Radiation-induced degradation of butyl rubber vulcanized by three different crosslinking systems

Butyl rubber (IIR) is an isobutylene/isoprene copolymer and is provided with good properties including low permeability to gases, good thermal stability and high resistance to oxygen and ozone action, among others. It is well known that the major effect of ionizing radiations on butyl rubber is chain scission accompanied with a significant reduction in molar mass. This work aimed to study the effects of gamma radiation on the properties of butyl rubbers vulcanized by three different curing systems, such as, the ones based on sulfur, sulfur donor and phenolic resin to identify which curing system is the most stable under irradiation. The butyl rubber vulcanized by three different systems was gamma irradiated with doses of 25 kGy, 50 kGy, 100 kGy, 150 kGy and 200 kGy. Irradiated and non-irradiated samples were characterized by the following techniques: tensile, elongation and hardness. It was observed that doses higher than 150 kGy practically destroy the assessed properties for all butyl compounds, irrespective of the vulcanization system used; however compounds cured with phenolic resin showed a decrease in properties proportional to the dose.

► Butyl rubber (IIR) has a great variety of applications.
► In butyl rubber, initial stages of degradation indicate a random breaking of bonds in the polymer chain.
► IIR vulcanized samples with “sulfur”, “sulfur donors” and “resin” had different sensitivities when irradiated.
► Mechanical properties of compounds vulcanized by the three systems are reduced.
► Above 100 kGy there was a major prejudice in assessed properties for all the three systems.