Characterization of a vulcanizate of the halogenated butyl rubber, MD-551. I. Gum properties

We have found that vulcanizates of MD-551 and butyl rubber at identical crosslink densities have similar properties in low deformation tests at room temperatures. At high extension, the butyl has considerably higher tensile strength which we have associated with crystallization. The MD-551, on the other hand, shows heat stability far superior to that of butyl. It is postulated here that both these differences follow from the nature of the crosslinks in each polymer. The crosslinks in the MD-551 are thought to be both mechanically and chemically more stable than those in butyl. This prevents crystallization on stretching and enhances high temperature stability. Thus far, we have been concerned only with the gum properties of the MD-551. From our previous work, we would expect carbon black to improve the tensile properties of MD-551. Furture work will therefore be concerned with properties of reinforced MD-551. In addition, studies will be made in order to learn more about the crosslinks and how they affect vulcanizate performance.