A Detailed Explanation of the Melting Point Range of Nylon Hot Melt Yarn

A Detailed Explanation of the Melting Point Range of Nylon Hot Melt Yarn

In numerous industries, including textiles, filtration, and automotive interiors, nylon hot melt yarn has become an indispensable core material due to its excellent bonding properties, abrasion resistance, and chemical stability. As a core technical parameter of nylon hot melt yarn, its melting point directly determines its processing, application scenarios, and the quality and stability of the final product. For foreign trade buyers and manufacturers, accurately understanding the melting point range of nylon hot melt yarn is key to avoiding production losses and improving product competitiveness.

1. Basic Understanding of Nylon Hot Melt Yarn’s Melting Point: Why is it a Key Factor in Product Selection?

Nylon hot melt yarn is essentially a thermoplastic fiber. Its core characteristic is that it melts into a liquid state at a specific temperature and resolidifies upon cooling, forming a strong bonded structure. The melting point refers to the critical temperature at which a thermofusible wire transitions from a solid state to a molten state. It not only determines key parameters during processing, such as the heating temperature and holding time, but also directly impacts the product’s heat resistance. For example, using a thermofusible wire with a low melting point for automotive engine compartment filters used in high-temperature environments can lead to adhesive failure at high temperatures. Similarly, a thermofusible wire with a high melting point for baby clothing linings can damage the fabric substrate during processing.

Unlike common nylon fibers (such as PA6 and PA66 textile yarns), the melting point of nylon thermofusible wire can be adjusted through formulation modification (such as the addition of plasticizers and copolymers) to suit the processing needs of various industries. Therefore, its melting point range is not fixed but rather offers a wide range of customization. This makes precisely matching the melting point with the application scenario a key step in procurement and production.

II. Common Melting Point Ranges of Nylon Thermofusible Fibers: Classification by Type and Application

Based on raw material type, modification process, and industry requirements, the melting point ranges of mainstream nylon thermofusible filaments currently on the market can be divided into three categories. Each range corresponds to a distinct application scenario, so careful selection should be made based on your own processing equipment and end-product requirements.

1. Low-Melting-Point Nylon Thermofusible Fiber: 80°C-120°C

Core Features: It melts at low temperatures, bonds quickly, and minimizes damage to the substrate, making it suitable for lamination with heat-sensitive materials (such as wool, silk, and thin synthetic fabrics).

Common Materials: Based on PA6, modified by adding a high proportion of plasticizers (such as dioctyl adipate) or with a low-melting-point comonomer (such as a copolymer of caprolactam and cinnamyl). Some products are labeled “PA6-L” (L stands for Low Melting). Typical Applications:

Apparel Industry: Linings for baby apparel, fusible interlining for lightweight shirts, and lace fastening to prevent high-temperature damage to fabric fibers;

Home Textile Industry: Bonding down quilt linings and curtain fabric splicing. Low-temperature processing maintains fabric softness;

Medical Industry: Bonding the inner layer of disposable protective clothing and securing bands for medical dressings to ensure no harmful substances are released during processing (low-melting-point formulas are more likely to pass biocompatibility testing).

Note: Low-melting-point hot-melt yarn has poor heat resistance. The end product should not be used at temperatures exceeding 50°C for extended periods. Avoid direct sunlight or high-temperature washing (recommended water temperature ≤ 30°C).

2. Medium-melting-point nylon hot-melt yarn: 120°C-160°C

Core Features: It offers both ease of processing and stable temperature resistance. It is currently the most widely used product in the market and is compatible with most conventional textile and industrial processing equipment (such as hot-melt bonding machines and ultrasonic welding machines). Common Materials: Based on PA66, the melting point is optimized by adjusting the copolymerization ratio (such as the molar ratio of adipic acid to hexamethylenediamine) or adding a small amount of modifiers (such as glass microspheres). Some high-end products are labeled “PA66-M” (M stands for medium melting). A small number of PA6 modified products are also available (medium melting points are achieved by controlling crystallinity).

Typical Applications:

Textile Composites: Interlining for men’s and women’s suits, splicing of sportswear fabrics, and carpet edge fixing. The processing temperature is moderate and suitable for a variety of substrates such as cotton, polyester, and nylon.

