Bonded Thread

Definition and Overview

Bonded thread is a sewing thread made by applying a bonding agent to thread twisted from multiple filaments, making the filaments that make up the thread easier to stay together. It helps prevent the thread from fraying during sewing and use, and contributes to seam stability.

It is used for sewing like ordinary sewing thread, but its defining feature is that it suppresses thread untwisting, meaning the twist does not return and the thread does not open up. It is sometimes chosen for thick thread or seams that are subjected to high loads.

Materials, Twist, and Structure

Nylon and polyester multifilament yarns are commonly used as materials. Multifilament is yarn made by bundling many fine continuous filaments, and while it is easy to achieve strength, the ends may fray more easily.

When the bonding agent penetrates to the inside of the yarn, it may be called in-bond; when it mainly coats the surface, it may be called out-bond. However, these names and the treatment details vary depending on the manufacturer and application, so specifications should be checked.

How Thickness Is Indicated

The thickness of bonded thread is indicated by ticket size, nominal ticket size, denier, and other measures depending on the product. Because the relationship between thickness and number differs by display system, it is important not to compare numbers directly across different systems, and to check the thread type and numbering system together.

Nominal ticket size is used as a thickness category that is easy to handle for sewing applications, but even with the same nominal ticket size, the apparent thickness, strength, and sewing feel vary depending on the material, number of plies, and bonding treatment. Check the needle and thread tension with test sewing.

Main Applications

It is used for bags, leather goods, shoes, belts, canvas products, workwear, and other items that are subject to friction and tension and require seam durability. If a thick ticket size is selected, it can also be used for decorative stitching that highlights the seam.

It is considered not only for textiles but also when sewing synthetic leather, leather, and heavy woven fabrics together. However, rather than choosing a thick thread simply because the material is hard, the decision should be made by considering the thickness of the sewing area, required strength, and the appearance of the seam as a whole.

How to Choose and Sewing Precautions

Select the material according to the product's usage environment and care label instructions. Nylon and polyester types differ in their tendencies for weather resistance, abrasion resistance, and dyeability, so in addition to matching the color to the textile, confirm the performance required for the application.

Adjust the machine needle size, needle hole, stitch pitch, and the tension of the upper and lower threads according to the thickness. If the thread is too thick, it may cause fabric damage from the needle hole, puckering, or thread breakage. If it is too thin, seam strength may be insufficient.

Bonded thread is not the same as high-tenacity thread that has not undergone bonding treatment. High-tenacity thread is a name focused mainly on strength, while bonded thread is a name focused on the structure and processing intended to keep filaments together and suppress untwisting.

Frequently Asked Questions