Initial mold shed fiber flexibility coefficient
(1) Initial modulus The initial modulus refers to the stress-strain ratio on the straightening extension line of the relatively straight part of the initial section of the fiber load-elongation curve (the section where the fiber is basically straightened and then stretched). As shown in Figure 1-2, the appropriate line at the beginning of the straight part of the curve extends to the horizontal line of the break point and intersects at point e. The vertical line passing through point e as the abscissa intersects at point Le. According to Pa, Le and the fiber According to the linear density Tt and the sample length L (i.e., the distance between the upper and lower clamps of the strength machine, mm), the initial modulus E can be obtained, and the unit is N/tex. The initial modulus indicates the ease with which the fiber deforms under small loads, and it reflects the rigidity of the fiber. A large initial modulus means that the fiber is not easily deformed under a small load, has good rigidity, and the product is relatively stiff; conversely, a small initial modulus means that the fiber is easily deformed under a small load, has poor rigidity, and the product is relatively soft. . The initial modulus of several common fibers is shown in Table 1-5. In Table 1-5, the initial modulus of polyester is high, and its wet state is almost the same as its dry state. Therefore, the polyester fabric is stiff and has good non-iron performance. The initial modulus of rich and strong fibers is also high in the dry state, but decreases more in the wet state, so the iron-free performance is poor. The initial modulus of nylon is low, so the fabric is soft and has no body bones. The initial modulus of wool is relatively low, so it has a soft feel; the initial modulus of cotton is high, and the hemp fiber is higher, so it has a hard feel. (2) Fiber flexibility coefficient In the United Kingdom and the United States, the fiber flexibility coefficient c is often used. The formula is as follows: c = 0, indicating that the tensile curve is linear. At this time, the flexibility is often poor, and the initial modulus must be combined. can make a correct judgment; for some fibers, such as polyamide fiber, c0, it means that the tensile curve is convex and the flexibility is good. Poor, but better plasticity. The higher the c value, the greater the plasticity.
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