Introduction to Rheology

Rheology is the science of flow and deformation of matter and is considered a branch of physics. The flow of materials has been a concern since the earliest times. Lucretius, a 

Roman poet and philosopher born at the beginning of the 1st century bc, wrote in his poem De Rerum Natura (On the nature of things)  

For water moves and flows with so very small a moving power because it is made of small roUing shapes. But on the other hand, the nature of honey has more cohesion, its fluid is more sluggish, and its movement more tardy, for the whole mass of its matter coheres more closely assuredly because it is not made of bodies so smooth or so delicate and round. 

The science of rheology encompasses the behaviour of both solid and liquid materials. This extends from a perfectly elastic solid, defined by Robert Hooke in 1678, to a perfectly viscous liquid, defined by Newton in 1687, and to the myriad of viscoelastic materials in between. The rheology of natural thickeners is primarily concerned with viscosity and viscoelasticity. 

The fabrication of an article from a polymeric material in the bulk state, whether it be the molding of a thermosetting plastic or the spinning of a fiber from the melt, involves deformation of the material by applied forces. Afterward, the fiiushed article is inevitably subjected to stresses hence, it is important to be aware of the mechanical and rheological properties of each material, as well as understand the basic principles imderlying their response to such forces. 

In a broad sense, the term rheology (rheo meaning to flow ) refers to both studies of deformation as well as flow of materials under the influence of applied forces. Thus, the rheological behavior of polymers encompasses a wide range of macroscopic phenomena including 

In classical terms, the mechanical properties of elastic solids can be described by Hooke s law, which states that an applied stress is proportional to the resultant strain but is independent of the rate of strain. For liquids, the corresponding statement is known as Newton s law, with the stress now independent of the strain but proportional to the rate of strain. Both are hmiting laws, valid only for small strains or rates of strain, and although it is essential that conditions involving large stresses, leading to eventual mechanical failure, be smdied, it is also important to examine the response to small mechanical stresses. Both laws can prove useful under these circumstances. 

In many cases, a material may exhibit the characteristics of both a liquid and a solid, and neither of the hunting laws will adequately describe its behavior. The system is then said to be in a viscoelastic state. A particularly good illustration of a viscoelastic material is provided by a silicone polymer known as bouncing putty. If a sample is rolled into the shape of a sphere, it can be bounced like a rubber ball, i.e., the rapid apphcation and removal of a stress causes the material to behave like an elastic body. If, on the other hand, a stress is applied slowly over a longer period the material flows like a viscous liquid, and the spherical shape is soon lost if left to stand for some time. Pitch behaves in a similar, if less spectacular, manner. 

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H. A. Barnes, J. E. Hutton, and K. Walters, An Introduction to Rheology, Elsevier AppUed Science, New York, 1989. 

Andrade, E. N. da C. (1947). Introduction to Rheology. London Oil Colour Chemists Association. 

Barnes HA, Hutton JF, Walters K (1989) An introduction to rheology. Elsevier, Amsterdam... 

H.A.Bames, J. F. Hutton, K. Walters 1989, An Introduction to Rheology, Elsevier, Amsterdam. 

HN Nae. Introduction to rheology. In D Laba, ed. Rheological Properties of Cosmetics and Toiletries. New York Marcel Dekker, 1993, pp 9-33. 

Barnes HA, JF Hutton, K Walters An Introduction to Rheology. New York Elsevier, 1989. 

Comprehensive and unique in approach, this book will provide the necessary introduction to rheology for many undergraduates and graduates, as well as being valuable for laboratory and industrial staff requiring an introduction to this fascinating subject. 

Barnes, H. A., Hutton, J. F., and Walters, K., An Introduction to Rheology, Elsevier, Amsterdam, Netherlands, 1989. (Undergraduate and graduate levels. A practical introduction to the rheology of suspensions and polymer solutions. Chapter 2 presents introductory concepts and measurement techniques at the undergraduate level. Effects of colloidal interactions are not described.)... 

Hunter, R., Foundations of Colloid Science, Vol. 2, Oxford University Press, Oxford, England, 1990. (Mostly graduate level. Chapter 18 presents a graduate-level introduction to rheology of dispersions.)... 

Agilent Technologies 2003. Palo Alto, California, Agilent Technologies Impedance Measurement Handbook (December) www.optics.arizona.edu/Palmer/OPTI380B/PDFdocs/5950-3000.pdf. Allais, C., Keller, G., Lesieur, P., Ollivon, M., Artzner, F. 2003. X-ray diffraction/calorimetry coupling. A new tool for polymorphism control. J. Thermal Anal. Cal. 74, 723-728. Barnes, H.A., Hutton, J.F., Walters, K. 1989. An Introduction to Rheology. Elsevier, Amsterdam. 

Acierno D and Collyer AA (Eds) "Rheology and Processing of Liquid Crystal Polymers", Chapmann Hall, London, 1996. Barnes HA, Hutton JF and Walters K, "An Introduction to Rheology", Elsevier, Amsterdam, 1989. 

This was an introduction to rheology. If you want to go further, you will find that it is a difficult subject. For three-dimensional problems you need sophisticated mathematics to get anywhere. You will need tensor equations the three stresses Xxy, Xyx and Xyy that you have seen are three of the nine components of the stress tensor (Figure C4-17). And that is just... 

Reiner, M. (1960). Deformation, Strain and Flow An Elementary Introduction to Rheology, 2nd rev. ed. Interscience, New York. 

Figure 6.3 Relative viscosity as a function of the fraction of large spheres in a bimodal distribution of particle sizes with a 5 1 ratio of diameters, at various total volume percentages of particles. The arrow P Q illustrates the 50-fold reduction in viscosity that occurs when monosized particles in a 60 vol% suspension are replaced by a 50-50 mixture of large and small spheres. The arrow P S shows that if monosized spheres are replaced by a bimodal size distribution, the concentration of spheres can be increased from 60% to 75% without increasing the viscosity. (Reprinted from Barnes et al., An Introduction to Rheology (1989), with kind permission from Elsevier Science - NL, Sara Burger-hartstraat 25, 1055 KV Amsterdam, The Netherlands.)...

Theories of dynamics for polymer systems, which can range from neat polymers to reactive filled polymer composites, require a combined discussion of the dynamics of suspensions, polymer solutions and polymer melts. However, prior to this discussion, one should give a brief introduction to rheological terminology. (For a detailed introduction to rheological... 

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