Antidegradants

Substances that protect rubber against oxygen, ozone, heat and fatigue. They are divided into antioxidants (TMQ, MB, SP) and antiozonants (6PPD, IPPD).

Rubber ages through three main effects: oxygen (accelerated by heat), ozone (cracking on surfaces under strain) and dynamic fatigue. Antidegradants protect against these effects; no single substance covers all of them.

Antioxidants (TMQ, MB, diphenylamine derivatives) slow heat and oxygen ageing. Antiozonants (6PPD, IPPD, 77PD) migrate to the surface and react with ozone before the rubber does. Microcrystalline waxes are also added for static ozone protection.

p-Phenylenediamines protect strongly but stain; in light-colored products, benzimidazoles (MB) and phenolic antioxidants (SP) are preferred.

Comparison

Group	Protects against	Color	Examples
p-Phenylenediamines	Ozone, fatigue, heat	Staining	6PPD, IPPD, 77PD
Quinoline	Heat, oxygen	Slightly staining	TMQ
Benzimidazoles	Heat (synergist)	Non-staining	MB, MBZ, MMB
Diphenylamine derivatives	High temperature	Low	KY-405, DDA
Phenolics	Heat, oxygen	Non-staining	SP
Nickel dithiocarbamates	Ozone (CR, CSM)	Green	NDBC