Bonded vs. Nonbonded Sewing Threads: How to Choose

Author	:	Robbie Owens
Position	:	Tech Service / Development Mgr
Words	:	1782
Read Time	:	9 minutes

Summary

The choice between bonded vs. nonbonded sewing thread affects sewability, thread handling, seam performance and the durability of the finished product. Bonded thread can provide advantages in demanding applications, such as when filament cohesion and resistance to abrasion and fraying are important. Nonbonded thread is appropriate when those performance requirements do not justify a bonded construction, which can carry a higher price tag. The right choice depends on the thread fiber and construction, sewing equipment and process, production conditions, material being sewn and requirements of the finished product.

Key Bonded vs. Nonbonded Thread Considerations

“Bonded” describes a thread that has undergone a bonding treatment. It is one of many characteristics that a thread can have. The process is usually performed on synthetic materials such as polyester and nylon thread. Liquid resin fuses the thread’s filaments and plies, creating a cohesive strand that will not fray during stitching or wear.

In practical terms, the primary questions to ask when choosing between a bonded or unbonded thread are:

• How much abrasion will the thread encounter?
• Does the sewing process place significant stress on the thread?
• Will the sewing machine operate at high speeds?
• Does the end use require seams to endure repeated flexing and stretching?
• Will the construction include multidirectional stitching?
• How important are appearance, seam strength, chemical resistance, UV resistance or other performance characteristics?

Champion Thread Company always consults with customers about their unique performance requirements and sewing conditions. Bonded vs. Nonbonded is just one of many factors.

Bonded vs. Nonbonded at a Glance

Bonded Does Not Equal ‘Better’

The bonding treatment does not replace the underlying fiber or construction. For example, regardless of whether a bonding treatment is applied,  polyester and nylon thread retain different performance characteristics and properties. So do corespun and spun threads. The raw materials and constructions provide various combinations of strength, elongation, flexibility, appearance and sewability. Likewise, thread size, twist, lubrication and other finishing treatments affect how a thread behaves during sewing. Bonding is just one variable.

 A nonbonded thread, sometimes referred to as a “soft” thread, can be designed and engineered for industrial sewing and excellent performance. Yet bonding can still provide meaningful advantages.

Why Is Bonding Used?

One of the principal purposes of bonding is to improve the cohesion of a filament thread. For industrial sewing threads, cohesion refers to the physical and chemical bond that fuses individual yarn plies into a single, unified strand. This is achieved through a protective liquid resin coating that prevents the thread from untwisting, fraying or separating during high-speed stitching.

During sewing, the thread passes repeatedly through guides, tension devices, the needle eye and the material. It is also subjected to bending, tension and friction. In demanding applications, maintaining thread integrity as it moves through this process can be important for consistent sewing performance. See also: Industrial Sewing Thread: Insights and Tips for Manufacturers and Buyers.

Bonding can also help control the individual filaments. When a multifilament thread is exposed to abrasion or mechanical handling, individual filaments can separate from the thread body. This can contribute to fraying and other sewing problems. Keeping the filaments together can help the thread maintain a more uniform structure.

This benefit is especially relevant when sewing heavy, abrasive or difficult-to-handle materials. For example, bonded nylon and polyester thread can suit applications including automotive covers, outdoor furniture, truck tarps, canvas awnings, geosynthetics and other sewn products.

That does not mean every heavy-duty application requires bonded thread. Thread size, fiber, construction and machine setup remain important. The objective is to match the thread to the actual performance requirements rather than specifying a bonded product solely because the material is heavy.

What Happens When Thread Is Not Bonded?

A nonbonded thread is not necessarily weaker or less suitable for industrial sewing. It can perform perfectly well for many applications. Its performance depends on how the thread is constructed and finished.

Spun threads, for example, use staple fibers and can provide characteristics that make them useful in apparel, uniforms and other sewn products. Core-spun threads combine properties of a continuous-filament core with an outer staple-fiber covering. Filament threads can also be twisted and finished without bonding. See also: Industrial Sewing Thread: Insights and Tips for Sewn Products Manufacturers and Buyers.

The key difference is that a nonbonded filament thread does not receive the same treatment intended to lock its filaments or plies together. Under certain sewing conditions, that can make filament separation or fraying more likely than with a comparable bonded thread.

However, a manufacturer should not assume that this automatically makes nonbonded thread unsuitable for demanding production. The appropriate comparison is between threads that meet the same application requirements. A properly specified nonbonded thread can provide the required seam performance without bonding.

