Properties of Polymeric Materials

The paper discusses the application of dynamic indentation method and apparatus for the evaluation of viscoelastic properties of polymeric materials. The three-element model of viscoelastic material has been used to calculate the rigidity and the viscosity. Using a measurements of the indentation as a function of a current velocity change on impact with the material under test, the contact force and the displacement diagrams as a function of time are plotted. Experimental results of the testing of polyvinyl chloride cable coating by dynamic indentation method and data of the static tensile test are presented. 

BAIRD, M. E., Electrical Properties of Polymeric Materials, The Plastics Institute, London (1973) BLYTHE, A. R., Electrieal Properties of Polymers, Cambridge University Press, Cambridge (1979) FROMMER, J. E. and CHANCE, R. R., Chapter in Encyclopedia of Polymer Science and Teehnology, 2nd Edn, Vol. 5, p. 462, Wiley, New York (1986)... 

In an overwhelming majority of investigations into the effect of fillers on the mechanical properties of polymeric materials (cf., e.g. [234]) it was noted that the... 

Vettegren VI, Dzyubenko PS et al. (1979) In Structure and properties of polymeric materials. Zinatne, Riga... 

This review tries to analyze and evaluate the new phenomena disclosed in this fresh field of polymer chemistry and to outline directions of its further development. The properties of polymeric materials and the methods of their synthesis will be considered only so far as is required for the fulfilment of that task. The semiconductive properties of PCSs will not be discussed in detail, since this problem is dealt with in a number of special reviews2-8 and monographs9-11 including those written with the participation of the present authors4,8 10. Apart from the literature data, the results obtained during the last 15 years by a research team headed by the authors will be considered. The studies have been carried out mainly in the following directions ... 

After a temptative structure-based classification of different kinds of polymorphism, a description of possible crystallization and interconversion conditions is presented. The influence on the polymorphic behavior of comonomeric units and of a second polymeric component in miscible blends is described for some polymer systems. It is also shown that other characterization techniques, besides diffraction techniques, can be useful in the study of polymorphism in polymers. Finally, some effects of polymorphism on the properties of polymeric materials are discussed. 

Some relevant effects of the polymorphism on the properties of polymeric materials are shown in the final section. In particular, it is shown that, while the occurrence of transitions between polymorphic forms can be detrimental for some systems, a precise knowledge of the polymorphic behavior and of the physical properties of the single forms can be used advantageously to improve the in use properties as well as the processing conditions of some polymeric materials,... 

When we consider the mechanical properties of polymeric materials, and in particular when we design methods of testing them, the parameters most generally considered are stress, strain, and Young s modulus. Stress is defined as the force applied per unit cross sectional area, and has the basic dimensions of N m in SI units. These units are alternatively combined into the derived unit of Pascals (abbreviated Pa). In practice they are extremely small, so that real materials need to be tested with a very large number of Pa... 

This second group of tests is designed to measure the mechanical response of a substance to applied vibrational loads or strains. Both temperature and frequency can be varied, and thus contribute to the information that these tests can provide. There are a number of such tests, of which the major ones are probably the torsion pendulum and dynamic mechanical thermal analysis (DMTA). The underlying principles of these dynamic tests have been covered earlier. Such tests are used as relatively rapid methods of characterisation and evaluation of viscoelastic polymers, including the measurement of T, the study of the curing characteristics of thermosets, and the study of polymer blends and their compatibility. They can be used in essentially non-destructive modes and, unlike the majority of measurements made in non-dynamic tests, they yield data on continuous properties of polymeric materials, rather than discontinuous ones, as are any of the types of strength which are measured routinely. 

In order to modify the properties of polymeric materials or create new materials with specific properties, various techniques have been used including polymer blending, copolymerization, and... 

Electrokinetic processes are widely used in different fields of science and technology. We had already mentioned the use of electrokinetic processes for research into the electric properties of surface layers of insulating materials. Such measurements are used, in particular, when studying the surface properties of polymeric materials, their behavior in different media, and their interactions with other materials (e.g., with adsorbing surface-active substances). The results of this research are used in textile, cellulose and paper, and other industries. 

What is meant by weather resistance What environmental factors can alter the properties of polymeric materials ... 

It Is well known that mechanical properties of polymeric materials are greatly deteriorated by UV exposure (2-j)). The nature of this deterioration was determined using non-strained samples which were photooxidized at 37°C. Engineering stress-strain curves as a function of UV exposure are shown in Figure 1. The numbers next to each curve represent days of UV exposure. In terms of degradation, the points of interest are ... 

Polymerization processes represent an extremely important aspect of the chemical processing industry. Since many of the properties of polymeric materials are markedly affected by their average molecular weight and their molecular weight distribution, the design of reactors for polymerization processes offers many opportunities for the use of the principles presented earlier in this chapter. 

The. aiftlicatiaiL at qtgssuis. has. a. djamaJk. dta. oa. tjjfi. mo aiusaL properties of polymeric materials. The precise nature of this effect varies with such factors as temperature, polymer, molecular weight and distribution, and magnitude of applied pressure. Each material must be evaluated separately under the specific conditions of use. 

It is known that the structures present in a polymer reflect the processing variables and that they greatly influence the physical and mechanical properties. Thus, the properties of polymeric materials are influenced by their chemical composition, process history, and the resulting morphology. Morphological study usually requires two preparatory steps prior to the study itself selection of instrumental techniques and development of specimen preparation techniques. Structural observations must be correlated with the properties of the material in order to develop an understanding and applications of the material. Figure 22.1 illustrates the types of optical microscope (OM) techniques commonly used to examine polymer specimens [2]. 

Dynamic properties Mechanical properties of polymeric materials exhibited under repeated cyclic deformation. 

Apicella, A., Nicolais, L., Mikols, J. K., Seferis, J. J. Sorption mechanisms in glassy thermosets in Interrelations between processing structure and properties of polymeric materials , J. C. Seferis and P. S. Theocaris (Eds.), Elsevier 1984... 

Mercaptopropylene sulfide has been used to modify the physical and chemical properties of polymeric materials.88... 

Many of the published reports of the application of isotopic methods in polymer chemistry have been concerned with reactions occurring during the growth of polymers by radical mechanisms. These methods, of course, are not confined either to the study of radical reactions or even to the examination of problems connected with the process of polymerization. They can be applied equally well to studies of reactions proceeding by non-radical mechanisms and to examination of certain of the chemical and physical properties of polymeric materials. 

Radiation grafting [83, 84, 85, 86, 87, 88, 89] is a very versatile and widely used technique by which surface properties of almost all polymers can be tailored through the choice of different functional monomers. It covers potential applications of industrial interest and particularly for achieving desired chemical and physical properties of polymeric materials. In this method, the most commonly used radiation sources are high-energy electrons, y-radiation, X-rays, U.V.-Vis radiation and, more recently, pulsed laser [90], infrared [91], microwave [92] and ultrasonic radiation [93]. Grafting is performed either by pre-irradiation or simultaneous irradiation techniques [94, 95]. In the former technique, free radicals are trapped in the inert atmosphere in the polymer matrix and later on the monomer is introduced into... 

The properties of polymeric material are strongly linked to the molecular weight of the polymer as shown schematically in Fig. 1.2. A polymer such as polystyrene is stiff and brittle at room temperature with a degree of polymerization, n, of 1,000. Polystyrene with a degree of polymerization of 10 is sticky and soft at room temperature. 

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