How to improve the moisture absorption of fabrics with acrylic yarn

Acrylic fiber, as an important synthetic fiber, has many excellent properties such as fluffiness, warmth retention, light resistance, and chemical resistance. However, its poor moisture absorption has always been the main bottleneck restricting its application in certain fields. The moisture regain of traditional acrylic fiber is only 1.2-2.0%, far lower than the 8.5% of cotton fiber and the 16% of wool. This low moisture absorption makes fabrics made from it less comfortable to wear, prone to static electricity, and has a stuffy feeling in humid environments.

The fundamental reason for the poor moisture absorption of acrylic fiber is its molecular structure. Although there are polar cyano groups (- CN) on the polyacrylonitrile polymer chains, these groups are tightly arranged inside the fibers and most of them are encapsulated in hydrophobic acrylic copolymer components, making it difficult to form effective hydrogen bonds with water molecules. In addition, the highly crystalline structure and lack of hydrophilic groups of acrylic fiber also limit the penetration and diffusion of water molecules.

2、 Technical Path for Moisture Absorption Modification of Acrylic Yarn

1. Chemical modification technology

Co modification is the most direct method to enhance moisture absorption. By introducing second or third monomers such as acrylic acid, methacrylic acid, vinyl pyrrolidone, and other hydrophilic monomers during the acrylonitrile polymerization process, the moisture absorbing group content of fibers can be significantly increased. Research has shown that when the acrylic acid content reaches 6-8%, the moisture regain of modified acrylic fiber can be increased to 5-7%.

Grafting modification is another effective method of grafting hydrophilic monomers onto acrylic polymer chains using radiation or chemical initiators. Common grafting monomers include acrylamide, hydroxyethyl methacrylate, etc. When the grafting rate is controlled at 10-30%, it can ensure improved moisture absorption without significantly damaging the mechanical properties of the fiber.

Surface treatment techniques such as plasma treatment and alkali reduction treatment can introduce hydrophilic groups such as carboxyl and hydroxyl groups on the fiber surface, while increasing surface roughness and improving capillary effect. Low temperature oxygen plasma treatment for 30-60 seconds can reduce the contact angle of acrylic fiber from 85 ° to below 45 °.

2. Physical blending technology

Hydrophilic additive blending is the process of blending hygroscopic substances such as polyvinyl alcohol (PVA), polyethylene glycol (PEG), or sodium alginate with acrylic fiber spinning solution into fibers. When the molecular weight of PEG is selected within the range of 2000-6000 and the addition amount is 5-10%, it can form continuous hydrophilic channels without affecting spinning stability.

Inorganic nanomaterials composite is an emerging modification method. Disperse nanomaterials such as porous silica, graphene oxide, or carbon nanotubes in the spinning solution to enhance moisture absorption by utilizing their large specific surface area and rich pore structure. 0.5-1.5% graphene oxide can increase the moisture regain of acrylic fiber by 40-60%.

3. Innovation in yarn structure design

The development of fibers with irregular cross-sections has changed the limitations of traditional circular cross-sections. Irregular cross-sections such as trilobites and crosses can increase the specific surface area of fibers and form more capillary channels. Experimental results have shown that the core suction height of trilobal acrylic fiber is 20-30% higher than that of circular cross-section.

Hollow porous structure design involves introducing pore forming agents or special spinning processes during the spinning process to manufacture fibers with micropores or hollow structures. This structure not only increases the adsorption sites for water vapor, but also enhances the transport of liquid water through capillary action. Acrylic yarn with a hollow degree of 15-20% can increase its moisture absorption rate by more than 50%.

Composite yarn technology blends or wraps hydrophilic fibers with acrylic fibers. Common combinations include:

Core sheath structure: using absorbent fibers (such as adhesive) as the sheath and acrylic fiber as the core

Blended yarn: Acrylic/Cotton (30/70), Acrylic/Modal (50/50) and other proportions

Wrapping yarn: wrapping acrylic short fiber yarn with moisture absorbing long filaments (such as Tencel)

3、 Improvement of moisture absorption by post-processing technology

1. Application of hydrophilic finishing agents

Polymer hydrophilic finishing agents such as polyurethane and polyacrylate finishing agents can form hydrophilic films on the surface of fabrics through immersion rolling drying processes. The new generation of responsive finishing agents can also adjust their moisture absorption and release rates according to environmental humidity.

Nanocoating technology uses the sol gel method or layer by layer self-assembly technology to build nano hydrophilic layer on the fiber surface. The titanium dioxide/silicon dioxide composite coating can produce a superhydrophilic surface (contact angle<10 °) after UV catalysis.

2. Biological enzyme treatment

For acrylic/natural fiber blended fabrics, cellulase or protease is used to selectively remove some surface substances of natural fibers, exposing more hydrophilic groups and increasing inter fiber pores. Optimizing process conditions (temperature 50-55 ℃, pH 4.5-5.5) can increase moisture absorption by 15-20% without damaging strength.

4、 Moisture absorption testing and evaluation system

1. Standard testing methods

Moisture regain test (GB/T 9995)

Core suction height test (FZ/T 01071)

Moisture permeability test (GB/T 12704.1)

Static attenuation test (GB/T 12703)

2. Comprehensive evaluation indicators

We have developed the Moisture Absorption Composite Index (MCI), which integrates three parameters: moisture absorption rate, equilibrium moisture absorption, and moisture diffusion rate, with weights of 30%, 40%, and 30%, respectively. The MCI of high-quality moisture absorbing modified acrylic yarn should be ≥ 0.75.

5、 Application Fields and Prospects

Acrylic yarn modified by moisture absorption has been successfully applied to:

In the field of sportswear: moisture absorbing quick drying sportswear with moisture management performance reaching the same level as Polyester

Medical textiles: surgical drapes, dressings and other products, with a moisture absorption rate increased by more than 3 times

Home textile products: The improved acrylic blanket has moisture absorption and breathability similar to wool, and is easier to care for

Future development trends include:

Intelligent moisture regulating fiber: dynamic moisture absorption and release regulation achieved through temperature sensitive or moisture sensitive polymers

Biomimetic structural design: mimicking the hierarchical moisture absorption channels of plant transpiration or skin sweat glands

Green modification technology: developing a fluorine free and formaldehyde free hydrophilic finishing system

Through interdisciplinary innovation, the moisture absorption performance of acrylic yarn is breaking through the inherent limitations of synthetic fibers, opening up new avenues for the development of functional textiles.