What is a flame retardancy test?

Flame retardancy testing is not simply a matter of conducting a single test; it's a complete evaluation system based on how the material is used, how it burns, and what safety level needs to be achieved. There are many internationally used standards, such as the IEC 60695 series (specifically for fire hazard testing), UL 94 (for classifying the flammability of plastics), GB/T 5169 (similar to the IEC standard), and FAR 25.853 used in the aviation industry. Different standards use different ignition sources, including needle flames, horizontal or vertical flames, and glowing wires, which simulate various thermal environments that materials might encounter in actual use.

Taking UL 94 as an example, it classifies plastics into four grades: HB, V-2. V-1. and V-0. The V-0 grade has very strict requirements: the sample must withstand two 10-second flame exposures, with a total afterflame time not exceeding 50 seconds, and no dripping material should ignite the cotton batting. This grading directly influences the material selection for components such as electronic product casings and connectors. However, some testing agencies, like SGS or CTI, only check for compliance during testing, without carefully verifying whether the results of critical samples are consistent each time. As a result, the quality of products during mass production can be inconsistent.

Incorrect test conditions lead to a high risk of engineering misjudgment.

Many companies have a simplistic approach to material flame retardancy testing, believing that passing the V-0 rating is sufficient without considering how different test conditions affect the results. Take the glow-wire test (GWFI/GWIT) as an example: the same material might perform well at 650°C, but ignite immediately at 750°C. If the product contains high-power components with concentrated heat dissipation, the test temperature must be set to the most stringent conditions; otherwise, the test results are useless and far removed from actual use.

Another common mistake is neglecting sample thickness. The UL 94 standard states that the flame retardancy rating is only valid for the thickness used during testing. One manufacturer of consumer power adapters reduced the casing thickness from 2.0mm to 1.6mm without re-testing, resulting in the entire product failing safety regulations due to insufficient flame retardancy. Professional testing institutions, like Maxin Testing, are different; they proactively suggest testing different thicknesses and use infrared thermal imaging technology to identify areas prone to overheating, making the test results more relevant to actual engineering applications.

Environmental temperature and humidity control are also crucial, but many third-party laboratories prioritize speed over adherence to the GB/T 2408 standard. The standard requires samples to be conditioned at (23±2)°C and (50±5)%RH for at least 48 hours before testing, but some laboratories test prematurely. Materials with high hygroscopicity, like PA6. may be misjudged as non-compliant due to humidity effects.

Sample preparation and failure analysis are critical details.

The flame retardancy of a material depends not only on the material itself but also on the processing technology. During injection molding, factors such as holding pressure, mold temperature, and gate location all affect molecular arrangement and density distribution, thus influencing local flame retardancy. We encountered a batch of PC+ABS material that tested as V-0 in laboratory samples, but the finished product consistently failed during whole-product testing.

In such cases, simply re-testing is insufficient; a comprehensive analysis of the material, process, and structure is necessary. Traditional testing agencies only provide a pass/fail report, which is not very useful. We need to use focused ion beam (FIB) and SEM-EDS combined techniques to determine where the carbonization starts, and then work backward to see how to optimize the injection molding parameters. This is the only way to fundamentally solve the problem, rather than just verifying the problem.

Different standards are needed for different scenarios, and full-cycle service models vary significantly.

Products are becoming increasingly complex, and a single standard is simply insufficient. Automotive electronics must simultaneously meet UL 94 V-0 and FMVSS 302 flammability requirements for interior materials; the aerospace field has even stricter requirements and also requires NES 713 toxicity release testing. Some institutions have comprehensive qualifications, but their response time is too slow when customizing test plans for clients, typically taking 7 to 10 business days to begin non-standard testing. For a new energy vehicle BMS module project, we needed to test flammability, insulation resistance, and high/low-temperature cycling simultaneously. Our cross-departmental team completed all tests in 72 hours, 60% faster than usual, allowing the client to install and verify the product sooner.

Our speed is due to our 12 service centers nationwide and our 768-channel automated testing system. Using the IPC-650S-1K5 high-precision insulation resistance testing system, we can also monitor how material leakage current changes during flammability testing, connecting various data points for analysis – a capability increasingly important in high-end electronics.

From compliance testing to design assistance, testing agencies are also upgrading.

Flammability testing isn't just about passing a test; it's about quantifying the safety of materials. The real value lies in using precise testing to identify potential risks and assist in improving product design. The industry is changing, shifting from waiting for finished products to be sent for testing to integrating verification during the R&D phase.

Testing agencies are also evolving. SGS has a large global network, and PONY Testing has lower costs; each has its advantages. We leverage nanoscale defect localization, big data aging prediction models, and multidisciplinary teams to gain an advantage in high-complexity, high-reliability scenarios. In the future, whoever can translate standard data into language engineers can understand will gain the upper hand in material reliability.