Abstract: A carbon reinforced, partially cross-linked butyl rubber matrix sealant composition as described is particularly suitable for use as a self-healing tire puncture sealant. The sealant composition comprises a high average molecular weight butyl rubber and a low average molecular weight butyl rubber in a ratio of high to low molecular weight butyl rubber of between about 20/80 to 60/40, in admixture with a tackifier present in an amount between about 55 and 70 weight % of the composition. A partially hydrogenated block copolymer may be included in the admixture.