Analysis of Differences in Flame Retardant Performance Test Methods for Fireproof Adhesives and Their Impacts

In the field of flame retardant performance testing for materials, fireproof adhesives, as a critical fire-resistant material, require accurate evaluation of their flame retardant properties. Internationally, standards such as UL and EN, and domestically, the GB standard system, specify different testing methods. Vertical combustion testing and cone calorimeter testing are two commonly used approaches. Understanding the differences in testing methods across these standards, as well as their impacts on product certification and practical applications, is of significant importance for the production, sales, and utilization of fireproof adhesives.

Differences in Vertical Combustion Test Methods

UL Standards

UL 94 is a widely applied flammability standard for plastic materials, used to evaluate their flame retardant performance across multiple rating levels, such as HB, V-0, V-1, V-2, 5VA, and 5VB. Take the V-0 rating test as an example: a Bunsen burner is positioned 150 mm from the test specimen, with the flame height adjusted to 20 ± 2 mm (blue flame). The specimen is exposed to the flame for 10 seconds, after which the ignition source is removed, and the flaming combustion time is recorded. Once the flaming combustion extinguishes, the flame is reapplied for another 10 seconds, and both the post-ignition flaming and smoldering combustion times are recorded. The V-0 rating requires a afterflame time ≤ 30 seconds, with no dripping capable of igniting cotton.

EN Standards

In EN standards, the vertical combustion test shares similarities with UL in principle but differs in specific details such as flame height, flame application time, and sample dimensions. For instance, tests on certain materials may specify different flame heights or angles compared to UL, influencing the material’s combustion behavior and evaluation results.

GB Standards

GB/T 2408 specifies methods for determining the combustion performance of plastics, including vertical combustion testing. A Bunsen burner is lit at a specified distance from the specimen, with flame height and condition adjusted before applying the flame to the vertically positioned specimen. Data such as flaming combustion time and smoldering combustion time are recorded. While the basic procedure resembles UL, differences exist in details like sample pretreatment conditions, number of flame applications, and time intervals. For example, GB standards may impose different requirements for environmental humidity and pretreatment duration, affecting the specimen’s initial state and subsequent test results.

Differences in Cone Calorimeter Test Methods

UL Standards

Based on the oxygen consumption principle, cone calorimeter testing under UL standards focuses on combustion parameters such as heat release rate (HRR), total heat release (THR), effective heat of combustion (EHC), and time to ignition (TTI) under specific heat flux conditions. Clear specifications for equipment parameters (e.g., heat flux selection, sample placement) ensure data accuracy and comparability.

EN Standards

EN-based cone calorimeter testing shares the same principle but differs in test condition settings and data processing. For example, EN may adopt different methods and evaluation metrics for smoke and toxicity parameters, such as measuring smoke density, particle size, and types/concentrations of toxic gases differently from UL.

GB Standards

GB standards define specific requirements for testing equipment, sample preparation, and result criteria in cone calorimeter testing. Compared to international standards, differences may exist in heat flux ranges, test duration, etc. For instance, GB standards may specify heat flux values and test times tailored to domestic building fire scenarios when evaluating fireproof adhesives for construction applications.

Impacts on Product Certification

Increased Certification Complexity

Due to differences in testing methods between international and domestic standards, enterprises face higher certification complexity and costs, as they must meet requirements across multiple standards. Repeated testing may be necessary, leading to increased time and financial investments. For example, a fireproof adhesive seeking both UL and domestic certification must undergo separate testing under UL and GB standards. If results under one standard are unsatisfactory, product modifications and retesting are required, delaying market entry.

Confusion in Standard Selection

Different certification standards apply to specific regions and industries, posing challenges for enterprises in standard selection. Inappropriate choices can result in market rejection and limited sales reach. For example, enterprises unfamiliar with EN standards for the European market may rely solely on UL certification, encountering barriers when entering Europe.

Impacts on Practical Applications

Variations in Performance Evaluation

Identical fireproof adhesives may yield divergent flame retardant performance evaluations under different standards, confusing consumers and users in product selection. A product rated highly under UL may show lower performance under GB, making it difficult for users to assess real-world fire resistance based on diverse test reports.

Adaptability to Application Scenarios

Regions and industries adopt standards aligned with their specific needs, requiring fireproof adhesive designs to cater to diverse performance requirements. For example, domestic construction materials must comply with GB standards to ensure fire resistance in local applications, while exports to the U.S. must meet UL standards for compatibility with American construction and industrial scenarios.

Conclusion

International standards (e.g., UL, EN) and domestic GB standards differ in flame retardant testing methods for fireproof adhesives, particularly in vertical combustion and cone calorimeter tests. These differences increase certification complexity and create evaluation discrepancies in practical use. To promote industry development and enhance product versatility, harmonizing international and domestic standards is crucial. Enterprises must deeply understand varied standard requirements, optimize R&D and manufacturing processes, and ensure products meet diverse market and application needs.

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