Start
Dec 12, 2013 - 17:00
End
Dec 12, 2013 - 18:00
Venue
Creativity Hall (Room 118) Chemical Engineering
Event Type
Speaker
Prof. Sathish K Sukumaran.Ryohei Komuro Masataka Sugimoto and Kiyohito Koyama Graduate School of Science and Engineering Yamagata University Japan
Title
Slip at the interface between immiscible polymer melts
Abstract : When fluids flow the tangential component of the velocity is assumed to be continuous at phase boundaries (the no-slip boundary condition). Experimental work on Newtonian fluids especially in confined geometries has cast doubt on this assumption and the situation is currently unclear. For non-Newtonian fluds such as polymer melts shear dependent slip has been observed during flow in contact with a solid wall (wall slip). Evidence for slip at the interface between immiscible non-Newtonian fluids (interfacial slip) also exists. However even when compared to wall slip interfacial slip remains poorly understood and will be the focus of this talk. Studies that use only rheological data to deduce the slip velocity usually involve applying a shear deformation to a stack of parallel multilayers. In order to understand slip in the context of polymer extrusion we have investigated slip at the interface between two immiscible polymer melts undergoing pressure driven flow through a capillary die. To enable the measurement of slip velocity at the polymer/polymer interface we have adapted the Mooney method a method usually used to study wall slip. Using the method we measured the dependence of the interfacial slip velocity on the interfacial shear stress for cylindrical core-sheath samples of Polypropylene and Polystyrene. In agreement with prior work on multilayer sandwiches we found two distinct power-law regimes in the relationship between the interfacial slip velocity and the interfacial shear stress. The power-law exponent changes from a value of approximately 3 at low shear stress values to approximateley 2 at high shear stresses. We then investigated the effect of varying the temperature on the slip velocity and explore the consequences of time-temperature superposition for the two polymers. Interestingly the interfacial slip velocities can be superposed using the WLF parameters of one of the polymers but not the other. Finally if time permits I will discuss the connection if any between slip at the interface between the two polymers and the roughness observed at the polymer/polymer interface.Bio of speaker: Sathish K. Sukumaran is currently Assistant Professor (Tenure-track) of Polymer Science and Engineering at Yamagata University Japan. He received his education at the IIT in Chennai (B.Tech Metallurgical Eng. 1995) and at the University of Cincinnati USA (Ph.D Materials Science and Eng. 2002). During his post-doctoral fellowship at the Max-Planck Institute for Polymer Research in Mainz Germany he jointly developed a method to analyse the topological state of entangled polymer liquids (Primitive Path Analysis). He followed this with a stay at the University of Leeds UK where he performed molecular simulations of entangled polymers and on establishing the use of software correlators. There he also developed novel tube models for entangled bidisperse blends. He has been at Yamagata University since 2009. His current research efforts are mainly directed at two areas. One is on the dynamics and rheology of entangled polymer liquids using mainly computer simulations and analytical theory. Areas of interest include hierarchical modelling of entangled polymer dynamics using simulations (molecular dynamics primitive path analysis Brownian dynamics of slip-link models etc.) and analytical theory (tube models). For his work on entangled polymer dynamics he was awarded the Encouragement Award of the Society of Rheology Japan in 2013. More recently he is also leading an experimental endeavour to understand slip at polymer/polymer interfaces using mainly rheological and optical techniques. Current interests include methods to measure interfacial slip physical understanding of the phenomena and applications in polymer processing especially processing instabilities.