During the processing process, the control of fabric width is one of the very important indicators. In fact, fabric design has the most direct impact on the finished door width. The width of the gray fabric on the machine, the model of the reed, the fineness of the raw material, the organizational structure of the fabric, the warp and weft density of the gray fabric, etc., all have a direct impact on the width of the finished product. Taking polyester woven fabrics as an example, common woven fabrics mainly include: conventional flat fabrics, strongly twisted silk-like finishing fabrics, elastic fabrics and short fiber blended wool-like fabrics, etc. The dyeing and finishing process also has a great impact on the width of the fabric.
Influence on processing
1 Cloth preparation
The main tasks of the cloth preparation process are embroidery and sewing and weigh. Although the length of parking time of the rolled gray fabric after unwinding has an impact on the weaving shrinkage of the gray fabric, this effect is also weak. If the warp elastic fabric, weft elastic fabric and warp and weft two-way elastic fabric are parked for too long after unwinding, the weaving shrinkage of the gray fabric will also increase. The shrinkage of the width of the weft elastic fabric gray cloth directly affects the finished width. The shrinkage of the warp yarns of the warp stretch fabric will cause the weft yarns to become more tortuous, ultimately leading to a narrowing of the weft width. After cloth preparation, the pressure on the upper and lower fabrics on the cloth cart is different. Whether it is an elastic fabric or a strongly twisted fabric, if the gray fabric is unevenly affected by the outside world during the process of releasing internal stress after unwinding, it will lead to uneven changes in the width of the entire vat of gray fabric, which will eventually lead to uneven width after pre-shrinking or pre-scheduling. Unification will bring adverse effects to subsequent processing. After unwinding and preparing the polyester woven strong twist fabric, especially the elastic fabric, the storage time should not be too long. If the time is too long, the width of the fabric after preshrinking will be inconsistent, which will have a greater impact on subsequent processes.
2 Refining
Scouring includes rope refining and flat refining. Rope scouring is the pre-treatment of ordinary polyester woven fabrics. Its purpose is to remove impurities on the fabric without affecting the processing quality of subsequent processes. The heating rate, maximum process temperature, additive concentration and holding time of the pre-treatment process are the most important process parameters. Polyester, as a thermoplastic fiber, will always change when exposed to heat and humidity. The higher the temperature, the faster the heating rate, and the more obvious this change is. In order to weaken this change, the pre-treatment temperature will not exceed the glass transition temperature of polyester fiber. Therefore, rope scouring has little impact on the finished width of ordinary flat polyester woven fabrics.
For elastic fabrics, especially weft elastic and double elastic fabrics, in order to effectively control the shrinkage of the gray fabric width, open width scouring is required. Open width scouring needs to be carried out in an open width scouring machine. Multiple flat washing tanks in the open-width scouring machine can provide different scouring temperatures. Cold water first, then warm water; while scouring in open width and continuously expanding the width at the same time, the gray fabric width of the weft stretch fabric can be evenly shrunk by more than 20% after being unloaded from the machine. Slow and even shrinkage is the basis and key to keeping the finished fabric surface flat. Open-width scouring at low temperatures is a simple and effective process route to achieve slow and even shrinkage of polyester elastic fabrics. Using an open-width scouring machine to scouring wide-width plain stretch fabrics can eliminate the internal stress of the gray fabric in a milder humid and hot state and reduce the chance of wrinkles on the fabric surface during subsequent processing. If the door width shrinks too much, the speed of the open-width refining machine can be reduced. For 210cm weft stretch (double stretch) gray fabric on the machine, the width after getting off the machine is generally about 180cm (including selvage). If the door width is greater than 160mn after refining, it means that the refining speed of the flat-width machine is too fast.
