Jitka Rotschová

Antioxidants and stabilisers—Part XCII: Activity of 2,2′-thiobis(4,6-di-tert-butylphenol) as a hydroperoxide decomposer. A model study

The effect of an antioxidant, 2,2′-thiobis(4,6-di-tert-butylphenol) (I) and of the derived sulphoxide (II) and sulphone (III), on the decomposition of tert-butyl hydroperoxide (IV) at 65, 75, 85 and 100°C was investigated. The results indicate a change in the rate of decomposition of IV with sulphide, I, after consumption of about 2 moles of IV per mole of I and the active role played by II and III in the process. The formation of new compounds in the reaction mixture, which may be connected with an acceleration of the decomposition of IV, was identified by means of TLC. 7

Antioxidants and stabilizers: Part CXII—Influence of 1-phenylamino-4-(sec-alkylamino)-3,6-bis(4-phenylaminophenylimino)-1,4-cyclohexadiene on the vulcanization and ageing of natural rubber☆

Abstract Commercial antidegradants having the structure of N-sec-alkyl-N′-phenyl-1,4-phenylenediamine (I) are contaminated with dark coloured compounds. Quinone imines having the structure of 1-phenylamino-4-(sec-alkylamino)-3,6-bis(4-phenylaminophenylimino)-1,4-cyclohexadiene (III) were isolated from 1,4-phenylenediamines (Ia, b) and their influence on the vulcanization of natural rubber and ageing of vulcanizates was tested. It was found that compound (III) has no harmful effect on ageing characteristics. This finding was confirmed by studies on autoxidized squalene. The processing safety of rubber compounds containing a sulphenamide accelerator is slightly reduced by (III) but the rate of crosslinking, the temperature dependence of the latter and physical properties of the vulcanizate are not influenced. The contamination of commercial (I) with quinone imine (III) has no harmful effect on the properties of the diamine (I). (III) contributes to the discoloration of rubber doped with (I).

Antioxidants and stabilizers: Part C—Decomposition of tert-butylhydroperoxide by polyolefin melt stabilizer 2,2′-Thiobis(4,6-di-tert-butylphenol)

Abstract 2,2′-Thiobis(4,6-di-tert-butylphenol) (I) was used in a model study as a tert-butylhydroperoxide (TBH) decomposer. Independent measurements with the corresponding sulfoxide (II) and sulfone (III) reveal the contribution of both the thermal instability of (II) and the presence of the phenolic moiety in (III) to the integrally observed TBH decomposition efficiency which involves participation of the consecutive transformation products (II) and (III), respectively, at least one of them having peroxidolytic efficiency. Because of the properties of (II), the hydroperoxide decomposing activity of (I) may be exploited explicitly during polyolefin melt stabilization only.

Antioxidants and stabilizers: 93. A model interaction of polyolefine melt stabilizer 2,2 -thiobis(4,6-di-tert. butylphenol with tert. butylhydroperoxide

SummaryThe efficiency of polyolefine melt stabilizer 2, 2′-thiobis-(4,6-di-tert.butylphenol) (I) as a hydroperoxide decomposing antioxidant was studied under model conditions.tert.Butylhydroperoxide was used to simulate the reaction with polypropylene hydroperoxide. The reaction was performed at 85°C in chlorobenzene solution. Decomposition of tert.butylhydroperoxide by I and formation of the sulphoxide II and the sulphone III from sulphide I were followed quantitatively. Formation of small amounts of effective peroxidolytic species from II or III, responsible for acceleration of hydroperoxide decomposition was considered.

Antioxidants and stabilizers : LXXXVII. The chromatographic behaviour of transformation products of an antioxidant, N,N′-diphenyl-1,4-phenylenediamine

Abstract The antidegradant N,N′-diphenyl-1,4-phenylenediamine, its products formed by atmospheric ageing of polymeric materials and some compounds of related structure were analyzed by thin-layer and liquid chromatography. The colour reactions of the individual compounds with sulphuric acid and aqueous ammonia were also determined. The combination of these analytical methods makes possible identification of the individual compounds in complicated mixtures.

Detection of a tris(alpha-methylbenzylphenyl)phosphite antioxidant

Abstract Commercial tris(alpha-methylbenzylphenyl)phosphites consist of a complicated mixture of phosphites formed from technical styrenated phenol and of unreacted styrenated phenols. Detection of the presence of the phosphite moiety in a rubber extract exploits the formation of characteristic spots in TLC or peaks in HPLC and/or absorption bands at 870 cm −1 in IR spectral measurements.