Thermal fuse combustion performance test: the key to ensure product quality and safety

Thermal fuse combustion performance test: the key to ensure product quality and safety

In the research and development, production and application of thermal fuse products, combustion performance testing plays a vital role. This article will explore in depth various aspects of thermal fuse combustion performance testing, including its importance, common test methods, relevant standards and specifications, test equipment requirements, and precautions in actual operation, etc., aiming to provide comprehensive and detailed information for international wholesale buyers, helping everyone to better understand the quality and safety of thermal fuse products, so as to make wise purchasing decisions.

1. The importance of thermal fuse combustion performance testing
As a material widely used in electronic appliances, automobiles, ships and other fields, the combustion performance of thermal fuses is directly related to the safety and reliability of products. In actual use, thermal fuses may be affected by various heat sources, such as heat generated by current overload, high temperature in the surrounding environment, etc. If its combustion performance is poor, it is easy to cause safety accidents such as fire, which will cause huge loss of life and property to users.
By conducting combustion performance tests, the flame retardant, ignition, combustion diffusion and other characteristics of thermal fuses under different conditions can be accurately evaluated, providing a scientific basis for product design, material selection and quality control. This not only helps to improve the safety and stability of products, but also enhances the competitiveness of enterprises in the market, meets the regulatory requirements of different countries and regions for product safety performance, and avoids legal risks and market access barriers due to quality problems.

2. Common methods for thermal fuse combustion performance testing

At present, there are many methods for thermal fuse combustion performance testing, each of which has its own unique principle, scope of application and test purpose. The following are some common thermal fuse combustion performance test methods:

(I) Glow-Wire Test

The glow-wire test is a test method that simulates the combustion of materials caused by heat sources. It is mainly used to evaluate the ability of electrical and electronic products and their components to resist ignition by heat sources under high temperature conditions. During the test, the glow-wire of specified material and shape is electrically heated to the specified temperature, and then the top of the glow-wire is contacted with the thermal fuse sample. After reaching the standard time, the glow-wire is removed to observe and record whether the thermal fuse ignites, the burning time, and the situation after the combustion stops.

The temperature range of the glow-wire test is usually between 500℃ and 960℃, and the specific temperature depends on different product standards and material properties. For example, for some thermal fuses used in home appliances, a test temperature of 650℃ or 750℃ may be used, while for thermal fuses in automotive electronic components, the test temperature may be higher to more strictly evaluate their flame retardant properties.
The test results are usually determined based on the following aspects:
Whether the thermal fuse is ignited and how long the ignition time is.
Whether the thermal fuse can self-extinguish after burning and how long it will self-extinguish.
Whether there are drips during the burning process and whether the drips are flammable.
The glow wire test can effectively evaluate the fire risk of the thermal fuse when it is close to high-temperature components or overloaded and heated. It is a commonly used test method for the combustion performance of thermal fuses. Its relevant standards include IEC 60695-2-11, IEC 60695-2-12, IEC 60695-2-13, etc.
(II) Needle-Flame Test
The needle-flame test is mainly used to evaluate the combustion characteristics of materials under the action of a small flame heat source, and to simulate the impact of small flame failures such as arcs and sparks on materials that may occur during the use of the product. During the test, a needle-shaped burner with a tip of 0.9mm is used to apply a butane flame to the thermal fuse sample at a specific angle (usually 45° or 90°) to observe the combustion of the sample, including whether it continues to burn, the flame height, the burning time, and whether molten drips are produced after the combustion stops.
The flame parameters of the needle-flame test are clearly defined, such as the flame height is generally around 20mm and the flame temperature is about 1000℃. The test sample usually needs to meet certain size and installation requirements to ensure the accuracy and repeatability of the test results.
Compared with the glow wire test, the needle flame test focuses more on the combustion continuation ability of the thermal fuse under the direct action of a small flame and the impact on the surrounding environment. It is of great significance for evaluating the safety of the thermal fuse in some special use scenarios. Its reference standard is IEC 60695-11-5.
(III) Horizontal vertical combustion test (UL 94 Test)
The horizontal vertical combustion test is one of the classic methods for evaluating the combustion performance of materials, and is also widely used in the combustion performance test of thermal fuses. This test method installs the thermal fuse sample in two states, horizontal and vertical, and then ignites the free end of the sample with a flame of specified size and temperature, and observes and records the sample’s burning speed, flame propagation range, whether there is dripping combustion material, and burning stop time.
In the horizontal combustion test (UL 94 HB), the burning rate of the thermal fuse when placed horizontally is mainly measured, expressed in mm/min. The lower the burning rate, the better the flame retardant performance of the material. The vertical combustion test (UL 94 V) focuses more on the combustion of the thermal fuse in a vertical state. According to the combustion stop time and the dripping combustion situation, the flame retardant level of the material is divided into V-0, V-1, V-2 and other levels. Among them, V-0 level is the highest, indicating that the material has the best flame retardant performance.
The UL 94 standard has been widely recognized and applied worldwide. Many industries and enterprises use it as the basic requirement for material combustion performance. The horizontal and vertical combustion test can help users quickly understand the approximate performance of the thermal fuse under different combustion conditions, thereby providing a reference for material selection and quality control.
(IV) Hot-Wire Ignition Test
The hot-wire ignition test is mainly used to assess the flame retardant performance of the material when it is close to the electric heating wire or other heat source. During the test, the hot wire is first annealed, and the hot wire is wound around the hot fuse sample with a standard tool, and then the wound sample is clamped on the fixture. The free end of the hot wire is connected to the test circuit, and the power switch is turned on to start the test until the test sample ignites or melts through.
The results of the hot wire ignition test are usually evaluated using the performance level category (PLC) evaluation standard, which is divided into 6 levels from 0 to 5. The smaller the number, the higher the thermal fuse tolerance level and the better the flame retardant performance. This test method can simulate the ignition of the thermal fuse when it is in contact with or close to the electric heating element during actual use. It has a high practical significance for evaluating its fire safety inside electrical equipment. Commonly used standards include UL 746A Clause 32, ASTM D3874, GB 14048 Appendix M, IEC 60695-2-20, etc.

