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Banerjee, Dasarathi (1938) The mechanism of the vulcanisation of rubber and the structure of the vulcanisate, as shown by a study of the apparent unsaturation of vulcanised rubber under varying conditions. Doctoral thesis, Northern Polytechnic.
An analytical method of determining true iodine indices of vulcansied rubber has been developed. Iodine chloride reacts with a small proportion of combined sulphur in vulcanised rubber. The amount of this halogen-reactive sulphur is approximately 3% in soft rubber, and with ebonite it increases to approximately 5.5%. The types of sulphur linkages in vulcanised rubber have been suggested. Additional evidence to justify the suggested types of sulphur linkage has been obtained from the reaction of iodine chloride on known sulphur compounds.
Unsaturation of vulcanised rubber has been followed by ozone. An organic acidic thio-compound has been isolated from the ozonolysis products of vulcanised rubber. The amount of this compound increases with progressive vulcanisation. Laevulinic aldehyde and volatile fatty acids are obtained in proportions dependent on the sate of vulcanisation of the original rubber. Sulphuric acid is another constituent of the reaction products.
The effect of ozone on stretched rubber is chemical. It attacks part of the combined sulphur in vulcanised rubber producing H₂SO₄. The chain is broken into smaller units still unsaturated and these are capable of forming addition compounds with bromine. The tensional force in stretched rubber as distinct from mere elongation has been shown to be essential in the developing of surface-cracks in ozone. It is demonstrated that great elongation of rubber renders it more resistant to physical break-down in ozone, although the degree of chemical attack is increased.
The addition of sulphur monochloride to rubber, under varying conditions, has been studied. The importance of the tensional force in stretched rubber in attributing a greater reactivity to the rubber has confirmed. Maximum chemical compbination of S₂Cl₂ by stretched vulcanised rubber is 190%. With rubber in solution a maximum of 203% has been attained. The sulphur and chlorine contents are in indefinite ratio. The adlieation of the rubber molecules on stretching has been demonstrated by the fibrous character of the cold-vulcanised products.
The reactions of neoprene are compared with those of rubber under similar conditions.
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