Fibers are substances composed of continuous or discontinuous filaments, broadly classified into natural fibers and chemical fibers. Please refer to the above text for specific classifications. Chemical fibers are artificially manufactured through chemical methods. They are produced by pressurizing a chemical liquid, causing it to be ejected from a small hole, thus forming uninterrupted, continuous columnar or fine linear fibers. These are relatively flexible, thin, and long materials, with an aspect ratio generally greater than 1000:1. Typical textile fibers have diameters ranging from a few micrometers to tens of micrometers, lengths exceeding 25 mm, and linear densities on the order of 10⁻⁵ g/mm². The basic concepts related to chemical fibers are as follows:

1.Filament

In the manufacturing process of PP granules into filaments, the spinning fluid is continuously extruded from the spinneret, cooled by air, or solidified in a coagulation bath to form a continuous filament. This filament then undergoes post-processing steps such as stretching, twisting, or texturing for further processing and application. The resulting fiber, measured in kilometers, is called a filament. Filaments include monofilaments, multifilaments, and tire cord filaments.

① Monofilament: A continuous single fiber spun from a single-hole spinneret.

② Multifilament: A filament composed of dozens of monofilaments.

③ Cord filaments are composed of more than one hundred to several hundred single fibers and are used to manufacture tire cord fabric.

2. Silk bundle

A filament bundle is a large number of continuous filaments, essentially untwisted, long bundles of chemical fibers, used to cut into short fibers or to produce chemical fiber strips through a slitting process. After spinning, chemical fibers consist of a considerable number of single filaments assembled into a filament bundle. Common products made from cut short fibers include spun cotton fillings and blended short fiber fabrics.

1) After spinning, the filament bundle is assembled, stretched, oiled, crimped, dried, and shaped before being cut into short fibers;

(2) Acetate fibers or polypropylene fibers, after spinning, bundling, stretching, and crimping, are used to make cigarette filter rods from filament bundles;

(3) After spinning, stretching, and shaped, the filament bundle is directly made into tow-to-top using a tow-to-top machine. This is also known as the direct tow-to-top method. The direct tow-to-top method is commonly used for chemical fibers such as polyester and acrylic to produce chemical fiber tows for use in wool spinning mills, either in pure or blended applications.

(4)After vinylon spinning, the long filament bundle is drawn, cut and spun into slivers, which are called drawn-cut fibers, equivalent to roving slivers in cotton spinning.

3. Short fibers

Chemical filaments are cut into lengths ranging from a few centimeters to over ten centimeters; these fibers are called staple fibers. Based on their cut length, staple fibers can be classified into cotton-type, wool-type, and medium-length staple fibers.

① Cotton-type staple fibers are 25–38 mm long, relatively fine (linear density 1.3–1.7 dtex), similar to cotton, and mainly used in blends with cotton—polyester-cotton fabrics—and as fillings like silk-like cotton.

② Wool-type staple fibers are 70–150 mm long, relatively coarse (linear density 3.3–7.7 dtex), similar to wool, and mainly used in blends with wool—wool-polyester fabrics.

③ Medium-length staple fibers are 51–76 mm long, with a linear density between cotton-type and wool-type (2.2–3.3 dtex), and are mainly used to manufacture medium-length fiber fabrics.