3. Relevant standards and specifications for thermal fuse combustion performance testing
The thermal fuse combustion performance test involves many international, national and industry standards. These standards have detailed and strict regulations on test methods, test conditions, test equipment, result judgment, etc. to ensure the accuracy and reliability of the test results, promote the improvement of product quality and the smooth progress of international trade. The following are some common standards related to the combustion performance test of thermal fuses:
(I) International Electrotechnical Commission (IEC) standards
The IEC 60695 series of standards are internationally recognized standards for fire hazard tests of electrical and electronic products, covering a variety of combustion performance test methods such as glow wire test, needle flame test, horizontal vertical combustion test, etc. For example, IEC 60695-2-11 specifies the finished product glow wire flammability test method (GWEPT), which is used to evaluate the fire hazard of thermal fuses after they are made into final products; IEC 60695-2-12 and IEC 60695-2-13 respectively specify the material glow wire flammability index (GWFI) test method and glow wire ignition temperature (GWIT) test method, which are suitable for evaluating the combustion performance of thermal fuse raw materials.
(II) Underwriters Laboratories (UL) Standards
The UL 746 series of standards mainly conduct safety assessments on the application of polymer materials in electrical equipment. The UL 746A standard specifies the methods and requirements for hot wire ignition testing, which is used to assess the flame retardant properties of materials such as thermal fuses under heat source conditions such as electric heating wires. The UL 94 standard is a classic standard for evaluating the horizontal and vertical combustion performance of materials. It provides a clear basis for the combustion performance classification of thermal fuses and has an important influence in the global electronic and electrical industry.
(III) Chinese National Standards (GB)
China also has corresponding national standards for thermal fuse combustion performance testing, such as GB/T 5169.11-2017, GB/T 5169.12-2013, GB/T 5169.13-2017, etc. These standards are equivalent to or modified from the IEC 60695 series of standards, which specify the specific methods and requirements for hot wire testing of thermal fuses, and provide unified technical specifications for the production and quality inspection of domestic thermal fuse products. In addition, standards such as Appendix M of GB 14048.1-2012 also stipulate relevant contents such as hot wire ignition test, ensuring the safety and quality consistency of thermal fuse products in the domestic market.

