VULCANISATION PHENOMENA

The second phenomenon due to carbon black on a proposed scheme based on the vulcanisation process shown in Figure 9.12. During the vulcanisation process, the reactions (1) and (2), and (3) and (4) form polysulfidic Ale and Bit, respectively. Considering the fact that Ale polysulfide reduces its sulfur rank to monosulfide and reaction (3) and (4) is the predominant process in the later stage of cure, the system may favour reaction (3) and (4) rather than (1) and (2) in the whole reaction scheme. BtSH is formed from the... 

Even before the discovery of vulcanisation by Goodyear [1], the effects on rubber of heat, light, acids and alkalies were studied. Testing became necessary when early investigators faced problems with rubber and its vulcanisates. Possibly the earliest chemical resistance test on rubber was undertaken by Goodyear when he treated rubber with nitric acid and this yielded a hardened mass [2, 3]. He mistakenly called this phenomenon vulcanisation, before he accidentally discovered vulcanisation with sulfur at a later point. 

The factors inhibiting macro-flow in vulcanised rubber are the chemical cross links due to vulcanisation (and probably also molecular entanglements), considerably assisted by the phenomenon of crystallisation. In unvulcanised raw rubber macro-flow may occur to a certain extend. In cellulose crystalline junction points of a high degree of stability are responsible for the exclusion of macro-flow. In rubber the chains are very flexible and consist of a large number of statistical chain sections in cellulose the chains are stiffer and consist of a small number of chain elements. In the former case the intermolecular forces are weak, in the latter case they are strong. 

The phenomenon of reversion which occurs in a NR compound when vulcanised using a conventional cure (CV) system is well known. Reversion leads to the... 

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