Fourth, the sewing performance The performance of clothing materials should also include the sewing processability, that is, the characteristics of the fabric in the sewing process, its ease of operation, how the seam performance and the appearance of the sewing product appearance and so on. Only sewing fabrics that meet the requirements of the fabric can be said to have good performance.
(a) Fabric use
Fabrics to meet the needs of sewing processing, should have certain basic properties, such as elongation, lubricity, melt adhesion and tension to prevent stretching. These basic properties depend on the physical and mechanical properties of the fabric itself.
1. Elongation mainly refers to the elongation of the fabric, the rapid and elastic recovery rate. Since knitted fabrics are highly stretchable fabrics, most of them need to shrink by themselves after being laid out. This is the reason why the knitted fabrics are difficult to handle during sewing, and the shape of the stitches in the stitches is flat. If sewing is made with ordinary stitches, the stitches are not prone to breakage or shrinkage, so stretch-resistant, stitch-resistant stitches should be used.
2. Slit-off phenomenon Knitted fabrics, especially knitted fabrics, rib knitted fabrics, double-knitted fabrics, etc., may be detached if tension is applied to the seams or cuts during sewing or wearing. The phenomenon of seam separation not only hinders the sewing operation, but also affects the wearing effect of the garment. Therefore, consideration and thought must be avoided. It can be detected and evaluated by Instron.
3. Lubricity of fabrics The lubricity of fabrics is an important factor in the usability of woven fabrics. Because in the process of fabric coating, cutting, and sewing, the cloth often shifts due to excessive or thin lubrication. The direct factor influencing the lubricity of fabrics is the frictional properties of the fabrics. The fabrics with large friction coefficients are less displaceable and therefore easier to sew and easier to sew.
4. Melt-bonding The melt-adhesion of fabrics is necessary for cutting, enabling multi-layer fabrics to be positioned without cutting away. Melt-adhesion is essentially determined by the melting point of the fibers. Knitted fabrics and woven fabrics of synthetic fibers and cellulose fibers are different in melt-adhesion state due to different blending rates or different tissue structures and thicknesses. The melt adhesion was visually evaluated by the degree of actual adhesion at the time of cutting.
(b) Sewing
Seamability is a comprehensive evaluation index of the pros and cons of fabric sewing. It includes the degree of seaming of the fabric, the quality of the seams and the degree of fracture.
1. The crease of the fabric The crepe of the fabric refers to the degree of undulation produced by the fabric next to the stitches when the fabric is sewn by the machine. It depends to a large extent on the characteristics of the fabric, affecting the appearance and applicability of the garment. It is generally assessed by sewing rate and visual rating.
2. Cutting of the bottom line When sewing clothing with machines, due to the fabric relationship, the machine needle often cuts the bottom line, resulting in deterioration of the stitch quality, decreased durability of the clothing, and impaired sewing efficiency. Therefore, the sewing fabric must be evaluated for bottom thread cutting. The specific evaluation method is: Split the two overlapped fabric samples from the middle, knead the joints by hand, and then read the number of bottom thread cuts in a certain length, and use the cutoff rate of the bottom thread of the unit number of stitches. In knitted fabrics, there is also a method of measuring the number of cut lines in the lower thread with a magnifier using an empty seam through which no suture passes.
(C) Ironing
During the sewing process, the garment material must be ironed several times and at multiple locations in order to achieve the purpose of flatness, shape, and fit of the finished product. Therefore, the ironing property of the fabric becomes an important aspect of the sewing processability. The ironing properties of the fabric include heat shrinkage, crease effect and appearance change.
1. Heat Shrinkage Heat shrinkage of the garment material is the assessment of the form of the fabric after it has been heated and pressed. It provides data on the dimensional change of the fabric after shrinkage, and prepares and guarantees how much allowance is required for sewing and cutting to meet the specified dimensions. General determination of fabric wet heat shrinkage and steam shrinkage two indicators.
2. Folding effect Folding effect refers to the crease effect of pressing or ironing of the fabric after sewing in the sewing process. On the one hand, it depends on the operation skills of the fabric in the sewing process (affecting the aesthetic effect), and on the other hand, it mainly depends on the fiber raw material, and the fiber material is different, and the performance of the crease effect is also different. In general, the natural fiber is easy to iron, but the crease effect is poorly maintained, while the chemical fiber is difficult to iron, but the crease effect is good. To evaluate the method, the fabric is given a crease under specified conditions and then evaluated with the eyes. Then a small crease is cut out from the fabric and the angle is measured with a wrinkle meter. The crease effect is calculated by the following formula: crease effect ( %)=100-fold angle/(180-100)X100
3. Appearance change Appearance change mainly evaluates the aurora (the phenomenon that the fabric structure is flattened due to the increase of the gloss of the fabric structure), the flatness of the sewing head (the leveling phenomenon after pressing the outer surface of the seam head) and the bending hardness change ( The bending performance and stiffness-based style change caused by the ironing process). These changes will directly affect the appearance of the clothing wearing effect and use value, should be given attention. Appearance changes after the garment material is ironed are likely to occur in the knitted fabrics. In terms of raw materials, it is easy to appear in the heat-sensitive fiber fabrics such as polypropylene. The evaluation method is: using the eyes to observe the change of the gloss of the reverse side of the seam head and the leveling state of the seam; the bending hardness change rate is obtained by measuring the bending hardness and the bending recovery rate.
In addition, the evaluation of the sewing processability should also include tests such as the joint strength and the degree of seam irregularity.
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