Tear resistance test of hot melt wire: the key to ensure quality and performance

Tear resistance test of hot melt wire: the key to ensure quality and performance

Among the many performance indicators of hot melt wire, tear resistance is a crucial parameter. For enterprises engaged in the production and sales of hot melt wire and international wholesale buyers, it is of great significance to have a deep understanding of the tear resistance test of hot melt wire. This article will start with the basic characteristics of hot melt wire and deeply explore the principles, methods, equipment and influencing factors of tear resistance test, aiming to provide comprehensive and practical knowledge reference for relevant practitioners.

1. Overview of hot melt wire
Hot melt wire is a special fiber material, usually made of polymers such as low melting point polyester and low melting point polyamide. It has unique performance characteristics, such as relatively low melting point, rapid melting at a specific temperature and good bonding performance. These characteristics make hot melt wire widely used in many fields, such as webbing, lace, chenille yarn, trouser leg stickers, Bondi line, 3D flying woven uppers, automotive interiors, filter materials, flakes, etc., playing an important role in improving the quality and performance of products.

2. Importance of tear resistance test
In practical applications, hot melt wires are often subjected to various external forces, especially tensile and tearing forces. If the tear resistance of hot melt wires is poor, they are prone to breakage and damage during use, which will not only affect the appearance of the product, but also cause product failure, causing losses to production and users. For example, in automotive interiors, if the tear resistance of hot melt wires is not enough, the seat fabric may tear during use, affecting the interior quality and service life of the vehicle; in 3D flying woven upper applications, hot melt wires with poor tear resistance will make the uppers easy to break during wear, reducing the durability and wearing experience of the shoes. Therefore, evaluating the performance of hot melt wires through tear resistance tests is of vital importance to ensuring product quality, improving product competitiveness and meeting customer needs.

3. Principle of tear resistance test
The tear resistance test mainly measures the ability of hot melt wires to resist tearing under external forces. The basic principle is to make the hot melt wire into a specimen of a specific shape, and then apply tensile or tearing force to cause the specimen to tear. The tear resistance of the hot melt wire is evaluated by measuring the force value change during the tearing process, the length of the tear extension and other parameters. Common tear resistance test methods include the Elmendorf method, trouser tear method, etc. Different test methods are suitable for different types of hot melt wires and product application requirements.

4. Detailed explanation of tear resistance test methods
(I) Elmendorf method
The Elmendorf method is a commonly used fabric tear resistance test method, and is also suitable for evaluating the tear resistance performance of hot melt wires. Its test equipment mainly includes the Elmendorf tear tester, which consists of a rotatable disc and a pendulum with a clamping device. During the test, the hot melt wire sample is fixed on the disc, and a notch is cut on the sample. Then the pendulum is released. The pendulum swings under the action of gravity and drives the disc to rotate, so that the sample is subjected to tearing force. By measuring the change in potential energy of the pendulum before and after the tearing of the sample, the magnitude of the tearing force can be calculated. This method can simulate the tearing conditions that hot melt wires may be subjected to during actual use, and the test results are relatively accurate and reliable. It is widely used in quality inspection and performance evaluation of various hot melt products.
(II) Trouser-shaped tearing method
The trouser-shaped tearing method is another commonly used tearing resistance test method. Its characteristic is that the hot melt wire sample is made into a trouser-shaped shape, and then a tensile force is applied between the two “trouser legs” of the sample to cause the sample to tear along the “crotch”. The test equipment is usually a universal material testing machine equipped with a special trouser-shaped tearing fixture. During the test, by controlling the tensile speed and load of the testing machine, the force value change curve of the sample during the tearing process can be accurately measured, so as to obtain key parameters such as the maximum tearing force and tearing expansion force. The trouser-shaped tearing method can better reflect the tearing resistance of the hot melt wire under complex stress, and is especially suitable for some hot melt wire products with high tearing strength requirements, such as hot melt wires used for industrial filter materials and high-strength fabrics.

