Nylon Thermal Fusile Tensile Strength Testing

Nylon Thermal Fusile Tensile Strength Testing: From Standards to Applications, Uncovering the Core Indicators of Product Reliability

In industries such as textiles, medical, filtration, and packaging, nylon thermal fuses play a crucial role as “invisible support”—they must not only withstand high-temperature melting during processing but also maintain long-term mechanical properties in the final product. Tensile strength, as a key indicator of nylon thermal fuses’ fracture resistance, directly determines the service life, safety rating, and market competitiveness of downstream products. Today, we will delve into the entire process of nylon thermal fuse tensile strength testing, helping you understand the technical logic behind the test and how to use the data to select products that truly meet your needs.

1. Why is tensile strength testing crucial for nylon thermal fuses?

Before discussing testing methods, we must first clarify: Why is tensile strength such an important factor in nylon thermal fuse procurement decisions? From an application perspective, insufficient tensile strength of nylon hot-melt filaments can lead to a series of cascading problems:

In the garment accessories sector: Low tensile strength in hot-melt filaments used to bond interlinings can lead to breakage after washing, causing wrinkling and delamination in clothing.

In the filter material sector: Weak tensile strength in hot-melt filaments supporting filter media can cause deformation and damage to the filter bag due to airflow pressure, resulting in loss of filtration effectiveness.

In the medical sector: Hot-melt filaments used in surgical sutures or wound dressings must maintain stable strength in the human body environment to avoid breakage and medical risks.

Critically, the tensile strength of nylon hot-melt filaments is not a single value; rather, it forms a comprehensive mechanical property system along with elongation at break (the maximum elongation before breaking) and yield strength (the critical strength at which the material begins to plastically deform). For example, hot-melt filaments with high tensile strength but low elongation are suitable for applications requiring rigid support, while products with medium strength and high elongation are more suitable for applications requiring deformation buffering. This is why tensile strength testing requires the integration of multi-dimensional data.

II. Standards and Core Parameters for Nylon Thermofusible Filament Tensile Strength Testing
Professional testing must be based on internationally recognized standards to ensure data comparability and credibility. Currently, the mainstream global standards for nylon therofusible filament tensile strength testing include:
ASTM D885 (American Society for Testing and Materials): General test method for tensile properties of textile fibers, defining key requirements such as sample preparation, environmental control, and loading rate;
ISO 5079 (International Organization for Standardization): Applicable to tensile testing of synthetic fibers, with detailed definitions for the calculation methods of breaking strength and elongation;
GB/T 14344 (Chinese National Standard): Equivalent to the ISO standard, suitable for domestic supply chains and products exported to the Asian market. In actual testing, we focus on the following core parameters, which directly reflect product performance:

Test Parameters
Definition and Significance
Typical Range of Nylon Thermal Fusible Wire
Tensile Strength
The maximum stress a sample experiences at break, expressed in MPa or cN/dtex. Higher values ​​indicate greater fracture resistance.
3.5-5.0 cN/dtex (conventional models)
Elongation at Break
The percentage of elongation at break to the original length, reflecting the material’s toughness.
25%-45% (adjusted based on melt temperature)
Yield Strength
The critical stress at which a material transitions from elastic to plastic deformation. Permanent deformation occurs if this value is exceeded.
2.8-3.8 cN/dtex
Young’s Modulus
The stiffness of a material in its elastic state, expressed in MPa. Higher values ​​indicate stiffer materials.
80-120 MPa

Note: The above typical ranges are based on PA6/PA66 nylon thermal fuses. Specific values ​​should be adjusted based on product model and application scenario.

III. Complete Practical Procedure for Testing the Tensile Strength of Nylon Thermal Fusiles

To obtain accurate and repeatable test data, strict adherence to standardized procedures is essential. The following are the practical steps in our ISO 17025-certified laboratory, serving as a reference for our international customers:

1. Sample Preparation: The Key to Eliminating “Initial Error”

Sampling Guidelines: Randomly select at least 10 samples from the same batch of nylon thermoplastic filament, each with a length of at least 200mm (ensure the clamping end is separated from the test section);

Preconditioning: Equilibrate the samples for 24 hours at a temperature of (23±2)°C and a relative humidity of (50±5)%. Nylon thermoplastic filament absorbs moisture easily, and humidity fluctuations can cause strength fluctuations (strength may decrease by 5%-10% after moisture absorption);

Sample Fixing: Use a dedicated fiber clamp (to avoid slipping or damage to the sample), set the clamping distance to 100mm (according to ASTM D885), and ensure that the sample axis is aligned with the centerline of the clamp.

2. Equipment Commissioning: Select the appropriate testing instrument

Equipment Type: Use an electronic universal testing machine (accuracy class 0.5 or higher) equipped with a 100N or 500N tensile force sensor (select based on the estimated strength to avoid errors caused by excessive range).

Loading Rate: Set to 300mm/min (ISO 5079 standard). A loading rate that is too fast will result in an overestimated value (the material will not have enough time to deform), while a rate that is too slow will result in an underestimated value. This requires strict control.

Data Calibration: Calibrate the sensor with a standard weight before testing to ensure a force error of no more than ±1%.

