What kind of appearance changes occur when rubber is aging

Different varieties of rubber, different conditions of use, the changes that occur are also different.
Softening and sticking: Thermal oxidation of natural rubber, aging of chlorohydrin rubber.
Hardening and brittleness: Thermo-oxidative aging of male-butadiene rubber, aging of nitrile rubber and styrene-butadiene rubber.
Cracking: Ozone aging of unsaturated rubber, photo-oxidative aging of most rubbers, but the shape of cracking is different.
Mold: Biological microbial aging of rubber.
In addition: spots, cracks, frosting, chalking and whitening.