ABSTRACT METHOD FOR LOW AREAL DENSITY MATERIAL STRUCTURE CHARACTERI- ZATION: SOFT X-RAY FORMATION AND COMPRESSIBILITY MEASUREMENT by Guizhou Wang In this paper, a new method of characterizing nonwoven structure and a modification of paper towel compression study were discussed. Though nonwoven technology is not a new one, there is a lack of research on its structural properties. Due to its bulky nature, we used soft X-ray to take the radiographic images of nonwoven and paper towel sam- ples. After preprocessing, the soft X-ray films of nonwoven samples were used to calcu- late the areal density using specific Matlab code on the workstation. Then the compressi- bility measurements were performed on the modified Continuous Micro Compression Tester for paper towel samples. Direct visualization of the compression process was ob- tained. METHOD FOR LOW AREAL DENSITY MATERIAL STRUCTURE CHARACTERIZATION: SOFT X-RAY FORMATION AND COMPRESSI- BILITY MEASUREMENT A Thesis Submitted to the Faculty of Miami University In partial fulfillment of the requirements for the degree of Master of Science Department of Chemical, Paper and Biomedical Engineering by Guizhou Wang Miami University Oxford, Ohio 2015 Advisor: Dr. Steven Keller Reader: Dr. Shashi Lalvani Reader: Dr. Douglas Coffin Contents Chapter 1: Introduction ......................................................................................................... 1 1. Background ....................................................................................................................... 1 1.1 Materials ...................................................................................................................... 2 1.1.1 Tissue Paper .......................................................................................................... 2 1.1.2 Nonwovens ........................................................................................................... 6 What is nonwoven? ............................................................................................... 7 The manufacturing of nonwovens ......................................................................... 7 1.2 Structure Characterization ........................................................................................... 9 1.2.1 Formation Measurement ........................................................................................ 9 1.2.2 Local Thickness Mapping ................................................................................... 10 1.2.3 Z-directional Compressibility Property ............................................................... 11 2. Statement of problem and objectives .............................................................................. 14 2.1 Problem Statement ..................................................................................................... 14 2.2 Objectives .................................................................................................................. 15 Chapter 2: Formation Characterization for Low Areal Density Materials ......................... 16 1. Principles for Soft X-ray Formation Measurement ......................................................... 17 2. Materials .......................................................................................................................... 18 3. Methods ........................................................................................................................... 19 3.1 Soft X-ray Imaging .............................................................................................. 19 ii 3.2 X-ray Film Development..................................................................................... 20 3.3 Image Preprocessing and Processing .................................................................. 20 4. Results and Discussion .................................................................................................... 21 4.1 Textile-based Nonwovens ..................................................................................... 21 4.2 Paper-based Nonwovens ........................................................................................ 25 4.3 Extrusion-based Nonwovens ................................................................................. 29 4.4 X-radiographic Grammage vs Gravimetric Grammage of Nonwovens ................ 33 4.5 Formation Analysis ................................................................................................ 34 Chapter 3: Compressibility Measurement for Paper Towel ............................................... 35 1. Review of Feng’s Compressibility Measurement ........................................................... 36 2. Materials .......................................................................................................................... 40 3. Experiment Methods ....................................................................................................... 41 3.1 Strain gauge calibration ......................................................................................... 42 3.2 Determination of Z-strain ...................................................................................... 45 3.3 Young’s Modulus .................................................................................................. 46 4. Results and Discussion .................................................................................................... 47 4.1 Compressive Response of CWP Embossed Features .......................................... 47 4.2 Compressive Response of TAD Patterns ............................................................... 51 4.3 Young’s Modulus .................................................................................................. 54 4.4 Comparison of CWP & TAD ................................................................................ 57 Chapter 4: Conclusions and Future Work ........................................................................... 60 i ii 1. Conclusions ..................................................................................................................... 60 2. Future work ..................................................................................................................... 61 References ........................................................................................................................... 62 i ii List of Tables Table 1-1. Basic Nonwoven Fabric Manufacturing Systems. 8 Table 2-1. Nonwoven Samples. 18 Table 2-2. Comparison of Gravimetric and X-radiographic Grammage. 33 Table 2-3. Comparison of COV. 34 Table 3-1. Compression Test Samples. 40 Table 3-2. Collapse Value of CWPs and TADs. 58 Table 3-3. Young’s Modulus of CWPs and TADs. 59 iv List of Figures Figure 1-1. A Yankee Dryer with a tissue web dried on it. 3 Figure 1-2. Schematic figures of a tissue web before and after creping and rewetting after- wards. 4 Figure 1-3. A Through Air Dryer with a tissue web dried on it. 4 Figure 1-4. Schematic figures of a TAD tissue web before and after wetting. 5 Figure 1-5. Depictions of three embossing types. 6 Fig. 2-1 AXR Minishot Instrument for soft X-ray formation measurement. 19 Fig. 2-2. Structural maps of T1. 22 Fig. 2-3. Structural maps of T2. 23 Fig. 2-4. Structural maps of T3. 24 Fig. 2-5. Structural maps of P1. 26 Fig. 2-6. Structural maps of P2. 27 Fig. 2-7. Structural maps of P3. 28 Fig. 2-8. Structural maps of E1. 30 Fig. 2-9. Structural maps of E2. 31 Fig. 2-10. Structural maps of E3. 32 v Fig. 3-1. Two Sided Compression (A) Versus Single Sided Compression (B) 36 Fig. 3-2. Compression of Tissue and Towels. 38 Fig. 3-3. Compression of Ideal Solid Foam. 39 Fig. 3-4. Continuous Micro Compression Instrument. 41 Fig. 3-5. Out of limit test for both strain gauges. 43 Fig. 3-6. Strain gauge force calibration. 44 Fig. 3-7. Stain gauge deflection calibration. 45 Fig. 3-8. Compression Plots of CWP1 Embossed Features. 48 Fig. 3-9. Feng’s work as a comparison. 48 Fig. 3-10. CWP1 embossed point 1. 50 Fig. 3-11. Compression Plots of CWP2 Embossed Features. 51 Fig. 3-12. Compression Plots of TAD1. 52 Fig. 3-13. Compression Plot of TAD1 Embossed Point 1. 53 Fig. 3-14. Compression Plots of TAD2. 53 Fig. 3-15. Compression Plot of TAD1 Embossed Point 1. 55 Fig. 3-16. Young’s modulus of each sample. 56 vi ACKNOWLEDGEMENTS First, I want to give my deepest and sincere thanks to my advisor, Dr. Keller! Thanks for his patience, guide, and thoughtful ideas to help me both on my research and thesis during my graduate study here. I also want to thank Dr. Lalvani and Dr. Coffin, for being my committee members and giving me precious suggestions and advices for my thesis. I would also like to give my gratitude to Michael Weeks, for the LabVIEW programming of the micro compression instrument utilized in this research. Finally, I want to thank all the professors, technicians, graduate students and my friends for their help and encouragement throughout my study here. vii Chapter 1: Introduction 1. Background Low density (LD) fibrous materials hold an important place in society. From consumer goods such as hygienic tissues, kitchen towels, and nonwoven textiles, to more specialized applications such as filters, fuel cell components or thermal insulation, LD fibrous products are ubiquitously a part of everyday life. This research focuses on low density (low grammage and low volumetric apparent density) web materials that fall within the categories of, 1) paper