Polymer-reactive antioxidant reactions rubbers

Another polymer reactive antioxidant which can be combined with rubber during vulcanization involves the 1,3 addition reaction of nitrones to the double bond in rubbers, reaction 4 (11). 

Reactions of Antioxidants with Preformed Functional Groups. The reactive chlorine in epichlorohydrin polymers is a specific though typical example of this approach (11). A more general reaction is the epoxidation of the double bonds in rubbers and subsequent reaction of the epoxide group with an amine antioxidant (reaction 1)... 

Reactions of Reactive Antioxidants with Polymers by Normal Chemical Procedures. Grafting of vinyl antioxidants e.g., VI, into rubbers has been used to produce modified rubber latices (26). Even simple... 

The above approach of mechanochemically initiated addition of reactive antioxidants on different polymers, such as rubbers and unsaturated thermoplastics such as ABS is illustrated here for thiol-containing antioxidants. For example, using thiol compounds (37) and (38) as the reactive antioxidants, Kharasch-type addition of the thiol function to the polymer double bond takes place during melt processing to give bound antioxidant adduct (see reaction 7) the polymer becomes much more substantive under aggressive environments. 

The proximity of the methyl group to the double bond in natural rubber results in the polymer being more reactive at both the double bond and at the a-methylenic position than polybutadiene, SBR and, particularly, polychlor-oprene. Consequently natural rubber is more subject to oxidation, and as in this case (c.f. polybutadiene and SBR) this leads to chain scission the rubber becomes softer and weaker. As already stated the oxidation reaction is considerably affected by the type of vulcanisation as well as by the use of antioxidants. 

In the case of BR or SBR, the efficiency can be much greater than 1.0, especially if all antioxidant materials are removed. A chain reaction is indicated here. It might be explained by steric considerations. In butadiene-based rubbers, double bonds are quite accessible. Radical addition to double bonds could give highly reactive radicals, which would be likely to add to other polymer double bonds. A chain of additions might be more likely in butadiene rubber than in the presence of hindering methyl groups in isoprene rubbers. 

Chem. Descrip. Triphenyl phosphite CAS 101-02-0 EINECS/ELINCS 202-908-4 Uses Costabilizer for PVC and other polymers such as PP vise, modifier, reactive diluent for a variety of resin systems, esp. epoxies antioxidant for syn. rubbers, butyrates flame retardant for PU foams in transesterification reactions lubricant oil additive chem. intermediate for prod, of other phosphite esters and phosphonates Features Improves adhesion, elec, props., dimensional stability Properties Colorless mobile liq. 10% P Albrite Tributyl Phosphate [Huntsman Surf. Sciences]... 

Reaction of conventional antioxidants with functionalised polymers. Many unsaturated rubbers can be made reactive toward conventional antioxidants by chemical modification. W ys in which this can be... 

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