In the field of materials science, as a widely used polymer material, the aging problem of silicone rubber has always attracted much attention. In - depth understanding of the aging mechanisms of silicone rubber and the construction of accurate life prediction models are of crucial significance for improving the reliability of silicone rubber products and extending their service life.

The aging of silicone rubber is mainly affected by various factors such as heat, oxygen, ultraviolet light, and mechanical stress. During the thermal aging process, high temperatures cause the molecular chains of silicone rubber to break and rearrange. Although the silicon - oxygen bond (Si - O) has a relatively high bond energy, under continuous high temperatures, some bonds will break, triggering the degradation of molecular chains, resulting in a decrease in the molecular weight of silicone rubber and the deterioration of its mechanical properties. At the same time, cross - linking reactions may occur between molecular chains, and excessive cross - linking will make the material hard and brittle. Thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) are often used to study the thermal aging process. By monitoring mass changes and heat flow changes, parameters such as thermal decomposition temperature and thermal stability are analyzed to reveal the thermal aging mechanism.
Oxygen aging is an important cause of silicone rubber aging. Oxygen can react with silicone rubber molecules to form peroxide intermediates. These intermediates are unstable and will further decompose to generate free radicals, triggering a chain reaction and accelerating the scission and cross - linking of molecular chains. In an aerobic environment, the aging rate of silicone rubber increases significantly. Fourier - transform infrared spectroscopy (FTIR) can be used to detect the characteristic peaks of oxidation products, track the progress of the oxidation reaction, and clarify the impact of oxygen aging on the molecular structure.
Ultraviolet (UV) irradiation is also a key factor in the aging of silicone rubber. UV light has high energy and can directly break the molecular chains of silicone rubber. At the same time, it can excite oxygen molecules to generate reactive oxygen species, such as singlet oxygen and hydroxyl radicals, exacerbating the oxidation reaction. Silicone rubber products used outdoors, such as building sealants and automotive weatherstrips, are exposed to UV light for a long time, and aging phenomena such as discoloration and cracking are likely to occur on their surfaces. Through artificial accelerated aging tests, simulating the UV environment and combining with scanning electron microscopy (SEM) to observe the changes in the surface microstructure, the UV aging mechanism can be studied in depth.
Under the action of mechanical stress, micro - cracks will be generated inside the silicone rubber. As the number of stress cycles increases, the cracks gradually expand, eventually leading to material failure. Dynamic mechanical analysis (DMA) can measure parameters such as storage modulus and loss modulus of silicone rubber under alternating stress, evaluate the impact of mechanical stress on material properties, and explore the fatigue aging mechanism.
Based on the above research on aging mechanisms, researchers have constructed a variety of life prediction models. Empirical models establish empirical relationships between aging properties and factors such as time and temperature through fitting a large amount of experimental data. For example, the Arrhenius equation is used to describe the relationship between the thermal aging rate and temperature. Physical models start from the molecular level, consider the physical and chemical changes during the aging process, such as molecular chain scission and cross - linking, and establish mathematical models to predict the service life. In recent years, artificial intelligence models, such as neural network models, with their powerful data processing and learning capabilities, can comprehensively consider various aging factors and predict the life of silicone rubber more accurately. The development of these life prediction models provides a powerful tool for the rational application and life assessment of silicone rubber materials.


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