1. Types and Classification of Chemical Fibers

• Chemical Fiber: Fibers produced through chemical processing using natural or synthetic polymers as raw materials.

• Regenerated Fiber: Fibers made from natural polymer compounds through chemical treatment and mechanical processing.

• Synthetic Fiber: Fibers produced from petroleum, natural gas, coal, or agricultural by-products via a series of chemical reactions to synthesize polymer compounds, followed by processing.

2. Characteristics of Chemical Fibers

(1) Filament
In chemical fiber production, the spinning fluid is extruded from spinnerets, cooled in a spinning sleeve or solidified in a bath to form a continuous fine stream. After further processing, smooth and lustrous fibers with lengths measured in kilometers are obtained, known as filaments.

(2) Staple Fiber
For blending with other fibers, chemical fiber products are often cut into short segments ranging from a few centimeters to over ten centimeters. These short fibers are commonly referred to as "staple fibers."

(3) Tow
Tow consists of hundreds to millions of single filaments bundled together, which can be cut into staple fibers or stretched and broken into sliver (also known as stretch-broken fiber).

(4) Profiled Cross-Section Fiber
During synthetic fiber formation, non-circular spinneret holes are used to create fibers with various cross-sectional shapes or hollow structures. These fibers improve properties such as hand feel, resilience, pilling resistance, and luster, and are called profiled cross-section fibers, or simply "profiled fibers."

(5) Composite Fiber
Also known as bicomponent fiber, composite fibers are produced by combining two or more types of polymer melts or solutions with different compositions, ratios, viscosities, or properties. These components are fed into the same spinneret assembly, merged at an appropriate point, and extruded from the same spinneret hole to form a single fiber.

(6) Textured Yarn
Filaments that undergo various texturing processes to alter their appearance, geometric shape, internal structure, and properties are called textured yarns.

(7) Differentiated Fiber
Chemical fibers are evolving toward higher quality, diversity, and specialized functionalities.

3. Properties of Chemical Fibers and Their Representation Methods

1) Linear Density: An indicator of fiber fineness. The internationally accepted units are tex (T) or decitex (dtex). The weight in grams of a 1000-meter-long fiber is called "tex," and one-tenth of a tex is a decitex. The chemical fiber industry previously used "denier" (den) as the unit for linear density: 1 den ≈ 1.1 dtex.

2) Breaking Strength: The maximum load a fiber can withstand under continuously increasing tension until breaking, expressed per unit linear density. Units include N/tex and cN/dtex.

3) Breaking Elongation (Extension): Generally expressed as a percentage (%), it represents the increase in fiber length at break relative to its original length.

4) Additional Quality Indicators for Staple Fibers

• Cut Length: Determined based on spinning equipment type and textile requirements. Cotton-type products require lengths below 40mm, with strict control of over-length fibers (fibers exceeding the nominal length by more than 7mm).

5) Crimp Level and Crimp Frequency
These parameters characterize the crimp properties of fibers. To meet textile processing requirements, enhance yarn cohesion, and improve fabric hand feel, polyester staple fibers undergo crimping. Crimp effectiveness is measured by crimp frequency, crimp level, crimp uniformity, and stability.

• Crimp Uniformity: Includes transverse uniformity (dependent on tow thickness consistency) and longitudinal uniformity (dependent on feeding tension consistency and stuffing box pressure stability).

• Crimp Level (Crimp Ratio): The percentage increase in apparent fiber length when straightened relative to its straight length.

• Crimp Frequency: The number of crimps per 25mm of fiber length.