Associate Professor of Chemical Engineering
B.S.: Ege University
M.S.: Ege University
Ph.D.: The Pennsylvania State University
Assoc. Prof.: Izmir Institute of Technology
Tel: (+90) 232 750 6658
The common thread of my research interests is the aplication of transport phenomena principles to systems involving polymers and macromolecules. In particular, my activities span experimental, modeling and theoretical studies in polymeric systems which are of interest to scientists and engineers involved in the design , control and operation of various polymer processes including devolatilization of polymers and production of films, coating , paints, foams and membranes.Modeling of the Drying of Multicomponent and Multilayer Polymer Films
The production of polymer films and coatings from the drying of polymer-solvents solutions is a key process in the production of numerous materials from adhesive tapes, photographic films to various functional coatings. Modeling of this process is critical for optimal design and operation of dryers. This modeling involves simultaneous heat and mass transfer mechanisms in the polymer phase with similar transport processes in the gas phase. Key components of modeling such processes are incorporation of an accurate theory for predicting concentration and temperature dependency of mutual diffusion coefficients of polymer solution as well as the phase equilibria relationships at polymer-polymer and polymer solution-gas interfaces. The predictions from the models provide detailed information about the relative importance of internal and external resistances to drying, effect of operating conditions, effect of multiple zone approach as well as sensitivity of all physical properties on the drying rate. The experimental aspect of this work consists of evaluating data obtained from industry and data collected using Ohaus Moisture Determination Balance.Modeling of Diffusion in Closed Cell Polymeric Foams
Closed cell foams made of polymers have the lowest thermal conductivity of any currently available insulation material other than vacuum insulation systems. The increase of foam conductivity with age occurs as air diffuses into the foam while the blowing agent diffuses out, thus modifying the cell gas composition. Also, the change in cell gas composition influences the dimensional stability of the foams. To predict the long term aging behavior and dimensional stability of these foams, the diffusion characteristics of the different components need to be known. For this purpose, an unsteady state model is derived which has a potential to incorporate any form of equilibrium relationship and concentration dependent diffusion coefficients.The numerical solution algorithm is developed to efficiently solve the large number of coupled equations resulting from this model.
Supercritical Devolatilization of Polymers
The presence of impurities such as residual solvents, unreacted monomer, catalysts and side reaction products can adversely affect the end use properties of polymeric materials. Conventional devolatilization techniques have limited effectiveness. Devolatilization with supercritical fluids, however can enhance the impurity removal by increasing thermodynamic driving force and molecular diffusivity. Modeling of this process indicated that in addition to these two effects, the nonideal volumetric bahavior of polymer solution can cause convection induced by diffusion which can influence the transport of impurities out of the poymer. Preliminary experiments conducted at Penn State, Chemical Engineering Department indicated that a unique mechanism in glassy polymers may lead to significant enhancement of impurity removal during depressurization stage of the extraction process.
Modeling of Multicomponent Diffusion
Most important industrial seperation technologies and physiological processes involve simultaneous diffusion of multiple components. The applicability of generalized Fick�s law to simple liquids or polymeric systems is limited since information about the relationships between self and mutual diffusion coefficients remains unavailable. In this work, two methods of accurately predicting multicomponent diffusion coefficients from self diffusion and thermodynamic data are proposed. The models are applied to predict drying behavior of ternary system and have been tested using experimental data for low molecular weight mixtures.My research activities involve collaboration with a Center For the Study of Polymer-Solvent Systems (CSPS) at The Pennsylvania State University in Chemical Engineering Department and with individual industrial partners from Europe as well as the United States. I�m currently focused on basic understanding of diffusion in multicomponent systems and analysis of different multicomponent diffusion theories in terms of their consistencies. Current efforts at CSPS labarotories aim at multicomponent diffusion measurements which will be very useful in testing these theories. My activities have always been centered on the numerical analysis of complex nonlinear partial differential equations resulting from coupled heat and mass transfer, moving boundaries, diffusion induced convection, coupling of mass transfer with changes in polymer morphology, and highly non-ideal multicomponent polymer systems. These attempts include development of efficient numerical algorithms to solve large number of equations in a reasonable time without using any expensive computational sources.
