Since the dawn of human civilization, textiles have been an indispensable part of life. In the vast world of fibers, cotton (natural) and polyester (synthetic) undoubtedly hold dominant positions, forming the two major pillars of our daily apparel and industrial applications. Cotton, with its natural comfort and skin-friendliness, carries a history spanning thousands of years, while polyester, with its superior functionality and economic viability, represents a triumph of modern material science.

This article aims to provide a comprehensive and deep comparative analysis, detailing the core differences between cotton and polyester from the aspects of microstructure, historical evolution, production processes, macroeconomic applications, and future trends. Through a thorough understanding of these two fibers, readers can make the most informed material selection based on specific use cases and performance requirements.

Cotton fiber, as a pure natural plant fiber, holds value not only in its comfort but also in its long history and unique biological structure.

Cotton fiber originates from the epidermal hairs of the seeds of plants belonging to the Gossypium genus of the Malvaceae family. Several cultivated species exist, with upland cotton (G. hirsutum, accounting for the vast majority of global production) and Sea Island cotton (G. barbadense, or extra-long staple cotton) being the most important. Sea Island cotton is preferred for high-end textiles due to its long staple length and fineness.

Historical Use: Archaeological evidence shows that cotton textiles were discovered in the Tehuacán Valley, Mexico, as early as 5000 BCE. Cotton was also widely used by the Indus Valley Civilization during the same period. Cotton cultivation techniques spread globally through trade routes, making it the most critical textile raw material before the Industrial Revolution.

The microstructure of the cotton fiber is the determining factor for its properties. It is composed of approximately 90% cellulose, essentially a natural high-molecular-weight polymer.

• Lumen: The cotton fiber possesses a central channel during its growth, known as the lumen. As the fiber matures and dries, the protoplast disappears, and air gradually replaces the moisture inside the lumen. This structure causes the fiber to contract and undergo characteristic twisting (or convolutions) upon drying, which is crucial for identification and is key to its good cohesiveness, making it easy to spin.
• Layered Structure: The cotton fiber consists of five layers: the Cuticle, Primary Wall, Secondary Wall, and Lumen. The Secondary Wall is the main body of the fiber, determining its strength and shape.

Native Properties: The surface of untreated cotton fiber is covered by a natural cuticle or wax layer, giving it a certain degree of hydrophobicity in its native state. This wax is meant to protect the developing seed.

Hydrophilicity Transformation: To give cotton fibers the moisture absorption and dyeing properties we are familiar with, wet processing steps like "scouring" and "bleaching" must be performed before textile use to remove the wax layer and impurities. Once the wax layer is removed, numerous hydroxyl groups (-OH) on the cellulose molecules are exposed, giving it extreme hydrophilicity and the ability to absorb and retain a significant amount of water.

The cotton fiber production process, from the field to the yarn, is complex and meticulous:

1. Ginning: Separating cotton seeds from the fibers.
2. Scutching: Removing large impurities from the raw cotton.
3. Carding: Preliminary straightening and separation of fibers.
4. Drawing: Combining multiple slivers to improve uniformity and further straighten the fibers.
5. Spinning: Twisting the straightened slivers to form yarn.

• Skin-Friendly Comfort and Soft Hand Feel: Cotton's natural convolutions and lumen structure give it excellent bulkiness. Furthermore, cellulose molecules are non-irritating to human skin, providing unparalleled comfort (corresponds to: cotton is breathable, comfortable).
• Excellent Breathability and Moisture Absorbency: The hydrophilicity of cellulose allows it to quickly absorb sweat and retain moisture. The lumen structure ensures air circulation, making it the top choice for summer clothing and intimate apparel.
• Heat Resistance and Easy High-Temperature Ironing: Cotton fibers can withstand high ironing temperatures, making them easy to set and sterilize.
• Biodegradability: As a natural organic material, cotton fiber is easily degradable in the natural environment, resulting in a low environmental footprint.

