Elongation Stress
Elongation stress is a property that indicates the force required to stretch an elastic band or stretch tape to a certain length, and it serves as a guideline for assessing tightness and holding power.
Contents6 sections
Definition and Overview
Elongation stress refers to the stress that occurs when a specimen is stretched to a specified percentage, or the required tensile force. In the materials field, it is sometimes called modulus, and it is used as a guideline for the difficulty of stretching elastic band and the force used to tighten it.
Even when stretched to the same length, elastic band with higher elongation stress requires greater force and tends to have stronger holding power when worn. However, the actual wearing feel is also affected by width, thickness, feel against the skin, and sewing specifications.
Difference from Elongation Rate and Elongation Recovery Rate
Elongation rate is a value that shows, as a percentage, how much longer something stretches compared with its original length. Elongation stress indicates the force needed to reach a certain elongation rate, so it expresses the strength of resistance to stretching rather than the amount of stretch.
Elongation recovery rate is the property that shows how much it returns to its original length after being stretched. Even elastic band that stretches well may have weak holding power if its elongation stress is low. Also, if recovery is poor, residual stretch is more likely to remain after use.
- Elongation rate: how far it stretches
- Elongation stress: how much force is needed to stretch it to a certain point
- Elongation recovery rate: how much it returns after stretching
Changes Due to Material and Structure
Elastic tape is made by enclosing elastic materials such as elastic yarn in woven, knitted, or braided structures. Depending on the type of elastic material used, its thickness and number of ends, the yarns forming the outer structure, and the weave or knit structure, elongation stress and texture can change even with the same width.
In general, woven elastic tends to keep its shape more stably, while knitted elastic tends to have a softer feel. Braided elastic is also used for round elastic and cord-shaped products, and its stretch behavior and load distribution vary according to its cross-sectional shape.
How Width and Stretch Are Expressed
Specifications for elastic and stretch tape are selected by checking the width, elongation rate, and elongation stress at a specific elongation rate. As the width becomes wider, the area in contact with the body increases, so even with the same material and structure, the perceived tightness and holding method differ.
When comparing, confirm whether the measured elongation rate, specimen width, unit, and test conditions are the same. Values measured at different elongation rates, or values showing force per width and force for the entire product, cannot be directly compared in a simple way.
Applications, Selection, and Handling
Elongation stress is important for areas where fit and resistance to slipping are required, such as the waist, cuffs, underwear, sportswear, and mask ear loops. For areas where you want to reduce pressure on the body, choose a lower value; for areas where firm retention is needed, choose one that provides enough force within the required elongation range.
Long-term stretching, heat, ultraviolet light, sweat, and detergent can cause elastic to harden, become sticky, crack, or retain stretch. Before mass production, it is important to check sewing samples at a stretch amount close to actual use and evaluate post-wash dimensions, recovery, and appearance.
Frequently Asked Questions
Does elastic with higher elongation stress stretch more easily?
Not necessarily. Elongation stress is the force required to stretch to a certain amount; the higher it is, the harder it is to stretch, and the stronger the holding power and tightness tend to be. How far it stretches is confirmed separately by elongation rate, and how easily it returns by elongation recovery rate.
Can the tightness of elastic tape be determined by width alone?
No. Tightness is affected by elongation stress, elongation rate, thickness, structure, the length used, and the amount stretched when sewn in. Even at the same width, characteristics can differ greatly, so make a sewing sample and check the pressure and holding power when worn.
If elastic loosens after washing, what should be checked?
Check not only elongation recovery rate, but also elongation stress, dimensional change, and appearance after washing and drying. Performance may decline due to deterioration caused by heat, chemicals, or long-term stretching. It is important to evaluate it according to the product's washing conditions and expected number of uses.
