Yuri G. Yanovsky

Rheological and Relaxation Properties of Filled Polymers

The study of viscoelastic properties of filled polymers is of important scientific and practical significance. We can argue here about the priority of the theoretical or applied approach to the problem, but one thing is certain: the filling of the polymer leads to practical purposes, extending the possibilities of its applications. Some of the questions concerning the creation of new filled polymeric compositions could probably be solved within the framework of applied investigation only. Nevertheless, it is quite obvious that a sufficiently full measure of generalization can be achieved only by using a set of data obtained by physicomechanical, thermodynamic, thermophysical, structural and other methods.

Rheological and Relaxation Properties of Copolymers

The tremendous interest exhibited in copolymers by both scientists and experimentalists is explained by the features of their physicomechanical and physicochemical properties. The practical significance of these systems is associated with the hope of obtaining novel materials with ‘exclusive’ properties in comparison with homopolymers. It can be seen from the other chapters of the present book that this goal can be achieved in different ways, in particular by creating various compositions—blends, filled, combined ones, etc. Analysis of the literature broadly reveals two typical means of ‘constructing’ such compositions. The first, and apparently the simpler is the mechanical blending of several ingredients which may be either polymers or nonpolymers. The second is ‘chemical’ blending. The ‘chemical’ filling technique, which is briefly described in Chapter 5, can be considered to a certain extent as one of its variants. But it will be expedient to consider the formation of copolymers as the ‘classical’ way of chemical blending.

Some Theoretical and Numerical Approaches to Describing the Viscoelastic Properties of Polymer Systems

Polymers are widely used in practice and have a number of unique rheological and physicomechanical properties [1, 2, 3, 4, 5]. They differ from other substances in the size of their molecules, which are correctly called macromolecules. At temperatures above the glass transition temperature or melting point, a polymer system (concentrated solution or melt of a polymer) can be considered as a viscoelastic liquid whose behavior is determined by a system of weakly bound macromolecules. When a system is excited (mechanically or by heat), the macromolecules easily change their neighbors, but the intactness of each of them is not disturbed.

Rheological and Relaxation Properties of Polymer Blends

Blending is one of the most available and effective technological ways of modifying the properties of polymers. It improves the workability of a given material and imparts the required properties to it. The components of a blend are generally incompatible systems. According to numerous publications, the properties of blend both when melted and when solid depend on many factors. They include the chemical nature of the polymers, the composition of the blends, the level of rheological action, and the influence of additives making the components compatible.

Rheological Properties, Relaxation Behavior, and Rupture of Polymers at Temperatures above their Glass Transition Temperature

At temperatures above the melting point and glass transition temperature, the physical state of a polymer system depends on the ratio of the rates of external action and of relaxation processes occurring therein caused by thermal motion. This problem is of paramount importance for understanding the features of the viscoelastic properties of polymer systems depending on their nature, rate of deformation, and temperature. It is important both for understanding the features of the structure and for determining the workableness of polymer systems.