Study Of The Equation Of State Of The Polymer Solution And Liquid

In this work two equations of state have been developed in two ways for polymer solutions and liquids. The first is to develop a simple practical model with good accuracy for chemical engineering needs by reasonably simplifying the existing complicated theoretical model. The second is to propose an "open-cell" concept and derive a model on better theoretical basis to overcome the defects of the cell theory. The two models have been extensively tested with experimental data for pure liquids and mixtures, in particular, for large molecules and polymers.The hole theory equation of state proposed by Simha and Somcynsky(SS EOS) is one of the models with good theoretical background and accuracy for polymer solutions and blends. However, the model is complicated and difficult to apply, because there is not an explicit expression for the occupied-site fraction. By applying the statistical theory for thermal defects of an imperfect crystal to polymer liquids, a simple relation between the occupied—site fraction and the reduced temperature has been derived and the SS EOS is simplified to a so called simplified hole theory equation of state (SHT EOS). The SHT EOS has been then extended to long chain hydrocarbon liquids, organic solvents and polymer solutions and blends tested with their experimental data, including P—V—T, the excess volume, the excess enthalpy, activity of solvents in polymers, and phase behavior. The results show that, the SHT EOS has the same quality as the SS EOS but with much less computing efforts.The molecular parameters for pure components in the SHT EOS have been treated by the group contribution method in this work. 14 group parameters have been obtained. Furthermore, the group contribution SHT EOS (GCSHT EOS) has been successfully used to predict the properties for n-paraffins, isoparaffins, cycloparaffins, aromatic hydrocarbons and some polymers which leads to great convenience in practical calculations.Currently, most existing models for polymer solutions are based on the concept of the cell or free volume (for example, the well— known Flory EOS and SS EOS). In practice, the cell concept stems from the solid structure, it is therefore unable to describe the features of liquids completely. Consequently, the models based on this concept can not be used to estimate the properties of polymer solutions and liquids with good accuracy. As a result, a new concept called "open— cell" is presented in this work. All the cells in liquids are assumed as "open" ones, and the molecule at the center of a cell can move out of the...