Bonded thread is a specialized, high-strength product engineered for demanding applications that require superior durability. It is classified as an industrial-grade material, typically made from synthetic fibers like nylon or polyester. The defining characteristic is a protective coating applied to the thread structure, which fundamentally alters its performance profile. This bonding process transforms a standard twisted thread into a robust component capable of withstanding significant stress and friction.
The Bonding Process and Unique Properties
The manufacturing of bonded thread involves a post-treatment process after the individual plies of fiber have been twisted together. This process applies a resin or chemical agent, often a specialized polymer, to the exterior of the thread structure. The coating is then cured, fusing the twisted filaments together into a single, cohesive strand. This chemical treatment gives the thread its name and its distinct performance advantages.
The primary benefit imparted by the bonding agent is a significant increase in tensile strength, meaning the thread can withstand a much greater pulling force before breaking. Furthermore, the smooth, uniform coating drastically reduces the friction generated as the thread passes through dense or multiple layers of material. This low-friction characteristic helps prevent heat buildup and thread degradation during high-speed industrial sewing operations.
The bonding also acts as a shield against abrasion, protecting the core fibers from wear and tear. Crucially, the resin prevents the thread’s individual plies from separating or unraveling, a common issue known as ply separation with standard threads. This structural integrity ensures consistent loop formation and stitch quality, even when working with tough, unforgiving substrates.
Where Bonded Thread Excels
Bonded thread is the preferred choice for projects where the finished product must endure heavy use, environmental exposure, or significant structural stress. It is widely used in the production and repair of leather goods, such as wallets, belts, and heavy-duty bags, where the thread must resist the constant flexing and pulling inherent in these items. Bonded nylon is particularly favored in leatherwork due to its high strength-to-size ratio and excellent resistance to rot and mildew.
The automotive and furniture upholstery industries rely heavily on bonded thread to secure thick fabrics and foams that are subject to constant friction and weight. For outdoor applications, bonded polyester is often selected because the synthetic fibers offer superior resistance to ultraviolet (UV) light degradation. This UV stability is paramount for items like boat covers, sails, tents, and heavy canvas tarps that are continuously exposed to sunlight and moisture.
Footwear manufacturing and repair also benefit from the thread’s robust nature, ensuring seams on boots and shoes remain intact despite repeated impact and exposure to dirt and water. The thread’s ability to resist abrasion is particularly valuable in these environments, where the stitching is often in direct contact with rough surfaces. Selecting the correct fiber—nylon for maximum strength or polyester for superior UV resistance—allows the thread to be precisely matched to the specific demands of the end product.
Tips for Sewing with Bonded Thread
Working with bonded thread requires specific adjustments to standard sewing practices due to its increased thickness and stiffness. A larger, heavy-duty needle is necessary to create a sufficiently large hole for the thread to pass through without excessive friction or fraying. Needles in the size range of 18/110 or higher, often with a specialized leather or wedge point, are typically recommended to prevent needle deflection and breakage.
The machine’s tension settings often need to be adjusted to accommodate the thicker diameter of the thread. A slightly looser upper tension is frequently required to allow the thread to form a balanced stitch without snapping or causing the material to pucker. Furthermore, the stiffness of the bonded coating can cause the thread to retain the shape of the spool, leading to kinking or curling as it feeds through the machine.
To mitigate this issue, using a thread stand that allows the spool to unwind smoothly, rather than pulling the thread directly off the top, can significantly improve feed consistency. It is also beneficial to increase the stitch length setting on the machine, as shorter stitches can overcrowd the seam and weaken the material. Bonded thread is generally intended for use with non-stretch, heavy-duty materials, and attempting to use it on lightweight or delicate fabrics will likely result in damage.