01. Polyester: The Leading Synthetic Fiber

Understanding Chemical Fibers

The industry uses the term “chemical fiber” to describe fibers that manufacturers obtain through chemical or physical processing. These processes utilize either natural or synthetic polymer substances as raw materials. In general, the industry categorizes them into two main types:

  • Man-made Fibers (Regenerated Fibers): Manufacturers produce these from natural polymer compounds like cellulose. Specifically, the process involves chemical treatment and mechanical spinning. Main products include viscose and acetate, while raw materials consist of bamboo, wood, and cotton linters.

  • Synthetic Fibers: Producers create these by synthesizing high-molecular compounds from petroleum, natural gas, coal, and agricultural by-products.

Ultimately, the primary difference between the two lies in the source of their raw materials.

 

Chemical Fiber Classification

Defining Polyester

“Polyester” serves as the commercial name for polyester fiber in China. Internationally, however, the trade uses various names: Terylene (UK), Dacron (USA), Tetoron (Japan), and Lavsan (former Soviet Union).

Because the macromolecules contain ester groups, technical experts term it polyester fiber. While most polyester fibers consist of Polyethylene Terephthalate (PET), other variants include PBT, PTT, and PEN. Furthermore, polyester exists in two forms: filament yarn and staple fiber. This article focuses specifically on the production of Polyester Filament Yarn (PFY).

02. Development History of Polyester Filament

  • 1941: J.R. Whinfield and J.T. Dickson (UK) invented polyester.

  • 1947: Imperial Chemical Industries (ICI) conducted the first industrial trials.

  • 1951: DuPont (USA) built the first commercial plant with an annual capacity of 16,000 tons.

  • Late 1950s: Companies like Hoechst, Toray, and Teijin introduced UK technology, thereby leading to a boom in staple fiber production.

  • 1960–1985: Filament yarn entered a rapid growth phase. In fact, output increased by 314% annually.

  • 1972: Polyester claimed the top spot as the world’s most-produced synthetic fiber.

  • 2007: Global production reached 30.7 million tons, with filament yarn accounting for over half of that volume.

03. Classification of Polyester Filament Yarn

Polyester is highly versatile due to its available raw materials, durability, elasticity, corrosion resistance, and cost-effectiveness. It is used in clothing, bedding, upholstery, and industrial textiles.

I. Classification by Production Process

  1. UDY (Un-Drawn Yarn): Molecules have almost no orientation and are un-crystallized. It has low strength and high elongation; usually not used directly.

  2. MOY (Medium Oriented Yarn): Slight molecular orientation; structure is unstable and requires further processing.

  3. POY (Pre-Oriented Yarn): Moderately stretched with some crystallinity. It is the primary precursor for producing DTY.

    Note on POY Chip Spinning: This process involves pre-crystallizing polyester chips to a moisture content below 0.01%, melting them at 260–290°C, and extruding them through a spinneret. The fibers are cooled by side-stream air and wound at speeds of 2500–3500 m/min.

  4. HOY (High Oriented Yarn): Produced via ultra-high-speed spinning. It has good dyeability but high thermal shrinkage.

  5. DY (Drawn Yarn): Produced via low-speed drawing. It is smooth and straight but lacks bulkiness.

  6. FDY (Fully Drawn Yarn): Produced by a one-step spinning and drawing process. It is high-quality with fewer breakages and excellent dyeing uniformity, ideal for high-speed weaving.

  7. DTY (Drawn Textured Yarn): Produced from POY through simultaneous drawing and false-twisting. It has good elasticity and a soft “hand-feel,” widely used in apparel (suits, shirts) and home decor.

  8. ATY (Air Textured Yarn): Uses air-jet technology to create loops on the yarn surface, giving it a natural, spun-like appearance without the “waxy” feel of synthetic yarn.

II. Classification by Application & Performance

  • Civilian Filament: Dominates the market; used primarily in apparel and home textiles.

  • Industrial Filament: High-strength yarn used for tire cords, conveyor belts, and seatbelts.

  • Differential Fibers: Modified versions with enhanced properties like fine denier, moisture-wicking, flame retardancy, or anti-static capabilities.

04. Performance Characteristics

1. General Properties of Polyester Fiber

(1) Strength: The fiber possesses high strength, generally ranging from 4.5 to 8 cN/dtex, while high-tenacity variants reach 5.6 to 8.0 cN/dtex. Furthermore, due to its low moisture absorption, its wet strength remains essentially identical to its dry strength.