5. Tear resistance test equipment and instruments
(I) Tear strength tester
The tear strength tester is a precision instrument specially used to measure the tearing resistance of materials. It has the characteristics of simple operation, high test accuracy, and good data repeatability. It usually consists of the following main parts:
Clamping system: used to firmly clamp the hot-melt sample to ensure that the sample will not slip or move during the test, thereby ensuring the accuracy of the test results. Common clamping devices include pneumatic clamps and manual clamps. Pneumatic clamps have the advantages of uniform clamping force and wide adjustable range, which are suitable for hot-melt samples of different thicknesses and hardnesses; manual clamps have simple structures and low costs, which are suitable for some small enterprises and laboratories.
Loading system: Provides the tensile or shear force required for tearing for the sample. The loading system is generally composed of a motor, a screw drive device and a force sensor, which can achieve precise force control and measurement. By adjusting the speed of the motor and the stroke of the screw, the test requirements of different types of hot-melts can be met. At the same time, the force sensor can monitor the force changes during the tearing process in real time and transmit the data to the data processing system for analysis and recording.
Data processing system: Process and analyze the data collected during the test, including drawing the force curve, calculating the maximum tearing force, determining the tearing expansion force, and storing and outputting the test results. The data processing system of modern tear strength testers is usually equipped with professional software, with a friendly user interface and powerful data processing functions. Users can easily set test parameters, view test results, generate test reports, etc., which improves the efficiency and accuracy of testing work.
(II) Universal material testing machine
The universal material testing machine is a general-purpose mechanical property testing equipment. In addition to tear resistance testing, it can also perform various mechanical property tests such as tension, compression, and bending. Therefore, it has been widely used in the performance testing of thermal fuses. It has the following main features:
Versatility: It can meet the needs of different mechanical property tests of thermal fuses. Only by replacing the corresponding fixtures and test accessories, you can switch between multiple test functions, which greatly improves the utilization rate and cost performance of the equipment. For example, when performing tear resistance tests on thermal fuses, a trouser-shaped tear fixture can be configured; when performing tensile strength tests, it can be replaced with a tensile fixture; when performing peel strength tests, a peeling fixture can be installed, etc., achieving the purpose of one machine for multiple uses.
High precision and high stability: The universal material testing machine adopts advanced servo motor drive technology and high-precision sensor measurement system, which can accurately control the parameters such as loading speed, load size and displacement during the test, ensuring the accuracy and stability of the test data. At the same time, its sturdy body structure and optimized mechanical transmission system effectively reduce the vibration and noise of the equipment during operation, improve the reliability and service life of the equipment, and provide a stable test environment for the performance test of the thermal fuse.
High degree of automation: It has the functions of automatic control, automatic acquisition, automatic analysis and automatic report generation. The tester only needs to install the sample on the test machine, set the corresponding test parameters, and start the test program. The test machine can automatically complete the entire test process such as loading, data acquisition, data analysis and output of test results, which greatly reduces the intensity and error of manual operation, improves the efficiency and quality of testing work, and also reduces the influence of human factors on test results, ensuring the objectivity and fairness of test data.

6. Factors affecting the tear resistance of thermal fuse
(I) Raw material characteristics
The type and quality of raw materials of thermal fuse have a decisive influence on its tear resistance. Different polymer raw materials have different molecular structures and performance characteristics. For example, low-melting polyester and low-melting polyamide are two commonly used raw materials for hot melt wires. Their crystallinity, molecular weight and distribution and other factors will affect the mechanical properties of hot melt wires. Generally speaking, hot melt wires produced by raw materials with larger molecular weight and narrower distribution have higher strength and toughness and better tear resistance; while raw materials with higher crystallinity can make hot melt wires have better rigidity and hardness, but may also increase its brittleness, affecting the tear resistance to a certain extent. In addition, the impurity content, type and amount of additives in the raw materials will also have a certain impact on the tear resistance of hot melt wires. Therefore, choosing high-quality and suitable raw materials is the basis for improving the tear resistance of hot melt wires.
(II) Production process
The production process of hot melt wires includes multiple links such as spinning, stretching, and shaping. The control of process parameters in each link is crucial. During the spinning process, parameters such as spinning temperature, spinning speed, and cooling speed will affect the morphological structure and molecular orientation of the hot melt wire, thereby affecting its tear resistance. For example, a suitable spinning temperature can make the polymer melt smoothly extruded and form uniform fibers, while too high a temperature may cause polymer degradation, reducing the strength and toughness of the fiber; the speed of spinning will affect the degree of stretching orientation of the fiber, and thus affect its mechanical properties. The stretching process is an important process to improve the strength and modulus of the hot melt. Parameters such as the stretching multiple, stretching temperature and stretching speed need to be precisely controlled to ensure that the fiber can be fully oriented and form a good crystalline structure, thereby improving the tear resistance. The shaping process is mainly to keep the stretched hot melt stable at a certain temperature and tension, eliminate internal stress, and prevent the fiber from shrinking or deforming during subsequent use. It also has a certain impact on the dimensional stability and tear resistance of the hot melt.
(III) Environmental factors
The environmental conditions in which the hot melt is used during use will also affect its tear resistance. For example, temperature changes will affect the molecular movement and mechanical properties of the hot melt. In a high temperature environment, the strength and toughness of the hot melt may decrease, and the tear resistance will deteriorate; while in a low temperature environment, the hot melt may become brittle and hard, and it is also easy to tear. In addition, environmental factors such as humidity and chemical media may also have a certain impact on the performance of thermal fuses. For example, in a humid environment, thermal fuses may absorb moisture, resulting in a decrease in strength and an increase in viscosity, affecting their tear resistance. Under the action of some chemical media such as acids and alkalis, the molecular structure of thermal fuses may change, thereby reducing their tear resistance. Therefore, in practical applications, it is necessary to take corresponding protective measures according to the specific use environment of thermal fuses to ensure the stability and reliability of their performance.

