Viscoelastic Properties of Polymers

Polymers owe much of their attractiveness to their ease of processing. In many important teclmiques, such as injection moulding, fibre spinning and film fonnation, polymers are processed in the melt, so that their flow behaviour is of paramount importance. Because of the viscoelastic properties of polymers, their flow behaviour is much more complex than that of Newtonian liquids for which the viscosity is the only essential parameter. In polymer melts, the recoverable shear compliance, which relates to the elastic forces, is used in addition to the viscosity in the description of flow [48]. 

Ferry J D 1980 Viscoelastic Properties of Polymers (New York Wiley)... 

Ferry, J. D., Viscoelastic Properties of Polymers, Wiley, New York, 1980. 

In principle, the relaxation spectrum H(r) describes the distribution of relaxation times which characterizes a sample. If such a distribution function can be determined from one type of deformation experiment, it can be used to evaluate the modulus or compliance in experiments involving other modes of deformation. In this sense it embodies the key features of the viscoelastic response of a spectrum. Methods for finding a function H(r) which is compatible with experimental results are discussed in Ferry s Viscoelastic Properties of Polymers. In Sec. 3.12 we shall see how a molecular model for viscoelasticity can be used as a source of information concerning the relaxation spectrum. 

How do the viscoelastic properties of polymers change upon filling ... 

C. Friedrich, K. Mattes, and D. Schulze, Non-linear Viscoelastic Properties of Polymer Melts as Analyzed by LAOS-FT Experiments, lUPAC Macro 2004, Paris, France, July 4—9, 2004, Paper 6.1.3. 

Ferry, JD (1980) Viscoelastic properties of polymers. John Wiley, New York... 

JD Ferry. Viscoelastic Property of Polymers. 2nd ed. New York John Wiley, 1970. 

R. F. Landet and R. F. Fedors, in Mechanical Behavior of Materials, Vol. III. Materials Science,1 Kyoto, Japan. 1972. p. 496. See also J. O. F erry, Viscoelastic Properties of Polymers, 1st cd., Wiley. New York, 1961. p. 463 lor tabulated values of the Marvin function. 

Ferry JD (1986) Viscoelastic properties of polymers. Wiley, New York Doi M, Edwards SF (1986) The theory of polymer dynamics. Oxford Meissner J (1975) Pure Appl Chem 42 551-574... 

In this introduction, the viscoelastic properties of polymers are represented as the summation of mechanical analog responses to applied stress. This discussion is thus only intended to be very introductory. Any in-depth discussion of polymer viscoelasticity involves the use of tensors, and this high-level mathematics topic is beyond the scope of what will be presented in this book. Earlier in the chapter the concept of elastic and viscous properties of polymers was briefly introduced. A purely viscous response can be represented by a mechanical dash pot, as shown in Fig. 3.10(a). This purely viscous response is normally the response of interest in routine extruder calculations. For those familiar with the suspension of an automobile, this would represent the shock absorber in the front suspension. If a stress is applied to this element it will continue to elongate as long as the stress is applied. When the stress is removed there will be no recovery in the strain that has occurred. The next mechanical element is the spring (Fig. 3.10[b]), and it represents a purely elastic response of the polymer. If a stress is applied to this element, the element will elongate until the strain and the force are in equilibrium with the stress, and then the element will remain at that strain until the stress is removed. The strain is inversely proportional to the spring modulus. The initial strain and the total strain recovery upon removal of the stress are considered to be instantaneous. 

Ferry, J. S. "Viscoelastic Properties of Polymers" (second ed.) Wiley New York, 1970. 

J. D. Ferry, "Viscoelastic Properties of Polymers," Wiley, New York (1970). 

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