The mechanism of biscitraconimides (BCI) as antireversion agents for sulfur vulcanized diene rubber was investigated choosing squalene as a model substrate. Curing of squalene with sulfur in the presence of accelerator, activator and BCI at 170°C gave BCI bridged adducts. The products were identified by spectroscopic methods as being results of a Diels-Alder reaction of BCI (dienophile) with conjugated polyenes that are formed as a result of reversion. The rate at which the sulfur network degrades is comparable to the rate in which BCI adduct is formed. As a result of this, a nearly constant crosslink density is obtained after optimum cure time (t90). Based on this concept, the advantage of using 1,3-bis-(citraconimidomethyl) benzene (BCI-MX), a representative of the BCI-class, in NR based compounds is examined.

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Rubber Division, American Chemical Society, Inc.
1996
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