Popular Science | What is the resilience of chemical fiber yarn?

The resilience of chemical fiber yarn refers to the ability of the sample yarn to recover immediately from its deformation in a short period of time (3 minutes) after a certain load is applied to the sample yarn, stretched to a certain length, maintained for a certain period of time, and then the load is released. Resilience is generally expressed as rebound rate. There are currently two methods, one is constant load rebound rate and the other is constant elongation rebound rate.

(1) Fixed load rebound rate: This method is generally a method native to textile mills. The method is simple and the measured value is only for Relative comparison (Figure 11). Take a sample wire, fix and mark the upper end, add pre-tension 0.05cN/dtex to the lower end, keep the wire straight, then mark 50cm downward from the upper end mark, add a certain load of 0.15cN/dtex, and keep it After a certain period of time (3 to 5 minutes), remove the load and allow the sample yarn to retract naturally. After 30 seconds, add the original pretension to the lower end of the sample yarn, then measure the recovery length of the sample yarn, and calculate it according to the following formula:

Determined compliance rebound rate=▲(L’/L)*100%=(L1-L2)/(L1-L0) *100%

In the formula: L1 – the length of the sample wire after loading;

L2——The recovery length of the sample silk after the load is released

Lo——original length of sample silk

▲L’——the remaining length of the sample after deformation

▲L——Like The deformation length is the difference between the length of the wire after loading and the original length of the sample wire.

(2) Fixed elongation rebound rate: The fixed elongation rebound rate is the elasticity of the sample after a certain elongation. The length is the difference between the length after recovery and the fraction of the difference between the length after elongation and the initial length of the sample.

Currently, constant elongation resilience is often used to test the resilience performance of chemical fiber filaments. The constant elongation giant elasticity test is generally performed on a monofilament strength machine. The specific test method is as follows:

Take 60cm of this wire, fix the upper end in the upper chuck of the strength machine, and hang the pre-tension 0.05cN/ on the lower end. After dtex, clamp the lower chuck and make a mark M on the jaws of the chuck. Then lower the gripper at the slowest speed of the strength machine until the original wire is stretched to 3 % or 5%, lower the Ligen stop and keep it for 1 to 3 minutes, then return the lower holder to the original position, relax the lower holder, wait for the sample wire to naturally retract for 30 seconds, and then add pressure to the lower end of the sample wire. Apply the original pretension and clamp down the holder. Mark M’ on the jaw of the lower holder. Open the lower holder and measure the distance between M and M’, which is the remaining length of the sample wire. Then calculate:

Elongation elasticity=(L1-L2)/(L1-L0)*100%

Formula: L0—— The original clamping length of the sample (the distance between the upper holder and the M mark of the lower holder);

L1——Sample The length after elongation according to the specified elongation rate;

L2——The recovery length of the sample after stretching (Lo+MM’ distance ).

The rebound rate of chemical fiber yarns is related to the durability of silk fabrics, because silk fabrics are often subjected to more stress than silk fabrics in daily use. The breaking strength and elongation at break are much smaller than the external force stretching, resulting in elongation deformation.

A silk with a high rebound rate will have a small elongation variable every time it is stretched by an external force, and the accumulation rate of elongation deformation will be slow. In this way, the yarn can withstand repeated stretching of loading and unloading, and the fiber has good fatigue resistance. The fabric made of it not only has good elasticity and stiffness, but also is strong and durable. On the contrary, the yarn with low rebound rate , each time it is stretched, the elongation deformation is large, and the elongation accumulation speed is fast. When the elongation deformation exceeds the breaking elongation of the filament, the filament will break. Due to the poor fatigue resistance of the fiber, the fabric will not be worn. , Not wear-resistant.

In addition, the resilience of filaments also directly affects the dimensional stability and fabric folding resilience of the fabric. Silk with good resilience has good fold retention during use due to its small elongation and deformation.

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