Phenolic curative

Another vulcanizing agent for diene rubbers is m-phenylenebismaleimide. A catalytic free-radical source such as dicumyl peroxide or benzothiazyldisulfide (MBTS) is commonly used to initiate the reaction [61]. Phenolic curatives, benzoquinonedioxime, and m-phenylenebismaleimide are particularly useful where thermal stability is required. 

The accelerated-sulfur vulcanization of these rubbers along with the vulcanization of other rubbers, which are vulcanized by closely related technology, comprises more than 90% of all vulcanization. These rubbers include ethylene-propylene-diene-monomer rubber (EPDM), butyl rubber (HR), halobutyl rubbers, and nitrile rubber (NBR). Nevertheless, we give some consideration to vulcanization by the action of other vulcanization agents such as organic peroxides, phenolic curatives, and quinoid curatives. 

This is another example of what has variously been called a pseudo-Diels-Alder, ene, or no-mechanism reaction (Hoffmann, 1969). It is similar to the reaction written for the attack of rubber molecules by phenolic curatives or the in situ formed nitroso derivative of the quinoid (e.g., benzoquinonedioxime) vulcanization system. It is also closely related to the sulfurization scheme written for accelerated-sulfur vulcanization. Comparisons between accelerated sulfur, phenolic, quinoid, and maleimide vulcanization can then be visualized as follows ... 

Table 7.5 gives selected recipes for vulcanization by phenolic curatives, benzoquinone-dioxime, or m-phenylenebismaleimide. Vulcanizates based on these types of curatives are particularly useful in cases where thermal stability is required. 

TABLE 7.5 Recipes for Vulcanization by Phenolic Curatives, Quinone ... 

VII. Vulcanization by Phenolic Curatives, Benzoquinone Derivatives, or Bismaleimides... 

VII. VULCANIZATION BY PHENOLIC CURATIVES, BENZOQUINONE DERIVATIVES, OR BISMALEIMIDES... 

This is an explanation for the fact that this type of vulcanization is not enabled by double bonds per se, without aUyic hydrogens in the elastomer molecules [4,74]. (It should be pointed out that the phenolic curative can also act by a slightly different mechanism to give crosslinks which contain chromane structural moieties [75], the allylic hydrogens stUl being required.)... 

TABLE V Recipes for Ynlcanization by Phenolic Curatives, Quinone Derivatives, or Maleimides"... 

EPDM Dimethylol-phenolic curative, peroxide/coagents... 

Figure 6.15 The phenolic curative (methylol terminated, para-alkyl substituted, phenol-formaldehyde resin) synthesis...

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