A) Oxygen: Oxygen undergoes free radical chain reaction with rubber molecules in the rubber, and molecular chains are broken or excessively cross-linked, causing changes in rubber properties. Oxidation is one of the important reasons for rubber aging.

B) Ozone: The chemical activity of ozone is much higher than that of oxygen, and it is more destructive. It also breaks the molecular chain, but the effect of ozone on rubber varies with the deformation of the rubber. When used as deformed rubber (mainly unsaturated rubber), cracks appearing in the direction of stress, so-called "ozone cracking"; when acting on deformed rubber, only an oxide film is formed on the surface without cracking.

C) Heat: Increasing the temperature can cause thermal cracking or thermal crosslinking of the rubber. But the basic effect of heat is still activation. Increasing the rate of oxygen diffusion and activating the oxidation reaction, thereby accelerating the rate of rubber oxidation reaction. This is a common aging phenomenon-thermal oxygen aging.

D) Light: The shorter the light wave, the greater the energy. What destroys rubber is ultraviolet energy with higher energy. In addition to ultraviolet rays, which can directly cause the breaking and cross-linking of rubber molecular chains, rubber absorbs light energy to generate free radicals, triggering and accelerating the oxidation chain reaction process. Outside light plays a heating role. Another feature of light effect (different from heat effect) is that it mainly grows on the surface of oak. For samples with a high gel content, reticular cracks will appear on both sides, which is called "light outer layer cracking".