EFFECT OF DEFORMATION ON AGING OF RUBBERS
|Date Published||September 12, 2006|
Deformation is found to accelerate oxidative crosslinking of rubbers irrespective of the type of deformation, dynamic or static. The extent of acceleration increases with increasing strain in both types. At the same strain, however, it is strikingly larger under dynamic condition than under static condition. The acceleration under dynamic deformation arises mainly from mechanochemical oxidative reaction cycle where radical species are continuously supplied by bond rupture to maintain the oxidative chain cycle. The activation energy of the oxidative crosslinking under dynamic deformation decreases with increasing strain toward the level of the unit reactions of the oxidative reaction cycle. On the other hand, the acceleration under static deformation mainly arises from increased area of exposure to the oxidative atmosphere, and the extent of acceleration is slight in this case. In static deformation, radical species are also supplied initially but not sufficient to maintain the chain cycle and decay soon so that mechanochemical acceleration is merely expended to compensate for the loss in network chains upon deformation.