First, the definition
Fabric under the action of external stress caused by the relationship between deformation and the reflection of the performance is called the physical and mechanical properties of the fabric. It contains properties such as strength, elongation, elasticity and abrasion resistance.
Second, the strength of performance
1 . Fabric tensile strength and elongation at break
Fabric in use, by a larger tensile force, will produce tensile fracture. Tensile strength when the fabric is broken by rupture is called the rupture strength; the percentage of the deformation and the original length when the rupture is broken is called the rupture elongation. Tensile properties of fabrics depends on the properties of the fibers, the structure of the yarns, the texture of the fabric and the finishing of the fabrics.
⑴ fiber properties: the nature of the fiber tensile fracture properties of the determinants. The breaking strength of a fiber is the maximum tensile force that a unit of fineness can withstand, in units of CN / dtex. Among natural fibers, hemp fibers have the highest breaking strength, followed by silk and cotton, with the worst wool. In chemical fiber, the highest strength of nylon, and living in all the first fiber, followed by polyester, polypropylene, vinylon, acrylic, vinylon, fiber and viscose fiber. Among them, the viscose fiber strength is low, but slightly higher than the wool, in the wet state, its strength dropped a lot, almost wet strength is only dry 40 ~ 50%. In addition to the viscose fibers, the wet strength of wool, silk, vinylon, and rich fibers also declined, except for cotton and hemp fibers, which not only did not decrease in wet strength, but increased the wet strength. Polyester, polypropylene, vinylon, nylon, acrylic, etc. due to hygroscopicity, leaving it dry, wet strength is almost the same. As for the elongation at break, it belongs to the smallest hemp fiber, only about 2%, followed by cotton, only 3 to 7%, silk 15 to 25%, while wool is the first natural fiber, up to 25 to 35%. In chemical fiber, vinylon and viscose fibers have the lowest elongation at break of about 25%, and other synthetic fibers are above 40%.
Therefore, the tensile properties of various types of textile fibers are different: the type of high-strength low-stretch cotton genus, low-strength high-stretch type of wool, and nylon, polyester, acrylic and other high-strength high elongation type, in addition, Silk is a strong mid-stretch type. Generally thin and long fiber woven fabric thicker and shorter than the good tensile properties of fiber fabric.
⑵ yarn structure: under normal circumstances, the more coarse yarn, the tensile properties of the better; increased twist, is conducive to the tensile properties; twist the same configuration, fabric strength has increased; high strength strand fabric In a single yarn fabric.
⑶ fabric organizational structure: under other conditions the same circumstances, within a certain length of yarn staggered times, the shorter the float, the greater the fabric strength and elongation at break. Therefore, the three plain plain weave tensile properties as the best, followed by twill, satin fabric worst.
⑷ after dyeing and finishing: fabric finishing on the tensile properties of the impact, as the case may have, there are pros and cons.
Tensile properties of fabrics available fracture strength, elongation at break, the length of the fracture, elongation at break, fracture work and other indicators to express. International general latitude and longitude to the sum of fracture work as a toughness index of the fabric.
2 . Tear strength of fabric
During use, the yarn on the fabric will be hooked and broken by foreign bodies, or the fabric is partially pulled and torn in half. This damage to the fabric is called tearing or tearing. At present, China has been in the resin-based cotton fabric and other chemical fiber fabric testing, there are items to assess the fabric tear strength. The influencing factors of the fabric tear strength are the same as the tensile properties. The difference is that the tear performance is also related to the yarn resistance in the fabric, thus showing the lowest tear strength of the plain weave fabric, the largest square weave fabric, Striae and twill tissue are in between. To some extent, the fabric tearing performance can reflect the fabric activity, knot and other style characteristics.
Test method of fabric tear strength, there are three provisions of national standards: single seam method, trapezoidal method, drop hammer method. The three methods are suitable for the testing of dyeing and finishing processing of the fabric, all kinds of woven fabrics and lightweight non-woven fabrics. Knitwear is generally not for tearing test.
3. Cracking strength of fabric
The fabric is partially damaged by the load perpendicular to the plane of the fabric, which is called as the top cracking or bursting. The bursting is related to the arching and arching phenomenon of the fabric. Bursting test provides information on the multi-directional stretch characteristics of fabrics, especially for knitted fabrics, three-directional fabrics, non-woven fabrics and parachutes.
