Antidegradants in rubber

Plasticiser/oil in rubber is usually determined by solvent extraction (ISO 1407) and FTIR identification [57] TGA can usually provide good quantifications of plasticiser contents. Antidegradants in rubber compounds may be determined by HS-GC-MS for volatile species (e.g. BHT, IPPD), but usually solvent extraction is required, followed by GC-MS, HPLC, UV or DP-MS analysis. Since cross-linked rubbers are insoluble, more complex extraction procedures must be carried out. The determination of antioxidants in rubbers by means of HPLC and TLC has been reviewed [58], The TLC technique for antidegradants in rubbers is described in ASTM D 3156 and ISO 4645.2 (1984). Direct probe EIMS was also used to analyse antioxidants (hindered phenols and aromatic amines) in rubber extracts [59]. ISO 11089 (1997) deals with the determination of /V-phenyl-/9-naphthylamine and poly-2,2,4-trimethyl-1,2-dihydroquinoline (TMDQ) as well as other generic types of antiozonants such as IV-alkyl-AL-phenyl-p-phenylenediamines (e.g. IPPD and 6PPD) and A-aryl-AL-aryl-p-phenylenediamines (e.g. DPPD), by means of HPLC. 

British Standards (1985). BS6630 1985 Method for identification of antidegradants in rubber and rubber products by thin layer chromatography. British Standards Institute, London. 

Used as antidegradants in rubber, foamed polymers, and high-temperature functional fluids, and antioxidants in finished rubber articles. 

ISO 4645 (1984) Procedure for the determination of antidegradants in rubbers and rubbery products by means of TLC. 

METHOD 47 - DETERMINATION OF AMINE ANTIOXIDANTS AND ANTIDEGRADANTS IN RUBBER. GEL PERMEATION, CHROMATOGRAPHY. ... 

This method is capable of determining down to 0.02% of amine antioxidants and antidegradants in rubbers with an accuracy of 5%. 

See also Tire compounding antidegradants in, 21 785—790 antioxidants in, 21 789 butyl and halobutyl rubber in, 21 766 elastomers used in, 21 759—772 ethylene-propylene rubber in, 21 765-766... 

The substances listed in Table 28 correspond to the basic structure of elastomeric closures. The other components in rubber formulations are curing or vulcanizing agents, accelerators, activators, antidegradants, plasticizers, fillers, and pigments. The most common additives used to compound rubber for the pharmaceutical industry are listed in Table 29. The amount of each component may vary from rubber to rubber, and, depending on the component, the amount can reach more than 50% of the total mass of a formulation. While accelerators are used in amounts of around 1%, fillers may make up more than 50% of the formulation mass. 

These were first investigated and used in rubber as accelerators. Their effect in improving the vulcanizing and ageing properties of rubber was utilized for several years. Primary diamines, primary secondary amines and aminophenols are much more active than simple primary amines. Aminophenol and phenolamine salts are effective antidegradents. 

Fortunately, no such conflict of interests arises with diphenylamines 9 and phenylenediamines lla-d. Various DPA were tested and approved as AO not only in rubbers, their traditional application field the physically persistent 9b and 9a have also been approved for stabilization of plastics in contact with nonfatty food [307]. Derivatives of PD are the most versatile nowadays as mbber antidegradants. Oral administration to experimental animals indicated some danger of necrosis of skeletal and/or cardiac muscles [311]. This has been explained by in vivo oxidation of PD lid into quinone imine by muscle mitochondria and establishing an alternative pathway for electron transport in the physiological respiratory chain. 

Antidegradants are added in rubber compounds in order to increase the ability of the vulcanized products to resist the various deteriorative influences like oxygen, ozone, sunlight, etc., to which it may be subjected to during service. 

Plasticisers in rubbers are usually at high concentrations, and although concentrations of antidegradants (antioxidants and antiozonants) are much lower, they are all very critical in food contact rubber products. 

Heavy transition metal ions such as iron, manganese, and copper catalyze oxidation of elastomers. Compounds of manganese or copper such as oleates and stearates are readily soluble in rubber, enabling rapid oxidation of the polymer. /7flra-Phenylenediamine antidegradants are used to hinder the activity of such metal ions. 

Uses antidegradant in natural rubber, styrene-butadiene and chloroprene rubber... 

Uses protection of rubber against oxidation, ozone, flex-cracking, and poisoning by copper and manganese antidegradant in natural rubber, styrene-butadiene, nitrile-butadiene, butadiene, and chloroprene rubber A... 

Gotti [95] described a procedure for the identification of antidegradants in vulcanised rubber mixes in which part of an extract of the sample is acetylated and then analysed by GC and the remainder is subjected to thin-layer chromatography. The results of the two analyses are interpreted separately, then, compared with each other. He discusses the characteristics displayed by a range of commercial antidegradants. The technique is suitable for compounds containing amino- or phenolic-hydroxy groups. 

Amine and Phenolic Antioxidants and Antidegradants, Guanidines and Accelerators in Rubber... 

Soiubiiity. Another desirable property of an antidegradant is its high solubility in rubber, but poor solubility in water and solvents that come in contact with rubber. Poor solubility in the rubber means that only small quantities of antioxidants can be dissolved without producing a bloom, a migration to the surface. As an example, N-isopropy-N -phenyl-p-phenylenediamine (IPPD) has limited use because of its poor solubility in, for example, natural rubber (less than 2.0 phr). On the other hand, phenolic and phosphite antioxidants have high solubility and... 

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