A thermomechanical method was used to study the topological and molecular structure of model rubber compounds. This structure changes because of mastication during compounding. It was found that raw butyl rubber has a diblock structure. The molecular weight distribution of the chains between the junctions of the polymer network, the coefficient of polydispersity, a share of low-temperature and high-temperature blocks, and changes in their glass transition temperatures as a result of the mixing of butyl rubber depend on both the presence of sulfur and the kind of sulfur (polymeric or mineral).