The purpose of this course is to provide undergraduate students with the knowledge to understand the basic principles of rheology and polymer processing. Students are first introduced to the concept of polymer, its basic properties (e.g. average molecular weight, glass transition temperature, macromolecular architecture), in order to understand how polymers and why they differ from other common materials. Students are then introduced to the concept of shear viscosity and viscous non‐ Newtonian fluids through various constitutive equations. The constitutive equations are then used to analyze one‐dimensional flow problems in conduit‐type geometries. Students are then introduced to the basic types of rheological measurements of polymeric melts and solutions: capillary viscometry and melt flow indices, which are accompanied by experimental data calculations and regression. The concepts of elongational viscosity (and melt strength), normal stresses and how they are measured are presented. Subsequently, the problems of polymeric melt instabilities that occur as they exit flow channels are introduced. It is presented how the elastic behavior of polymer melts is related to the type and extent of instability. Students are then introduced to dynamic rheological measurements and how one can derive information about molecular architecture and how it relates to the final properties of the product. The next piece of material is devoted to the basic method of making polymeric products: single‐screw extrusion. The types of extruders, the structure and geometry of the screw are introduced, as well as how the polymer flow within the screw is modeled. Mixing elements (e.g. Maddock, Egan etc) mounted at the end of the screw are also presented. Detailed calculations are performed for torque and extruder power consumption. Next, the types of extrusion dies and extruders for film, film, tube and profile type are analyzed. Part of the analysis is devoted to describe the flow within the heads through calculations. How the flow is related to polymer rheology is also discussed. The heat transfer of the extruder and the die is then shown and calculated. Methods for designing extrusion dies through one‐dimensional flow calculations and flow simulation software are presented and analyzed, combined with real rheological measurement data.

Basic properties of polymers: Glass transition temperature, average molecular weight and molecular weight distribution, density, macromolecular architecture, etc.
Shear viscosity: Non‐Newtonian Rheological Models: Ostwald‐De Waele, Carreau‐Yasuda, Cross. One‐dimensional non‐Newtonian flow in a conduit, between parallel and converging conduits. Non‐ Newtonian Couette flow. Flow analysis in capillary viscometer and melt flow indices (melt flow rate‐ MFR). Rabinowitsch correction. Non‐isothermal flow. Method of measuring slip on the wall. Shear viscosity models for 3D flow analysis.
Viscoelasticity: Some unusual rheological phenomena. Deborah number and Weissenberg number. Maxwell fluid model. First and second normal stress difference. Extensional/elongational viscosity. Flows in sudden contractions. Bagley correction. Extensional viscosity calculations using the Cogswell method. Constitutive equations: Generalized Newtonian Fluid, Convected Maxwell Model, De Gennes model, K‐BKZ model. Die swelling. Melt elasticity and stress relaxation phenomena.
Polymer instabilities at the exit of channels: sharkskin, melt fracture, die lip build‐up (drool) and surface tearing of an extrudate containing natural fillers (such as wood chips, rice hulls, etc.).

Dynamic rheological measurements in rotating viscometers: Cone‐plate and parallel plate rheometer. Small Amplitude Oscillatory Shear (SAOS) viscometry. Storage modulus, loss modulus, complex viscosity, Cox‐Merz rule. Melt strength.

Single‐Screw Extrusion (SSE): Melt pump design, melt‐fed extruder flow calculations, Couette flow with positive and negative pressure gradients, extruder operating point, solid transport, types of rough barrels, melting in the extruder, pumping, screws with Maddock and Egan mixing elements, dispersive and distributed mixing, power consumption calculations, multi‐flighted screws, calculations and analysis of a typical extruder.
Extrusion dies: (i) flat film extrusion dies, flat film design, polymeric materials used, (ii) blown film extrusion and relevant polymeric materials, blown film bubble shape, (iii) multilayer co‐extrusion in flat film and blown film extrusion dies, instabilities due to viscosity incompatibility of layers, interfacial instabilities and multilayer one‐dimensional flow analysis, (iv) pipe and tube extrusion, types of extrusion dies, weldlines, pipe calibration unit, corrugated pipes, Barlow equation for peripheral pipe burst strength, (v) profile extrusion, balanced and unbalanced flow, types of profile dies.
Twin Screw Extrusion (TSE): operating principles, types of screws, co‐rotating and counter‐rotating twin screw extruders, co‐rotating fully intermeshing TSEs, Low speed counter‐rotating intermeshing twin screw extruders.

Προτεινόμενη Βιβλιογραφία :

• J. Vlachopoulos and N.D. Polychronopoulos, Understanding Rheology and Technology of Polymer
  Extrusion, First Edition, Polydynamics Inc, Dundas, Ontario, Canada (2019).
•  S. Middleman, Fundamentals of Polymer Processing, McGraw Hill (1977)
•  R.B. Bird, R.C. Armstrong, O. Hassager, Dynamics of Polymeric Liquids vol. 1, Wiley (1987)
•  D.H. Morton‐Jones, Polymer Processing, Chapman and Hall, London (1989).
•  C.W. Macosko, Rheology: Principles, Measurements and Applications, VCH Publishers (1994).
•  J.M. Dealy, K.F. Wissbrun, Melt Rheology and its Role in Plastics Processing, Chapman and Hall,
  London (1996)
•  T.D. Papathanasiou and D.C. Guell, Flow Induced Alignment in Composite Materials, Woodhead Publishers (1997)

Related Academic Journals

• Journal of Rheology
• Rheologica Acta
• International Polymer Processing
• Polymer Engineering and Science
• Advances in Polymer Technology
• Journal of Polymer Science Part
• Polymer Physics
• Applied Rheology
• Macromolecules

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Lectures