This can be an important consideration when evaluating material costs, production requirements and product specifications.

Sewing Conditions Matter

Thread performance does not depend on the thread alone. Sewing speed, needle selection, machine settings, fabric or substrate characteristics, tension and lubrication can all affect the sewing process.

This is particularly important in high-speed industrial sewing. Friction between the needle, thread and material generates heat, and excessive needle temperature can contribute to thread breakage and weak seams. A 2025 study by Adnan Mazari and Funda Buyuk Mazari examined lubrication levels for sewing threads and their effects on friction, tensile properties, needle temperature and seam performance. The researchers identified thread lubrication as one approach to reducing needle heat during sewing of technical and medical textiles.

Earlier research by Selin Hanife Eryuruk and Fatma Kalaoglu at Istanbul Technical University similarly examined how different lubricant amounts affected several sewing-thread types. Their study measured properties including elongation, frictional forces, coefficient of friction, electrostatic charging and seam breaking strength.

These studies do not directly compare bonded and nonbonded threads. However, the research demonstrates why thread selection should not be reduced to one characteristic. The finish applied to a thread, the friction it experiences and the conditions under which it is sewn can all influence performance.

A sewing thread should be evaluated as part of the complete sewing system, not as an isolated component. The best thread provides the required performance while working reliably with the machine, material, seam construction and production conditions

When Is Bonded Thread the Better Choice?

Bonded thread is often worth considering when the sewing process or finished product places significant demands on thread integrity.

Heavy or Abrasive Materials

Leather, heavy textiles, coated fabrics, webbing and other abrasive substrates can subject thread to substantial mechanical stress. Bonding, like that found in CTC’s ThermaBond® bonded polyester and bonded nylon threads, can help maintain filament cohesion as the thread passes through the material and during subsequent use.

This can be relevant in furniture, automotive products, outdoor products, protective equipment, luggage, footwear and other industrial sewn products.

Multidirectional Sewing

Changes in sewing direction can increase the mechanical demands placed on thread. Bonding can help keep the filaments together during handling and stitching, particularly when the thread encounters repeated changes in direction.

This does not mean that every multidirectional sewing operation requires bonded thread. Machine type, thread construction, material and stitch design all influence the result. Bonding is one tool for addressing thread integrity.

High-Speed Production

High-speed sewing creates additional friction and heat and can increase the consequences of inconsistent thread performance. A thread that performs adequately at one sewing speed may behave differently as production speed increases.

In these environments, thread selection should be based on actual machine conditions rather than nominal thread strength alone. A thread’s ability to move consistently through the sewing system, resist damage and maintain its structure can affect production efficiency.

Products Exposed to Abrasion During Use

The sewing process is only one part of a thread’s service life. Finished products may experience repeated flexing, rubbing, tension and environmental exposure.

When the thread remains exposed or encounters significant abrasion, maintaining thread cohesion becomes an important consideration. Fiber selection and environmental resistance also become important. For example, polyester and nylon respond differently to UV exposure, chemicals, moisture and other environmental conditions.

When Is Nonbonded Thread Appropriate?

Nonbonded thread can be a practical choice when the application does not require the additional filament cohesion bonding provides. For starters, nonbonded thread is usually less costly and more widely available.

Apparel is an example of an application where bonding might not add much value. However, the correct thread depends heavily on garment construction, fabric, stitch type, appearance requirements and production conditions. Whether it is fashion, first-responder gear, or outdoor furniture, there are multiple ways to reach a satisfactory end. Depending on the end product construction,  spun, core-spun or nonbonded filament threads might provide the required combination of strength, flexibility, appearance and sewability.

Sometimes, a particular thread construction matters more than whether the thread is bonded. A manufacturer might require the feel or appearance of a particular thread, a specific elongation profile, a particular fiber, or compatibility with a specialized sewing process.

The important point is that nonbonded should not be interpreted as inferior. It simply means that the thread does not rely on a bonding treatment to achieve its construction and performance characteristics.

Conclusion

Bonded and nonbonded sewing threads each have a place in industrial sewing. Bonding can improve filament cohesion and help a thread withstand demanding sewing and service conditions, while nonbonded constructions can perform well when their characteristics match the application.

For manufacturers, the most reliable approach is to evaluate the complete sewing system and select thread based on product and production-process requirements. A thoughtful comparison of construction, fiber, finish, sewing conditions and end-use performance can help manufacturers achieve reliable seams without specifying more thread performance than the application requires.

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