4. Requirements for thermal fuse combustion performance test equipment
In order to ensure the accuracy and reliability of the thermal fuse combustion performance test results, the test equipment needs to meet the strict requirements of the corresponding standards. The following are some common thermal fuse combustion performance test equipment and their requirements:
(I) Glowing wire tester
The glowing wire tester is the key equipment for glowing wire testing. Its main components include glowing wire, heating power supply, temperature control system, sample clamping device, timing device, etc.
The glowing wire is usually made of nickel-chromium alloy wire (Ni80/Cr20) with a diameter of 4mm to form a ring of a specified shape. Its heating temperature range should meet the requirements of room temperature to 1000℃, and the temperature fluctuation should be less than 3℃. The heating power supply should be able to stably provide sufficient current to quickly heat the glowing wire to the set temperature. The temperature control system generally uses a K-type thermocouple (level 1) in conjunction with a temperature control instrument to achieve accurate measurement and control of the glow wire temperature, and the temperature control accuracy should be within ±1°C.
The sample clamping device should be able to firmly clamp the hot fuse sample and can be adjusted as needed during the test to ensure that the contact position between the glow wire and the sample is accurate and the pressure is stable. The timing device is used to accurately record the time the glow wire contacts the sample, as well as the time of the sample combustion process, with an accuracy of ±0.1s.
(II) Needle flame tester
The needle flame tester is mainly composed of a needle burner, a gas supply and control system, an ignition device, a sample clamping device, and a timing device. The inner diameter of the needle burner is 0.5mm, the outer diameter is 0.9mm, and the length is about 100mm. Its flame height should be able to be accurately adjusted between 10mm and 30mm to meet the requirements of different test standards. The gas supply system usually uses a butane gas cylinder and is equipped with a pressure reducing valve, flow meter and other devices to ensure that the gas flow is stable and controllable, thereby ensuring the stability and repeatability of the flame.
The ignition device should be able to reliably ignite the gas in the needle burner to produce a stable needle flame. The sample clamping device should be able to easily fix the thermal fuse sample and make necessary position adjustments during the test, such as changing the angle and distance between the sample and the needle flame. The timing device is used to record key parameters such as the needle flame action time and the sample combustion time, and its accuracy should also reach ±0.1s.
(III) Horizontal vertical combustion tester
The horizontal vertical combustion tester mainly includes a combustion test chamber, a Bunsen burner or a propane burner, an ignition device, a sample clamping device, a measuring tool and a timing device. The combustion test chamber should have sufficient volume and good ventilation conditions to ensure safety during the test and the accuracy of the test results. Generally, the test chamber volume is required to be greater than 0.5 cubic meters and be equipped with an exhaust system and an observation window.
The Bunsen burner or propane burner should be able to produce a flame height and temperature that meets the standard requirements. The flame height can be precisely controlled by adjusting the gas flow rate and air mixing ratio, and is usually adjustable between 20mm and 100mm. The ignition device is used to ignite the burner and should be easy to operate, safe and reliable. The sample clamping device should be able to firmly fix the thermal fuse sample in a horizontal or vertical position, and can easily adjust the installation angle and position of the sample. The measuring tool is used to measure the burning length, burning speed and other parameters of the sample, and should have high accuracy and resolution. The timing device is used to record the flame action time, sample burning time, etc., and its accuracy should not be less than ±0.1s.
(IV) Hot Wire Ignition Tester
The hot wire ignition tester is mainly composed of hot wire, heating power supply, annealing device, sample clamping device, timing device, etc. The hot wire is usually made of nickel-chromium alloy wire with a diameter of about 0.5mm and a length of about 250mm. Its thermal resistance should meet the requirements of the corresponding standards, such as the thermal resistance of about 5.28Ω/m specified in the IEC 60695-2-20 standard. The heating power supply should be able to provide a stable current to heat the hot wire to the set temperature, and can perform precise temperature control and adjustment.
The annealing device is used to anneal the hot wire to eliminate the internal stress generated by the hot wire during the production process and ensure the stable performance of the hot wire. The sample clamping device should be able to firmly clamp the hot fuse sample and facilitate the winding and fixing of the hot wire. The timing device is used to record the heating time of the hot wire, the contact time with the sample, and the time of the sample combustion process, and its accuracy should reach ±0.1s.

