Characteristics of Polymers

How do the unique characteristics of polymers influence the way in which these materials are used ... 

From about 1910 onwards, physical chemists began studying the characteristics of polymer solutions, measuring such properties as osmotic pressure, and found them... 

It is evident from the foregoing discussion that MW is the fundamental characteristic of polymer, controlling the performance properties. However, simple correlation of this molecular parameter can be misleading without taking the MWD into consideration. Control of MWD provides a proper balance of polymer performance characteristics. The effect of change in MWD on the properties of PEs is given in Table 6. 

In this section the electronic structure of metal/polymcr/metal devices is considered. This is the essential starting point to describe the operating characteristics of LEDs. The first section describes internal photoemission measurements of metal/ polymer Schottky energy barriers in device structures. The second section presents measurements of built-in potentials which occur in device structures employing metals with different Schottky energy barriers. The Schottky energy barriers and the diode built-in potential largely determine the electrical characteristics of polymer LEDs. 

Kuznetsov GK, Irgen LA (1976) In Thermodynamic and structural characteristics of polymer interphases, Naukova Dumka, Kiev, p 94... 

The basic issues of scaleup are the same for pol5mier reactors as for ordinary chemical reactors. The primary problem is that the capacity for heat and mass transfer increases less rapidly than the reactor volume and throughput. The remedies are also similar, but the high viscosities characteristic of polymers... 

A surface is that part of an object which is in direct contact with its environment and hence, is most affected by it. The surface properties of solid organic polymers have a strong impact on many, if not most, of their apphcations. The properties and structure of these surfaces are, therefore, of utmost importance. The chemical stmcture and thermodynamic state of polymer surfaces are important factors that determine many of their practical characteristics. Examples of properties affected by polymer surface stmcture include adhesion, wettability, friction, coatability, permeability, dyeabil-ity, gloss, corrosion, surface electrostatic charging, cellular recognition, and biocompatibility. Interfacial characteristics of polymer systems control the domain size and the stability of polymer-polymer dispersions, adhesive strength of laminates and composites, cohesive strength of polymer blends, mechanical properties of adhesive joints, etc. 

For a polymer to form, monomers must react with one another to form links. Most monomers are organic molecules containing particular functional groups. These are groups of atoms that impart specific chemical functions. In this section, we introduce ftinctional groups that can form the linkages that are characteristic of polymers. 

In the present chapter we shall be concerned with quantitative treatment of the swelling action of the solvent on the polymer molecule in infinitely dilute solution, and in particular with the factor a by which the linear dimensions of the molecule are altered as a consequence thereof. The frictional characteristics of polymer molecules in dilute solution, as manifested in solution viscosities, sedimentation velocities, and diffusion rates, depend directly on the size of the molecular domain. Hence these properties are intimately related to the molecular configuration, including the factor a. It is for this reason that treatment of intramolecular thermodynamic interaction has been reserved for the present chapter, where it may be presented in conjunction with the discussion of intrinsic viscosity and related subjects. 

Table 10.1 Characteristics of polymers used in this study, a indicates the label content.

It should be pointed out that the employment of the statistical method in all its versions is, in essence, of a purely formal character. The expressions for statistical characteristics of polymers are traditionally obtained via speculative... 

Name at least three characteristics of polymers that exhibit statistical distributions. 

The molecular weight distribution in Fig. 5.3 a) exhibits a most probable molecular weight distribution , which is characteristic of polymers produced by metallocene catalysts. This distribution contains relatively few molecules with either extremely high or low molecular weights. Products made with this type of distribution are relatively difficult to process in the molten state, exhibit modest orientation, and have good impact resistance. 

It is through the solid state characteristics of polymers that we - as users - primarily interact with them. For convenience, we can divide the principal properties of polymers into five categories mechanical, optical, surface contact, barrier, and electrical. Weather resistance is a sixth category that can influence each of the other five categories. In order to understand these properties we must be able to quantify them. In this chapter we shall concentrate on measurement techniques, since it is through these methods that we learn how a polymer will behave during use. 

The functionalized polymers have catalytic properties similar to those of their soluble analogues.1 A solution-like character is characteristic of polymer gels. As polymers become more highly cross-linked, they lose the solution-like character and their properties approach of those of inorganic solids. 

From the above considerations, it appears that chain length is a main characteristic of polymers. Natural macromolecules, particularly in living bodies, can exhibit exact lengths, thus exact molecular masses. For instance haemoglobin molecular mass is known to within one dalton. However, a synthetic polymer... 

As a summary to this chapter focusing on polymer chemistry and microstructure, major characteristics of polymers are reported in Table 9, classified under... 

F.J. Boerio and S. Wirasate, Measurements of the chemical characteristics of polymers and rubbers by vibrational spectroscopy. In N.J. Everall, J.M. Chalmers and P.R. Griffiths (Eds.), Vibrational Spectroscopy of Polymers Principles and Practice, Wiley, Chichester, 2007, pp. 113-141. 

A general characteristic of polymers is that their hardnesses tend to be proportional to their elastic moduli, particularly their shear moduli (Flores et al., 2000). However, the shear modulus is often anisotropic so an average value may not be an appropriate measure of hardness. The modulus for the plane of shear should be a better indicator. 

The important characteristics of polymers oxidation were obtained as a result of the study of their initiated oxidation. In the presence of initiator (I) which generates the chains with the rate v, = /c,[I], the oxidation of polymer PH occurs with the constant rate v. When the macroradical P of the oxidized polymer reacts with dioxygen very rapidly (at [02]... 

The shape of the curve obtained at -78 °C was the same for all the solvents and shows a steep rise in the DP with increasing monomer concentration up to a maximum at a relatively low monomer concentration, followed by a more gradual fall to the DP characteristic of polymers obtained from undiluted monomer. The monomer concentration at which the DP maximum occurs varied from one solvent to another, as did the height of the DP peak. 

Table 1.8 displays some thermal and electrical characteristics of polymers and conventional materials. 

Table 1.9 displays some thermal characteristics of polymer and conventional materials. Metals have minimum melting points higher than 400°C and often higher than 1000°C, whereas ... 

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