3. Test Execution and Data Recording
Test Start: The testing machine stretches the sample at a constant rate, recording the force and displacement changes in real time until the sample breaks.
Anomaly Troubleshooting: If the sample breaks at the grip end (not the test section), the data is invalid and requires retesting. If this problem occurs for three consecutive samples, check the gripper pressure or sample flatness.
Data Calculation: Tensile strength is calculated using the formula (tensile strength = breaking force / sample cross-sectional area). The average and standard deviation (reflecting batch stability) of the 10 samples are calculated. A smaller standard deviation indicates greater product consistency.

4. Report Output: Providing “Traceable Trust” to Customers

A professional test report should include:

Basic Information: Sample model, batch, test date, operator;

Environmental Conditions: Temperature and humidity during testing;

Raw Data: Breaking force, tensile strength, and elongation at break for each sample;

Graphical Analysis: Force-displacement curve (visually showing the entire process from elastic deformation to fracture);

Conclusion: Whether the test meets the customer’s specified standards (e.g., “Meets ASTM D885 Class A requirements”).

IV. Three Key Factors Affecting the Tensile Strength of Nylon Hot-Fuse Fiber

After understanding the testing process, it’s even more important to understand the factors that influence final strength. This helps customers avoid risks when purchasing and demonstrates our thorough control over product quality:

1. Raw Material Purity: The “Innate Gene” that Determines Strength

The core raw material for nylon hot-fuse filament is PA6 or PA66 resin. If excessive amounts of recycled (recycled) material are mixed into the raw material, the molecular chain structure will be incomplete, resulting in a direct decrease in tensile strength of 15%-25%. Our products are manufactured using 100% virgin material and raw material purity is tested using infrared spectroscopy (FTIR) to ensure strength from the source.

2. Production Process: A Precisely Controlled “Cultivation”

Extrusion Temperature: The optimal extrusion temperature for PA6 is 230-250°C. Excessively high temperatures (above 260°C) can cause thermal degradation of the resin, leading to molecular chain breakage and reduced strength. Excessively low temperatures can cause incomplete resin melting, resulting in internal bubbles and increased rupture during stretching.

Stretching Ratio: The stretching process aligns the molecular chains, increasing strength. Conventional nylon hot-melt filaments have a stretching ratio of 3-4x. Too low a ratio results in disordered molecular chains and insufficient strength. Too high a ratio can lead to brittleness and reduced elongation at break.

Heat Treatment (Setting): After stretching, the material must undergo a heat treatment at 80-100°C to eliminate internal stresses. If the heat treatment time is insufficient, the product will experience strength loss during subsequent use due to stress release.

3. Storage and Usage Environment: Avoiding “Acquired Damage”

Nylon thermo-fusible yarn should be stored in a sealed, moisture-proof environment (it is recommended to use aluminum foil bags with built-in desiccant). Prolonged exposure to high humidity (relative humidity > 65%) will absorb moisture, resulting in a decrease in strength. Furthermore, contact with strong acids or bases (such as certain textile auxiliaries) during use can damage the amide bonds in the nylon, leading to an irreversible decrease in strength.

V. Practical Application of Tensile Strength Test Data: Customizing Solutions for Customers

For customers, test data is not just “hard numbers” but a “selection guide.” We have encountered several issues caused by ignoring tensile strength, which were ultimately resolved through targeted testing and product adjustments:

Case 1: “Wash-induced Cracks” Issue for a Customer in Fusible Interlining for Clothing

A European clothing brand purchased nylon thermo-fusible yarn (tensile strength 3.2 cN/dtex). The bonds broke after five washes. Through testing, we discovered that the customer’s requirement for “20 wash-resistant” nylon was insufficiently strong at 3.2 cN/dtex to withstand the tensile stress of repeated washing. Ultimately, we provided a customized model with a tensile strength of 4.5 cN/dtex and an elongation at break of 35%. This model, tested to withstand 30 washes, addressed the customer’s pain point.

Case 2: A Filter Material Customer’s “Pressure Deformation” Issue

An environmental protection company producing bag filters used nylon hot-melt filaments with insufficient tensile strength (3.0 cN/dtex). This caused deformation when the filter airflow differential pressure reached 2000 Pa. Based on the application scenario (high temperature and high airflow), we recommended a model that had undergone high-temperature curing (tensile strength of 4.2 cN/dtex and elastic modulus of 110 MPa). Testing showed that the nylon hot-melt filament maintained a stable structure even at a pressure differential of 3000 Pa.

Sixth, Choosing a Nylon Hot-melt Fiber Supplier: First, Consider “Testing Capabilities”

How can you determine if a supplier’s products meet your expectations? The most direct way to assess a company’s testing capabilities is to examine:

Does it have a laboratory that meets international standards (such as ISO 17025 accreditation);

Does it provide “batch-by-batch test reports” (rather than just “typical values”);

Does it support customized testing (such as post-aging tensile testing to simulate customer usage environments)?

Our laboratory is equipped with three electronic universal testing machines and two constant temperature and humidity chambers. We can provide customers with real-time test reports based on multiple ASTM/ISO/GB standards and offer free sample testing. Simply provide your requirements, and we’ll verify your product’s compatibility.