National standards stipulate that the cracking test using marbles or air pressure cracking test machine. Test indicators for the bursting strength and bursting elongation.
Third, wrinkle resistance and flexibility
Crease resistance refers to the ability of the fabric to resist bending deformation, also known as crease recovery; elasticity refers to the resilience of the fabric after deformation. Both belong to the fabric bending performance. The fabric is not completely elastic, the fabric under the action of external force will have a variable elastic deformation and the immutable plastic deformation. When the external force to remove the fabric can immediately restore the original shape or gradually restore the status of the performance after a period of time known as the variable elastic deformation, including the elastic deformation and slow elastic deformation; when the external force can not restore the fabric after the original performance known as the inflexible plastic deformation. The main factors that affect wrinkle resistance and elasticity are fiber properties, yarn structure, fabric structure and post-processing.
⑴ fiber properties: fiber wrinkle resistance and flexibility are the main factors that affect the fabric wrinkle resistance and flexibility, wrinkle resistance depends on the size of the fiber's initial modulus. The initial modulus is the ratio of the smaller tensile stress to the deformation stress. The greater the initial modulus, the better the crease resistance; the smaller the initial modulus, the worse the crease resistance. In natural fibers, the initial modulus of hemp fibers is the first, and the largest value in all fibers, cotton, silk followed, the worst wool. In chemical fiber, the initial modulus in descending order are polyester, viscose, acrylic, vinylon, polypropylene, vinylon, nylon. Elasticity and fiber in the small deformation of the tensile recovery performance of a linear relationship between natural fibers in the best wool flexibility, spandex, also known as elastic fibers, followed by nylon, polypropylene, polyester, acrylic, vinylon and vinylon to stick Glue elasticity is the worst.
Therefore, the initial modulus of polyester is good, the elasticity is good, the fabric is not easily wrinkled, and the shape retention is good. However, although the elasticity of the polyamide is better than that of the polyester, the initial modulus is low and the stiffness of the fabric is not as good as that of the polyester fabric. Cotton, viscose and other fibers higher initial modulus, but the flexibility is poor, the fabric once the formation of wrinkles, not easy to disappear.
⑵ yarn structure: moderate yarn twist, the fabric wrinkle resistance, or wrinkle resistance due to twist too large or too small and worse.
⑶ fabric organizational structure: the general organization less wrinkle point of the fabric good, so forgivable fabric anti-wrinkle fabric better, while plain weave fabric is poor.
⑷ post-processing: fabric heat setting and resin finishing, can improve wrinkle resistance.
The index of expressing wrinkle resistance of fabric is crease recovery angle, and the indicator of elastic size is elastic recovery rate. Their determination of national standards have a unified test methods.
Fourth, wear resistance
Fabrics in the process of wearing and use will be subject to a variety of wear and tear caused by fabric damage, the fabric wear resistance is called wear resistance. The influencing factors are still the nature of the fiber, the structure of the yarn, the texture of the fabric and the post-processing properties.
⑴ the nature of the fiber: In a variety of fibers, the wear resistance of nylon as the best, followed by polyester, vinylon, polypropylene, vinyl chloride, acrylic wear the worst. In natural fibers, wool wear resistance is very good, cotton, silk and linen wear resistance in general.
⑵ yarn structure: yarn thick, good wear resistance of the fabric; twisting fabric is also good wear resistance; strand fabric wear better than single yarn fabric.
⑶ fabric organizational structure: in the warp and weft density of loose fabric, plain weave fabric wear the best, forging the weakest organization; in the tight weft density of close fabric, the conclusion is the opposite, the wearable fabric Worst, wearable fabric best wear resistance. In general, too loose, too tight fabrics are not conducive to the wear resistance of the fabric.
⑷ post-processing: fabric after resin finishing, can improve its wear resistance.
Testing of wear resistance of fabrics (apparatus test). Evaluation of the many indicators of fabric wear can be broadly divided into the following categories:
① After a certain number of friction, physical changes in the fabric that the use of equipment to measure the strength, weight, thickness, air permeability and other changes.
② to the sample on the emergence of certain physical changes (such as the production of holes) when the number of friction to represent.
③ using a comprehensive wear-resistant value
(Addtime：2018-1-22)