Automotive Interiors: Bonding car seat fabrics to sponges and securing door trim fabrics. The end product can withstand short-term high temperatures in the vehicle interior (in summer, the temperature inside the vehicle is approximately 80°C-100°C). Medium-melting-point hot-melt adhesives provide a stable structure.

Filtration Industry: Seam bonding of bag filters, capable of withstanding the moderate temperatures (≤80°C) of filter media (such as industrial wastewater and dust). Highlights: Medium-melting-point thermal fuses have a wide processing window (the temperature range in which they remain liquid after melting is approximately 10-15°C), offer high tolerance for errors during production, and are suitable for mass industrial production. The end product’s temperature resistance meets the requirements of most everyday and industrial applications.

3. High-melting-point nylon thermal fuses: 160-200°C

Core Features: Excellent high-temperature resistance and high bond strength after melting, making them suitable for applications exposed to long-term medium- and high-temperature environments or where bond stability is critical.

Common Materials: Based on high-crystallinity PA66, or modified with glass fiber reinforcement or high-temperature copolymers (such as hexamethylenediamine terephthalate). Some products are labeled “PA66-H” (H stands for “High Melting”). A few specialty products (such as those used in electronic packaging) have melting points exceeding 200°C. Typical Applications:
Industrial Filter Materials: Seam bonding for high-temperature flue gas filter bags (such as dust collectors in power plants and steel mills), withstanding flue gas temperatures of 120°C-160°C and preventing bond failure over long periods of use.
Electronics Industry: Electronic component packaging and fixation (such as wire harness bundling and circuit board insulation bonding), withstanding the localized high temperatures (≤150°C) experienced during electronic equipment operation.
Specialty Textiles: Fabric lamination for firefighter uniforms and high-temperature workwear, ensuring the garment structure does not fall apart in high-temperature environments (such as short-term exposure to 180°C at a fire scene).
Processing Tips: High-melting-point hot-melt filaments require high-temperature processing equipment (e.g., the heating roller temperature must be set to 180°C-220°C). The high-temperature resistance of the substrate must also be carefully considered during processing. For example, when laminating with polyester fabric, ensure that the polyester melting point (approximately 250°C) is higher than the hot-melt filament processing temperature to avoid deformation of the substrate.

III. Key Factors Affecting the Melting Point of Nylon Thermofusible Fiber: A Complete Analysis from Formulation to Production

Why does the melting point of the same type of nylon thermofusible filament fluctuate by 5-10°C? Understanding the key factors influencing the melting point not only helps you assess product quality stability but also enables precise communication of parameters for customized requirements.

1. Raw Materials: Essential Differences Between PA6 and PA66

The base materials for nylon hot-melt filaments are primarily PA6 (polycaprolactam) and PA66 (poly(hexamethylenediamine adipate). Their different molecular structures lead to significant differences in their base melting points:

PA6: Its molecular chain has a low density of amide bonds and relatively low crystallinity, resulting in a base melting point of approximately 220°C-230°C. This can be lowered to 80°C-180°C through modification (a mainstream base material with low and medium melting points).

PA66: Its molecular chain has a high density of amide bonds and high crystallinity, resulting in a base melting point of approximately 250°C-260°C. After modification, the melting point ranges from 120°C-200°C (a core base material with medium and high melting points).

Therefore, if you require a high-melting-point product, PA66 is the preferred base material. For low-temperature processing, modified PA6 products offer a more cost-effective solution.

2. Modification Process: Formulation Determines Melting Point Range

Modification is the core method for adjusting the melting point of nylon hot-melt filaments. Common processes include:
Plasticizer Addition: Adding adipate or phosphate ester plasticizers to the base material can reduce intermolecular forces and lower the melting point (for example, the melting point of PA6 with 20% plasticizer can be reduced from 220°C to around 100°C);
Copolymerization Modification: Mixing PA6 or PA66 with low-melting-point monomers (such as caprolactam and octanediamine) to alter the molecular chain structure and achieve precise control of the melting point (for example, the melting point of PA6 and PA610 can be stabilized at 140°C-150°C);
Filling Modification: Adding fillers such as glass fiber and carbon nanotubes can increase crystallinity and raise the melting point (for example, the melting point of PA66 with 15% glass fiber can be raised from 250°C to above 260°C). Reputable manufacturers will provide test reports for modified formulations (such as DSC melting point test reports). These can be requested during purchase to verify the accuracy of the parameters.

