The filament is composed of multiple individual fibers, such as 165dtex/48f, indicating that 48 individual fibers are combined to form a filament with a total denier of 165dtex. During the production process, the filament undergoes various processes such as winding, combining, twisting, and finishing while under tension. In the weaving process, it experiences repeated friction from guide rollers, heddles, and steel reeds. The filament undergoes friction tens of thousands of times, and during weaving on water jet looms, the weaving speed is generally between 500r/min to 700r/min. High-speed friction of individual fibers can easily lead to fuzzing, affecting weaving efficiency, and severe cases may result in the inability to weave, significantly decreasing product quality. To address this, untwisted or low-twist synthetic long filaments need to undergo sizing. Sizing allows the warp yarn to withstand friction during the manufacturing process and ensures smooth weaving, maintaining product quality.
The mechanism of sizing is as follows: after the sizing process, a sizing film is formed around the yarn to resist various equipment frictions. The sizing solution penetrates between individual fibers, sticking them together, and enhancing the bundling and strength of the filament. This ensures the successful completion of subsequent processing tasks. Short staple yarn, due to its higher fuzziness, requires mainly coating during sizing. In contrast, sizing for long synthetic filaments focuses on penetration with coating as a secondary consideration. Due to the low regain of synthetic filaments, e.g., the standard regain of polyester is 0.4%, and nylon is 4%, they are hydrophobic fibers, showing low affinity to water. Therefore, sizing synthetic filaments is not as straightforward as with viscose fibers. Two conditions must be met: the sizing solution must have excellent viscosity, and it should form a good sizing film around the yarn to ensure excellent wear resistance. During sizing, it is essential to maintain a certain distance between sized yarns to prevent them from sticking together and impeding the weaving process.
It is crucial to strictly control the sizing material preparation and sizing process according to the sizing process requirements. Hubei Decon can supply water-soluble polyester resin as a sizing agent. For more information, you can refer to https://www.polyestermfg.com/portfolio-items/water-soluble-polyester-resin/. To prevent antistatic agents from being removed from the yarn during sizing, an appropriate amount of antistatic agent should be added to the sizing solution. To maintain the yarn’s softness, a certain amount of softener can be added, along with a suitable amount of penetrant and defoamer. During sizing, it is necessary to strictly follow the prescribed sizing operation procedures to ensure that the sizing material meets production requirements.
In production, it is essential to strictly follow sizing process requirements, achieving “seven determinations,” namely determining sizing viscosity, determining sizing concentration, determining sizing temperature, determining warp speed, determining warp elongation, determining warp regain rate (determining the temperature of the drying cylinder or drying chamber), and determining sizing rate. Viscosity indicates the degree of sizing material stickiness, while concentration indicates the amount of solid glue in the sizing material. In general, both should be controlled.
Higher viscosity and concentration result in increased yarn strength and surface wear resistance but lower elasticity, making the yarn more prone to brittle breakage. Additionally, higher viscosity and concentration may lead to more sizing drop-offs, so it is crucial to control them correctly. Excessive warp speed may increase production efficiency, but due to inadequate yarn penetration and poor coating, the quality of sized yarn decreases. During sizing, the yarn undergoes elongation due to tension from rollers, sizing rollers, and the drying cylinder. However, synthetic fibers such as polyester and nylon are heat-shrinkable, and the yarn undergoes contraction during sizing, which can counteract the elongation. Excessive elongation can lead to yarn breakage, but too little elongation may result in poor penetration of the sizing film, and fibers may fuzz. High regain in sized yarn can lead to sticking, uneven shrinkage, sagging, and even axis splitting. However, low regain can cause static electricity, leading to fiber fuzzing. Therefore, it is crucial to explore the optimal sizing yarn process through practical production and implement it rigorously, representing an essential measure to ensure the quality of sized warps and products.
Currently, sizing machine automation control technology is advanced. By inputting the required process parameters into the computer monitoring system, it can automatically control and detect online. Images can be displayed on the infrared touch screen, and data can be automatically recorded. Importantly, technical personnel need to input correct process parameters and promptly adjust them based on recorded data and actual production conditions.
Which materials can be directly woven without sizing?
Materials used for weaving are typically categorized into warp materials (yarn) and weft materials (weft yarn). In general, weft yarn materials can be used directly on the water jet loom without any processing. Conversely, warp yarns undergo repeated stretching, friction, and bending caused by healds and reeds during the weaving process. This mechanical action can lead to a decline in the warp yarns’ performance, resulting in fiber disarray and fuzzing, ultimately affecting the smooth progression of weaving. Therefore, when opting for untwisted or low-twist synthetic long filament yarns as warp yarns, it is essential to undergo sizing treatment. This enhances their weaving performance, allowing them to adapt to high-speed machine operations and ensuring seamless weaving.
Depending on fabric requirements and material availability, sizing-free yarns can be selected for direct weaving as warp yarns. Sizing-free yarns refer to warp yarn materials that do not require sizing treatment and can be directly used in weaving. The English abbreviations are NOY or NSY.
Sizing-free yarns mainly include the following types:
Network Yarn: This filament undergoes compressed air blowing in the leno nozzle, causing some fibers to locally intertwine without loosening, forming yarns with network points. These yarns are less prone to breakage during weaving. Network yarns with more than 150 network points/m can be woven directly without sizing. Sizing-free yarns mainly refer to network yarns. However, excessively high network density may result in uneven refractive indices on the fabric surface, affecting appearance and feel. To enhance weavability, applying oil (wax) or light sizing treatment during beaming makes it more suitable for high-speed water jet looms.
Twisted Yarn: Refers to yarns that undergo twisting. Generally, when the twist reaches 6-8 twists/cm or more, sizing is unnecessary during weaving. However, increased processing steps and costs may affect product quality. Except for varieties requiring twisted warp yarns, it is generally not advisable to use twisted yarns in water jet weaving projects.
Reducing Single Filament Count in Synthetic Long Filaments: Synthetic long filament fabrics necessitate a smooth, full surface and a soft feel. Thus, when selecting raw materials, preference is given to composite filaments with a higher count of single filaments. For instance, nylon filaments with a total denier of 77.8 dtex (70 deniers) may consist of 16, 18, 36, or 48 single filaments. Such composite filaments often require sizing before machine weaving. However, sizing becomes unnecessary by reducing the number of single filaments and increasing the diameter, e.g., reducing the number of single filaments in nylon filaments to below 10. Only oil or wax treatment during warping is needed for the warp beam to be woven on the machine. However, this method may result in a harder feel and a poorer appearance due to the reduction in the number of single filaments or the increase in diameter, especially for polyester filament fabrics, making it challenging to adopt.