Rubber aging refers to the rubber or rubber products in the processing, storage and use of the process, due to a variety of external factors, and gradually lost the original excellent performance, resulting in the final loss of the use value. The aging process is an irreversible chemical reaction, accompanied by changes in appearance, structure and performance.
- Changes in the process of aging of the rubber
- 1. Appearance change
- Different varieties of rubber, the different use conditions, the changes are also different.
- Softening sticky: thermal oxidation of natural rubber, aging of chloroprene rubber.
- harden and brittle: thermal aging of butadiene rubber, nitrile rubber, styrene butadiene rubber aging.
- Cracking: Unsaturated rubber ozone aging, most of the rubber’s photo-oxygen aging, but the crack shape is not the same.
- Moldy: Rubber bio-organisms are aging.
- In addition, there are spots, cracks, frosting, whitening and so on.
- Performance changes (the most critical changes)
- changes in physical and chemical properties: specific gravity, thermal conductivity, glass transition temperature, melting point, refractive index, solubility, swelling, rheology, molecular weight, molecular weight distribution; heat resistance, cold, breathable, permeable, translucent Variety.
- 2 Changes in physical and mechanical properties: tensile strength, elongation, impact strength, bending strength, shear strength, fatigue strength, elasticity, abrasion resistance are reduced.
- Changes in electrical properties: electrical resistance, dielectric constant, dielectric loss, breakdown voltage and other electrical properties, electrical insulation decreased.
- The appearance of changes, performance changes are due to structural changes.
- Structural change
- Crosslinking between molecules, molecular weight increases; appearance becomes harder and brittle.
- Molecular chain degradation (fracture), molecular weight reduction, the appearance of soft and sticky performance.
- Other changes in the molecular structure: modification of the main chain or side chain, lateral basis of weak bond breakage (occurring in special rubber).
The following article will analyze the reasons for the aging of rubber and rubber aging protection