EFFECT OF GAMMA-RADIATION ON THERMAL AGEING OF BUTYL RUBBER COMPOUNDS

Butyl rubber has a comprehensive use in sealing systems, especially in tires inner tubes, due to their low permeability to gases.So, it is required that butyl rubber compounds show a better performance, more and more.Butyl rubber is provided with excellent mechanical properties and oxidation resistance.Besides showing these properties, radiation exposures impart modifications in physical-chemical and morphological properties on butyl rubber materials.When exposed to gamma-radiation, rubbers suffer changes in their mechanical and physical properties, caused by material degradation.The major radiation effect in butyl rubbers is chain-scission; besides, ageing promotes too the same effect with further build-up of free radicals.This work aims to the study of gamma-radiation in physical-chemical properties of butyl rubber subjected to thermal ageing.Doses used herein were: 25 kGy, 50 kGy, 100 kGy, 150 kGy and 200 KGy.Samples were evaluated before and after ageing according to traditional essays, such as: hardness, tensile strength and elongation at break.From accomplished assessments it is possible to affirm that at doses higher than 50 kGy it was observed a sharp decreasing in butyl rubber physical-chemical properties, before and after exposure to ageing.