Research on Detection of Service Life and Flame Retardant Performance Degradation Law of Fireproof Adhesive and Accelerated Aging Test

Fireproof adhesives are widely used in multiple fields such as construction, electronics, and transportation. Their service life and flame retardant performance are directly related to fire safety and the long-term stable operation of facilities. Over time, fireproof adhesives are affected by various environmental factors such as temperature, humidity, light, and chemical corrosion, leading to gradual performance degradation. Therefore, accurately detecting the service life and flame retardant performance degradation law of fireproof adhesives, and predicting their long-term safety through accelerated aging tests, is of great significance for ensuring the rational application of fireproof adhesives and public safety.

Detection Methods for Service Life and Flame Retardant Performance Degradation Law of Fireproof Adhesive

(Ⅰ) Service Life Detection Methods

1. Mechanical Property TestingThe mechanical properties of fireproof adhesives, such as bond strength, tensile strength, and shear strength, change over time. Mechanical property indicators are measured by regularly conducting tensile tests, shear tests, etc., on fireproof adhesive specimens. When the mechanical properties drop to a specified failure threshold (e.g., 50% of the initial strength), the fireproof adhesive is considered to have reached the end of its service life. For example, in the application of building sealing fireproof adhesives, if the bond strength drops to a level that cannot meet the requirements of building structure sealing and fire separation, it means the fireproof adhesive has lost its use value.
2. Microstructural AnalysisScanning electron microscopy (SEM), transmission electron microscopy (TEM), and other equipment are used to observe the microstructural changes of fireproof adhesives at different service stages. Over time, phenomena such as molecular chain breakage, uneven filler dispersion, and void formation may occur inside the fireproof adhesive, which directly affect its macro properties. By analyzing the evolution law of the microstructure, the service life of the fireproof adhesive can be indirectly evaluated. For example, the crack propagation inside the fireproof adhesive observed in SEM images can be used to infer its remaining service life.
3. Thermal Analysis TechniquesDifferential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) are used to study the thermal performance changes of fireproof adhesives. DSC can detect information such as phase transitions and reaction heat of fireproof adhesives during heating, while TGA can measure their mass loss at different temperatures. As the service time increases, the thermal stability of fireproof adhesives decreases. By comparing the thermal performance data at different stages through DSC and TGA tests, the degree of aging can be evaluated, and the service life can be inferred.

(Ⅱ) Detection Methods for Flame Retardant Performance Degradation Law

1. Combustion Performance TestingStandard combustion test methods such as the UL 94 vertical combustion test and the oxygen index (LOI) test are used to evaluate the combustion performance of fireproof adhesives at different aging stages. The UL 94 vertical combustion test can determine the flame retardant grade based on the combustion time and dripping conditions of the specimens; the LOI test characterizes the flame retardant performance by measuring the minimum oxygen concentration required to maintain material combustion. As the fireproof adhesive ages, its flame retardant grade may decrease, and the LOI value may decrease. The degradation law of flame retardant performance can be mastered through the changes in these indicators.
2. Flame Retardant Component AnalysisAnalytical techniques such as X-ray fluorescence spectroscopy (XRF) and Fourier transform infrared spectroscopy (FT-IR) are used to detect the content and chemical structure changes of flame retardants in fireproof adhesives. Flame retardants play a key role in the flame retardancy of fireproof adhesives. During the aging process, flame retardants may undergo migration, decomposition, and other phenomena, leading to a decline in flame retardant performance. By analyzing the changes in flame retardant components, the internal causes of flame retardant performance degradation can be deeply understood. For example, XRF can detect the content changes of metal elements in flame retardants, and FT-IR can analyze the structural changes of flame retardant molecules.

Accelerated Aging Test Methods for Predicting Long-Term Safety of Fireproof Adhesive

(Ⅰ) Thermal Aging Test

Fireproof adhesive specimens are placed in a high-temperature environmental chamber for aging at a temperature higher than the actual service temperature. The general temperature range is between 60-150°C, and a suitable temperature is selected according to the heat resistance of the fireproof adhesive. By controlling different aging times (such as 24h, 48h, 72h, etc.), the aging of fireproof adhesives under the influence of temperature during long-term use is simulated. Specimens are regularly taken out for mechanical property testing and flame retardant performance testing to establish a relationship curve between performance degradation and aging time, and then predict their service life and flame retardant performance degradation law under actual service temperatures. For example, in a high-temperature environment, the molecular chains of fireproof adhesives break faster, and the mechanical and flame retardant properties decline more rapidly. The performance change trend can be quickly obtained through thermal aging tests.

(Ⅱ) Hygrothermal Aging Test

Fireproof adhesive specimens are placed in a high-temperature and high-humidity environmental chamber, with common temperature and humidity conditions being 70°C and 95% relative humidity. In this environment, water accelerates the penetration into the interior of the fireproof adhesive and reacts with the chemical components in the adhesive, while high temperature accelerates the degradation of molecular chains, simulating the aging process of fireproof adhesives in humid environments. After hygrothermal aging treatment for different times, various performance tests are carried out on the specimens to analyze the impact of hygrothermal environment on the service life and flame retardant performance of fireproof adhesives. For example, in a hygrothermal environment, the flame retardants in fireproof adhesives may undergo hydrolysis, leading to a reduction in flame retardant performance.

(Ⅲ) Ultraviolet (UV) Aging Test

A UV aging test chamber is used to simulate the aging effect of ultraviolet rays in sunlight on fireproof adhesives through UV irradiation. Ultraviolet rays cause photooxidation reactions in polymer materials of fireproof adhesives, leading to molecular chain breakage, discoloration, and other phenomena. During the test, parameters such as UV intensity, irradiation time, and temperature can be controlled. The performance of specimens after UV aging is regularly detected to study the influence law of UV on the service life and flame retardant performance of fireproof adhesives, so as to predict their safety in outdoor service environments.

(Ⅳ) Reliability Verification of Accelerated Aging Tests

To ensure that the results of accelerated aging tests can accurately predict the long-term safety of fireproof adhesives, the reliability of the test methods needs to be verified. A common method is to compare the results of accelerated aging tests with those of natural aging tests. Fireproof adhesive samples in actual service environments are selected for long-term natural aging observation and performance testing, while corresponding accelerated aging tests are carried out in the laboratory. By comparing the trends and degrees of performance degradation of fireproof adhesives under the two aging methods, the accuracy and reliability of the accelerated aging test methods are evaluated. If the results of accelerated aging tests can reasonably reflect the laws of natural aging, it indicates that the method has high reliability and can be used to predict the long-term service safety of fireproof adhesives.

Conclusion

Accurately detecting the service life and flame retardant performance degradation law of fireproof adhesives, and predicting their long-term safety through reliable accelerated aging tests, are key to ensuring the application safety of fireproof adhesives. Detection methods such as mechanical property testing, microstructural analysis, thermal analysis techniques, and combustion performance testing can comprehensively understand the performance changes of fireproof adhesives. Accelerated aging test methods such as thermal aging, hygrothermal aging, and UV aging provide effective means for quickly predicting the long-term performance of fireproof adhesives in different environments. The reliability verification of accelerated aging test methods further improves the accuracy of prediction results. In the future, with the continuous development and improvement of detection technologies and aging test methods, more powerful technical support will be provided for the quality control and safe application of fireproof adhesive products. In practical applications, multiple detection and test methods should be comprehensively used to ensure that fireproof adhesives play a good fireproof and bonding role throughout their service life and protect people’s lives and property safety.

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