Humidity and heat comfort are important aspects of clothing comfort, as well as significant indicators reflecting the new concepts of health and comfortable living. This article introduces the current developments in moisture-wicking and quick-drying fibers related to humidity and heat comfort and focuses on analyzing the processing methods of humidity and heat comfort fabrics, providing a basis for the development of functional textiles.
1. Research Progress on Moisture-Wicking Quick-Drying Fibers
The research and development of moisture-wicking quick-drying fibers mainly occur through two approaches: physical modification and chemical modification. Physical modification refers to changing the shape of the spinneret holes to spin fibers with grooves on their surfaces, utilizing capillary principles to allow the fibers to quickly transport, diffuse, and evaporate moisture, rapidly removing sweat and moisture from the skin's surface and allowing it to evaporate outward. Alternatively, blending spinning or composite spinning methods can be used with polymers containing hydrophilic groups (such as hydroxyl, amide, carboxyl, and amino groups) to produce fibers with moisture-wicking and quick-drying properties. Chemical modification involves graft copolymerization methods to introduce hydrophilic groups into the macromolecular structure, thereby increasing the moisture absorption and quick-drying capabilities of the fibers.
(1) Physical Modification
Physical modification includes three methods: changing spinneret hole shapes, composite spinning of raw materials, and bicomponent composite spinning.
DuPont developed the high-moisture four-groove polyester Coolmax fiber; Japan’s Toyobo developed Y-shaped cross-section polyester "Triacotr," which forms three moisture-wicking grooves on the fiber surface. Far East New Century Corporation developed Topcool moisture-wicking quick-drying fibers. Guangdong Zhujiang Jinfang Group created moisture-wicking polyester filaments by altering the fiber cross-sectional shape, significantly enhancing moisture-wicking performance due to increased surface area and capillary effects. Jiangsu Yizheng Chemical Fiber Co., Ltd. produced Coolbest fiber with an "H" shaped cross-section. Taiwan's Chung Hsing Textile Co., Ltd. produced Y-shaped and cross-shaped “Coolplus” fibers. Taiwan Hero developed W-shaped Technofine fibers. Donghua Haotian Company produced coolDry. Shunde Jinfang Group, in collaboration with Donghua University, developed Coolnice moisture-wicking polyester fibers with a “+” shape cross-section.
(2) Composite Spinning of Raw Materials
Polyester and other hydrophilic polymers are composite spun using a double-screw method, researching new types of moisture-absorbing and sweat-wicking fibers with a skin-core composite structure. This improves their water absorption and appearance, wherein hydrophilic materials serve as the core layer while conventional polyester acts as the skin layer, with each component fulfilling the roles of hydrophilic moisture absorption and moisture-wicking. Japan's Unichika developed a new high moisture-absorbing and releasing fiber called HYGRA, which features a skin-core composite structure. Its skin layer consists of conventional nylon, providing a smooth feel when wet and superior moisture absorption and release capabilities compared to cotton fibers. Japan's Kuraray used a composite spinning method to develop the sophista fiber, with its outer layer having hydrophilic groups (—OH) and the core layer being polyester.
2. Chemical Modification
Chemical modification is achieved by graft copolymerization methods to introduce hydrophilic groups within the macromolecular structure to enhance moisture absorption and sweat-wicking functionality. Typically, hydrophilic groups such as carboxyl, amide, hydroxyl, and amino groups are introduced to increase affinity for water. Alongside raw material modification, appropriate spinning processes must also be employed to ensure that the fibers have a porous structure and a larger specific surface area.
Japan’s Toyobo developed breathable polyester fabric “Ekslive” by incorporating polyacrylic acid powder into polyester blend spinning to achieve moisture-absorbing and sweat-wicking functions, thereby improving the water saturation of polyester fabrics through moisture absorption and heat exclusion. Komatsu Serien grafted silk compounds onto polyester fibers to produce moisture-absorbing and sweat-wicking polyester. Xu Bi et al. treated cotton fabric with nano-silica before reacting it with trimethylsilane to impart hydrophobicity. Eef Temmerman improved the capillary effect of cotton yarns using low-temperature plasma discharge treatment. Soon Cheon Cho et al. employed low-temperature plasma techniques to graft hexamethyldisiloxane onto cotton fabrics, enhancing their water repellency.
