Study on the relationship between the tensile strength and the twisting of the composite yarn of filament staple fiber. Studying the performance difference of the composite yarns in the composite yarn of Wang Li (Yancheng University of Technology) (Donghua University of Technology) Will have a huge impact. In the case of reverse twisting of the composite yarn, the relationship between the breaking strength and elongation at break of the composite yarn and the twist of the single yarn and the twist of the composite yarn were analyzed by experiments. The composite yarn also has a critical twist coefficient. The elongation at break of the composite yarn is positively linearly related to the twist coefficient of the composite yarn, and the composite yarn has strong breaking strength. The elongation at break is positively linearly related to the single yarn twist factor.
Rumors: With the change of people's consumption concept and the improvement of material living standards, the demand for apparel has also become more fashionable and comfortable. The fine, light and smooth fabrics have become more and more popular among consumers. The mainstream trend of development. Filament staple fiber composite yarns are yarns used to develop such new structural products. There are large differences in the structure between composite yarns and conventional staple fiber yarns, which will inevitably affect the performance of yarns and their fabrics. . Therefore, in order to make good use of composite yarns to produce high-quality fabrics, it is necessary to thoroughly study the structure and properties of filament and cotton staple fiber composite yarns, especially the relationship between their basic mechanical properties and structure.
1 Test method The Plyfil composite yarn used in the test used two different raw materials, namely polyester low elastic yarn and pure cotton combed yarn. The indexes of polyester low-elastic yarn and pure cotton combed yarn are shown in Table 1.
Table 1 Index of polyester low-elastic yarn and pure cotton combed yarn Item Fineness Fracture Strength Mean Breaking Strength Mean Variance /% Elongation at Break Equivalent/% Elongation at Elongation Mean Variance /% Polyester Cotton Yarn Polyester/Cotton Composite The processing of the yarn is firstly carried out by the doubling process and then by the twisting process, in order to prevent the crepe yarn from being easily generated during the joint process of the cylinder. The yarn is mainly used to ensure the number of composite strands, the tension of each yarn is balanced, the unevenness of the composite yarn is reduced, the strength of the composite yarn is improved, and the appearance is improved. The main purpose of the twist line is to combine the yarns of two different properties, and at the same time improve the distribution of the stress on the fibers in the yarn, thereby improving the quality of the composite yarn.
The strength of the composite yarn and the strength of the components in the composite yarn are related to the process of the parallel processing. Therefore, in order to find the main factors affecting the tensile strength of the composite yarn, the test parameters must be used to determine the process parameters. The twist is the most important factor affecting the tensile strength of the composite yarn. The test is to use the processed composite yarn to solve the twisting and twisting on the Y331 type twist tester, and then measure its tensile strength. Considering that the reverse twisting of the composite yarn is relatively stable, the composite yarn is reversely twisted, and the length of the twisted twist is 2. The tensile strength of the composite yarn 2.1 The main factors affecting the tensile strength of the composite yarn For the sample variety, the determination of the factor level in the test should take into account the following two aspects, one is that the requirements are the most commonly used; the second is that the requirements are relatively obvious. Therefore, all factors take three levels. According to the orthogonal test design of the composite yarn test scheme, the test factor level is shown in Table 2. The orthogonal test results are shown in Table 3. And the fracture fdM of the composite yarn is established (the elongation generated by the Fuk break elongation iblish crack is due to The yarns in the yarn body slip each other rt table 2 factor level water factor composite yarn single yarn æ» multifilament æ» flat tension æ» coefficient coefficient meaning 4 number breaking strength F / cN elongation at break to establish breaking strength and elongation at break and each The multivariate regression mathematical model between variables is obtained as follows: After analysis of variance, the equations and coefficients are significant. The enthalpy coefficient of the composite yarn and the æ» coefficient of the single yarn are strong significant factors.
