Chapter 6 Performance Cognition and Detection
This chapter will focus on the various properties of apparel materials to explain (from the outline of the chapters), designed to consider the factors that affect the performance of the material (including fiber, yarn, organizational structure, post-processing, etc.) to consider, comprehensive analysis of materials Performance.
1. Basic requirements: Understand and understand the various wearing properties of clothing materials: physical and mechanical properties, chemical properties, appearance properties, health care performance, and sewing processing performance.
2. Key points: Examine the definition, influencing factors, detection methods and indicators of various performances of garment materials.
3. Difficulties: Master how changes in taking performance change with factors and take effect.
4. Teaching methods: combining classroom teaching with experiment.
introduction
The performance of different garment materials varies, and the scope of application and end use of the garments will vary greatly. Therefore, understanding and mastering the various properties of clothing materials, choosing the materials correctly, designing the clothing reasonably, and wearing the clothing satisfactorily will be of great help and produce a multiplier effect. The properties of the garment material include physical and mechanical properties, chemical properties, appearance properties, and health care performance and sewing performance.
Section 1 Physical and Mechanical Properties of Garment Materials
First, the definition
The performance of the relationship between the stress and deformation caused by the external force of the fabric is called the physical and mechanical properties of the fabric. It contains properties such as strength, elongation, elasticity and wear resistance.
Second, strength performance
1. The tensile strength and elongation at break of the fabric
In the course of taking the fabric, when it is subjected to a large tensile force, tensile fracture occurs. The tensile force when the fabric is broken by a force is called the breaking strength; the percentage of the original length when the tensile fracture occurs is called the breaking elongation. The tensile fracture properties of fabrics are determined by the properties of the fibers, the structure of the yarns, the organization of the fabrics, and the processing after dyeing and finishing.
(1) Properties of the fiber: The properties of the fiber are the determinants of the tensile fracture properties of the fabric. The breaking strength of a fiber refers to the maximum tensile force that the fiber of a unit fineness can withstand, in CN/dtex. Among the natural fibers, the hemp fiber has the highest breaking strength, followed by silk and cotton, and the worst wool. In chemical fiber, nylon has the highest strength, and ranks first among all fibers, followed by polyester, polypropylene, vinylon, acrylic, chlorinated, rich fibers and viscose fibers. Among them, although the strength of viscose fiber is low, but slightly higher than wool, in the wet state, its strength drops a lot, almost the wet strength is only 40 to 50% of dry strength. In addition to viscose fiber, the wet strength of wool, silk, vinylon, and strong fiber also declined, but with the exception of cotton and hemp fiber, the wet strength not only decreased, but also increased. Polyester, polypropylene, vinyllon, nylon, acrylic, etc., due to low moisture absorption, make their dry and wet strength almost the same. As for elongation at break, the hemp fiber is the smallest, only about 2%, followed by cotton, only 3 to 7%, silk 15 to 25%, and wool is the first of natural fibers, up to 25 to 35%. In chemical fiber, the elongation at break of vinylon and viscose fiber is the lowest, about 25%, and other synthetic fibers are all above 40%.
Therefore, the tensile properties of various types of textile fibers are different: cotton and linen are high-strength and low-stretch, wool is low-strength and high-stretch, and nylon, polyester, acrylic and other high-strength and high-stretch type, in addition, there are vinylon and Silk is a medium-stretch type. Generally thin and long woven fabrics have better tensile properties than thick and short fibrous fabrics.
(2) Yarn structure: Under normal circumstances, the thicker the yarn, the better the tensile properties; the increase in twist is conducive to the improvement of tensile properties; When the configuration of the twist direction is consistent, the strength of the fabric is increased; the strength of the strand fabric is high For single yarn fabrics.
(3) Structure of the fabric: under the same conditions, the more the number of interlaced yarns in a certain length, the shorter the float length, and the greater the strength and elongation at break of the fabric. Therefore, the tensile properties of the plain texture were the best in the Sanyuan organization, followed by the diagonal pattern, and the satin fabric was the worst.
(4) Post-dyeing and finishing: The effect of the finishing of the fabric on the tensile properties should be determined according to the circumstances, which has both advantages and disadvantages.
The tensile properties of fabrics can be expressed by such indicators as breaking strength, elongation at break, breaking length, elongation at break, and work of fracture. The sum of the universal warp and weft fracture work in the world is used as an indicator of the toughness of the fabric.
2. Tear strength of fabric
During the garment wearing process, the yarn on the fabric is caught by foreign matter and broken, or the fabric is partially torn and pulled in half. This damage to the fabric is called tearing or tearing. At present, China has evaluated the tear strength of fabrics in the testing of resin-finished cotton fabrics and other chemical fiber fabrics. The factors affecting the tear strength of fabrics are the same as the tensile properties. The difference is that the tearing properties are also related to the interweaving resistance of the yarns in the fabric, thus exhibiting the smallest tear strength of the plain weave fabric, the largest of the square weave fabrics, and the forgings. Stains and twill weaves are in between. The tearing performance of the fabric can reflect the style characteristics of the fabric, such as looseness and compaction, to some extent.
The method for testing tear strength of fabrics is stipulated in national standards in three ways: single-slit method, trapezoidal method and drop hammer method. These three methods are respectively suitable for testing dyed and finished fabrics, various woven fabrics and light and thin non-woven fabrics. Knitwear is generally not torn test.
3. Top crack strength of fabric
The fabric is partially destroyed under load perpendicular to the plane of the fabric and is referred to as top crack or top break. The breakage is related to the phenomenon of vaulting and arching of the clothing and fabric, and it is similar to that of gloves and socks. The top breaking test can provide information on the multi-stretch and strong stretch characteristics of fabrics, especially for knitted fabrics and three-dimensional fabrics.
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