Measurement of Sorption and Transport Properties of Polymer-Solvent Systems
Transport behavior of small molecules in polymers plays an important role in many areas of polymer processing and applications of polymers. A few examples include i) Time controlled release products ii) Paints and coatings iii) Polymerization reactions iv) Controlled morphology v) Film production vi) Packaging and barrier membrane synthesis vii) Dyeing of fabrics viii) Membrane separation processes . In order to design or optimize these various diffusion controlled processes, it is necessary to measure diffusivity and solubility of small molecules in polymers .We are using magnetic suspension balance to measure both diffusivity and solubility of small molecules in polymers. This is a relatively new concept which allows to weigh samples contactlessly under nearly all ambient conditions. Instead of hanging directly at the balance , the polymer sample is linked to a suspension magnet.An electromagnet maintains the freely suspended state of the suspension magnet through an electronic control unit. Using this magnetic suspension coupling, the measuring force is transmitted contactlessly from the measuring chamber to the microbalance located outside the chamber under ambient atmospheric conditions. The apparatus can be used to measure both low and high pressure sorption data in a wide temperature range. The diffusivity data obtained in a limited temperature and concentration range is correlated using Vrentas-Duda free volume theory. These correlations can then be practically used in modeling diffusion controlled processes mentioned above.
Modeling of Asymmetric Membrane Formation and the Application of Asymmetric Membranes in Controlled Release of Drugs
After the development of asymmetric membranes by Loeb and Sourirajan in 1962, polymeric membranes have achieved commercial importance in many separation applications in the chemical, food, pharmaceutical and biotechnology industries. The alternative uses of membranes in biomedical applications are increasing everyday. People whose kidneys fail to function properly due to disease, injury or birth defects undergo hemodialysis to remove metabolic waste products from their blood.The majority of asymmetric membranes are produced by phase inversion process in which a solution of the polymer in a solvent is spun or injected into a non-solvent or a homogeneous polymer solution consisting of solvent(s) and nonsolvent(s) is cast on a support. During these processes, the solvent will diffuse out of the polymer solution and the non-solvent will diffuse in or both solvent and nonsolvent will evaporate under convective conditions. Consequently, in both techniques, initially homogeneous polymer solution thermodynamically becomes unstable and phase separates into polymer lean and polymer rich phases. The polymer rich phase forms the matrix of the membrane , while, the polymer lean phase rich in solvents and nonsolvents, fills the pores. The major challenge in all these techniques is to form defect free membrane structures having both high permeability and selectivity. The permeability and high selectivity is imparted by the skin layer while the mechanical strength is provided by the porous sublayer. Based on specific application, desired purity of the permeate and operating costs, structural characteristics of the membrane such as, fraction of the dense top layer and porous sublayer , size and shape of the pores, can be adjusted by optimizing the membrane preparation conditions. The optimization usually requires time consuming, extensive trial and error experimentation. This difficulty can be greatly overwhelmed by accurate and reliable mathematical models required to understand and to control membrane formation process and morphology. A fundamental description of this membrane formation process involves detailed information concerning the phase equilibria and the thermodynamics of this three-component polymer-solvent-non-solvent system as well as the diffusion characteristics of the solvent and the non-solvent. My research activities in this area involve modeling of membrane formation by phase inversion techniques. These activities include i) formulation and numerical solution of models, ii) verification of model predictions using real time gravimetric measurements iii)measurement and correlation of thermodynamic and diffusion behavior of the polymer -solvent-nonsolvent system.In my group, the application of asymmetric membranes is in the area of controlled release of drugs. In conventional controlled release systems, the structure of the membrane surrounding the drug tablet is usually dense and symmetric, thus, influx of water into the membrane is slow, prolonging the release of drug. To achieve useful drug release rates, we are applying the asymmetric type membrane coating on drug tablets. Our aim is to determine the permeability of the coating to drug molecules and release kinetics as well as to investigate the structure of the membranes prepared under different conditions.
Publications in Journals Cited By Science Citation Index
- Alsoy, S., and J.L. Duda, "Influence of Swelling and Diffusion-Induced Convection on Polymer Sorption Processes ", AIChE Journal, 48, 1849-1855 (2002).
- Alsoy, S., "Predicting Drying in Multiple-Zone Ovens", Industrial and Engineering Chemistry Research, 40, 2995-3001 (2001).
- Zielinski, J.M., and S. Alsoy, "Onsager Consistency Checks For Multicomponent Diffusion Models", Journal of Polymer Science: Part B : Polymer Physics, 39, 1496-1504 (2001).
- Alsoy, S., and J.L. Duda, "Processing of Polymers with Supercritical Fluids", Chem. Eng.& Tech., 22, 971-973 (1999).
- Alsoy, S. and J.L. Duda, "Modeling of Multilayer Drying of Polymer Films", J. Polym. Sci: Part B: Polym. Phys, 37, 1665-1675 (1999).
- Alsoy, S. and J.L. Duda, "Modeling of Multicomponent Drying of Polymer Films", AIChE Journal, 45, 896-905 (1999).
- Alsoy, S. "Modeling of Diffusion in Closed Cell Polymeric Foams", J. of Cellular Plastics, 35, 247-271 (1999).
- Alsoy, S. and J.L. Duda, "Supercritical Devolatilization of Polymers", AIChE Journal, 44, 582-590 (1998).
