Woodruff School of Mechanical Engineering
Faculty Candidate Seminar
The Development and Subsequent Investigation into Structural Properties of Novel Microcapillary Films (MCFs)
Dr. Dora Medina
Monday, March 3, 2014 at 3:00:00 PM
MRDC Building, Room 4211
Dr. Kyriaki Kalaitzidou
MCFs are a novel thermoplastic extrudate that have been manufactured by the entrainment of gas within nozzles positioned in an extrusion die. The film resembles a plastic tape but contains an array of equally spaced parallel microcapillaries that run along its entire length. In order to increase the range of potential applications of MCFs both capillary diameter and voidage were manipulated by downstream mechanical processing. Low-voidage MCFs were manufactured from linear low density polyethylene (LLDPE) using a novel die design, melt drawing the polymer to produce an essentially isotropic MCF. The Low-voidage MCF X-ray results show that the original melt cast MCF contains little orientation and consequently there is scope for further capillary hole size reduction and development of molecular orientation by the simple application of downstream mechanical drawing at either room or elevated temperature. In addition polyether urethane (PEU) was found experimentally to draw more easily than polyethylene and a series of post drawn samples are reported for this material. This film was termed Small diameter low-voidage MCF. By altering the process conditions of the Low-voidage MCF, a high higher voidage MCF was produced, termed High voidage. This MCF was brittle when drawn in the capillary direction but showed unusual mechanical transverse drawing when drawn transversely and necked down causing a progressive sequential necking of capillary regions. Optical and SEM sections of the Ultra-high voidage MCF show that very thin wall ultra high voidage structures have been achieved. Experiment details are presented for the manufacture of the different MCF structures together with mechanical properties and X-ray orientation data. From this, qualitative explanations for the mechanisms to achieve the different structures are given. This work demonstrates the possibility of controlling both capillary size and voidage within MCFs and their mechanical properties are dependent on molecular orientation and geometry.
Dr. Dora Medina is from Tamaulipas, Mexico. She earned her B.S. in Chemical Engineering from the National Polytechnic Institute in Mexico City. After working in industry for a year, Dr. Medina moved to Riverside, CA, to pursue her MS in Chemical and Environmental Engineering. She received her MS from the University of California in 2005 with the thesis entitled “High-silica-zeolite BEA Spin-on Low-k Dielectric Films for Future Generation Computer Chips”. Then she moved to Cambridge, UK to pursue her PhD degree, she received her PhD in Chemical Engineering and Biotechnology from the University of Cambridge in 2009. Her thesis work was the development of microcapillary films and microcapillary monolith structures to produce controlled capillary diameters and voidage. For her work Dr. Medina was highly commended in the Sellafield Ltd Award for Engineering Excellence (IChemE awards) and invited as a Keynote speaker in the Annual Meeting of the Polymer Processing Society (2008). She then moved to MIT as a UNESCO-L’ORÉAL “For Women In Science” International Fellow to work on the development of an innovative triborheometry fixture/design to study the frictional dynamics of solid-liquid systems at the Hatsopoulos Microfluids Laboratory in the Non-Newtonian Fluid Dynamics Research Group in the Mechanical Engineering Department.
Refreshments will be served.