Handbook of Fiber Finish Technology - PDF

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					                                    NTC Project: C04-NS07
                                              1

              Static Generation and Control in Textile Systems
                                          C04-NS07

Principal Investigators

Abdel-Fattah SEYAM (Leader, North Carolina State University)
William OXENHAM (North Carolina State University)
Peter CASTLE (University of Western Ontario)

Graduate Research Assistants

Yiyun CAI (North Carolina State University)
Chris MOSES (North Carolina State University)

Website

http://www2.ncsu.edu/unity/lockers/project/ntcprojects/projects/C04-NS07/

                                           ABSTRACT

    The properties of static electrical phenomena have important impacts on textile materials and
processes. This project carried out studies in order to provide a better understanding on static
generation and control to the textile industry. This report investigated the research backgrounds
in several aspects, discussed the technical approaches that are used in different phases, and
reviewed current direction and progress of this research.

                                        PROJECT GOAL

    The goal of this project is to obtain a better understanding on the mechanism of static
generation on low energy polymer surfaces and to relate these findings to the issues of static
generation in fibers processing, fiber structures and fabrics. This research will also investigate
the interaction between topical applied materials (surface applied molecular films, fiber and
fabric finishes, grafted surface materials, etc.) and the tendency of surfaces to generate or
dissipate static charge.

    Laboratory work carried out under this project will be coordinated with fiber manufacturers
and finish producers for results observed in large-scale fiber process environment. This is
expected to provide the industry with chemical and structural models and evaluation techniques
that support the development of fiber products with enhanced processing and performance
properties.

                                        INTRODUCTION

     Electrical based technology is at the core of modern existence. While there are many useful
attributes of electrical phenomena, there exists some negative properties and one in particular


                    National Textile Center Annual Report: November 2004
                                     NTC Project: C04-NS07
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concerns the issues surrounding static electricity and its generation during fiber processing or use.
Textile technologists are concerned about the need to control static charge during modern, high
speed textile processes, and consumers are very aware of issues such as the static charge
generated in walking on carpet or static cling in fabrics. Despite these negatives attributes, textile
static is used in some manufacturing processes such as flocking, selected non-woven fabrics and
in electrets filters to assist in the absorption of airborne dust. Given the growing significance of
static electrical phenomena in textiles and textile processing, a better understanding of this
property is critical to the future of the textile industry.

                     TECHNICAL BACKGROUND AND LITERATURE REVIEW

The Generation of Static

     The generation of static electricity, observed in ancient times, was initially characterized in
the 1500’s. The initial tribo-electric series, developed in the 1757 by Wilche, was ultimately
interpreted as the transfer of electrons between two surfaces that are in contact with each other
[1,2]. The “tribo series”, despite its 245-year existence, is still variable; dependent on the
literature source [3] and a mechanistic explanation of its origins is still the subject on ongoing
research [2, 3]. This problem has been particularly complicated by the development of man-
made polymer fibers that tend to be highly resistive.

    There is a general consensus that when surfaces come into contact with one another, they
exchange electrons. If the surfaces are conductive, the excess charge will be dissipated to ground.
But if the surfaces are insulators, the charge will be retained and, as the surfaces are separated,
will appear as static charge. After separation, this charge will attempt to dissipate and the
mechanisms for dissipation have been well documented [4]. While there has been considerable
discussion concerning the control of static through the use of ionizing atmosphere or through air
conduction [5], the most prevalent approach to controlling static in fibers and plastics is to
modify the surface conductivity of the product.

Performance of Antistatic Agents

    Traditional anti-static agents have been selected based on their ability to provide conductive
dissipation of charge along the fiber surface. There have been many reviews of the chemistry and
general performance properties of traditional anti-static agents [6, 7, 8]. They have generally
focused on chemistry, structure of materials or the relationship between conductivity and
dissipation performance of the materials on fiber. These “Edisonian” observations have been
useful when it comes to designing processing aids (finishes) that support the manufacture and
conversion of synthetic fibers, but have done little to address theoretical or model development
issues relating to the performance/non-performance of specific chemistries and the overall
performance of the system. Questions relating to the effectiveness of various materials and
observed synergistic interactions of components remain unaddressed [9].