- Alsoy, S. and J.L. Duda, "Drying of Solvent Coated Polymer Films", Drying Technology, 16, 15- 44(1998).Publications in Proceedings of International Conferences
- Altinkaya, S. Alsoy, H. Yenal, S. Akkurt, "Asymmetric Membrane Tablet Coatings for Controlled Release of Drugs", 3rd Mediterranean Chemical Engineering Conference ,
- Alsoy, S. and B. Özbaş, "Modeling of Asymmetric Membrane Formation By Dry- Casting Method", 2001 Prague Meetings on Macromolecules, 41st Microsymposium Polymer Membranes, Prague, SL7, International Union of Pure and Applied Chemistry, Czech Chemical Society, 2001.
- Özbaş, B., H. Yenal and S. Alsoy, "Preparation of Cellulose Acetate Films By Dry Casting Method and Investigation of Properties", 2nd International Packaging Congress and Exhibition, İzmir, 261-267, Kimya Mühendisleri Odası Ege Bölge Şubesi, 2001.
- Alsoy, S. and J. L.Duda, "A Novel Approach To Predict Multicomponent Diffusion", Eastern Mediterranian Chemical Engineering Conference, Ankara , 333-334, Middle East Technical University, 2001.
- Alsoy, S., "Modeling of Multicomponent Polymer Drying Processes in Multiple Zone Industrial Dryers", Proceedings ECS'99 3rd European Coating Symposium , Advances in Coating and Drying of Thin Films, Nürnberg, 393-398, Shaker Verlag, Aachen, Germany, 1999.
- Alsoy, S., and J.L. Duda, "A Physical Model For Drying of Multicomponent Polymer Films", The 35th Annual Conference and the Tri-National American-Turkish-Israeli Conference, Haifa, Israel, 31 -33, Israel Institute of Chemical Engineers, 1999.
- Alsoy, S., and J.L. Duda, "Modeling of Multilayer Drying of Polymer Films", 9th International Coating Science and Technology Symposium, Newark, Delaware, USA, 339-342, International Society of Coating Science and Technology, 1998.
- Alsoy, S., and J.L. Duda, "Modeling of the Drying of Multıcomponent Polymer Films", PPS-13, 13th International Meeting, Secaucus, NJ, USA, 9-G1-9G2, The Polymer Processing Society, 1997.Publications in Proceedings of National Conferences
- Alsoy, S. and B. Özbaş, "Kuru Döküm Metoduyla Asimetrik Membran Oluşumunun Matematik Modellemesi", 4.cü Ulusal Kimya Mühendisliği Kongresi, İstanbul Üniversitesi, 2000.
- Alsoy, S. and J.L. Duda, "Polimer Teknolojisinde Süperkritik Akışkanların Kullanımı", 4.cü Ulusal Kimya Mühendisliği Kongresi, İstanbul Üniversitesi, 2000.
- Alsoy, S., "Polimer Köpüklerindeki Difüzyonunun Modellenmesi," KÖPÜK,Teori ve Uygulamaları Sempozyumu, İzmir, 169-190, Ege Üniversitesi, 1999.
- Alsoy, S., and J.L. Duda, "Drying of Solvent Coated Polymer Films", Proceedings of the Second Turkish Chemical Engineering Congress, İstanbul, 96-122, İstanbul Technical University, 1996.Presentations at International Conferences
- Zielinski, J.M. and S. Alsoy, "Onsager Consistency Checks For Multicomponent Diffusion Models", AICHE Annual Symposium, Dallas, Texas, 1999.
- Alsoy, S., and J.L. Duda, "Modeling of Multilayer Drying of Polymer Films", AICHE Annual Symposium, Miami, Florida, 1998.
- Alsoy, S., and J.L. Duda, "Modeling of the Drying of Multicomponent Polymer Films", AICHE Annual Symposium, Los Angeles, California, 1997.
- Alsoy, S., and J.L.Duda, "Drying of Solvent Coated Polymer Films", AICHE Annual Symposium, Chicago, Illinous, 1996.
- Duda, J.L. and S. Alsoy, "The Role of Diffusion Induced Convection and Relaxation in Supercritical Devolatilization of Polymers", AICHE Annual Symposium, Chicago, Illinous, 1996.
- Alsoy, S., and J.L. Duda, "Modeling of Drying of Binary Polymer Solutions", NATO Summer School, Antalya, 1995.
- Ülkü, S., and S. Alsoy, "Natural Zeolites in Water Treatment", AICHE Annual Symposium, San Francisco, California, 1994.Reviewer in Journals
- Environmental Science and Technology , 2000.
- Journal of Polymer Science:Part B: Polymer Physics, 2001.Chairs in Conferences
- 4th International Thermal Energy Congress, ITEC2011, Heat and Mass Transfer II, 8-12 Temmuz 2001, Altınyunus, Çeşme, İzmir.
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