• Structural Weakness: The molecular structure of cellulose in cotton has coexisting crystalline and amorphous regions, with a large proportion of the latter. This results in poor elastic recovery, making it highly susceptible to wrinkles and creasing (poor wrinkle resistance).
• Wet Strength Reduction and Shrinkage: In the wet state, water enters the fiber, replacing hydrogen bonds and weakening intermolecular forces, leading to a 10%–20% reduction in wet strength. Simultaneously, the fiber expands upon absorbing water, and internal stresses are released during drying, causing easy shrinkage.
• Substitution Trend: Due to the drawbacks mentioned above (like poor wrinkle resistance), production costs, and reliance on water resources for cultivation, cotton faces substitution pressure from synthetic fibers in modern applications, especially in the functional apparel market.

Polyester fiber, commonly referring to Polyethylene Terephthalate (PET), is the most produced synthetic fiber. It has fundamentally changed the textile industry through its industrial scale and high functionality.

Definition: Polyester is a thermoplastic synthetic fiber, with PET as its main chemical component. PET is a high-molecular-weight polymer synthesized from purified terephthalic acid (PTA) and ethylene glycol (EG) through esterification and polycondensation reactions (corresponds to: usually a thermoplastic synthetic fiber made from PET plastic).

Development History: The concept of polyester fiber was first proposed in 1941 by Whinfield and Dickson in the UK. It was subsequently industrialized in the mid-20th century by DuPont (under the Dacron brand) in the US and Imperial Chemical Industries (under the Terylene brand) in the UK, quickly becoming a mainstay of the global textile industry.

• Molecular Structure: Polyester molecular chains possess high symmetry and rigid benzene ring structures, leading to a tendency to form a highly crystalline structure. This high crystallinity and orientation are the source of its high strength and excellent dimensional stability.
• Hollow Structure: Polyester fibers are typically solid and lack a natural lumen. However, modern technology allows for the artificial creation of hollow fibers (for warmth) or fibers with specialty cross-sections (to improve hand feel) through profiled cross-section spinning or chemical modification.
• Manufacturing Forms: The main method for manufacturing polyester fiber is Melt Spinning, as PET has a moderate melting point and good melt stability. It can be made into:
  • Filament: Continuous fibers used to create silky, smooth fabrics.
  • Staple Fiber: Cut into short fibers similar in length to cotton, used for blending with cotton or wool.
  • Microfibers: Used to greatly enhance hand feel and create suede-like effects.

The key to polyester fiber production lies in the Drawing process following melt spinning, which imparts high orientation to the fibers:

1. Polymer Preparation: Synthesis of PET polymer chips from PTA and EG.
2. Melt Spinning: Melting the polymer chips and extruding them through a spinneret.
3. Drawing: Extruded fibers are stretched several times their length, leading to high molecular chain orientation, significantly increasing the fiber's strength and modulus.
4. Heat Setting: Stabilizing the fiber's structure through heat treatment to eliminate internal stress and impart dimensional stability.

• Excellent Dimensional Stability (Wrinkle Resistance): Due to the rigidity of the molecular chain and high orientation, polyester fiber has superior elastic recovery and wrinkle resistance. Garments are durable, dimensionally stable, and resist shrinkage, achieving a "wash-and-wear" effect.
• High Durability and Chemical Resistance: Polyester fiber exhibits outstanding abrasion resistance, tensile strength, and tear resistance, with a lifespan far exceeding cotton. It is also light-resistant, chemically resistant (except to strong alkalis), and mildew-resistant, making it suitable for outdoor and industrial uses.
• Functional Application Trends:
  • Sun Protection and UV Resistance: The PET structure itself offers good UV absorption, forming the basis of outdoor sun-protective fabrics.
  • Thermal Insulation: When making hollow fibers or high-loft staple fibers, trapped air can be utilized for warmth (e.g., in filling materials).

