Thick needles, due to their unique knit structure and large inter-loop gaps, present unique challenges in balancing water repellency and breathability. The finishing stage requires a synergistic combination of material selection, process optimization, and structural design to achieve both functionality and comfort.
Achieving water repellency relies on adjusting the thick needle's surface tension and water contact angle. Thick needles are typically finished with fluorine-free or C6 water repellents. These agents reduce the fiber's surface tension to below 10 mN/m, causing water droplets to roll onto the needle rather than penetrate. For example, the fluorine-free water repellent M380 forms a nano-scale hydrophobic layer on the surface of fibers like cotton and polyester, imparting excellent water repellency while maintaining the thick needle's inherent breathability. This treatment avoids the environmental pollution associated with traditional fluorine-based water repellents and offers improved washability, maintaining the water repellency even after repeated washings.
Maintaining breathability requires careful attention to both the thick needle's structure and the finishing process. Thick needles, due to their large interloop gaps, naturally possess high breathability. However, excessive waterproofing can clog these gaps, reducing breathability. Therefore, the penetration depth and film thickness of the water-repellent agent must be controlled during finishing. Microporous waterproof membranes or hydrophobic porous coatings are preferred. These materials allow water vapor molecules to pass through while blocking liquid water, achieving a "breathable but waterproof" effect. For example, using a dry direct coating process, the viscosity and coating amount of the coating can be adjusted to create a uniform microporous film on the thick needle surface, ensuring water repellency while avoiding excessive loss of breathability.
Thick needle structural design plays a key role in achieving this functional balance. Thick needles can optimize pore distribution by adjusting loop density, yarn thickness, and weave structure. For example, using an interlock weave can increase the thickness of the thick needle while maintaining large interloop gaps, promoting breathability. Locally denser weaves can enhance water repellency in key areas (such as shoulders and elbows) and reduce wear of the waterproof layer due to friction. In addition, the use of blended yarns can also enhance functional coordination. For example, blending polyester with cotton leverages the hydrophobicity of polyester and the hydrophilicity of cotton to achieve a balance between water repellency and moisture wicking.
Refined control of the finishing process is key to achieving this functional balance. When padding thick knitted needles with waterproofing agents, a double dip and double padding process is required to ensure uniform penetration of the agent into the fiber while preventing excess residue that could cause the needle to harden. Temperature and time must be controlled during the drying process to prevent high temperatures from damaging the fiber structure or over-curing the waterproofing agent. For example, the drying temperature of fluorine-free waterproofing agent M380 should be controlled at 120-140°C for 3-5 minutes to ensure waterproofing while maintaining the softness of the needle.
Environmental adaptability is also a key consideration in achieving this functional balance. In outdoor applications, thick knitted needles must withstand both rain and perspiration, so the finishing process must balance water repellency with moisture permeability. Moisture permeability is achieved through a hydrophilic, nonporous membrane. The principle is that sweat, after being absorbed by the membrane, is expelled through the pores via micro-Brownian motion. Choosing a breathable coating that is compatible with the water repellent can prevent interference between the two functions. For example, when using a polyurethane-based breathable coating, it is important to ensure that its chemical properties match those of the water repellent to prevent reactions between the coatings that could degrade performance.
Long-term durability is the ultimate goal of achieving a balanced performance. After repeated washings, the waterproof layer of thick knitted needles may break off due to friction or chemical reactions, resulting in a loss of water repellency. Therefore, a crosslinking agent is added during finishing to strengthen the bond between the water repellent and the fiber. For example, adding triethylenediamine to a fluorine-free water repellent forms a stable chemical bond, ensuring that the thick needle maintains its water repellency rating after 50 washes. Furthermore, selecting a yarn and weave structure with high abrasion resistance can extend the functional life of the thick needle.
Achieving a balance between water repellency and breathability in thick knitted needles requires a comprehensive application of material innovation, process optimization, and structural design. In the future, with the continuous development of technologies such as fluorine-free waterproofing agents and microporous coatings, thick needle knitting will further enhance its water-repellent performance while maintaining its natural breathability, meeting the dual needs of functionality and comfort in outdoor and sports scenarios.
