Shock Cord

Definition and Overview

Shock cord is a cord made of an elastic core and an outer textile layer that protects it. It is used for gathering the openings of clothing and bags, or for holding items in place, and is also called bungee cord.

Unlike ordinary round cord, which is used to keep its shape, shock cord differs in that it takes advantage of stretch, fit, and recovery. It is often used together with a cord stopper to adjust length and the degree of tightening.

Materials and Structure

The core is made of rubber materials such as natural rubber, and the outer sheath is made of textile fibers such as polyester or nylon. The outer sheath protects the core from friction, UV exposure, snagging, and more, and also affects the look and feel.

The outer sheath is generally a braided structure made by intertwining many yarns into a tube. The way the sheath is braided, the amount of yarn, and the amount of core material all affect surface density, firmness, the force needed to stretch it, and how it returns. It is distinguished from woven or knitted tape in that it is made as a three-dimensional cord.

Checking Thickness and Specifications

Shock cord is usually specified by outside diameter in millimeters rather than by width like a flat tape. However, check the supplier's specifications to confirm whether the thickness is measured in the unstretched state and what measurement method is used.

Even with the same outside diameter, stretchability and holding power differ depending on the structure of the core and outer sheath. Design it not only for the required length, but also for the stretch ratio during use, the length when it returns, and the compatible diameters of the cord stopper and cord end.

• Outside diameter and hole diameter of the auxiliary materials used
• Required stretch amount and recovery
• Pulling force and the weight of the item to be held
• Outer sheath material, color, and surface texture
• End finishing method and resistance to fraying

Main Applications

In outerwear, sportswear, and outdoor clothing, it is used to adjust the fit of hood openings, hems, waists, and more. Because it stretches, it is less likely to restrict body movement, and it can balance ease of putting on and taking off with a snug fit when worn.

In bags and pouches, it is used for tightening openings, securing external pockets, and temporarily fastening luggage. Since durability and safety requirements differ for non-apparel uses, it is necessary to check the specifications suitable for the intended environment.

Selection and Handling Notes

If used for a long time while highly stretched, the core may fatigue, resulting in residual stretch or reduced recovery. When sewing it in, secure it so the core is not damaged by the needle, and design it so that excessive load is not concentrated on the sewn-in section.

The cut ends are prone to unraveling, so finish the ends by heat cutting, tying, using hardware, a cord end, or similar methods depending on the material. When using heat treatment, test in advance because the core or outer sheath may melt or harden.

Washability, dryability, heat resistance, and weather resistance vary depending on the combination of core and outer sheath. Follow the care label and avoid strong heat, bleach, and excessive pulling.

Frequently Asked Questions