Antidegradants, Staining

N-1,3-Dimethy lbuty -N -phenyl-p-phenylenediamine, antidegradant - staining. 

Acetone-diphenylamine condensation product, antidegradant - staining. 

Butylated hydroxytoluene, (2,6-Di-fert.-butyl-p-cresol), antidegradant - non-staining. 

Products derived from amines, mostly aniline or diphenylamine, are usually called staining antidegradants as they tend to discolour nonblack vulcanisates on exposure to light. 

Two long-standing deficiencies with the PPD antidegradants, lack of persistence and discoloration/staining, have been addressed, respectively, in recent additions to the field 6-QDI, a dehydrogenated PPD, and TAPDT, a trimeric, high MW form of PPD. 

TAPDT [2,4,6-tris-(A(-l,4-dimethylpentyl-p-phenylenediamino)-l,3,5-triazine. Table 15 provides reduced discoloration as a result of its increased molecular size which imparts reduced mobility in the rubber matrix (91). Discoloration results from bloom of ozonation by-products of the antidegradant to the rubber surface. PPD containing compounds will stain adjacent compounds in a composite structure because of migration of the PPD. An example is a black sidewall protected by PPD staining the white sidewall of a tire. TAPDT does not... 

N,N -Dibutylthiourea is a nitrosamine free accelerator, antidegradant, and corrosion inhibitor. Ultra-accelerator for mercaptan-modified CR. It is slightly safer than DETU. It is also used as a secondary accelerator for NR and synthetic rubbers. It disperses easily in rubber. It is non-staining and does not bloom. It is practically odorless. Antioxidant for NR, antiozonant for NR and SR, particularly SBR. 

Mazzeo, R.A., Non-staining, Non-discoloring Antidegradants, Paper E, Uniroyal Chemical Company, Inc., presented at the 143rd Rubber Division, A.C.S. Meeting in Denver, May 18-29, 1993. 

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