University of Kentucky UKnowledge University of Kentucky Master's Theses Graduate School 2011 BENCH-SCALE, MULTIFILAMENT SPINNING CONDITIONS EFFECT ON THE STRUCTURE AND PROPERTIES OF POLYACRYLONITRILE PRECURSOR FIBER Elizabeth Ashley Morris University of Kentucky, [email protected] Right click to open a feedback form in a new tab to let us know how this document benefits ou.y Recommended Citation Morris, Elizabeth Ashley, "BENCH-SCALE, MULTIFILAMENT SPINNING CONDITIONS EFFECT ON THE STRUCTURE AND PROPERTIES OF POLYACRYLONITRILE PRECURSOR FIBER" (2011). University of Kentucky Master's Theses. 107. https://uknowledge.uky.edu/gradschool_theses/107 This Thesis is brought to you for free and open access by the Graduate School at UKnowledge. It has been accepted for inclusion in University of Kentucky Master's Theses by an authorized administrator of UKnowledge. For more information, please contact [email protected]. ABSTRACT OF THESIS BENCH-SCALE, MULTIFILAMENT SPINNING CONDITIONS EFFECT ON THE STRUCTURE AND PROPERTIES OF POLYACRYLONITRILE PRECURSOR FIBER Due to its unique characteristics, carbon fiber is one of the leading materials for light weight, high strength and stiffness applications in composite materials. The development of carbon fibers approaching theoretical strengths and stiffness is a continuing process which has led to improved mechanical and physical properties over the recent years. Improvements in carbon fiber properties are directly dependent on the quality of the precursor fiber. Research and development of PAN precursor fiber requires extensive experimentation to determine how processing conditions affect the structure and properties of the precursor fibers. Therefore, it is the goal of this thesis to analyze the results of varying coagulation rates on fiber shape, density and porosity, to determine the effect of cross-sectional shape, density, and fiber diameter on the tensile strength of the fiber, and to investigate the most effective method for the reduction of fiber diameter. Results indicate a low temperature, high solvent concentration coagulating bath leads to a rounder cross section with lower void content. Reduction in fiber diameter was found to increase tensile strength while increased molecular orientation experienced during high draw down ratios led to an increase in fiber modulus. KEYWORDS: Carbon Materials, Carbon Fiber, Precursor, Polyacrylonitrile, Wet Spinning Elizabeth Ashley Morris May 6, 2011 BENCH-SCALE, MULTIFILAMENT SPINNING CONDITIONS EFFECT ON THE STRUCTURE AND PROPERTIES OF POLYACRYLONITRILE PRECURSOR FIBER By Elizabeth Ashley Morris Rodney J. Andrews, Ph.D. Director of Thesis James M. McDonough, Ph.D. Director of Graduate Studies April 5, 2011 RULES FOR THE USE OF THESES Unpublished theses submitted for the Master’s degree and deposited in the University of Kentucky Library are as a rule open for inspection, but are to be used only with due regard to the rights of the authors. Bibliographical references may be noted, but quotations or summaries of parts may be published only with the permission of the author, and with the usual scholarly acknowledgments. Extensive copying or publication of the thesis in whole or in part also requires the consent of the Dean of the Graduate School of the University of Kentucky. A library that borrows this thesis for use by its patrons is expected to secure the signature of each user. Name Date THESIS Elizabeth Ashley Morris The Graduate School University of Kentucky 2011 BENCH-SCALE, MULTIFILAMENT SPINNING CONDITIONS EFFECT ON THE STRUCTURE AND PROPERTIES OF POLYACRYLONITRILE PRECURSOR FIBER ____________________________________ THESIS ____________________________________ A thesis submitted in partial fulfillment of the requirements for the degree of Master of Science in Mechanical Engineering in the College of Engineering at the University of Kentucky By Elizabeth Ashley Morris Lexington, KY Director: Dr. Rodney Andrews, Professor of Chemical and Materials Engineering Lexington, KY 2011 Copyright © Elizabeth Ashley Morris 2011 For My Mom Acknowledgements I would first like to thank my advisor, Dr. Rodney Andrews, for being a constant encouragement and guide throughout my academic career. Without his words of advice, this thesis would not have been possible. I also want to thank Dr. Mark Meier and Dr. Kozo Saito for serving on my examining committee. I am very thankful for the devotion of their time and effort toward the discussion of my thesis. I would also like to thank Dr. Matthew Weisenberger for being a constant mentor in this field. His experience and dedication has been an inspiration to me in my own research. His technical support and advice throughout the years has led me to the completion of this thesis. I want to thank the staff of the University of Kentucky Center for Applied Energy Research and especially the Carbon Materials group. I give special thanks to my colleagues in the Carbon Materials group, including Terry Rantell, John Craddock, Mark Taylor, Keith Etheredge, and Dali Qian. Finally, I would like to thank my family and friends. My husband, Jad, has been a constant encouragement to me in all that I do. My mother, who has always believed in me and taught me the value of hard work and devotion and my brother and sister, who continue to be an inspiration to me. My friends and family have made me the person I am today and I am eternally grateful for their support and encouragement. iii TABLE OF CONTENTS Acknowledgements ........................................................................................................................ iii List of Figures ............................................................................................................................... vii 1 Introduction ............................................................................................................................. 1 1.1.1 Solvent and Polymer Selection ................................................................................. 1 1.1.2 Dry and Wet Spinning Processes .............................................................................. 3 1.1.3 Coagulation Mechanism ........................................................................................... 4 1.2 Precursor Fiber Structure ................................................................................................. 5 1.2.1 Skin-Core Structure .................................................................................................. 5 1.2.2 Void Development .................................................................................................... 7 1.2.3 Fiber Cross Section ................................................................................................. 10 1.2.4 Fiber Diameter ........................................................................................................ 11 1.3 Rheology ........................................................................................................................ 11 1.3.1 Shear Viscosity ....................................................................................................... 12 1.3.2 Extensional Rheology ............................................................................................. 13 1.4 Spinnability .................................................................................................................... 14 1.4.1 Modeling Spinnability ............................................................................................ 14 1.5 Conclusions .................................................................................................................... 15 2 Bench-Scale PAN Precursor Fiber Spinning Line ................................................................ 16 2.1 Introduction .................................................................................................................... 16 2.2 Bench Scale Spin Line ................................................................................................... 16 2.3 Die Configuration ........................................................................................................... 18 2.4 Pump Customization ...................................................................................................... 18 iv 2.5 Dope Preparation ............................................................................................................ 23 2.5.1 Polymer and solvent selection ................................................................................ 23 2.5.2 Dope Preparation .................................................................................................... 24 2.6 Rheology ........................................................................................................................ 27 2.6.1 Parallel-Plate Rheology .......................................................................................... 27 2.6.2 Extensional Rheometry ........................................................................................... 30 3 Influence of Concentration and Temperature ....................................................................... 34 3.1 Introduction .................................................................................................................... 34 3.1.1 Effect of Diffusion on Coagulation Rate ................................................................ 35 3.2 Materials and methods ..................................................................................................