2. Development of Moisture-Wicking Fabrics
1. Processing Methods for Moisture-Wicking Yarns
Currently, the common types of moisture-wicking and quick-drying yarns both domestically and internationally can be categorized into two main types: simple yarns and composite yarns. Simple yarns can be further divided into short fiber yarns and filament yarns based on fiber type.
Processing methods include multi-fiber blending, twisting, and special finishing. Developing and utilizing yarns with good moisture-wicking and quick-drying properties is a crucial approach to creating moisture-wicking, quick-drying, and cooling fabrics.
(1) Blended Yarns
Generally, moisture-wicking fibers have single functional characteristics, making it difficult to balance moisture absorption, wicking, and release simultaneously, which limits the moisture-wicking and quick-drying performance of the fabric. Therefore, blending moisture-absorbing fibers with moisture-wicking fibers is a simple and effective way to enhance the dryness and comfort of the fabric.
(2) Twisted Yarns
Single yarns or filaments with different moisture absorption and release functions can be processed into twisted yarns. By combining moisture-absorbing cotton single yarns with moisture-wicking Coolmax filaments, one can obtain yarns that possess moisture absorption, sweat-wicking, and quick-drying properties.
(3) Multi-Layer Structural Composite Yarns
Using different fiber forms or types and advanced spinning technologies, yarns can be designed with multi-layer structural distributions, facilitating the performance of various components to achieve moisture absorption and quick-drying goals.
2. Moisture-Wicking Fabrics
Moisture-wicking fabrics are developed through structural design or fiber modification to change the fabric's moisture absorption, transfer, and release properties, enabling them to possess both water absorption and quick-drying capabilities. Currently, common moisture-wicking and quick-drying fabrics include both knitted and woven types, classified by their structures into single-layer, double-layer, and multi-layer fabrics.
With the rapid development of post-processing techniques, various functional fabrics have emerged. Moisture-wicking quick-drying finishing was created in response to the requirements for comfort under humid conditions, aimed at improving the fabric's moisture transmission capacity to address issues such as discomfort and humidity during sweating.
(1) Single-Layer Unidirectional Moisture-Wicking Fabrics
In early research and development, the focus was primarily on single-layer fabrics, usually woven from pure or blended yarns made from moisture-absorbing quick-drying fibers. In recent years, with advancements in processing technology, fabrics possessing unidirectional moisture-wicking capabilities have been developed. Unidirectional moisture-wicking fabrics have different moisture absorption and release properties on their front and back sides or inner and outer layers. When the fabric comes into contact with sweat on the skin, moisture-wicking occurs in a highly directional manner; sweat can be continuously transported from the skin side to the outer surface and evaporated, maintaining skin dryness and comfort. This significantly improves the humidity comfort of the fabric, making the unidirectional moisture-wicking fabrics theoretically better in moisture absorption and quick-drying capabilities compared to fabrics with the same hydrophilic and hydrophobic properties on both sides.
Wang Nanfang et al. performed unidirectional hydrophobic finishing on pure cotton knitted fabrics using a paste point printing method, achieving strong wash resistance; compared to untreated fabrics, the breathability decreased by about 10%, and the hair effect decreased by 5-7%. Wu Jihong et al. first treated the yarn to be hydrophobic, then woven and dyed it to create moisture-wicking knitted fabrics, but faced complexities in the hydrophobic treatment process leading to issues like uneven dyeing during fabric coloration and high processing costs. Wu Yefang et al. achieved moisture-wicking quick-drying effects through one-sided finishing of cotton fabrics, although the breathability of the coated fabrics worsened, affecting their wear performance. He Tianhong et al. developed a dual-sided moisture-wicking quick-drying pure cotton knitted fabric using one-sided finishing techniques.
