Applied rheology for melt blown technology Jiří Drábek Bachelor thesis 2011 ABSTRAKT Tato práce se věnuje problematice experimentálního a teoretického hodnocení tokového chování dvou odlišných polymerů s velmi vysokým indexem toku taveniny, a to s ohledem na výrobu polymerních nanovláken pomocí technologie melt blown. Klíčová slova: polymerní nanovlákna, technologie melt blown, smyková viskozita, elongační viskozita, aplikovaná reologie, zpracovatelství polymerů ABSTRACT In this work, two different melt blown polymer samples with very high melt flow indexes have been rheologically characterized by using suitable experimental technique and theo- retical tools and the results have been discussed from the polymeric nanofiber production point of view. Keywords: polymeric nanofibers, melt blown technology, shear viscosity, extensional vis- cosity, applied rheology, polymer processing ACKNOWLEDGEMENTS I would like to express my sincere gratitude to all people who supported me during the work on the thesis. I am especially grateful to my supervisor, prof. Ing. Martin Zatloukal, Ph.D. for his pa- tience, guidance and support throughout the process of measuring and analyzing data and writing the thesis. I am also indebted to Ing. Luboš Rokyta for his advice concerning about 3D figures which are use in this thesis and its presentation. I would like to extend my gratitude to my family and all my true friends for their support. I declare that surrender release bachelor thesis and recorded in the electronic version of IS/STAG are identical. I agree that the results of my Bachelor Thesis can be used by my supervisor’s decision. I will be mentioned as a co-author in the case of any publication. I declare I worked on this Bachelor Thesis by myself and I have mentioned all the used literature. Zlín, May 23, 2011 Jiří Drábek CONTENTS INTRODUCTION ............................................................................................................... 9 I THEORY ................................................................................................................... 10 1 POLYMERIC NANOFIBERS ................................................................................ 11 2 MELT BLOWN TECHNOLOGY .......................................................................... 13 2.1 MELT BLOWN LINE ............................................................................................... 14 2.2 MELT BLOWN DIE DESIGN ..................................................................................... 15 2.2.1 Flat die .......................................................................................................... 16 2.3 DIE EXIT ............................................................................................................... 17 2.3.1 Post die area ................................................................................................. 20 2.4 MATERIALS .......................................................................................................... 22 2.5 PARAMETERS INFLUENCING MELT BLOWING PROCESS .......................................... 24 2.5.1 Materials ....................................................................................................... 24 2.5.2 Processing conditions ................................................................................... 25 2.5.3 Equipment design ......................................................................................... 27 2.5.4 Nanofiber structure morphology .................................................................. 28 3 EXPERIMENTAL RHEOLOGY ........................................................................... 30 3.1 DISK RHEOMETERS ............................................................................................... 30 3.2 CAPILLARY RHEOMETER ...................................................................................... 33 4 CONSTITUTIVE EQUATIONS FOR POLYMER MELTS ............................... 36 4.1 GENERALIZED NEWTONIAN MODEL ..................................................................... 36 4.2 MODIFIED WHITE-METZNER MODEL .................................................................... 38 II ANALYSIS ................................................................................................................ 41 5 MATERIALS ............................................................................................................ 42 6 EQUIPMENT AND METHODS ............................................................................ 43 6.1 CAPILLARY RHEOMETER ROSAND RH7-2 ............................................................ 43 6.1.1 Shear viscosity determination determination ............................................... 49 6.1.2 Uniaxial extensional viscosity determination .............................................. 50 RESULTS AND DISCUSSION ........................................................................................ 53 CONCLUSION REMARKS ............................................................................................. 88 BIBLIOGRAPHY .............................................................................................................. 89 LIST OF ABBREVIATIONS ........................................................................................... 93 LIST OF FIGURES ........................................................................................................... 97 LIST OF TABLES ........................................................................................................... 101 APPENDICES .................................................................................................................. 102 TBU in Zlín, Faculty of Technology 9 INTRODUCTION One of the key problem in the polymer processing operations optimization is unknown relationship between equipment design, processing conditions and rheological characteris- tics of the polymers. In order to assess such relationships, the modeling of the polymer processing is widely utilized for which the rheological characteristics of the polymer melts determined at the particular temperature range represents crucially important material input data. However, the selection of the proper constitutive equation for the polymer melt, which is able to represent the measured rheological data mathematically, is required to reach fully predictive capabilities of the performed polymer processing simulations. Thus, the polymer processing operation at which the full rheological polymer sample characteri- zation is very complicated or practically impossible by standard rheological tools is diffi- cult to optimize. The melt blown technology for the polymeric nanofibers production is one of them. In more detail, polymer melt viscosity during the nanofiber production has to decrease considerably (melt index > 1600 g/10 min). As the result, the measurement of basic rheological characteristics at the processing deformation rates for the melt blown polymer samples is challenging task. With the aim to extend the current knowledge in such a research field, the work is focused on the rheological evaluation of two different PP melt blown samples by using capillary rheometer in order to find out the way in which shear as well as extensional viscosities can be determined experimentally at wide range of deformation rates. In the second part of this work, fitting capabilities of two different constitutive equations for the melt blown polymer melts are tested and the obtained results are evaluated with respect to polymer nanofiber production. TBU in Zlín, Faculty of Technology 10 I. THEORY TBU in Zlín, Faculty of Technology 11 1 POLYMERIC NANOFIBERS Nanotechnology has enjoyed unprecedented global research and development support over the last few years. Their unusual physicochemical characteristics are primarily governed by their very high surface area to volume ratio or the ratio of surface atoms to the interior atoms in cluster (see Figure 1) [1]. Cosmetic Skin Mask Application in life science Tissue Engineering Scaffolding • Skin cleansing • Drug delivery carrier • Porous membrane for skin • Skin healing • Haemostatic devices • Tubular shapes for blood vessels • Skin therapy with medicine • Wound dressing and nerve regenerations • Three dimensional scaffolds for bone and cartilage regenerations Military Protective Clothing Filter media • Minimal impedance to air • Liquid filtration • Efficiency in trapping • Gas filtration aerosol particles • Molecule filtration Polymer nanofibers • Anti-biochemical gases Other Industrial Application • Micro/nano electronic devices Nanosensors • Electrostatic dissipation • Thermal sensor • Electromagnetic interference shielding • Piezoelectric sensor • Photovoltaic devices (nano–solar cell) • Biochemical sensor • LCD devices • Fluorescence optical • Ultra–lightweight spacecraft materials chemical sensor • Higher efficient and functional catalysts Fig. 1. The diversity of applications for polymer nanofibers [1] Nanofiber mats, having fiber diameter typically in order of tens and hundred nanometers, are very well suited for air filtration because low solidity and acceptable mechanical strength can be obtained. During the past decades, significant process has been done in the area of filtration science and technology, which follows increased needs of many advanced industries dealing with electronics, medical, pharmaceutical and biology to maintain clean room manufacturing environments. The increase in air velocity, viscosity and air