M. FOX 



fraction of the total number of radicals produced. This eliminates in this 

 case the possibility of protection by reaction with primary radicals. Reaction 

 with peroxidized polymer is assumed from the following observations : 



{a) Completely protected polymer shows a typical peroxide post effect 

 {see Table I), (b) Such apparently non-degraded polymer is no longer com- 

 pletely insoluble in polar solvents such as alcohol which completely precipi- 

 tate untreated polymer, (c) A solution of polymer was irradiated by gamma 



Table II. Various methods for producing the post-effect 



* Solution is 2 per cent polymer and irradiation refers to a dose of 35,000 r. 



rays in the presence of /^-bromophenol, dialysed and the polymer obtained 

 after solvent evaporation was irradiated in the pile. Radioactive **-Br w^as 

 detected of an activity 16 times that of a control sample subjected to similar 

 treatment except for the gamma irradiation. This reaction probably occurs 

 at the same stage as that postulated by Bolland^ for the reaction of phenols 

 with auto-oxidation chains. 



The action of the second type of protective agents is less clear. It may be 

 remarked that the action of the two types of protective agents is very similar 

 to their antioxidant action in the aging of rubber. The peroxides formed in 

 the presence of amines are thermally unstable ; however, Type 2 protective 

 agents can react with the peroxides formed on the rubber to render them 

 'harmless'^. 



REFERENCES 



1 Alexander, P. and Fox, M. J. Chim. Phys. 1953, 50 415. 



2 Bawn, C. E. H. and Williamson, J. B. Trans. Faraday Soc. 1 95 1 , 47 72 1 , 735. 



3 BoLLAND, J. L. and Ten Have, P. Trans. Faraday Soc. 1947, 43 201 



* Chapiro, a. Durup, J., Fox, M. and Magat, M. International Symposium on 

 Macromolecuar Chemistry, Milan. Sept. 1954. 



5 BoLLAND, J. L. and Ten Hav^, P. Faraday Soc. Discussion, 1947, No. 2,252. 



6 Le Bras, J. C.R. Acad. Sci. 1943, 217 297. 



Le Bras, J. and Le Foll, J. C.R. Acad. Sci, 1950, 231 145. 

 Le Foll, J. Rev. Gen. Caoutchouc, 1952, 29 114. 



63 



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