Cohesive energy density CED

The quantity AU JV° is the internal energy of vaporization per unit volume and is called the cohesive energy density (CED) of component i. The square root of the CED is generally given the symbol 6j for component i. 

Table 8.2 Values of the Cohesive Energy Density (CED) for Some Common Solvents and the Solubility Parameter 6 for These Solvents and Some Common Polymers...

The internal pressure is a differential quantity that measures some of the forces of interaction between solvent molecules. A related quantity, the cohesive energy density (ced), defined by Eq. (8-35), is an integral quantity that measures the total molecular cohesion per unit volume. - p... 

Table 8-6. Internal Pressure and Cohesive Energy Density (ced) of Solvents...

The cohesive pressure (c) of a solvent, otherwise known as cohesive energy density (CED), is a measure of the attractive forces acting in a liquid, including dispersive, dipolar and H-bonding contributions, and is related to the energy of vaporization and the molar volume (Equation 1.1) ... 

To incorporate the surfactant structure concept, it is now convenient to introduce the group additive concept for cohesive energy densities (CED) introduced by Burrell and others (24, 25). Molecular segments are given a molar-attraction constant G. The CED is then determined for the ith compound as... 

The value of TMWV is dependent on the cohesive energy density (CED) of amorphous polymers, the extent of crystallinity in crystalline polymers, and the effect of reinforcements in polymeric composites. Thus, while a low molecular weight amorphous polymer may be satisfactory for use as a coating or adhesive, a chain length generally above 100 is often required if the polymer is to be used as an elastomer or plastic. 

Secondary forces operate at longer distances (.25-50 nm) than covalent bonds. These secondary forces are much weaker than primary covalent bonds, but the forces are cumulative. Thus the cohesive energy of a polymer is equal to the summation of the cohesive energy density (CED) values for each mole of repeating unit ( < 2 kcal) in the chain. The CED of a liquid is defined as the energy of vaporization per unit volume, / E/V. 

Porter has shown for several solvents a correlation between the cohesive energy density (CED) and the Onsager reaction field parameter... 

FBZ precursor and can therefore be attributed to the segregated PFPE moiety. This kind of behavior is quite general for copolymers containing PFPE macromers and also in the Z1072 and Z1073 resins themselves. The driving force is the relevant difference in solubility parameters between fluorinated and nonfluorinated macromers, since the cohesive energy density (CED) of the perfluorocopolyethers is one of the smallest known. ... 

Since the unrelaxed bulk modulus, Ku e.g., determined by ultrasonic propagation velocity measurements, is a good measure of the cohesive energy density, CED (Ku 11 CED Chapter 10), and CED gives a good indication of the overall material s polarity, one can expect a correlation between Ku and W. This is shown in Fig. 14.3 for the amine-epoxy and styrene-vinyl ester networks. The following relationship is found ... 

A term to describe the aforementioned quotient is cohesive energy density (CED heat of vaporization/unit volume). To a first approximation, the lower the CED, the lower will be the surface tension and this is the source of the increased efficiency in surface tension reduction of fluorosurfactants versus hydrocarbon surfactants. Therefore, fluorosurfactants are often the choice for applications demanding ultimately low surface tension. Furthermore, fluorosurfactants are far less compatible with water than are hydrocarbon surfactants. This is the origin of the increased effectiveness compared to hydrocarbon surfactants. 

Solubility Parameter and Surface Tension. Cohesive energy density (CED) (9) is the energy, in calories per cubic centimeter, necessary for an infinite separation of the molecule in 1 cubic centimeter of liquid versus the action of intermolecular attraction ... 

In accordance with the equation for the activation energy of diffusion proposed by Meares [31], cohesion energy density (CED) of the polymer has a significant effect on diffusion coefficients of lower hydrocarbons. This is especially typical of mbbery polymers an increase in CED results in reduction of diffusion coefficients. Similar dependencies also apply to glassy polymers [9,32]. For example, Figure 9.8a shows the dependence of diffusion coefficient of propylene on CED of both glassy and mbbery polymers. 

It is known that Tg generally increases with increasing cohesive energy density (CED) according to the following equation (Gedde, 1995) ... 

The solubility parameter, 8i, has been defined [6] as the square root of the cohesive energy density (CED), AEpVi, and describes the strength of attraction between molecules ... 

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