There are many factors affecting the strength of staple fiber blended yarns. The main factors are two aspects: First, the properties of the fiber itself, such as length, fineness, strength and elongation (see Figure 1), breaking strength, surface friction performance; Line structure factors such as twist, fineness, processing technology, fiber arrangement geometry, blending ratio, etc.
Blended yarns are finished yarns obtained by mixing fibers at any stage of spinning preparation. After the fibers are fully separated and mixed, the desired homogenous mixing can be achieved, and the ideal homogenous mixing is difficult to achieve because it requires a large number of fiber performance tests, blending, and blending.
1 About bicomponent fiber blending
Hamburger is a pioneer in predicting the theoretical strength of blended yarns. When the fibers A and B of different tensile properties are blended, because the elongation at break is different, the fibers with smaller elongation at break first break, and the fibers of the two components in the yarn before the break share the external force, one of which is broken. Another type of continuous load is assumed. At this time, two peaks appear in the tensile curve of the blended yarn, and the highest peak is expressed as the breaking strength of the blended yarn. The breaking strength of the blended yarn is closely related to the blending ratio. The expression of the two peaks is:
The broken line ACB in Fig. 2 is the theoretical strength curve of the blended yarns of bicomponent fibers as a function of the blending ratio. The point C is the critical point when the strength of the blended yarn reaches the minimum when the blended bicomponent fiber is blended. The corresponding blending ratio is the critical blending ratio. At this point, there are:
From the above, it can be seen that there is a critical blending ratio when the two component fibers are blended, and the strength size is related to the ratio of the two fibers.
1.1 The performance indicators of different proportions of hemp and silk blended fibers are shown in Table 1.
Different proportions of hemp and silk reel were made into yarns of different numbers. The results of the strong test are shown in Table 2.
From the data in Table 2, it can be seen that as the hemp fiber content increases, the strength of the yarn gradually decreases. This fully complies with the above-mentioned tensile curve of the blended yarn. When spinning 17.9 tex yarns, when the yarn blending hemp/twist ratio increased from 55/45 to 80/20, the yarn strength had a critical point between 65/35 and 70/30.
1.2 Flax Drops and Polyester Blended Flax The same happens when blending linen and polyester blends.
The breaking strength of polyester fibers was 2.8 cN/dtex, and the breaking strength of flax hemp fibers was 3.3 cN/dtex. The breaking strength of the two is similar, but the elongation at break of the flax hemp fiber is about 10%, and the elongation at break of the polyester fiber is as high as 37%. When the pure polyester yarn is subjected to stretching, the cohesive force and friction force between the polyester fibers are relatively large, and the yarn exhibits high breaking strength and elongation at break. As the content of polyester decreases, the linen content of the linen increases, and when the yarn is stretched, the shorter linen hemp fibers first slip off or break, and only less polyester fiber withstands the effect of external forces, so that with the polyester content Gradually reduced, the strength of the yarn gradually decreased (see Figure 3).
When the linen linen fiber content increased to 60%, the breaking strength of the yarn showed an increasing trend, mainly due to the fact that more flax hemp fibers were subjected to external forces, and due to the shorter length of flax hemp fibers, In addition, the cohesion and friction between the fibers are small, and some fibers slip off. Therefore, although the yarn strength increases, it is lower than when the polyester fiber is the main component. At this time, due to the presence of a small amount of polyester fibers, The strength of the thread plays a reinforcing role. With the gradual reduction of the polyester fiber, this reinforcing effect is gradually reduced, and therefore, the breaking strength of the yarn tends to decrease. In addition, as the content of polyester increases, the number of fibers wrapped around the yarn increases, and the presence of this winding fiber increases the cohesion between fibers in the yarn. The increase in cohesion force enhances the strength of the yarn.
2 About Three-Component Fiber Blends
2.1 Testing of three-component blended yarns Three types of fiber cotton, polyester, and viscose were used for experiments. The results indicate a good application prospect. Some people think that the low strength of blended yarns is mainly due to the difference in elongation at break of the constituent fibers. It is also believed that all the high-strength fibers in the blended yarn do not break at the same time, and they still continue to bear part of the load after they break because the fracture and non-fracture fibers have frictional cohesion with each other. Therefore, the actual drawing shows a smooth curve with a change in slope.
The raw materials used in the experiment included cotton, polyester and viscose fibers. The properties are shown in Table 3.
In order to study the tensile properties of the yarn, all specimens have the same twist. Sample specifications are shown in Table 4.
The three-component blended yarn was extended by the following method to predict the same model: 1 The strengths of 100% cotton yarn, 100% polyester yarn, and 100% viscose yarn were respectively measured; 2 The strength-elongation curves were drawn in the same proportion; 3 Component blending curve, as a standard; 4 For three-component blended yarns, first consider the two-component blend of cotton and viscose, because they have low elongation compared with polyester; 5 in the three-component blended yarn, First consider the ratio of cotton and viscose, and then convert the ratio into the proportion of two-component blended yarns in the three-component blended spinning; 6 Converted two-component blended yarn strength from the cotton/viscous (C/V) blended spinning curve Given; 7 using these conversion values â€‹â€‹and polyester strength values, draw a polyester / viscose / cotton (P / V / C) strength curve.
The stress-strain curve of pure spinning is shown in Figure 4. The predicted strength curves of two-component blended yarns and three-component blended yarns are shown in Figure 5 and Figure 6, respectively.
2.2 Mechanical Properties Discussion The mechanical properties of all yarns are shown in Table 5. From Table 5, it can be seen that s 2 has the highest strength and s3 has the lowest strength, that is, the pure polyester yarn has the highest strength and the pure viscose yarn has the lowest strength. From Table 5, it can also be seen that the strength of S5 in the two-component blended yarn is the smallest of S4 to S6. Although 50% of the viscose is present, the polyester/viscous (P/V) blend exhibits better strength. This may be due to the better fiber blending due to the same fiber length and elongation. The low strength of s5 is caused by the lower strength of cotton fibers, and may also be due to differences in fiber elongation values.
For the three-component blended yarns S7 to S10. In terms of strength, s7 has the lowest strength, with 90% for cotton and viscose fibers and 10% for polyester. As the polyester component increases from 10% to 40%, the strength of the yarn also increases from S7 to S10. However, this increase is not linear, as shown in Figure 5, which was initially significant and later gradually flattened. However, the higher CV values â€‹â€‹of s3, s5, and s7 may be due to the higher CV values â€‹â€‹of cotton and viscose fibers. In the two-component blended yarns, the strength of S6 is the highest, which may be due to a good combination of fiber properties such as elongation and length. The strength of S4 is close to S1, S5 is close to S3, and S6 is between S2 and S3. This shows that the blended yarns of different fibers have different strengths. The strength of the three-component blended yarn of S7-S10 continues to increase as the proportion of polyester increases. However, it was slower initially and later it increased rapidly. Comparing measured and forecasted values â€‹â€‹indicates that the three-component fiber model assumptions are basically correct.
Through the analysis of the strength of multi-component blended fiber yarns, the influence of different blending ratios on the yarn forming strength of the yarn follows a certain rule, which can be utilized in the production process to achieve the best performance and production efficiency of the blended yarn. .
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