ABSTRACT LI, XINGYU. Key Material Factors of Digital Printing on Textiles. Case: Pigment on Woven Polyester. (Under the direction of Nancy Powell and Dr. Stephen Michielsen). Improved prepared for digital printing base materials or substrate fabrics contribute to the final product’s qualities in meeting end use performance requirements. This research seeks to determine the key factors (materials and processes) that affect digital printing on textiles’ qualities and to improve substrate fabrics for digital printing enhancements. Polyester samples developed in the laboratories of the College of Textiles and commercially available fabrics were analyzed and printed with the MS-JP5 Evo digital printer. Physical properties of the fabrics were evaluated for dry and wet crock fastness, tensile strength, tear strength, seam strength and clarity of printed test patterns. Best practices in preparing polyester woven fabric for direct digital printing were explored. A print clarity quantitative test method was created. Funded by a multi-national retail corporation, this study in basecloth factors impacting digital printing will contribute to the quality and efficiency of digital printing as an innovative advance in manufacturing. Following the analysis stage, industry interviews will be conducted in order to validate the contributing factors discovered in this research and reveal any new factors. © Copyright 2017 Xingyu Li All Rights Reserved Key Material Factors of Digital Printing on Textiles. Case: Pigment on Woven Polyester by Xingyu Li A dissertation submitted to the Graduate Faculty of North Carolina State University in partial fulfillment of the requirements for the degree of Doctor of Philosophy Fiber and Polymer Science Raleigh, North Carolina 2017 APPROVED BY: _______________________________ _______________________________ Professor Nancy Powell Dr. Stephen Michielsen Committee Co-Chair Committee Co-Chair _______________________________ _______________________________ Dr. Lisa Parrillo-Chapman Dr. Joel Pawlak DEDICATION To my mother and father. ii BIOGRAPHY Xingyu Li came from Shanghai, China. She received an undergraduate degree in Textile Engineering from Donghua University, and then attended North Carolina State University in the fall of 2013. After completing her Master of Science degree in Textile Engineering, she decided to pursue a doctoral degree in Fiber and Polymer Science. Her research involved various key material factors of digital printing on textiles and was supported by the Walmart Innovation Fund. iii ACKNOWLEDGMENTS I wish to acknowledge the time and expertise that contributed to the body of research by members of academia, industry and research institutes in the field of digital textile printing. First and foremost, I would like to express my sincere gratitude and appreciation to my advisors Professor Nancy Powell and Dr. Stephen Michielsen. Prof. Powell provided important oversight of digital printing in the textile industry and served as a female role model as a professor and researcher. Dr. Michielsen provided guidance on my research and life and helped me work through many technical issues. Thanks for their understanding, encouragement and support during my difficult and dark time in life. I cannot express my gratitude enough for their dedication, mentoring and friendship. I would also like to express my thanks to my advisory committee members Dr. Lisa Parrillo- Chapman and Dr. Joel Pawlak for their generous support and intelligent recommendations throughout the duration of this research. I am very grateful to Mr. William Barefoot, Mr. Jeffrey Krauss, Mr. Tri Vu and Ms. Teresa White and all the other staff in the College of Textiles for providing technical help and suggestions to make the research experiments successful. Thanks to the interview participants and companies who provided valuable, thoughtful inputs and observations in digital textile printing, and generously shared their experiences in the field. I also wish to acknowledge the support of Walmart Innovation Fund in Manufacturing for funding my dissertation research. iv TABLE OF CONTENTS LIST OF TABLES ................................................................................................................... ix LIST OF FIGURES ................................................................................................................. xi CHAPTER 1 INTRODUCTION .............................................................................................. 1 1.1 Background ..................................................................................................................... 1 CHAPTER 2 LITERATURE REVIEW ................................................................................... 6 2.1 Yarn and fabric formation ............................................................................................... 6 2.1.1 Polyester Fiber ......................................................................................................... 6 2.1.2 Yarn Characteristics ................................................................................................. 9 2.1.3 Woven Fabric Formation ....................................................................................... 12 2.1.4 Woven Fabric’s Durability .................................................................................... 19 2.2 Digital Inkjet Printing on Textiles ................................................................................ 22 2.2.1 Comparison between Digital Inkjet Printing and Conventional Printing .............. 24 2.3 Fabric preparation and processing for digital inkjet printing........................................ 31 2.3.1 Pretreatment ........................................................................................................... 31 2.3.2 Shrinkage ............................................................................................................... 33 2.3.3 Fabric Tension ....................................................................................................... 34 2.3.4 Warp and Weft Alignment (bow and bias) ............................................................ 34 2.3.5 Selvedge ................................................................................................................. 35 2.3.6 Post-treatment Process ........................................................................................... 35 2.4 Woven fabric properties' impact on digital printing image .......................................... 36 v 2.4.1 Fiber ....................................................................................................................... 38 2.4.2 Yarn........................................................................................................................ 40 2.4.3 Fabric construction................................................................................................. 40 2.5 Print Clarity (Image Sharpness) .................................................................................... 43 2.5.1 Modulation Transfer Function (MTF) ................................................................... 44 2.5.2 MTF Analysis ........................................................................................................ 46 CHAPTER 3 METHODOLOGY ........................................................................................... 47 3.1 Objectives ..................................................................................................................... 47 Key Factors ..................................................................................................................... 49 3.2 Testing Standards .......................................................................................................... 50 3.3 Design of Experiment ................................................................................................... 52 3.3.1 DOE theoretical sample plan ................................................................................. 54 3.3.2 Fabric structure simulation (EAT) ......................................................................... 56 3.3.3 Digital Printer......................................................................................................... 57 CHAPTER 4 EXPERIMENTAL WORK .............................................................................. 60 4.1 Fabric Preparation ......................................................................................................... 60 4.1.1 Yarn Physical Properties ........................................................................................ 60 4.1.2 Warp Preparation ................................................................................................... 61 4.1.3 Drawing-in of warp yarns ...................................................................................... 64 4.1.4 Weaving ................................................................................................................. 65 4.1.5 Scouring and Drying .............................................................................................. 66 vi 4.1.6 Pretreatment ........................................................................................................... 68 4.2 Digital Printing.............................................................................................................. 71 4.2.1 Calibration and Characterization ..........................................................................