In the manufacturing steps of rubber seals, due to the overall effect of internal and external elements, the physical properties and properties of rubber gradually change, and the use function is lost, resulting in a small life of the seal. This kind of change is called rubber aging. The surface manifestations of rubber aging are mainly:
1. Soft and sticky: such as thermal oxidation of natural rubber, aging of chlorohydrin rubber.
2. Hardening and brittle: for example, thermal oxidation aging of cis-butadiene rubber, aging of nitrile rubber, and styrene-butadiene rubber.
3. Cracking and fracture: such as ozone aging of unsaturated rubber, photo-oxidative aging of most rubbers,
4. Mildew: such as biological microbial aging of rubber. In addition to the above, discoloration and delamination are also common forms of aging.
The aging of the seal will cause its performance to change. The performance here mainly includes:
Changes in physical and chemical properties of seals: changes in specific gravity, thermal conductivity, glass transition temperature, melting point, refractive index, solubility, swelling, rheology, molecular weight, molecular weight distribution, cold resistance, air permeability, water permeability, light transmission, and other properties.
Changes in physical and mechanical properties of seals: tensile strength, elongation, shear strength, fatigue strength, elasticity, and wear resistance all decrease.
Changes in electrical properties of seals: changes in electrical properties such as insulation resistance, dielectric constant, dielectric loss, breakdown voltage, and electrical insulation decline.
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