5. Practical Operation Precautions for Thermal Fuse Combustion Performance Test
During the actual operation of thermal fuse combustion performance test, the following points should be noted to ensure the accuracy and reliability of the test results, and also to ensure the safety of the operator:
(I) Sample preparation
The preparation of thermal fuse samples should be carried out in strict accordance with the requirements of relevant standards, including the size, shape, surface state, cleanliness and other aspects of the samples. For example, for glow-wire test and needle flame test, the sample size is usually required to be 60mm to 125mm long, about 13mm wide, and the thickness is generally between 0.75mm and 3mm, depending on different test standards and material types. The surface of the sample should be flat and smooth, without obvious scratches, stains, oil stains and other defects to avoid these factors from interfering with the test results.
When sampling, representative samples should be selected from different batches or different locations of thermal fuse products to ensure that the test results can truly reflect the overall combustion performance of the product. At the same time, it should be noted that the number of samples should meet the requirements of the test method. Generally, multiple samples need to be prepared for each test item to facilitate repeated testing and statistical analysis of the results.
(II) Control of the test environment
The test environment has an important influence on the test results of the thermal fuse combustion performance, so it is necessary to strictly control the temperature, humidity, airflow and other parameters of the test environment. Generally speaking, the standard test environment temperature should be maintained at 23℃±2℃, and the relative humidity should be controlled within the range of 50%±5%. Such environmental conditions can make the test results have good repeatability and comparability.
During the test process, interference from external airflow should be avoided, such as avoiding airflow fluctuations caused by opening doors, opening windows, and walking of people, because airflow will directly affect the spread and combustion of flames, thereby causing deviations in test results. If the test environment cannot meet the standard requirements, the actual environmental conditions should be recorded in detail in the test report, and the test results should be explained and analyzed accordingly.
(III) Calibration and maintenance of equipment
In order to ensure the accuracy and reliability of the test equipment, the test equipment should be carefully calibrated and checked before each use. For example, for the glow-wire tester, the temperature of the glow-wire should be calibrated using a standard thermometer or temperature calibration instrument to ensure that the temperature display value is consistent with the actual temperature; for the needle flame tester, the size, shape and gas flow of the needle burner should be checked regularly to ensure that the flame height and temperature meet the standard requirements; for the horizontal vertical combustion tester, the flame height and temperature of the Bunsen burner should be calibrated, and the position accuracy and flexibility of the sample clamping device should be checked.
At the same time, the test equipment should be regularly maintained and serviced, including cleaning the surface of the equipment, checking and replacing vulnerable parts, lubricating moving parts, etc., to extend the service life of the equipment and ensure the normal operation of the equipment. If the equipment fails or has an abnormal condition, it should be stopped immediately and repaired and debugged in time until the equipment returns to normal and passes the calibration before it can be used again.
(IV) Safety protection of operators
The combustion performance test involves dangerous factors such as high temperature and flame, so the safety protection of operators is crucial. When conducting the test, the operator should wear appropriate protective equipment, such as protective gloves, protective glasses, protective clothing, etc., to prevent accidents such as high temperature burns and flame burns.
In addition, operators should be familiar with the operating procedures and safety precautions of the test equipment, and operate in strict accordance with the operating procedures to avoid safety accidents caused by misoperation. During the test process, the status of the equipment and samples should be closely observed. If abnormal conditions are found, such as equipment failure, sample explosion, etc., emergency measures should be taken immediately, such as cutting off the power supply and gas source, using fire extinguishers to extinguish fires, etc., to ensure the safety of the test process.

6. Application and analysis of thermal fuse combustion performance test results
The thermal fuse combustion performance test results have important application value for product quality control, research and development improvement, market promotion and user use. Through in-depth analysis of the test results, it can provide strong support for the production and operation decisions of enterprises.
(I) Product quality control
During the production process, by regularly testing the combustion performance of thermal fuse products, product quality fluctuations and potential quality problems can be discovered in time, such as unstable raw material quality, changes in production process parameters, etc., which lead to a decrease in combustion performance. According to the test results, enterprises can adjust the production process, optimize the raw material formula, and strengthen quality control measures in a timely manner to ensure the stability and consistency of product quality and meet relevant standards and customer requirements.
For example, if the ignition temperature of the hot-melt sample is found to be lower than the standard requirement in the glow-wire test, the enterprise can analyze the reason, which may be that the flame retardant content of the raw materials is insufficient or the mixing is uneven, so as to timely adjust the raw material formula and production process, improve the flame retardant performance of the product, and ensure that the product quality meets the standard.
(II) Product R&D Improvement
The combustion performance test results can provide an important reference basis for the research and development of hot-melt products, help R&D personnel understand the combustion characteristics and shortcomings of the products, and thus carry out targeted product improvements and innovations. For example, by analyzing the performance of hot-melts with different material formulas in various combustion performance tests, R&D personnel can choose more suitable raw materials and develop new products with higher flame retardant performance, lower smoke release, and better comprehensive performance to meet the market demand for high-performance hot-melt products.
In addition, the test results can also provide guidance for the structural design of the product, such as optimizing the shape, size, installation method, etc. of the product according to the flame propagation path and combustion conditions of the hot-melt under different combustion conditions, so as to improve the fire safety of the product.
(III) Market promotion and customer trust
Detailed thermal fuse combustion performance test reports and certification certificates are important passes for products to enter the international market. They can show customers that the quality and safety of products meet international standards, enhance customer confidence and trust in products, and promote product sales and market promotion. In international trade, many buyers and distributors require suppliers to provide product combustion performance test reports as one of the important bases for product quality assessment and purchasing decisions.
By providing comprehensive, accurate and authoritative combustion performance test results, companies can stand out from many competitors, establish a good brand image and reputation, and improve the market competitiveness and added value of products.
(IV) User safety guidance
Understanding the combustion performance test results of thermal fuse products can help users correctly select, install and use products during actual use, and avoid safety accidents caused by poor product combustion performance. For example, based on the combustion performance test results, users can choose thermal fuse products with appropriate flame retardant levels, slow burning speeds, and no toxic and harmful gases when burning, for different electrical equipment and use environments.
At the same time, users can understand the performance of the product in dangerous situations such as fire according to the description of the combustion characteristics in the test results, so as to take corresponding safety protection measures, such as equipping appropriate fire-fighting equipment, installing fire alarm devices, and formulating emergency evacuation plans, etc., to reduce the risk of fire and protect the safety of life and property.