The Mechanism of Static Generation for Fiber Polymers




                     National Textile Center Annual Report: November 2004
                                     NTC Project: C04-NS07
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    The generation mechanism and molecular surface location of static charge, on low energy
polymer surfaces, is still a matter of speculation. While there has been some recent research in
this area [10, 11], there are no systematic studies that provide either a practical or a theoretical
understanding in this area. The work we are proposing should allow us to probe the nature of
static generation sites, to develop models of the surface chemistry involved in static generation
and to provide models that explain the differences in static generation performance that is
observed in various commercial fiber polymers.

The Relationship between Applied Surface Materials and Static Charge Generation

    The most significant question to be addressed by this project is the interaction between fiber
surfaces and surface applied materials, leading to significant modification of static generation
properties. This effect has been clearly recognized for many years [8] and is actively utilized in
strategies to control static generation during high-speed processes. In specific cases, minor
changes in the composition of materials applied to the fiber surface have led to very large
changes in the static generation properties of the fiber [9]. While this phenomenon has been
widely recognized within the fiber industry, there have been no systematic studies in this area.
This project should provide a better understanding of current product performance and may open
the possibility of completely new approaches to the control of static in fiber processing
environments.

                         ACCOMPLISHMENTS AND WORK IN PROGRESS

The project started May 2004. Two graduate research assistants were recruited. One joined late
August and the other joined late September. The project leader and the principal investigators
have formally met with the industry collaborators from American Fiber Manufactures
Association, American Fiber & Yarns Company, Goulston Technologies, and Honeywell
companies on May 11, 2004. The meeting served as a kickoff meeting for reviewing project
background and objectives, discussing current industrial applications and practices, and setting
long- and short-term research goals of the project.

The following are the topics discussed during the kick-off meeting:

   1. Unsolved questions regarding static generation and dissipation were reviewed and
      discussed. For example: different material’s static generation characteristics, surface
      location of static charge, impacts of surface applied materials, effects of humidity,
      process speed, friction and frictional surface, material’s conductivity, mechanism of
      antistatic agents, etc.

   2. Static generation and control experience in industry were reviewed, such as antistatic
      agent technology and charge generation control.

   3. The importance of choosing and developing experimental methods was discussed. For
      example, techniques for static probe on polymer surface and polymer conductivity test.

   4. Standards for static test will be decided from US and/or EU standards.



                     National Textile Center Annual Report: November 2004
                                     NTC Project: C04-NS07
                                               4


   5. The choice of experimental sample was discussed:
         a. Materials:
                 i. Polypropylene, Polyester, Nylon
         b. Geometrical configurations and dimensions:
                 i. Fiber, monofilament, film, and tape
                ii. Film thickness, fiber denier, particle size, etc.
         c. Surface properties

   6. Three phases regarding the approach of this research were reviewed (see project
      proposal).

   7. The idea of bringing in more industries together to discuss different aspects related with
      static generation and dissipation was proposed, such as nonwovens, paper, and plastic, etc.
      At the same time, over commitment needs to be avoided.

   8. Project goal for this summer and early fall is to complete a thorough and extensive
      literature review; a major effort will be focused on different test methods. In addition,
      developing test methods and preparing experiments were also proposed.

   9. Next meeting will be held in late summer or early fall, late July or late September is
      preferred by several participants. This date will be determined by the availabilities of
      participants.

Research Approaches

   This research is carried out in three phases:

    Phase 1: A number of tests to characterize polymer surfaces for static generating potential
(film and fiber) will be put in place and methods for use developed. There methods include
standard literature methods and standard industrial methods [12, 13], others will represent
recently develop methods to probe the surface of materials [10, 14]. Methods developed from
industrial partners will also be utilized. Specific conditions and polymers materials that will form
the basis of the project will be identified with industrial partners. Techniques for characterizing
the static holding properties of a polymer surface will also be developed with project participants
from the electrostatic area and industrial polymer consultants [11] to obtain a better
understanding on the structural characteristics of the surfaces that are involved in static
generation and to apply earlier work on charge transfers in polymers to the fibers area.

