Elongation Rate

Definition and Overview

Elongation rate indicates the proportion of increased length during stretching, based on the sample's original length. It is used to compare the stretchability of elastic bands, stretch textiles, tape, and similar materials, and is generally expressed as a percentage.

However, the displayed value changes depending on the load during measurement, stretching speed, sample width and length, measurement direction, and other factors. For this reason, it is not possible to judge the stretch of different products in actual use uniformly based only on the number.

Differences by Material and Structure

In elastic materials, the elongation rate is affected by the combination of elastic materials such as polyurethane and the fibers and threads that make up the surface. Not only the material blend, but also thread thickness, weave or knit density, and finishing affect how the material stretches.

Woven elastic has stability from its woven structure, while knit elastic tends to stretch more easily due to the movement of the knit loops. Braided elastic makes it easier to create roundness and flexibility through its braided structure, and depending on the applications, the behavior in the width direction and length direction is checked.

How Width and Stretch Are Expressed

The width of elastic is generally shown as the product width in its unstretched state. When pulled during use, not only the length but also the width may become narrower, so when considering finished dimensions, the width is also checked in the actual stretched state.

In product information, expressions such as "stretches up to X times" may be used, but this indicates the reached length relative to the original length. Because this may differ from the elongation rate, check the original length, the length after stretching, and the measurement conditions.

• For example, the elongation rate is the value obtained by dividing the amount increased from the original length by the original length and converting it to a percentage.
• Width, elongation rate, and required tensile force are checked as separate specifications.

Main Applications and Selection

Elongation rate is important in areas where fit and ease of putting on and taking off are required, such as the waist, cuffs, hems, underwear, sportswear, and around masks. Selection is made from both the required range of motion and the degree to which tightness should be reduced.

Even with the same elongation rate, wearing comfort changes if the force required to stretch it differs. In prototyping, it is important to check the actual sewn-in length, the amount to be sewn while stretched, the stretch of the textile, and the amount of gathers after sewing, and to make adjustments through wear testing.

Recovery from Stretch and Handling Precautions

Elongation rate is a value that indicates how much a material stretches, and it does not indicate the property of returning to its original state after being stretched. Check recovery after repeated stretching, residual stretch, and changes over time, and conduct tests for applications that require stretch recovery.

Elastic materials may deteriorate due to heat, ultraviolet light, sweat and sebum, detergents, and similar factors. Match washing and drying conditions to the product specifications, and avoid storing the product in a strongly stretched state to reduce the risk of performance decline.

Frequently Asked Questions

If the elongation rate is high, is the recovery from stretch also good?

Not necessarily. Elongation rate indicates how long the material can become, while how much it returns to its original state after being stretched is a separate property. Depending on the applications, also check residual stretch and recovery after repeated stretching.

How is the elongation rate of elastic used during sewing?

It serves as a guideline when considering the finished length of the elastic and the length required when worn. However, because the results also change depending on textile stretch, the amount sewn in, and the required tightness, it is necessary to confirm by prototyping rather than deciding based only on the specification value.

Do elongation rate and stretch mean the same thing?

Stretch is often used to refer generally to the property of a material or product stretching. Elongation rate, on the other hand, is a measurement value that shows the increased length due to tension as a percentage. Elongation rate is used as one indicator when evaluating stretchability.