(2) Modulus: Polyester exhibits a high initial modulus. Specifically, for civil-use filaments, this value is no less than 90 cN/dtex, whereas industrial-use yarns can reach up to 132.5 cN/dtex.

(3) Elasticity: Additionally, the fiber possesses excellent elasticity. Under a tensile strain of 2%, its recovery rate is 96%. Consequently, fabrics made from it are wrinkle-resistant and exhibit superior dimensional stability.

(4) Heat Resistance: Polyester has a high melting point of 255–260°C. Even when heated in air at 150°C for 1,000 hours, it undergoes only slight discoloration with strength loss not exceeding 50%.

(5) Shrinkage: In terms of stability, polyester fabrics exhibit very minimal shrinkage, or virtually no shrinkage at all.

(6) Moisture Absorption: However, polyester has poor moisture absorption properties, with a regain rate of only 0.4%. This is primarily because the macromolecules contain very few polar groups.

(7) Pilling: Polyester is prone to pilling, and these pills do not easily detach. This occurs because the pills are formed by loose monofilaments and broken ends. Due to the fiber’s high strength, they remain anchored to the surface; nevertheless, modified fibers with lower tensile strength can be used to mitigate this issue.

(8) Dyeing: Similarly, since the macromolecules lack polar groups, they cannot be dyed using conventional methods. Instead, better results are achieved through disperse or non-ionic dyes.

(9) Flammability: Regarding flammability, polyester is more combustible than nylon. Nevertheless, it tends to melt and self-extinguish during the burning process.

(10) Chemical Resistance: Its resistance to hydrolysis and acids is superior to that of nylon. On the other hand, it lacks resistance to alkalis. By leveraging this specific characteristic, the alkali reduction method can be employed to modify the fiber.

2. Characteristics of Polyester Filament

In comparison to staple fiber, polyester filament possesses several distinct characteristics:

(1) Production Mode: Filament production utilizes a single-spindle manufacturing mode. As a result, passing over dozens of friction points makes the yarn prone to generating fuzz. Furthermore, because production occurs across multiple spindles, performance may vary between positions; in fact, differences can even exist between the inner and outer layers of a single yarn package.

(2) Physical Modification: By utilizing physical texturizing methods, filaments can be engineered to simulate differentiated fibers. For instance, altering spinneret shapes can produce silk-like fibers. Moreover, techniques such as false twisting or bicomponent spinning can impart a wool-like aesthetic. In addition to this, intermingling yarns with different melting points can yield a linen-like appearance, while high-twist methods allow for the creation of crêpe yarns.

(3) Chemical Modification: Alternatively, polyester filaments can be engineered through chemical methods. For example, techniques like copolymerization and grafting are employed to endow fibers with specialized properties. Consequently, this allows for the production of materials with enhanced flame retardancy, antistatic properties, or high water absorption capabilities.

05. The Industry Chain

Polyester is produced via the polymerization of PTA (Purified Terephthalic Acid) and MEG (Monoethylene Glycol).

  1. Upstream: Crude Oil →Naphtha → Paraxylene (PX) → PTA.

  2. Midstream: PTA + MEG → Polyester (PET) → Spinning.

    • Melt Direct Spinning: Uses molten polymer directly; energy-efficient and low waste.

    • Chip Spinning: Uses polyester chips; offers higher production flexibility for different grades.

  3. Downstream: * Apparel: Underwear, shirts, jackets, suits, sportswear.

    • Home Textiles: Bedding, curtains, carpets, sofa covers.

    • Industrial: Sewing threads, tire cords, filter cloths, ropes.

    • Non-fiber: Films, bottles, and synthetic leather.

Polyester Filament Industry Chain

Cost Analysis: Raw materials (PTA & MEG) account for approximately 85.8% of the total cost. Consequently, the price of polyester filament is highly sensitive to fluctuations in global crude oil prices.

The Future of Polyester: It Starts with the Chip

The polyester filament market is rapidly shifting toward high-end and differentiated applications. Standard products are no longer enough to meet the diverse needs of Industry 4.0.

We specialize in the R&D and supply of functional polyester chips, offering tailored raw material solutions for manufacturers of specialty yarns and high-performance textiles. By optimizing the polymer structure at the molecular level, we help our clients create products that stand out in a competitive global market. Let’s collaborate to redefine what polyester can achieve.

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