A Group Contribution-Based Model to Predict Organic Solvent Diffusivities in Amorphous Rubbery Polymers

Abstract

ABSTRACT:A modified free-volume model was developed to predict solvent diffusion coefficients in amorphous rubbery polymers, with the introduction of the Sanchez-Lacombe equation-of-state (EOS) into the free-volume theory. The characteristic parameters of the EOS are the only introduced parameters, and they can be determined with the knowledge of polymer structural units. Since all of the parameters with respect to the polymer can be determined by the group contribution method, this model provides feasibility to correlate the solvent diffusivities with polymer structures, without the knowledge of any diffusion or viscoelastic data. The calculations of infinite dilution diffusion coefficients and solvent self-diffusion coefficients for seven kinds of organic solvents in seven kinds of polymers were generally consistent with the published experimental results. The diffusion phenomena of organic solvents in polymers play an important role in many industrial processes, such as polymer processing and drying of solvent coated polymer films. More particularly, estimation of solvent diffusivities is one of the key factors to develop a design methodology for polymeric membrane based organic mixture separation, such as pervaporation (PV) and vapor permeation (VP).During the past 50 years, the free-volume theory, especially the one developed by Vrentas and Duda, has served as the main basis for the description of transport properties in polymer solutions.1-10 The distinct characteristic of this representative model is that there are no adjustable constants and most parameters can be obtained from pure component data. According to this model, the free volume is the controlling factor for solvent jumping in an amorphous rubbery polymer, and the free-volume parameters of some common solvents and polymers have been published, using the viscosity-temperature data.4,10 However, due to the lack of viscosity data in the literature, the available free-volume parameters are still insufficient especially for polymers, the physical properties of which are more complicated and uncertain than those of solvents. In recent papers, 11,12 equations-of-state (EOSs) have been introduced to estimate the free volume of polymer, and the complicated process of measuring polymer viscoelasticity has been avoided. However, it still suffers from the limitation that the characteristic parameters of the polymers summarized in the literature are also limited, which obviously restricts the application of the diffusion model. In addition, predictions of infinite dilution diffusion coefficient, which can provide convincing examination of the reliability of the modified model, are not given. In order to remove these shortcomings, the present work will predict the solvent diffusivities in polymers from group contribution method, using the chemical formula of polymer structural units as input. EXPERIMENTALAccording to the free-volume model established by Vrentas and Duda, 4,10 for an amorphous rubbery polymer-solvent system, the solvent self-diffusion coeffic...

Stability Enhancement of a Plastic Additive (Dimethyl Phthalate,DdMP) with Environment-Friendly Based on 3d-QSAR Model

“…The frequency values of the seven DMP derivatives were all greater than 0, so the newly designed DMP derivatives could theoretically exist stably in the environment [33]. The relative molecular mass of the plasticizer affects its mobility and diffusion rate in the polymer when the larger relative molecular weight of plasticizer is; it has larger molecular group volume and less easy to jump in the polymer hoes [42]. The larger the relative molecular weight, the more difficult it is for the molecules to diffuse in the plastic products; further, if the amount of plasticizer reaching the plastic surface is low, the volatilization from the plastic surface and the migration probability will be low [43].…”

Prediction of Solvent Diffusivities in Amorphous Polymers by Free-Volume Theory: Group Contribution and PALS Methods

“…While much work developed approaches from viscoelastic data, [6][7][8][9][10][11][12][13] or EOSs, [16][17][18] the characteristic parameters of which have to be obtained from pressure-volume-temperature (PVT) data for polymers inspected. The amount of such available experimental data is insufficient, especially for polymers containing non-hydrogen atoms, rings or double bonds, or novel polymeric structures which have not yet been synthesized at present.…”

“…By contrast, the viscosity-temperature or PVT data must be collected and analyzed in the previous models. [6][7][8][9][10][11][12][13][16][17][18] The introduction of van der Waals volume into the model exhibits advantages from a design point of view, since all the parameters with respect to polymer can be determined with the knowledge of polymer structural unit. The van der Waals volume is a basic physical quantity of matter, meaning that this group contribution approach is not limited by group values as in the previous study.…”

“…The van der Waals volume is a basic physical quantity of matter, meaning that this group contribution approach is not limited by group values as in the previous study. 18 The parameters and D 01 are obtained with the methods in ref 9, in which sensitivity analysis is also given. Those evaluation methods of and D 01 are common treatment for the determination of solvent diffusion coefficient in most studied polymer-solvent systems, [9][10][11][12][13] and might possibly be improved by combining these two parameters with the van der Waals volume of polymer structural units.…”

“…[6][7][8][9][11][12][13] In our previous work, theoretical equations-ofstate (EOSs) (i.e., hole theory and lattice-fluid theory) were employed to determine the free volume of polymer, and measurements of viscoelasticity can be avoided. [16][17][18] These EOSs have a statistical-mechanical nature and a reduced dimensionless form to describe volumetric properties for polymer liquids. However, it is considered that modification of the free-volume theory is not limited to the EOS-approach.…”