7. The latest development and trend of thermal fuse combustion performance testing
With the continuous advancement of science and technology and the increasing requirements of people for product safety performance, the field of thermal fuse combustion performance testing is also constantly innovating and developing, showing the following new development trends:
(I) Standardization and internationalization of test methods
In order to promote international trade and technical exchanges, the thermal fuse combustion performance test standards of various countries are constantly moving closer to international standards to achieve standardization and unification. International organizations such as IEC are playing an increasingly important role in the formulation and improvement of thermal fuse combustion performance test standards, and the relevant standards they have issued have been recognized and adopted by more and more countries. This will help reduce the differences in test standards between different countries and regions, improve the comparability and mutual recognition of test results, and reduce the testing costs and market access barriers of enterprises.
(II) Intelligentization and automation of testing technology
With the help of advanced sensor technology, computer control technology and data analysis technology, thermal fuse combustion performance test equipment is developing in the direction of intelligence and automation. Modern testing equipment can realize precise control and real-time monitoring of the test process, automatically record and analyze test data, and generate detailed test reports, which greatly improves the test efficiency and accuracy and reduces human errors.
For example, some new types of glow-wire testers and needle-flame testers are equipped with automatic sampling systems, automatic temperature calibration systems, image acquisition and analysis systems, etc., which can realize automatic testing of samples and visual analysis of the combustion process, providing researchers with richer data support and more in-depth research methods.
(III) Increased attention to combustion products and environmental impact
In addition to paying attention to the combustion performance of thermal fuses themselves, more and more studies have begun to pay attention to the impact of their combustion products on the environment and human health. For example, the types and contents of smoke, toxic and harmful gases (such as carbon monoxide, hydrogen chloride, etc.) released by thermal fuses during combustion, as well as the pollution of these substances to the environment and the degree of harm to the human body. This will prompt enterprises to develop and produce low-smoke, low-toxic, and environmentally friendly thermal fuse products to meet the society’s higher requirements for environmental protection and health.
(IV) Combined application with other testing technologies
In order to more comprehensively and accurately evaluate the combustion performance and safety of thermal fuses, the combined application of combustion performance testing technology with other testing technologies (such as mechanical property testing, electrical performance testing, thermal stability testing, etc.) will become more and more common. Through multi-faceted testing and comprehensive analysis, we can deeply understand the performance and mutual influence of thermal fuses under different use conditions, and provide a more comprehensive and systematic basis for product design, development and quality control.
For example, combining the thermal deformation temperature test and combustion performance test of thermal fuses, we can evaluate their comprehensive performance in high temperature environments, ensuring that the products can meet the temperature requirements and have good flame retardant properties in actual use.

8. Conclusion
As an important means to evaluate product quality and safety, the combustion performance test of thermal fuses plays an indispensable role in the entire life cycle of thermal fuse products. By testing the thermal fuse with various methods such as glow wire test, needle flame test, horizontal vertical combustion test, hot wire ignition test, etc., according to relevant international, national and industry standards, with the help of accurate and reliable testing equipment, and strictly following the operating procedures for testing and analysis, it can provide strong support and guarantee for the quality control, research and development improvement, market promotion and user safety of thermal fuse products.
With the continuous development and innovation of testing technology, it is believed that the thermal fuse combustion performance test will play a more important role in the future, promote the thermal fuse industry to develop in the direction of higher quality, safer and more environmentally friendly, provide better quality and more reliable products for global users, and promote the prosperity and progress of related industries. If you are looking for high-quality thermal fuse products, it will be a wise choice to pay attention to the combustion performance test results of the products. We also hope that the relevant information we provide can help you better understand the characteristics and value of thermal fuse products, and work with us to promote the high-quality development of the industry.