Study of the Effect of Rubbing Materials on the Tribo-electrification of Textile Materials By IieZhao A Thesis Submitted to the Faculty of Graduate Studies in Partial Fulfillment of the Requirernents for the Degree of MASTER OF SCTENCE Department of Clothing and Textiles University of Manitoba Winnipeg, Manitoba @ Copyright by Jie Zhao,2003 THE T]NTYERSITY OF' MANITOBA FACULTY OF GRADUATE STUDIES ***** COPYRIGHT PERMISSION PAGE STI]DY OF TIIE EFF'ECT OF'RUBBING MATERIALS ON THE TRIBO.ELECTRIF'ICATION OF TEXTILE MATERIALS BY JIE ZHAO A ThesisÆracticum submitted to the Faculty of Graduate Studies of The University of Manitoba in partial fulfillment of the requirements of the degree of Master of Science JIE ZIIAO @ 2OO3 Permission has been granted to the Library of The University of Manitoba to lend or sell copies of this thesis/practicum, to the National Library of Canada to microfilm this thesis and to lend or sell copies of the film, and to University Microfilm Inc. to publish an abstract of this thesis/practicum. The author reserves other publication rights, and neither this thesis/practicum nor extensive extracts from it may be printed or otherwise reproduced without the authorrs written permission. Abstract This research describes a study of the effect of rubbing materials on the electrostatic propensity of textile fibers. The fibers included were cellulose-based f,rbers, protein-based fibers, manufactured fibers, and blends. The three rubbing materials were poly-tetra-fluorethylene (PTFE), polyvinyl chloride (PVC) and nylon 6. Peak static charges lvere measured and monitored from tribo-charged fabric surfaces. Experiments were conducted in an environmental chamber at 20'C and 30 o/orelatíve humidity. In general, the pattem of results for this study was predictable on the basis of other studies and the theory of static electricity. It has been previously stated that the amount of static charges generated by tribo-charging depends on the inner properties of the materials involved, but it is also affected by environmental conditions, rubbing mode and surface characteristics. Results showed that rubbing material had the greatest effect on the generated potential, but interaction effects with fiber content were also determined. Peak potentials were significantly different among fibers. It has been previously reported that tests using tribo-charging mechanisms were notoriously unreliable and considerable effort might be needed to achieve consistent charging, and that little control could be expected over the level and polarity of charging. Unlike previously reported results of charge variation of three orders of magnitude among different samples, results from this study yielded a variation of less than 500/o, which was perhaps due to the highly controlled conditions of the experiment. This tr confifins what other researchers have reported before during controlled füctional charging. It was found that peak potentials yrelded using various rubbing materials were not only different in magnitude but also in their polarify. Their relative position on rankings sorted by potential magnitudes changed when analyzedby rubbing material, determining that there was no signihcant correlation among those rankings. In addition, no significant correlation was found between these rankings and known tribo-electric series. Results from this study also suggest that surface characteristics may have a significant effect on the electrostatic properties of the fiber in addition to environmental conditions. Factors that may affect these surface properties include surface finish, dyeing, type of yarn (filament and spun yam), and type of weave. Chemical processes such as bleaching or dyeing that alter the electrolyte content may alter their electrical resistance. It has been reported that the resistance of synthetic fibers is greatly affected by the application of surface finishes. Electrostatic discharges from a charged object cannot be completely eliminated but their effects can be minimized and controlled based on better understanding of the phenomenon. Because static charges are affected by several factors, a comprehensive assessment incorporating these factors is highly recommended to decrease the hazards involving electrostatic discharges. m Acknowledgments The author wishes to express a special thank-you to her advisor, Dr. Jose Gonzalez, for his detailed and patient guidance and encouragement throughout the study. Special thanks are also extended to Dr. Norman Davidson, Department of Physics, and Dr. Jung Han, Department of Food Science, for their professional assistance and expert advice. The author would also like to thank the Human Performance and Activity Research Laboratory for providing the environmental chamber to carry out the testing component of this research. A special appreciation is expressed to Dr. Nelma Fetterman of the Department of Clothing and Textiles for her wise suggestions regarding my direction of study. Thanks are extended to my family members and my friends for their consistent support. Without them I could not have finished this study. v TABLE OF CONTENTS 1. CHAPTER INTRODUCTiON .............. 