Chemical Engineering / Kimya Mühendisliği
Permanent URI for this collectionhttps://hdl.handle.net/11147/14
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Article Citation - WoS: 8Citation - Scopus: 8Phase Equilibrium and Diffusion of Solvents in Polybutadiene: a Capillary-Column Inverse Gas Chromatography Study(John Wiley and Sons Inc., 2002) Cai, W. D.; Ramesh, N.; Tıhmınlıoğlu, Funda; Danner, Ronald P.; Duda, John Larry; De Haan, A.The capillary-column inverse gas chromatography method was used to measure the diffusion and partition coefficients of ethylbenzene, styrene, and acrylonitrile in polybutadiene (PBD) at infinite dilution of the solvents. Experiments were performed over a temperature range of 50-125°C. At temperatures well above the glass-transition temperature of PBD, the diffusivities were correlated using an Arrhenius expression. The Arrhenius parameters in turn were intercorrelated and shown to be a function of the occupied volume, thus providing a method for predicting the diffusion of other solvents in the same polymer. Further, the activation energy was predicted using the Duda-Vrentas free-volume approach. The activation energy thus obtained was compared with the activation energy of the Arrhenius approach. The weight-fraction activity coefficient data were compared to the predictions of the group contribution, lattice-fluid equation-of-state, and the UNIquac Functional-group Activity Coefficient (UNIFAC) free-volume models.Article Citation - WoS: 5Citation - Scopus: 5Solvent Sorption in a Polymer-Solvent System - Importance of Swelling and Heat Effects(Elsevier Ltd., 2006) Alsoy Altınkaya, Sacide; Ramesh, Narayan; Duda, John LarrySorption experiments are often conducted in gravimetric sorption columns where several deviations from ideal conditions could potentially occur. For example, heat effects due to solvent sorption, errors introduced due to concentration dependent diffusion coefficients and swelling are unavoidable. In this study, we develop a model to study the importance of the combination of these effects in obtaining diffusion coefficients from sorption experiments. The model is used to explore a wide range of operating conditions and physical parameters.Article Citation - WoS: 26Citation - Scopus: 28Influence of Swelling and Diffusion-Induced Convection on Polymer Sorption Processes(John Wiley and Sons Inc., 2002) Alsoy Altınkaya, Sacide; Duda, John LarryUnsteady-state sorption of a vapor or liquid by a polymer is modeled to include the influence of the moving phase boundary associated with the polymer swelling and diffusion-induced convection. A formulation presented clearly elucidates the influence of these two effects on the overall sorption process. Numerical solutions of the model equations indicate the errors that can be induced when swelling or convection are neglected. For most polymer-solvent systems, the influence of the diffusion-induced convection associated with volume changes in mixing can be neglected in the analysis of sorption processes. In contrast, the correction for the moving boundary or swelling of the polymer phase can be quite significant, particularly when a large step change in solvent concentration is considered.Article Citation - WoS: 19Citation - Scopus: 20Solvent Diffusion in Amorphous Polymers: Polyvinyl Acetate-Toluene System(John Wiley and Sons Inc., 2000) Tıhmınlıoğlu, Funda; Danner, Ronald P.; Lützow, Norbert; Duda, John LarryIn a previous publication (Tihminlioglu et al., J Polym Sci Part B: Polym Phys 1997, 35, 1279), we presented an extensive analysis of the polyvinyl acetate-toluene system. The inverse gas chromatography (IGC) technique was used to measure phase equilibria and diffusion coefficients above and near the glass-transition temperature of a polymer. At temperatures above the glass transition, the capillary column model developed by Pawlisch et al. (Macromolecules 1987, 20, 1564) was used. For the finite concentration region, the modified model of Tihminlioglu and Danner (J Chromatogr A 1999, 845, 93) was applied. Data obtained with the IGC method were in agreement with data measured with the gravimetric and piezoelectric sorption techniques. In this work, we revisit the partition coefficient issue and provide some new data at lower temperatures. At temperatures near the glass-transition temperature, the modification of the capillary column model proposed by Vrentas et al. (Macromolecules 1993, 26, 6670) was used for the infinite dilution region. The diffusion data correlated well with the Vrentas-Duda free-volume model.Article Citation - WoS: 24Citation - Scopus: 25Processing of Polymers With Supercritical Fluids(John Wiley and Sons Inc., 1999) Alsoy Altınkaya, Sacide; Duda, John LarryThe removal of impurities, such as residual solvents, unreacted monomers, catalysts, and side-reaction products from polymers represents an important step in polymer processing. Conventional devolatilization techniques for the purification of polymers have limited effectiveness. Devolatilization with supercritical fluids, however, can enhance impurity removal by increasing the thermodynamic driving force and molecular diffusivity.