There are many factors that cause rubber aging. Research shows that the main factors are oxygen, ozone, trace varicose metals, sunlight, ultraviolet light and mold corrosion. Flexural fatigue mainly increases the contact area of rubber molecules with oxygen, thus accelerating its aging.
P-phenylenediamine
This type of antioxidant can be divided into dialkyl, alkyl/aryl, diaryl p-phenylenediamine class. Among the dialkyl class, 44PD, 77PD, 88PD; among the alkyl/aryl class, IPPD, 6PPD, 8PPD; among the diaryl class, DP-PD, DNPD, etc. are available in the market.
Ketone/amine condensates
ETMDQ (antioxidant AW) has better flex resistance and ozone resistance. P-phenylenediamine antioxidants can delay the occurrence of ozone cracking, while ETMDQ can inhibit the growth of cracking after it is produced (of course, coupled with paraffin wax, the best effect of using all three at the same time).
Diphenylamine derivatives
Among the alkyl substituents of diphenylamine, there are octylated diphenylamine (ODPA), styrylated diphenylamine (SDPA), isopropylphenylated diphenylamine (CDPA), or sulfur yellow cyclized diphenylamine (TDPA). The alkylated diphenylamine (DPA) has good resistance to nibbling and heat, and is particularly suitable for use in CR.
Naphthylamines
Naphthylamine antioxidants are PBN (N-phenyl-2-naphthylamine), PAN (N-phenyl-1-aniline) two, PBN due to environmental problems, has now stopped using, only PAN is still in production, PAN as heat-resistant antioxidants, especially in CR is widely used.