Abstract: Provided are a curable composition comparable to a curing rate by conventional sulfur while maintaining performance required as a cured product even when a crosslinking agent is replaced with a peroxide, and a sealant containing a cured product of the curable composition. A curable composition containing a conjugated diene-based polymer (A) and a crosslinking agent (B), in which the conjugated diene-based polymer (A) has 100 moles or more of double bonds in a side chain per mole of the polymer.

Abstract: The present invention provides a modified liquid diene rubber that is capable of giving a crosslinked product with excellent adhesion evaluated in terms of shear bond strength, a rubber composition including the modified liquid diene rubber, and a sealing material obtained from the rubber composition. A modified liquid diene rubber (A) has a functional group (a) derived from an acid anhydride, and contains butadiene units in an amount of 50 mass % or more based on the total monomer units, and the polystyrene-equivalent weight average molecular weight (Mw) measured by gel permeation chromatography (GPC) is in the range of 5,000 to 50,000.