(2) Double-Layer or Multi-Layer Unidirectional Moisture-Wicking Fabrics
Influenced by the consumer preference for returning to nature, people are more focused on the use of cotton fibers. However, the wet-swelling characteristics of cotton fibers can lead to blockage of fabric gaps, hindering the exchange of heat and humidity between the body and the external environment. The moisture absorption process of cotton can also generate heat release; as moisture absorption reaches saturation, the heat release stops, while the evaporation process of moisture in the fabric can absorb heat from the skin, causing discomfort from initially feeling hot and then damp. In recent years, the development of double-layer or multi-layer structural fabrics has laid the foundation for developing unidirectional moisture-wicking fabrics. These fabrics typically use hydrophobic synthetic fibers for the inner layer and can be structured in four main types:
Inner Layer with Hydrophobic Fibers and Outer Layer with Hydrophilic Fibers
The inner layer of these fabrics is generally made of synthetic fibers, while the outer layer uses natural fibers. The inner layer has point contact with the skin, and its characteristic is that vapor sweat can be absorbed by natural fibers, while liquid sweat is transferred to the outer layer through the capillary phenomenon of the inner synthetic fibers, is absorbed by absorbent fibers on the outer layer, and then evaporates into the external environment. Because the fabric contacts the skin at points, the inner layer remains dry and the air layer formed provides warmth, preventing sticky, non-breathable, and cold sensations after sweating.
A widely used example is the cotton-polyester composite knitted fabric. The base yarn of cotton-polyester composite fabric uses hydrophobic polyester filament, while the surface yarn employs hydrophilic cotton yarn, which has characteristics of rapid moisture absorption and quick diffusion towards the outer layer of the fabric when treated for hydrophilicity. Wang Xiao et al. found that fabrics with cotton fibers in the outer layer and hollow polyester in the inner layer had better warmth and dryness than those with both layers made of cotton fibers. Moreover, these fabrics exhibited significantly better moisture-wicking and quick-drying effects than those constructed solely from regular yarns with hydrophilic properties. When the content of the hydrophobic fibers in the surface layer reached 30%, the fabric had the best moisture absorption and dryness performance.
Outer and Inner Layers Made of Different Specifications of Synthetic Fibers
This fabric uses synthetic fibers as raw materials, with varying specifications or types of hydrophobic fibers for the inner and outer layers. Its water absorption mechanism is distinctly different from that of natural fibers, achieving unidirectional moisture-wicking through the difference in capillary effects created by the inner and outer layers, a phenomenon also known as the cedar effect. Typically, the outer layer is constructed from fine fibers while the inner layer comprises coarse fibers. Because the pressure generated by capillaries built from the outer layer fibers is greater than that from the inner layer, there exists an additional pressure difference between the outer and inner layers, facilitating the transfer of sweat from the inner layer to the fabric surface, which then evaporates through the outer layer into the environment, maintaining relative dryness on the inner layer and a comfortable feeling for the body. The Airfine Field Sensor multi-layer knitted fabric produced by Toray Industries is a typical representative of this structure, capable of quickly absorbing sweat from the body and diffusing it from the inner layer to the surface layer, with moisture absorption and quick-drying capabilities twice that of sweat-absorbent knitted fabrics like Field Sensor. It is commonly used in sportswear, medical healthcare clothing, and workwear.
Composite Structural Fabrics with Lampwick-Like Absorption Points
This fabric represents a novel composite-layer knitted fabric structure with a high moisture transmission rate. It consists of two layers — a hydrophobic permeable layer (inner layer) and an absorbing layer (outer layer) — which are interconnected at many points, with these connections composed of yarns arranged in a lampwick structure, distributed in the fabric according to a predetermined pattern. These connection points contain hydrophilic fibers (such as cotton fibers), bridging the inner and outer layers of the fabric.
The Czech Bnro Knitting Research Institute utilized the V-LEC4BS computerized jacquard double-faced weft knitting technology from Japan to develop various natural colored cotton lampwick point structural fabrics and conventional air-layer structural fabrics. The double-faced fabrics developed by Hou Qiuping et al. utilize polyester and polyester-cotton blended yarns for the inner layer and brown colored cotton for the outer layer, with lampwick density distributions designed at 50%, 25%, and 12.5% of the fabric area. Testing results indicated that, when the raw materials of the inner and outer layers were identical, a smaller density of lampwick points resulted in improved moisture-wicking performance. Gu Zhaowen et al. designed a high transmission rate lampwick point structure moisture-wicking and quick-drying knitted fabric utilizing H-shaped cross-section moisture-absorbing quick-drying polyester fibers and colored cotton fibers, investigating the impact of hydrophilic treatments on fabric performance. The results demonstrated that, when the raw materials of the fabric's inner and outer layers were identical, reducing the density of lampwick points enhanced the fabric's permeability and drying performance; however, after hydrophilic treatment, the permeability decreased, and the fabric's moisture-wicking quick-drying performance declined, indicating that such fabrics are not suitable for hydrophilic treatments.