3. Production Process: Processing Parameters Affect Melting Point Stability

Even with the same formulation, fluctuations in production parameters such as extrusion, stretching, and cooling can lead to melting point deviations:

Extrusion Temperature: If the extruder temperature is too high (exceeding the substrate decomposition temperature), the molecular chains will break and the melting point will drop. If the temperature is too low, crystallization will be incomplete, increasing melting point fluctuations.

Cooling Rate: Cooling too quickly (such as cooling the bath too low) will result in low fiber crystallinity and a lower melting point. Cooling too slowly will result in high crystallinity and a higher melting point.

Stretch Ratio: If the stretch ratio is too high, the fiber molecular chains will be more oriented, resulting in higher crystallinity and a slightly higher melting point. If the stretch ratio is too low, the melting point will drop slightly (usually within a range of 3°C-5°C). High-quality suppliers use online testing equipment (such as real-time DSC monitoring) to control the production process, ensuring that the melting point deviation within the same batch is ≤±2°C and between batches is ≤±3°C.

IV. Nylon Hot Melt Filament Melting Point Selection Guide: 4 Steps to Accurately Match Your Needs

With a wide variety of melting point ranges, how can you quickly select the product that suits your needs? The following 4 steps can help you avoid selection errors and reduce trial and error costs.

Step 1: Determine the Temperature Range of Your Processing Equipment

First, confirm the maximum and minimum controllable temperatures of your existing processing equipment (such as hot melt bonding machines or hot press laminating machines):

If the equipment’s maximum temperature is only 150°C, products with high melting points above 160°C cannot be used.

If the equipment’s minimum temperature is 100°C, products with low melting points of 80-90°C may not be fully melted due to insufficient heating, resulting in insufficient bond strength. For example, if a garment factory uses a hot melt adhesive machine with a temperature range of 110°C to 180°C, a product with a medium melting point (120°C to 160°C) is the best choice. This avoids both incomplete melting due to low temperatures and damage to the fabric due to high temperatures.

Step 2: Analyze the end product’s operating environment.
The end product’s long-term operating temperature and exposure to chemicals or external forces directly determine the required melting point of the hot melt wire.

If the product is subject to long-term high temperatures (such as automotive engine compartment components or high-temperature filter bags), the hot melt wire’s melting point must be at least 30°C higher than the maximum operating temperature (e.g., if the operating temperature reaches 150°C, a product with a melting point ≥ 180°C should be selected).

If the product is used in low-temperature environments (e.g., refrigerated food packaging rope), a low-melting-point product can be selected to reduce processing costs.

If the product is frequently washed (e.g., clothing or home textiles), the washing temperature must be considered (e.g., a household washing machine with a high setting of approximately 60°C). The hot melt wire’s melting point must be higher than the washing temperature to prevent adhesive failure after washing.

Step 3: Matching the Substrate’s High-Temperature Resistance

When laminating a hot-melt filament with a substrate (such as fabric, film, or sponge), the processing temperature must be below the substrate’s melting or softening point to prevent deformation and yellowing.

If the substrate is silk (melting point approximately 110°C-120°C), choose a low-melting-point hot-melt filament with a temperature of 80°C-100°C.

If the substrate is polyester (melting point approximately 250°C), hot-melt filaments with medium or high melting points (120°C-200°C) are suitable.

If the substrate is sponge (softening point approximately 130°C), choose a medium-melting-point product with a temperature of 120°C-140°C to prevent shrinkage due to high temperatures.

Step 4: Small-batch testing to verify actual results

Even if theoretical parameters match, problems may still arise in actual production due to equipment accuracy and substrate batch variations. Therefore, we recommend:
Request samples from the supplier at different melting points (e.g., 1-2 rolls of samples at ±5°C of the target melting point);

Conduct small-batch testing based on the actual production process to check adhesion strength (e.g., peel strength test), temperature resistance (e.g., high-temperature oven aging test), and appearance (e.g., presence of substrate damage or hot melt adhesive bleed);

Determine the final melting point based on these test results to avoid losses caused by direct bulk purchases.