    Phase 2: Based on the results of Phase 1 and input from the industry, research program will
move from controlled surface experiments to more complex, lubricated surfaces and, in the
process, quantifies the specific variables that control the static generation process. Laboratory
work will be integrated with observations made in large-scale fiber processing situations. Based
on the results, specific directional information could be derived to supports the development of
improved process and products for the fiber industry.




                     National Textile Center Annual Report: November 2004
                                    NTC Project: C04-NS07
                                              5
    Phase 3: In conjunction with Phase 2, the research will develop a program directed at probing
the surface of static generating materials and utilizing model compounds that modify this
performance to study the surface chemistry of the static generation. Based on this work,
meaningful models that relate surface properties and topical treatments to the static charge
generating properties of the system will be developed. These models will be extended down to
the molecular level and up to the fiber processing level where it is expected that the work will
provide the basis for new and improved methods of static control on fibers.


                                PLANNED WORK FOR THIS YEAR

1. Acquisition, design, and construction of necessary test equipments and experiments are on
   the way. Existing equipment from industrial participants will also be utilized when it is
   possible. It is expected that a significant part of the experimental work will be carried out in
   the laboratories belongs to industrial partners.

2. Preparation of suitable polymer and fiber surfaces. Given the belief that the surface is a
   critical component in static generation, considerable effort will be given to the preparation of
   fiber and film surfaces for evaluation. Efforts will be made to provide controlled surface
   variation so as to access the impact of specific polymer surface conditions on the static
   generation process.

3. Acquisition and initial testing of several series of antistatic agents. These will be prepared
   and characterized by the industrial partners.


                                          REFERENCES

1. Slade, Philip E., Antistats, In Handbook of Fiber Finish Technology, New York, USA,
   Marcel Dekker, 1998, 273-274.
2. Bailey, Adrian G., 2001. The Charging of Insulators, Journal of Electrostatics, 51-52, 82-90.
3. Castle, G. S. P., 1997. Contact Charging Between Insulators, Journal of Electrostatics, 40-41,
   3-12.
4. Slade, Philip E., Antistats, In Handbook of Fiber Finish Technology, New York, USA,
   Marcel Dekker, 1998, 275-278.
5. Hersh, S. P., Resistivity and Static Behavior of Textile Surfaces, In Surface Characteristics of
   Fibers and Textiles. J. M. Schick, ed., New York, USA, Marcel Dekker, 1975, 229-237.
6.   Slade, Philip E., Antistats, In Handbook of Fiber Finish Technology, New York, USA,
     Marcel Dekker, 1998, 294-314.
7. Sello, S. B. and Stevens, C. V., Antistatic Treatments, In Chemical Processing of Fibers and
   Fabrics, Vol. 2B. New York, USA, Marcel Dekker, 1984, 298-313.
8. Profit, Thomas J., Phosphates as surfactants in Spin Finishes, Proceedings of the 3rd CESIO
   International Surfactant Congress and Exposition, Macclesfield, UK, 1992, 1-9.



                    National Textile Center Annual Report: November 2004
                                     NTC Project: C04-NS07
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9. Unpublished discussions with members of the American Fiber Manufactures technical
   committee on Finishes and Fiber Surface Modification, June, 2003.
10. Ohara, K., Nakamura, I., Kinoshita, M., 2001. Frictional Electrification Between Flat
    Surfaces of Polymers and of Langmuir-Blodgett Layers, Journal of Electrostatics, 51-52,
    351-358.
11. Arita, Y., Shiratori, S. S., Ikezaki, K., 2003. Methods for the Detection and Visualization of
    Charge Trapping Sites in Amorphous Parts in Crystalline Polymers, Journal of Electrostatics,
    57, 263-271.
12. Hersh, S. P., Resistivity and Static Behavior of Textile Surfaces, In Surface Characteristics of
    Fibers and Textiles. J. M. Schick, ed., New York, USA, Marcel Dekker, 1975, 243-267.
13. Chubb, John, 2002. New Approaches fir Electrostatic Testing of Materials, Journal of
    Electrostatics, 54, 233-244.
14. Greason, W. D., 2000. Investigation of a Test Methodology for Triboelectrification, Journal
    of Electrostatics, 49, 245-256.




                     National Textile Center Annual Report: November 2004

				
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