Twisting is the process of combining filaments into yarn by twisting them together or combining two or more parallel singles yarns (spun or filament) into plied yarns or cords. Twisting improves uniformity and smoothness, and can be used to optimize strength and elongation. Note that over twisting can significantly lower tensile properties.
Many high performance yarns benefit from the improved load sharing that twisting allows. Optimum twist level varies with the material, fiber size, yarn size, end use, etc. Table 19 illustrates Vectran’s tenacity response to varying twist level, suggesting tenacity optimums of 2.5 TPI for 400 denier and 1.5TPI for 1500 denier yarns. Similar tests determine ideal cord and cable pick levels (Figure 25, Figure 26).
Table 19: Vectran® HT Tenacity vs. Twists per Inch (TPI)
| TPI |
400 denier tenacity gpd |
1500 denier tenacity gpd |
(KAI) |
| 0 |
25.6 |
25.6 |
| 0.5 |
26.5 |
26.7 |
| 1.0 |
27.8 |
27.6 |
| 1.5 |
27.8 |
28.6 |
| 2.0 |
28.6 |
27.9 |
| 2.5 |
28.8 |
27.6 |
| 3.0 |
28.1 |
25.8 |
| 3.5 |
28.3 |
24.0 |
| 4.0 |
28.3 |
21.8 |
| 4.5 |
27.8 |
N/A |
| 5.0 |
27.8 |
N/A |
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Ratio 8x1500/1 Construction
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Single End S-Twist and 3-Ply Z-Twist
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