3 Pre-shrinking
The pre-shrinking temperature is higher than the scouring temperature and lower than the dyeing temperature. Pre-shrinking is a pre-treatment under high temperature and moist heat. In addition to removing slurry, oil, stains and other impurities on the fabric, it is also necessary to eliminate the internal stress of the fabric as much as possible through high temperature and moist heat processing, so that the width of the fabric shrinks slowly. Under high-temperature and humid heat conditions, areas with high crystallinity inside the fiber tend to de-orient, and areas with low crystallinity show an orientation trend. The orientation and deorientation phenomena that occur within the thermoplastic fibers cause the orientation of the entire fabric to become balanced, and the internal stress formed during the fabric’s manufacturing and storage processes is released. The end result is increased fabric dimensional stability, a flatter fabric surface and a more stable door width. Polyester woven fabrics are preshrunk similar to mercerized cotton fabrics.
During the pre-shrinking process, the warp tension of the fabric comes from the dye vat nozzle. The warp force is larger and the weft force is relatively small. When preshrinking, the weft yarns are shorter, and the number of warp yarns wound by each weft yarn is only equal to the first minute of the warp yarns of the fabric. The number of weft yarns wrapped around each warp yarn is equal to the weft density of the fabric multiplied by the length of the piece of cloth. Therefore, the resistance encountered by warp yarn shrinkage during preshrinking is much greater than that of weft yarn. At the same time, it becomes more difficult for the warp yarns to shrink under the action of nozzle tension, which ultimately leads to the shrinkage of non-elastic polyester woven fabrics in the weft direction being greater than the warp direction after preshrinking. When thermoplastic fibers shrink under high temperature and humidity conditions, the thickened weft yarns will make the warp yarns wrapped around the weft yarns shorter overall. In the same way, the warp yarns will also make the weft yarns overall shorter. After the pre-shrinking is completed, the yarns that interact with each other make the width and piece length of the fabric itself more reasonable. Understanding the shrinkage of gray fabrics with different twists, different raw materials, and different structures during the weaving, dyeing and finishing processes is the basis for rationally designing the finished product width.
During pre-shrinking, the nozzle pullsSome special style fabrics, such as bark crepe, pearl linen and other fabrics, need to be loosely dried after dehydration and opening in order to maintain the style of the fabric. Most polyester woven fabrics can be directly shaped after being opened.
9 Chengding
The final shape of ordinary flat polyester woven fabrics has the greatest impact on dimensional stability. Whether it is ordinary fabric, strongly twisted fabric, wool-like staple fiber fabric or elastic fabric, the finished width must be based on the width of the fabric itself before setting. Although trying to increase the warp tension when setting the fabric will help narrow the door width of the finished product, it is impossible to make the door width much narrower by setting the fabric with an excessively wide door width after dyeing. In the same way, it is impossible to increase the width of dyed fabrics that are too narrow in width by shaping the finished product, even if it can greatly reduce the warp tension of the finished fabric when shaping.
Tension adjustment for finished product shaping is more important than warp tension adjustment for fabric pre-ordering. By adjusting the tension bar, fabric tensioner, expansion roller and overfeeding device at the front end of the setting machine to adjust the warp tension of the finished fabric during setting, it can not only affect the weight and feel of the fabric, but also the final width of the finished product. After the rubber blanket is pre-shrunk, the door width of T/C fabrics will increase moderately. After the imitation wool fabric is steamed, the door width will also become slightly wider. After being washed, the width of the denim-like weft elastic fabric with viscose staple fiber as the warp yarn will also become wider. The needle plate setting machine is beneficial to maintaining the warp tension of the fabric when the finished product is being set. This tension includes both positive stretching tension and negative pre-shrinking tension. The function of the cloth clip type setting machine in this regard is inferior to that of the needle plate type setting machine.
The final width of the fabric does not depend on the final width of the finished product, but depends on the characteristics of the fabric itself and the entire dyeing and finishing process. With reasonable design and careful processing, the final width of the fabric will fully reflect the characteristics of the fabric itself, and the size of the width will be stable. </p
