Slit film

Slit-Film Fiber. A substantial volume of olefin fiber is produced by slit-film or film-to-fiber technology (29). For producing filaments with high linear density, above 0.7 tex (6.6 den), the production economics ate more favorable than monofilament spinning (29). The fibers are used primarily for carpet backing and rope or cordage appHcations. The processes used to make slit-film fibers are versatile and economical. 

The equipment for the slit-film fiber process is shown in Figure 15 (29). An olefin film is cast, and as in melt spinning, the morphology and composition of the film determine the processing characteristics. Fibers may be produced by cutting or slitting the film, or by chemomechanical fibrillation. 

The film is fibrillated mechanically by mbbing or bmshing. Immiscible polymers, such as polyethylene or polystyrene (PS), may be added to polypropylene to promote fibrillation. Many common fiber-texturing techniques such as stuffer-box, false-twist, or knife-edge treatments improve the textile characteristics of slit-film fibers. 

Film can be heated and/or stretched and cut eventually giving filament-like materials. Unfibrillated slit-film materials are used in weaving sacks and other packaging. Randomly fibrillated slit-film material is used to make twines and ropes, while controlled fibrillated material is used to make yarns for use in carpet backings and furnishing fabrics. 

Fig. 1. Schematic drawings of five types of geotextile fibers (a) monofilament, (b) multifilament, (c) staple fibers, (d) staple yam, and (e) slit film.

Gore-T3JXc. W L. Gore (expanded PTFK staple, filament, low. and slit film-RTt... 

Slit and Split Films. Thick incUistiial-giade yams aic often pioduccd by slitting films, providing a less expensive alternative to melt spun fiber. Cast film is slit in the machine direction by parallel rotary knives. The resulting tape can then be cold drawn in an oven in a manner similar to melt spun fibers to produce the final fiber. 

Early in the manufacture of PP, a concept was developed for dry spinning directly from the solution obtained in the polymerization operation. Had it been feasible, it would have been the realization of a chemical engineer s dream the gaseous olefin fed into one end of the equipment, and the packaged fiber, ready for shipment to a textile mill, coming out the other end. But it did not turn out that way, and today melt spinning is the accepted technique for the production of staple fibers, monofilament, and multifilament yams. To this usual method have been added the fibrillation and the slit film procedures for producing yams. 

Several methods are used to produce fibril-lated film. They are produced in much the same way as slit film, but these techniques take advantage of the tendency of PP to fib-rillate. In one method, a profiled tape is extruded and hot-drawn. It is drawn again to achieve a 10 1 ratio, and the film splits into separate filaments. In another method, called roll embossing, the film is hot-drawn, and then embossed using profiled rollers. The profiled film is drawn again, and fibrillation results. In the pin-roller technique, the film is drawn and cut by knives or pins on a rotating cylinder. This method can produce individual fibers or a controlled web network. 

Similar to slit film fiber, fibrillated tape fiber is produced. However a draw ratio of up to 1 10 is used and a fibrillation step is added to the process. The slit film tapes are fibrillated by passing them over a rapidly rotating roll fitted with staggered rows of pins. As the pins are traveling faster than the tapes, they make a series of short discrete cuts in the longitudinal direction of the tapes. 

Novoien . [BASF AG] Folyprt ylene for inj. molding and extrusion, automotive parts, elec, engineering, pkg., pharmaceuticals, medical technology, fibers, slit film yams, monofilaments. 

Slitting - This is a process to cut film and webs into narrower widths than the starting material. A roll of the wide film is unwound and passed over sharp knives positioned to obtain the required cut widths. The narrower films are wound up on separate cores. Special machines are available for slitting films. 

Polypropylene fibers are produced by a larger variety of processes than other melt-spun fabrics. At one end of the range, the long air-quench process produces high-quality multifilament yarns, and, at the other end, fibrillating slit film produces coarser fibers. The success of the lower-cost polypropylene slit-film fiber is due to the lower price of the polypropylene resin and the unique adaptability of polypropylene to the less expensive slit-fibn fibrillation process. The water-quench process for monofilament has long been an established technique... 

Polyolefin fibers, especially PP, are widely used in carpet backing, carpet face yam, laundry bags, sportswear and sweaters, rope and cordage, hosiery, undergarments, sewing thread, and knitwear. PP slit film and monofilaments are used in ropes. 

Polypropylene film fiber is becoming of great commercial interest in many applications such as carpeting and woven sacks. It consists of an extruded film that is slit along the machine direction into narrow, fiber-like ribbons. These ribbons are then woven to make strong fabrics, nets, and sacks. Low-density polyethylene (LDPE) is sometimes blended with PP in slit film applications in order to reduce fibrillation and improve processability. 

The classic geotextiles are fabricated in two steps, i.e. the production of fibres, filaments, slit films (tapes), or yams followed by converting these constituent materials into a fabric. The constituent materials required for the manufacture of geotextiles are produced using various techniques, as discussed below."... 

Slit films. The films are produced through a melt extrasion process using slit dies which are subsequently slit with sharp blades. These films can be further fibrillated and broken into fibrous strands, known as a fibrillated yam. 

The above linear elements, namely filaments, fibres, slit films, or yams, can be converted into several types of classic geotextiles, as briefly discussed below. 

Fibrillated-film yarn See slit-film yarn. 

Slit-film yarn n. Yarn of a flat, tape-like character produced by slitting an extruded film. 

Woven geotextiles have the appearance of two sets of parallel threads interlaced at right angles to each other in the plane of the fabric. Warp yarns lie along the length of the fabric and weft in the transverse direction, i.e. across the width of the fabric. The type of yarns used to produce a woven geotextile may be monofilament, multifilament, a combination of each type, or slit film yarns. Two kinds of slit film yarn can be used, either flat-tape yarns or flbrillated yarns. 

Staple, slit film and multifilament yarns used to make a fabric will have open spaces between the fibres, but these are very small in size and may be neglected when considering the geotextile functionalities. 

A great volume of PP finds its way into an area that may be classified as fibers and fabrics. Fibers, which broadly speaking includes slit-film or slit-tape, are... 

In slit-film production, wide web extruded film, which is oriented in the machine direction by virtue of the take-up system, is slit into narrow tapes. These tapes are woven into fabrics for various end uses. 

---