Group Contributions GC

Section 16.2 will discuss the concept and importance of the group-contribution (GC) approach in estimating two polymer properties, which are relevant for polymer solutions and blends the density and the solubility parameter. The GC technique is employed in several of the thermodynamic models discussed later in the chapter. 

Many properties of pure polymers (and of polymer solutions) can be estimated with group contributions (GC). Examples of properties for which (GC) methods have been developed are the density, the solubility parameter, the melting and glass transition temperatures, as well as the surface tension. Phase equilibria for polymer solutions and blends can also be estimated with GC methods, as we discuss in Section 16.4 and 16.5. Here we review the GC principle, and in the following sections we discuss estimation methods for the density and the solubility parameter. These two properties are relevant for many thermodynamic models used for polymers, e.g., the Hansen and Flory-Hug-gins models discussed in Section 16.3 and the free-volume activity coefficient models discussed in Section 16.4. 

The two most important bases for formulating correlations for estimating the properties of organic compounds (indeed of any compound) are the law of corresponding states (LCS), and the method of group contributions (GC). 

In group-contribution (GC) methods the properties of the system of interest (a pure compound or a mixture) are described in terms of the functional groups... 

In any group-contribution (GC) method, the basic idea is that whereas there are thousands of chemical compounds of interest in chemical technology, the number of fxmctional groups that constitute these compounds is much smaller. Assuming that a physical property of a fluid is the sum of contributions made by the molecule s functional groups, GC methods... 

Outputs emission to air, water, and soil Group-contribution+ (GC+) property models are used as the predictive models to calculate characterization factors (CFs) of 8 impacts ... 

C, shake flask-GC, calculated-group contribution, Polak Lu 1973)... 

After the seminal work of Guggenheim on the quasichemical approximation of the lattice statistical-mechanical theory[l], various practical thermodynamic models such as excess Gibbs energies[2-3] and equations of state[4-5] were proposed. However, the quasichemical approximation of the Guggenheim combinatory yields exact solution only for pure fluid systems. Therefore one has to resort to numerical procedures to find the solution that is analytically applicable to real mixtures. Thus, in this study we present a new unified group contribution equation of state[GC-EOS] which is applicable for both pure or mixed state fluids with emphasis on the high pressure systems[6,7]. 

Input data Group contributions from Tables 2-361 and 2-362. Description A simple GC method with first-order contributions with lower flammability limit (LFL) and upper flammability limit (UFL) in volume % given by... 

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