Elastomers antiozonants

Uses Antioxidant for polyunsaturated elastomers antiozonant for NR, IR, BR, SBR Manuf./Distrib. ChemService http //WWW. chemservice. com] Crompton/Uniroyal... 

Ai,Af-Disubstituted- -phenylenediamines, such as A/-phenyl-Af -(l,3-dimethylbutyl)-/)-phenylenediamine [793-24-8] (10), are used in greater quantities than other classes of antioxidants. These products protect unsaturated elastomers against oxidation as well as ozone degradation (see Antiozonants). 

The process yields a random, completely soluble polymer that shows no evidence of crystallinity of the polyethylene type down to —60°C. The polymer backbone is fully saturated, making it highly resistant to ozone attack even in the absence of antiozonant additives. The fluid resistance and low temperature properties of ethylene—acryUc elastomers are largely a function of the methyl acrylate to ethylene ratio. At higher methyl acrylate levels, the increased polarity augments resistance to hydrocarbon oils. However, the decreased chain mobiUty associated with this change results in less fiexibihty at low temperatures. 

Since this bloom is brittle, it is broken by flexing. Therefore, waxes only protect under static conditions. For serving conditions which involve continuous flexing, /j-phenylenediamines (A, A -alkyl-aryl derivatives) can be added. These chemical antiozonants scavenge the ozone before it reacts with the rubber. A barrier of ozonized products is created which protects both the rubber and antiozonant from further attack. However, p-phenylenediamines are staining compounds. Whenever colour is an important concern, blends of elastomers can be used elastomers loading should be higher than 30 phr to provide sufficient effectiveness. 

The changes in properties observed on aging of different elastomers and their vulcanizates, and of many other polymeric materials, are well known. Antiozonants and antioxidants are employed to limit these changes. However, the most effective antioxidant for one material may be ineffective. 

In order to support and meet this demand, an all-around development has taken place on the material front too, be it an elastomer new-generation nanofiller, surface-modified or plasma-treated filler reinforcing materials like aramid, polyethylene naphthenate (PEN), and carbonfiber nitrosoamine-free vulcanization and vulcanizing agents antioxidants and antiozonents series of post-vulcanization stabUizers environment-friendly process oil, etc. 

FAB has been used to analyse additives in (un) vulcanised elastomer systems [92,94] and FAB matrices have been developed which permit the direct analysis of mixtures of elastomer additives without chromatographic separation. The T-156 triblend vulcanised elastomer additives poly-TMDQ (AO), CTP (retarder), HPPD (antiozonant), and TMTD, OBTS, MBT and A,lV-diisopropyl-2-benzothiazylsulfenamide (accelerators) were studied in three matrix solutions (glycerol, oleic acid, and NPOE) [94]. The thiuram class of accelerators were least successful. Mixture analysis of complex rubber vulcanisates without chromatographic separation was demonstrated. The differentiation of matrix ions from sample ions was enhanced by use of high-resolution acquisition. 

There are two main approaches to avoidance of ozone damage. One is the addition of antiozonants. The more extensively used antiozonants are listed in Table 13-12. These antiozonants have limited solubility in elastomers and tend to bloom to the surface. The antiozonant action is not well understood chemically, but probably involves formation of a protective film. Crack initiation occurs at critical stress, which is strongly... 

Belts -NBRrn [ELASTOMERS,SYNTHETIC-NITRILERUBBER] (Vol8) -o2one protection [ANTIOZONANTS] (Vol 3) -precipitated silica m [SILICA - AMORPHOUS SILICA] (Vol 21)... 

Over half of the remaining market for products used in the processing of rubber is made up of antioxidants, antiozonants and stabilizers, either amino compounds or phenols. Aniline is used to manufacture vulcanization accelerators, antioxidants and antidegradants. Of the latter, several are A-substituted derivatives of p-phenylenediamine and octyl dipheny-lamine. Diphenylamines terminate free-radical reactions by donating the amino hydrogen, and are used to protect a wide range of polymers and elastomers. Many synthetic rubbers incorporate alkylated diphenylamine antioxidants. Other antioxidants include aryl amine resinous products from, e.g. condensation of aniline and acetone in the presence of... 

Santoflex 77PD is used as an antiozonant in natural and synthetic elastomer compounds that can tolerate discoloration (it will discolor compounds and cause severe contact and migration staining). It also protects against catalytic degradation by copper and other heavy metals. 

NqV -bis(l-methylheptyl)-p-phenylene-diamine. C6H4[NHCH(CH3)C6H,3]2. Properties Dark reddish-brown liquid. D approximately 0.90 at (26.6C), wt/gal 7.5 lb. Combustible. Use Antiozonant in polyunsaturated elastomers. 

Involvement of the Ozonized Rubber Moieties in Antiozonant Mechanism. The rubber chain relinking theory (30) is consistent in part with the self-healing film formation theory (37) a reaction between an antiozonant or some of its transformation products and ozonized elastomer is considered. Either scission of ozonized rubber is prevented in this way or severed parts of the rubber chain are recombined (i.e., relinked). A "self-healing" film resistant to ozonation is formed on the rubber surface. Such a film formed by the contribution of nonvolatile and flexible fragments of the rubber matrix should be more persistent than any film suggested in the protective film theory. 

The ozone concentration in the troposphere during the daytime is typically about 1 pphm (parts per hundred million parts of air by volume) [20], Values up to 100 pphm were measured in some photochemical smog areas. The molecular mechanism of the ozone aging of diene based elastomers was studied in detail and is well understood [19,21], Products or intermediates different from those arising in autoxidation or photo-oxidation of polymers were identified ozonides (3), zwitterions (4), diperoxides (5), polyperoxides (6), polymeric ozonides (7) and terminal aldehydes (8). Reactivity of aminic antiozonants (AOZ) with these species accounts for the protection of rubbers against atmospheric 03. AOZ must also possess antioxidant properties, because the free radical processes are concerted with ozonation due to the permanent presence of oxygen. 

The largest volumes of phenjienediamines are used for the production of polymers, primarily polyurethanes, where the diisocyanates of toluenediamines (meta isomer) are used. For the manufacture of polyamides both meta and para isomers are used. Another significant use for -phenylenediamines is as antioxidants and antiozonants for elastomers, plastics, and petroleum products. The /V-alkyl-/V-aryl- -phenylenediamines are by far the most commonly used and represent the bulk of the volume of the iV-substituted -phenylenediamines reported in Table 3. Some iV iV-dialkyl compounds ate also stiU used as antiozonants, but they oxidize more rapidly and lose activity sooner. The iV,iV-diaryl-/)-phenylenediamines ate used primarily as antioxidants, especially where copper and other harmful metals might be present. -Dinaphthalenyl- -phenylenediamine is especially effective in this application. The... 

The unsaturated nature of an elastomer accounts for its unique viscoelastic properties. However, the presence of carbon-carbon double bonds renders elastomers susceptible to attack by oxygen, ozone, and thermal degradation. A comprehensive review of elastomer oxidation and the role of antioxidants and antiozonants is available (Hong, 2004). 

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