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Additive Group Contribution Methods for Predicting the Properties of Polymer Systems

Nowadays, the permanent development of modern process industries is increasingly demanding the information about the properties of new materials which have never been determined experimentally ; this concerns polymeric substances especially. The design of production and process equipment requires thorough knowledge of properties, application, and final use of the processed materials and related compounds. Methods based on structure– property relationships for the estimation and/or prediction of important properties of polymers in the solid, liquid and dissolved states, in cases where experimental values cannot be found, are considered as unavoidable. They are usually based on correlation of the properties of known polymers with their chemical structure, with interpolation or extrapolation, as required. The simplest and yet very successful method exploits the concept of additive group contributions. It will be shown here that group contribution models may be used for prediction of properties of pure polymers, polymer– solvent and polymer– polymer mixtures. Examples of properties that group contribution methods can model are the density, the solubility parameter, the melting and glass transition temperatures, as well as the surface tension. Phase equilibrium for polymer solutions and blends can also be predicted by using these methods. During the last decade, dramatic development occurred in the applications of group contribution models for polymers. Many different models have been developed for polymeric systems, particularly for prediction of the vapor– liquid equilibrium (VLE), solubility limits in liquid– liquid (LLE) and solid– liquid equilibrium (SLE), selective dissolution, gas solubility, applications related to techniques for tailoring or modifying polymers with the desired physical properties, applications related to biotechnology, and many others. The state-of-the-art can be easily understood taking into account that polymer solutions and blends are complex systems, with frequent occurrence of liquid immiscibility in many forms, significant effect of temperature and polymer molar mass in phase equilibrium, the free– volume effects, and other factors causing these phenomena. The choice of a suitable model, as discussed here, usually depends on the given problem and demands, especially on the type of mixture (solution or blend, binary or multicomponent), type of phase equilibrium (VLE, LLE, SLE), conditions (temperature, pressure, concentration), and the type of calculation (accuracy, speed, yes/no answer, or complete design). These models together with factual data banks create powerful software tools for the reliable development of chemical processes. The status of the different approaches, the performance of various models, and important applications of industrial interest using either thermodynamic information derived from data banks or predictive thermodynamic models are presented in this review.

Group contribution (GC) methods, polymer systems properties, prediction, correlation, vapor– liquid equilibrium (VLE), liquid– liquid equilibrium (LLE)

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