• Poor Moisture Absorbency and Breathability: The polyester molecular structure lacks hydrophilic groups, resulting in extremely poor moisture absorption (regain about 0.4%). This means sweat is not absorbed by the fiber, potentially leading to a stuffy feeling when worn.
  • Solution: Achieving a moisture-wicking function by adding hydrophilic additives during spinning or designing specialty cross-sections (like cross-shaped or Y-shaped) to create "wicking channels."
• Static Electricity: Hydrophobic fibers easily accumulate static charge during friction, attracting dust.
• Aesthetic Drawbacks: Traditional polyester fibers have a relatively stiff hand feel and may become shiny upon friction, affecting appearance.
• Relatively Poor Thermal Insulation: Tightly woven polyester fabrics, lacking air-trapping pockets, are less warm than bulky cotton or wool.

"Which is better, cotton or polyester?" This is a classic question with no standard answer, as the choice depends entirely on the specific application goal.

The choice of fiber must strictly align with the end-use of the product, which is the core principle of material selection advice:

• Intimate/Children's Apparel (Underwear): Primary choice is Cotton. Given skin sensitivity and frequent perspiration, cotton's skin-friendly, highly breathable, and absorbent qualities are irreplaceable.
• Summer Clothing (T-shirts, Shirts): High-ratio Cotton. Focus on comfort and breathability.
• Outdoor/Athletic Apparel: Polyester (requires functional modification) or High-ratio Blends. In strenuous activity, polyester's quick-drying and durability are critical, as it wicks moisture away from the skin rather than absorbing it.
• Industrial Fabrics/Bags: Pure Polyester. Demands for extremely high strength, abrasion resistance, and chemical resistance.

Since both pure cotton and pure polyester have distinct limitations, Blended Fabric has become a mainstream strategy in the modern textile industry.

• Purpose: Cotton and polyester are often blended in various ratios to combine their respective advantages, achieving the best balance of performance and cost.
• Typical Blending Ratios:
  • T/C (Polyester/Cotton): Polyester content is usually higher than 50% (e.g., 65% Poly/35% Cotton). Characterized by durability, wrinkle resistance, and low cost, suitable for workwear and uniforms.
  • CVC (Chief Value Cotton): Cotton content is higher than 50% (e.g., 60% Cotton/40% Poly). Characterized by retaining cotton's comfort while significantly improving the fabric's wrinkle resistance and durability, making it an ideal choice for everyday casual wear.

• Wrinkle-Resistant and Easy-Care Technology: Using resin finishing (like formaldehyde/non-formaldehyde resins) to improve the resilience of cotton fabrics, compensating for their tendency to wrinkle.
• Sustainable Cultivation: Promoting the Better Cotton Initiative (BCI) and organic cotton cultivation to address the reliance of cotton on water resources and pesticides.

• Functional Modification: Developing various functional additives and spinning techniques (e.g., moisture-wicking, anti-static, anti-pilling) to enable its use in high-tech athletic apparel.
• Recycled and Bio-Based Polyester: Recycled Polyester (rPET), made by re-spinning discarded PET plastics (like bottles), significantly reduces the carbon footprint and is a current focus of sustainable textiles. Simultaneously, developing bio-based PET derived from plant sources further reduces dependence on petroleum resources.

Global Production Distribution: Polyester fiber is currently the largest and fastest-growing fiber by volume in the global textile market. Synthetic fibers (dominated by polyester) account for about 65% of the total global fiber production. Although cotton remains the largest natural fiber, its production and market share growth are under continuous pressure from synthetic substitutes. Key producing nations are concentrated in Asia:

• Cotton: China, India, USA, Brazil.
• Polyester: China is the world's largest producer and consumer of polyester, followed by India.

When choosing between cotton and polyester, there is no "best" fiber, only the "most suitable" fiber.

The final material selection must be based on a deep understanding of the fiber's characteristics and the final product's requirements. If you seek ultimate skin comfort, breathability, and moisture absorption (i.e., absorption of sweat), choose high-ratio cotton (e.g., underwear, children's clothing). If you seek high durability, no-iron wrinkle resistance, and quick-drying functionality, choose polyester or a high-ratio blend (e.g., outdoor apparel, workwear).

Core Principle: Determine the choice between cotton, polyester, or a blend based on the garment's frequency of use, functional needs (such as warmth, wicking, UV protection), and budget. Only by perfectly aligning the fiber's properties with the wearing scenario can the best wearing experience and economic efficiency be achieved.

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