1 8ackground.......,........ ....... 1 Statement of Problem and Justification of the Study .............3 Specific Objectives ...........4 Null Hypotheses ............... 5 Delimitations of the Study........ ..........5 Definition of Terms .......... 6 CHAPTER 2. LiTERATLIRE REVIEW ................... 11 Basic Theory of Static Electricity. ...................,.. 11 Charge Generation ..........,........ 11 Tribo-electrification... ..... L2 Mechanism of the contact or frictional charging .......12 Tribo-electrification series .....14 Factors affecting the tribo-electrification..................................... l5 lnduce charging .............. 16 Charge Dissipation ..................l7 Charge Decay ................. 1g Electrostatic Discharge.,.............. ..... i9 Resistance, Resistivity and Surface Resistivity ...........20 Environmental Factors Affecting Electrical Characteristics of Textiles.......... ........23 Humidity.. ..............23 Temperature.............. ...............25 Electrostatic Hazards in Textiles ......26 Human BodyModel ................26 Incendivity of ESD ..................27 Antistatic Solutions .................2g Measurement of Static Electricity in Textiles ......................29 Human Body Experiment................ ..........29 Small-scale Tests......... ............ 30 Resistivity measurement.............. ...., 30 Charge decaymeasurement.............. ..................30 Discharge measurement from a capacitor ..........32 Summary.. .....3Z CHAPTER 3. METHODS AND MATEzuALS ............... .........,34 Research Design .............34 Procedures ...................... 35 Fabric Sampling.. .....................35 Pretreatment of Specimen and Conditioning.............. ...................35 Test System and Measurement of Dependent Variables................ ........37 Data Collection......... ......3j Statistical Analysis: Hypotheses Testing... .........37 V CHAPTER 4. RESULTS AND DISSCUSION............ ....,.........,40 Development of Tribo-electric Series ...............,40 Results ..........41 Hypothesis One .......... ............,41 Hypothesis Two ......... ............,48 Hypothesis Three........ .............49 Discussion ....,50 Objective One........... ............... 50 Objective Two and Three ........59 CHAPTER 5. CONCLUSIONS AND RECOMMENDATIONS ........,,.,,...,62 Conclusions ............... .....62 Recommendations ..........63 Recommendations for lndustry .................63 Recommendations for Further Research .....................63 BIBLrOGRAPHY........... .......6s APPENDiX ..........70 Appendix Appendix Appendix Appendix Appendix VI LIST OF TABLES Table 1. Fabrics Used in the Experiment............. ..................., 36 Table2. Analysis of Variance: Peak Potentials of Different Fabrics at Three Rubbing Materials ......................47 Table 3. Correlation Coefficient of Peak Potential between Different Rubbing Materials ...................49 Table 4. Correlation Coefficient of Peak Potential among Different Rankings .......... 50 Vtr LIST OF FIGURES Figure 1. Diagram of the Electrostatic Discharge (ESD) Test System .....38 Figure 2. Peak Potential by Fiber and by Rubbing Material PTFE ..........44 Figure 3. Peak Potential by Fíber and by Rubbing Material PVC..............................45 Figure 4. Peak Potential by Fiber and by Rubbing Material Nylon 6................ .........46 CHAPTER 1. INTRODUCTION Background Static electricity forms part of our daily experience. Most people have experienced electric shocks when getting out of their car, or after walking across acarpet and, then, a spark can be generated after touching a metal door handle. The first understanding of the nature of electricity came from the study of the phenomena of static electricity in the eighteenth century, although the phenomena were observed as early as 600 B.C. (Morton & Hearle, 1993). Static has long been a problem in the industry. As early as the 1400s, European and Caribbean forts were using static control procedures and devices to prevent ignition of black powder stores caused by electrostatic discharges (The ESD Association, 1998). By the 1860s, paper mills throughout the US employed basic grounding, flame ionization techniques, and steam drums to dissipate static electricity from the paper web as it traveled through the drying process (The ESD Association, 1998). But after the discovery