2.2 Influence of the twist coefficient of the composite yarn on the tensile strength of the composite yarn For the strong elongation equation of the composite yarn, the twist coefficient of the composite yarn has a great influence on the breaking strength of the composite yarn. In the case of maintaining a single yarn twist factor of 460, a tension of 10 cN, and a multifilament twist coefficient of 0, the mathematical model between (L) and the composite yarn twist coefficient (x) is tested by changing the twist coefficient of the composite yarn. The regression equations are obtained as follows: After analysis of variance, the equations and coefficients are significant. The relationship between the breaking strength and the elongation at break of the composite yarn and the twist coefficient of the composite yarn are respectively shown.
The relationship between the breaking strength of the composite yarn and the twist coefficient of the composite yarn. The relationship between the elongation at break of the composite yarn and the twist coefficient of the composite yarn is known. The breaking strength of the composite yarn is within a certain range with the twist coefficient of the composite yarn. And after adding a certain value, the breaking strength will decrease. This is because the twisting of the composite yarn has two functions: on the one hand, the fracture of the composite yarn is generally broken by a single yarn having a small elongation at break, and therefore, the twisted yarn and the filament are intertwined by twisting. The slip-fracture of the spun yarn is effectively prevented, and the breaking strength of the composite yarn is relatively increased, and the strength unevenness of the composite yarn is improved by the twisting effect, which is also a factor for improving the strength of the composite yarn; On the other hand, when the twist coefficient of the composite yarn exceeds a certain value, the twisting action causes the fibers in the composite yarn to be prestressed, and at the same time, the fibers in the composite yarn are at different angles from the yarn axis, so that the fiber is strongly axially divided. The force is reduced, and the breaking strength of the yarn in the composite yarn decreases with the large coefficient of the twist. Therefore, the effect of twisting on the breaking strength of the composite yarn is the result of the opposite of the above two aspects.
It can be seen that the elongation at break of the composite yarn is large as the enthalpy coefficient is large. The composite yarn also has a critical twist coefficient when the composite yarn is broken under the tensile force. The composite yarn breaks under the condition that the pre-tension of the composite yarn is 5cN, and the crack strength is within a certain range along with the twist coefficient of the composite yarn. The increase is 1 to maintain the elongation of the composite yarn; the second is due to the elongation of the fiber itself due to the external force; and the third is the elongation due to the smaller twist angle of the yarn.
2.3 The influence of the single yarn twist coefficient on the tensile strength of the composite yarn The fracture of the composite yarn is always the first break of the single yarn with a small elongation at break, so the strength of the single yarn plays an important role in the strength of the composite yarn. In the case of maintaining the composite yarn twist coefficient of 317.5, the tension is 10cN, and the multifilament twist coefficient is 0, the test is performed by changing the single yarn twist coefficient, and the breaking strength (F) and elongation at break of the composite yarn are established. The mathematical model between the rate (L) and the single yarn twist coefficient (x), the regression equations are: the breaking strength of the composite yarn and the elongation at break are large with the single yarn twist coefficient. Because the twisting direction of the composite yarn is opposite to that of the single yarn, the range of single yarn twist coefficient selection is small, so the variation range of the single yarn twist coefficient is within the critical twist coefficient, therefore, the relationship between the composite yarn strength and the single yarn twist coefficient Not parabolic.
2.4 The combined effect of the single yarn twist coefficient and the composite yarn twist coefficient on the tensile strength of the composite yarn changes the twist coefficient of the composite yarn and the single yarn twist coefficient, and establishes the breaking strength (F) of the composite yarn. The mathematical model between the elongation at break a) and the single yarn twist factor (xi) and the composite yarn twist coefficient (x2) gives the regression equations: the breaking strength and fracture of the composite yarn within the critical twist coefficient. The elongation ratio is large with the twist coefficient of the composite yarn and the single yarn twist coefficient, and there is no interaction between the twist coefficient of the composite yarn and the single yarn twist coefficient.
However, after the critical enthalpy coefficient is exceeded, the breaking strength decreases; the elongation at break of the composite yarn is positively linear with the large æ» coefficient of the composite yarn; the breaking strength, elongation at break and single yarn of the composite yarn The æ» coefficient exhibits a positive linear correlation. In actual production, the strength and elongation of the composite yarn can be predicted and controlled according to the derived regression equations of breaking strength, elongation at break and composite yarn twist coefficient and single yarn twist coefficient.
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