response of a material is independent of the coordinate system (principle of material indifference). In the former, the polymer molecules are represented by mechanical models and a probability distribution of the molecules, and relationships between macroscopic quantities of interest are derived. Three models have found extensive use in rheology the bead-spring model for dilute polymer solutions, and the transient net work and the reptation models for concentrated polymer solutions and polymer melts. 

The zero-shear viscoelastic properties of concentrated polymer solutions or polymer melts are typically defined by two parameters the zero-shear viscosity (f]o) and the zero-shear recovery compliance (/ ). The former is a measure of the dissipation of energy, while the latter is a measure of energy storage. For model polymers, the infiuence of branching is best established for the zero-shear viscosity. When the branch length is short or the concentration of polymer is low (i.e., for solution rheology), it is found that the zero-shear viscosity of the branched polymer is lower than that of the linear. This has been attributed to the smaller mean-square radius of the branched chains and has led to the following relation... 

Concentrated polymer solutions. Proc. 5 th International Congress on Rheology, Vol. 4. Tokyo University of Tokyo Press 1969 (also MRC Tech. Summary Report No. 944, Oct. 1968, Mathematics Research Center, University of Wisconsin). 

Roy-Chaudhury, R, and Deuskar, V. D., Rheological properties of concentrated polymer solutions polybutadiene in good and theta solvents, J. Appl. Polym. Sci, 31, 145-161 (1986). 

Phenomenologically, the viscous stress is the stress which vanishes instantaneously when the flow is stopped. On the other hand the elastic stress does not vanish until the system is in equilibrium. The elastic stress is dominant in concentrated polymer solutions, while viscous stress often dominates in the suspensions of larger particles for which the Brownian motion is not effective. Whichever stress dominates, the rheological properties can be quite complex since both and are functions of the configuration of the beads and therefore depend on the previous values of the velocity gradient. Note that the viscous stress only appears in the system with rigid constraints.t... 

The rheological behavior of xanthan samples obtained in various fermentation conditions with dilute or concentrated polymer solutions in the presence of proteins has been investigated. 

Rheological Measurements Polymer solutions with various concentrations were prepared in a small sample bottle by moderately heating for several days, and then used for rheological measurements. The study was carried out using a cone-and-plate rheometer (Haake CV-20N) with a shear rate range of 0 300 s at 30 C. 

Polymer characterization is a well-developed field in and of itself, and involves many methods, some of which are discussed in detail in subsequent chapters. One of the main challenges of online polymerization monitoring has been to translate these characterization techniques from the off-line analytical laboratory to the reactor itself. This chapter focuses chiefly on the properties of polymer molecules themselves, with a very small amount of introductory concepts concerning viscoelastic and rheological behavior in concentrated polymer solutions and melts, and on solid-state properties. 

Important characteristics that describe static mass, conformations, and dimensions of polymer molecules have been surveyed. This has been followed by hydrodynamic properties such as diffusion and viscosity. A separate section has been used to describe the salient aspects of charged polymers and colloids in solution. From there, the collective properties of polymers were briefly introduced in terms of their solution thermodynamics, the relationship of these to the scattering of light, and to phase behavior and transitions. Concentrated polymer solutions and melts become extraordinarily complex, with time response behavior depending on polymer architecture and interactions, and this has been briefly discussed in the area of rheology. In the solid-state limit of rheology, polymers take on myriad applications in materials engineering applications, in electronics, optics, and other areas. 

In this chapter, we have presented the fundamentals of molecular theory for the viscoelasticity of flexible homogeneous polymers, namely the Rouse/Zimm theory for dilute polymer solutions and unentangled polymer melts, and the Doi-Edwards theory for concentrated polymer solutions and entangled polymer melts. In doing so, we have shown how the constitutive equations from each theory have been derived and then have compared theoretical prediction with experiment. The material presented in this chapter is very important for understanding how the molecular parameters of polymers are related to the rheological properties of homopolymers. 

Electrolyte Effect on Polymer Solution Rheology. As salt concentration in an aqueous poly(1-amidoethylene) solution increases, the resulting brine becomes a more Theta-solvent for the polymer and the polymer coil compresses(47) This effect is particularly pronounced for partially hydrolyzed poly(l-amidoethylene). The... 

There are three situations that appear to be relevant here. First, we may think of a solid polymer formed from the melt second, the much more compliant elastomers that initially come to mind when we think of rubber elasticity and third, polymer gels formed in polymer solutions. In each case the details of the physical chemistry of the macromolecules is crucial to the understanding of the structure that is formed. In this section we will concentrate on organic macromolecules because the rheology of these molecular systems is often the reason for their use. 

Graessley and co-workers have studied the rheological properties of solutions of branched PVAc in diethyl phthalate (178, 188), using polymer concentrations of 0.17, 0.225, and 0.35 g ml-1. At the lowest concentration, the low shear-rate viscosity was simply related to [17], so that it was lower for branched polymers the equation ... 

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