Fiber Technology

From Film to Fiber

Hans A. Krassig

• Publisher: CRC Press
• Year: 2020
• Topic: Technology & Engineering
• eBook ISBN:
  9781000146424
• Subtopic: Chemistry
• Index: Chemistry

This book is intended to fiber technologists, textile dealers, and textile salesmen a practical guideline to become acquainted with and to deepen their knowledge of the processes for the manufacture of film tapes, split-film yarns, and fibrillated film fibers.

1
Processes for Manufacturing Film, Film Tapes, and Film Fibers

In this chapter a general review of the processes for the manufacture of film, film tapes, and film fibers shall be given.

I. FILM PROCESSES

The first step in the manufacture of fibrous film products such as film tapes and film fibers is the film casting. It is understandable that the manufacture of such products is only economically feasible when the film processing is relatively simple and inexpensive. For this reason, film processing by melt extrusion, particularly of polyolefins, is widely applied. Other polymers calling for more elaborate film processing methods, such as casting from solutions, are only suited for film-to-fiber technologies when they yield special products for expensive enduse applications. Furthermore, uniaxial stretching methods are most generally applied in the manufacture of fibrous products from films.

Film processing comprises the following-steps: (1) extrusion of the polymer melt; (2) film solidification by cooling; (3) uniaxial stretch at elevated temperature; (4) heat relaxation or fixation; and (5) the final takeup. The cutting into tapes and the splitting or slicing into finer fibrous products is done either after the film solidification, during the stretching operation, or later in the processing before final takeup.

For the extrusion step (through a flat die or annular die) three methods are available; the extrusion through a flat die uses either water quenching or chill-roll cooling for the film solidification, and the extrusion through annular die normally uses air cooling. The three routes for casting polymer films by melt extrusion techniques as well as the processing conditions applied, such as extrusion temperature, extrusion speed, solidification conditions, etc., have a marked influence on the ease of stretching, the maximum stretch ratio achievable, and the final mechanical and thermal properties of the resulting products. The same can be said for the influence of stretching and annealing conditions applied later in the process. Details will be discussed in later chapters of this book.

II. FILM TAPE PROCESSES

The first step towards the production of fibrous products suitable for textile and related uses by way of the film was the development of film tapes. As mentioned before, until the early 1950s the production of tapes was limited to paper, leather, or films from regenerated cellulose, polyvinyl chloride, and polystyrene. These tape products, however, were either of only limited durability or too expensive. The appearance of the polyolefins, namely high-density polyethylene and isotactic polypropylene, changed the situation completely.

As recently as the early 1960s a German mechine manufacturer developed special machinery for the production of polyolefin film tapes suitable for weaving (Becker, 1962; Poelchau, 1966). In a matter of only a few years a large number of other manufacturers throughout the world (for instance, in Austria, England, France, Germany, Italy, United States etc.) have developed improved equipment for the same purpose. Descriptions of such machinery have been given by Kunststoffe (1966), Mod. Texl. Mag. (1968), Kunststoffe (1969), Z. Gesamte Textilind. (1969), Chemiefasern (1970), Chemiefasern & Text. Anw endungslech. / Text. Ind. (1972), Mod. Text. Mag. (1973), Tufting Needling News Bulletin (1973), Chemiefasern & Text.-Anwendungstech. /Text. Ind. (1974), Hensen (1968, 1969, 1973, 1974, 1978, 1979), Mozawa (1966), Slack (1968), Nightingale (1970), Hossack (1971), Barmag (1973), Braun (1975), Windmöller & Hölscher (1981).

Principally, there are two basic ways to produce monoacially stretched film tapes:

1. Processes where tape cutting is done before the stretching operation. The polymer film being delivered from an extruder equipped with a circular or flat slit die in the form of a tubular or a flat film is being cut into tapes of 1 to 20 mm width. The resulting primary tapes are stretched to such an extent as necessary to achieve the desired dimensions and properties. In Figure 1 schemes of production lines for stretched film tape are being given. The operation can either be performed continuously or discontinuously, separating in the latter case the film formation from the tape cutting and stretching step. Further information on film tape manufacture will be given in Chapter 2. Publications dealing with this subject have been written by Ford (1965, 1966, 1967, 1970), Burggraf (1967), Hensen and Klawonn (1967a, 1967b) Schwenkedel (1967), Weber (1967), Lennox-Kerr (1968), Mayer (1969), Nau (1968), Peuker (1968a, 1968b, 1968/1969), Schrader (1968), Hensen (1968, 1979), Moorwessel and Pilz (1969), Real (1969), and Schuur (1969; 2. Processes, where tape cutting-is performed after the stretching operation. The polymer film extruded as described under (1) is being-stretched to an extent necessary to achieve the desired thickness dimension and mechanical properties in the final tape before the separation in film tapes of desired width. In most cases the film stretching operation is done in such a way as to prevent width shrinkage of the film, such as by performing the length extension between heated rollers over a narrow distance. In addition, static charging is often used to achieve good adhesion of the film to the stretch rollers counteracting the width shrinkage tendency.

Figure 1 Scheme of production lines for stretched film...

Table of contents

• Cover
• Half Title
• Series Page
• Title Page
• Copyright Page
• Preface
• Contents
• Introduction
• 1. Processes for Manufacturing Film, Film Tapes, and Film Fibers
• 2. Tape Yarn and Film Fiber Processing
• 3. Machine Systems for the Manufacture of Film Tapes, Film Yarns, and Fibers
• 4. The Prospects of Film Tape and Film Fiber Products
• Bibliography
• Index