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Under the Direction of Dr ABSTRACT PHILLIPS, JASMINE SHAMERA. Organic Rinsing of Island-in-the-sea Nylon 6/PLA Bicomponent Fibers. (Under the direction of Dr. Ericka Ford). Hydroentangled nonwovens of polyamide 6 (PA6) microfibers are desired for soft and durable fabrics. Herein, the goal is to improve the efficiency of polylactic acid (PLA) removal by rinsing it from PA6 islands-in-the-sea bicomponent nonwovens. Challenges arise with rinsing PLA from the PA6 phase of bicomponent fibers at industrial scales. Caustic rinses leave PLA residue on PA6, which results in poor separation of the PA6 nanofibers. A non-caustic PLA rinse is desired to improve the dissolution of PLA during the rinse cycle. ETAC is a superb solvent for PLA; however, the operating rinse temperature drops due to the endotherm for PLA dissolution. Commercial implications of this work signify a reduction in reaction endotherms, while offsetting the cost of trying to maintain a constant operating temperature for dissolution at industrial scales. Thus, ancillary solvents were used to minimize the endothermic heats of PLA dissolution, while increasing the rate of PLA dissolution. ‘Good’ solvent baths unary, binary, and ternary mixtures (containing ethyl acetate (ETAC), methyl ethyl ketone (MEK), and dimethyl sulfoxide (DMSO)- all three are highly miscible solvents-) were tested against bicomponent PA6/PLA nonwovens. Thermogravimetric analysis (TGA) was used to quantify PLA on neat bicomponent nonwovens and those treated with promising candidates for PLA removal on the pilot scale. Promising solvent mixtures were tested against PLA removal using a 20:1 liquid ratio under accelerated laundering conditions. Launderometer experiments offered a comparative study of how the solvent compositions affected the efficacy of PLA removal from PA6 and PA6 microfiber separation during rinse cycles on the pilot scale. © Copyright 2020 by Jasmine S. Phillips All Rights Reserved Organic Rinsing of Island-in-the-sea Nylon 6/PLA Bicomponent Fibers by Jasmine Shamera Phillips A thesis submitted to the Graduate Faculty of North Carolina State University in partial fulfillment of the requirements for the degree of Master of Science Textile Chemistry Raleigh, North Carolina 2020 APPROVED BY: _______________________________ Dr. Ericka Ford Committee Chair _______________________________ _______________________________ Dr. Nelson Vinueza Benitez Dr. Abhay Joijode DEDICATION This work is dedicated to my parents, Cynthia and Cedric Phillips, for their love and undying support of me. My brother Draquel Phillips, for his constant encouragement. And to all of my loved ones and close friends- thank you. ii BIOGRAPHY Jasmine Phillips was born and raised in Savannah, Georgia. She holds a Bachelor of Science degree in chemistry from Savannah State University, the university where her parents met and graduated. She later decided to pursue the Master of Science degree in Textile Chemistry at North Carolina State University. ‘For I,’ says the Lord, ‘will be a wall of fire all around her, and I will be the glory in her midst.’ ~Zechariah 2:5 iii ACKNOWLEDGMENTS Next, I would like to thank my loved ones, family, and friends who have supported me and encouraged me throughout my graduate studies. Thank you for listening and not letting me give up along the way. Thank you to LUNA, for funding this work and giving me the opportunity to work on an industry project for my graduate research. Additionally, I appreciate the project management group in the NWI for helping organize this work. It has been a pleasure to be a member of the Ford Innovation Team and Nonwovens Student group. I have had the opportunity to meet intelligent, supportive, and quick-witted graduate students who have inspired and challenged me during this process. Thank you all for supporting me both in and out of the college. Thank you to the faculty, staff, and lab managers in the Wilson College of Textiles and Nonwovens Institute for your hard work. To my committee, Dr. Joijode and Dr. Vinueza, I am extremely grateful for your input, assistance, and suggestions throughout my project. Most of all, I have to express my sincere gratitude to my advisor and chair, Dr. Ericka Ford, who has taught me so much along this journey not only about research, but also myself. I thank you for giving me the opportunity to grow and learn as part of your research team. Thank you for your wisdom, enthusiasm, patience, and encouragement and for pushing me further than I thought I could go. iv This material is based upon work supported by the U.S. Army Command Center, Aberdeen Proving Ground, Natick Contracting Division ACC-APG-NCD under Contract No. W911QY-18-C-0003. Any opinions, findings and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the U.S. Army Command Center, Aberdeen Proving Ground, Natick Contracting Division ACC-APG-NCD. v TABLE OF CONTENTS LIST OF TABLES ...................................................................................................................... viii LIST OF FIGURES ...................................................................................................................... ix LIST OF APPENDICES ............................................................................................................... xi LIST OF ABBREVIATIONS ...................................................................................................... xii Chapter 1: Literature Review ..................................................................................................... 1 1.1 Introduction to Nonwovens...................................................................................................... 1 1.1.1 Web Formation .................................................................................................................. 4 1.1.2 Drylaid ............................................................................................................................... 5 1.1.3 Wetlaid ............................................................................................................................... 5 1.1.4 Polymer-Laid ..................................................................................................................... 6 1.1.5 Bonding Processes ............................................................................................................. 6 1.1.6 Finishing of Nonwovens .................................................................................................... 7 1.2 Extrusion Spinning................................................................................................................... 7 1.2.1 Spunbonding Process ......................................................................................................... 7 1.2.2 Resins for Spunbonding ..................................................................................................... 9 1.3 Nylon 6................................................................................................................................... 10 1.3.1 Nylon 6 Resins ................................................................................................................. 10 1.3.2 Mechanical Properties of Nylon 6 ................................................................................... 11 1.3.3 Physical Properties of Nylon 6 Resin .............................................................................. 11 1.3.4 Melt Spinning of Nylon 6 ................................................................................................ 11 1.3.4.1 Structure-Property Processing Relationships ............................................................. 13 1.3.5 Nylon 6 Fibers.................................................................................................................. 14 1.4 Polylactic Acid ....................................................................................................................... 15 1.4.1 Polylactic Acid Resins ..................................................................................................... 15 1.4.2 Mechanical Properties of Polylactic Acid........................................................................ 16 1.4.3 Physical Properties of Polylactic Acid Resin................................................................... 16 1.4.4 Melt Spinning of Polylactic Acid .................................................................................... 16 1.4.4.1 Structure-Property Processing Relationships ............................................................. 17 1.4.5 Polylactic Acid Fibers ...................................................................................................... 17 1.4.6 Polylactic Acid as a Sacrificial Fiber Among Bicomponent Fibers ................................ 18 1.4.7 Polylactic Acid Rinses ..................................................................................................... 19 1.5 Bicomponent Fiber Structures ............................................................................................... 19 1.5.1 Functional Bicomponent Fibers ....................................................................................... 21 1.5.2 Production of Islands-in-the-Sea Bicomponent Fibers ................................................... 22 1.5.3 Splittable Fibers ............................................................................................................... 22 1.6 Thesis Objectives
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