7. Application of tear resistance test in product quality control
By regularly testing the tear resistance performance, problems that may occur in the production process, such as fluctuations in raw material quality and unstable process parameter control, can be discovered in a timely manner, and corresponding measures can be taken to adjust and improve them, thereby ensuring the consistency and stability of product quality. For buyers, the tear resistance test report is one of the important bases for evaluating the quality and performance of thermal fuse products, which can help them choose suitable suppliers and products, ensure that the purchased thermal fuses can meet the needs of production and processing and final product applications, and reduce the risks of increased production costs and product recalls due to product quality problems.

8. Industry standards and specifications
In order to standardize the tear resistance test methods and index requirements of hot-melt wires and ensure that the quality and performance of products meet the needs of the market and users, a series of relevant industry standards and specifications have been formulated at home and abroad. These standards and specifications make detailed provisions on the classification, test conditions, test methods, and result evaluation of hot-melt wires, providing unified criteria and basis for the production, sales and use of hot-melt wires. For example, the FZ/T 01085-2009 standard for hot-melt adhesive interlining peeling strength test method clearly stipulates the relevant contents of tear resistance test, including the preparation of specimens, the requirements of test equipment, the test steps, and the calculation and representation of results, etc., which provides standardized test processes and methods for hot-melt wire manufacturers and quality inspection agencies, ensures the accuracy and comparability of test results, and promotes the healthy and orderly development of the hot-melt wire industry.

9. Actual case analysis
Take a hot-melt wire manufacturer as an example. The company strictly controls the raw material procurement link, selects high-quality low-melting point polyester chips as production raw materials, and optimizes the spinning, stretching and other process parameters during the production process, successfully improving the tear resistance of hot-melt wires. In the tear resistance test, the Elmendorf method was used to test the company’s thermal fuse products. The test results showed that the tear strength of its products has been significantly improved compared with the previous one, reaching the industry-leading level. This achievement not only improves the company’s competitiveness in the market, but also wins the favor of more international wholesale buyers. Through close cooperation with buyers, the company can timely understand customer needs and the performance of products in actual applications, further improve product performance, and achieve a win-win situation for the company and buyers.

10. Future Development Trends and Prospects
With the continuous advancement of science and technology and the increasing market requirements for product quality, the tear resistance testing technology of thermal fuses is also constantly developing and improving. In the future, tear resistance testing will develop in the following directions:
Innovation and optimization of test methods: Develop more efficient, accurate, and intelligent test methods and equipment to better simulate the complex stress conditions of thermal fuses in actual use, and provide more comprehensive and in-depth data support for product quality assessment. For example, combining computer simulation technology and mechanical models, the tear resistance of thermal fuses is predicted and analyzed to provide guidance for product development and process optimization.
Multi-performance integrated testing: Combine tear resistance testing with other mechanical performance testing methods to form a complete set of thermal fuse performance testing system, which can comprehensively evaluate the strength, toughness, wear resistance, fatigue resistance and other performance indicators of thermal fuses at the same time, providing a more powerful means for a comprehensive understanding of the performance characteristics and quality status of thermal fuses.
Green environmental protection and sustainable development: During the testing process, more attention is paid to the requirements of environmental protection and sustainable development, and environmentally friendly test materials and reagents are used to reduce energy consumption and waste emissions during the testing process. At the same time, the treatment and recycling of test waste are strengthened to achieve green and sustainable development of the testing process.