Effect of gamma radiation on chlorobutyl rubber vulcanized by three different crosslinking systems

The development of halogenated butyl rubber (chlorobutyl) in the 1950s and 1960s greatly extended the usefulness of butyl. Their properties allowed the development of more durable tubeless tires with the air retaining innerliner, chemically bonded to the body of the tire. Tire innerliners are by far the largest application for halobutyl. When polymers are subjected to high energy radiation, a number of chemical reactions may occur following the initial ionization and excitation events. These reactions lead to changes in the molecular weight of the polymer through scission (S) and crosslinking (X) of the molecules and affect the physical and mechanical properties. In the halobutyl rubbers the chain scission may predominate. This work aims to show effects of gamma radiation in properties of chlorobutyl rubbers vulcanized with sulfur, sulfur donor and phenolic resin. The butyl rubber has been already studied by us previously. The samples were characterized before and after irradiation. Gamma radiation doses used were: 25 kGy, 50 kGy, 100 kGy, 150 kGy and 200 kGy, in order to identify which cure system is the most stable under irradiation. In this study we observed that the properties of all samples were affected irrespective of the vulcanization system.

► Chlorobutyl rubber greatly extended the usefulness of butyl. ► Chlorobutyl rubbers vulcanized by three different crosslinking systems. ► Sulfur, sulfur donor and phenolic resin were gamma irradiated within 25, 50, 100, 150 and 200 kGy doses. ► All three curing systems were affected by irradiation at doses higher than 25 kGy, prejudicing mechanical properties by the shearing in the roll mill processing. ► The properties of all samples were affected irrespective of the vulcanization system.