A precure castable explosive composition comprising an explosive material, selected from RDX (cyclo-1,2,3-trimethylene-2,4,6-trinitramine), HMX (cyclo-1,3,5,7-tetramethylene-2,4,6,8-tetranitramine), FOX-7 (1,1-diamino-2, 2-dinitroethene), TATND (tetranitro-tetraminodecalin), HNS (hexanitrostilbene), TATB(triaminotrinitrobenzene), NTO (3-nitro-1,2,4-triazol-5-one), HNIW (2,4,6,8,10,12-hexanitrohexaazaisowurtzitane), GUDN (guanyldylurea dinitride), picrite, aromatic nitramines such as tetryl, ethylene dinitramine, nitroglycerine, butane triol trinitrate, pentaerythritol tetranitrate, DNAN (dinitroanisole) or trinitrotoluene, a polymerisable binder, said binder selected from polyurethanes, polyesters, polybutadienes, polyethylenes, polyisobutylenes, PVA (polyvinylacetate), chlorinated rubber, epoxy resins, two-pack polyurethane systems, alkyd/melanine, vinyl resins, alkyds,, butadiene-styrene block copolymers, polyNIMMO (poly(3-nitratomethyl-3-methyloxetane), polyGLYN (poly glycidyl nitrate), GAP(glycidyl azide polymer), and blends, copolymers and/or combinations thereof, and a cross linking reagent which comprises at least two reactive groups each of which is protected by a labile blocking group, wherein the cross linking reagent comprises a diisocyanate, the diisocyanate comprises two blocking groups B, one on each isocyanate reactive groups, blocking group B is selected from B is I. NHR 2 R 3, wherein R 2 and R 3 are alkyl, alkenyl, branched-chain alkyl, C R 12, aryl, phenyl, or together form a heterocycle. R 12 is alkyl, alkenyl, branched chain alkyl aryl, phenyl, or R 2 and R 3 together form a lactam. II. O-N=CR 9 R 10 wherein R 9 and R 10 are independently selected from alkyl, alkenyl, branched chain alkyl, aryl, phenyl, provided that at least one of R 9 or R 10 is a branched chain alkyl or aryl, or phenyl. a polymerisable binder, said binder selected from polyurethanes, polyesters, polybutadienes, polyethylenes, polyisobutylenes, PVA (polyvinylacetate), chlorinated rubber, epoxy resins, two-pack polyurethane systems, alkyd/melanine, vinyl resins, alkyds,, butadiene-styrene block copolymers, polyNIMMO (poly(3-nitratomethyl-3-methyloxetane), polyGLYN (poly glycidyl nitrate), GAP(glycidyl azide polymer), and blends, copolymers and/or combinations thereof, and a cross linking reagent which comprises at least two reactive groups each of which is protected by a labile blocking group, wherein the cross linking reagent comprises a diisocyanate, the diisocyanate comprises two blocking groups B, one on each isocyanate reactive groups, blocking group B is selected from B is I. NHR 2 R 3, wherein R 2 and R 3 are alkyl, alkenyl, branched-chain alkyl, C R 12, aryl, phenyl, or together form a heterocycle. R 12 is alkyl, alkenyl, branched chain alkyl aryl, phenyl, or R 2 and R 3 together form a lactam. II. O-N=CR 9 R 10 wherein R 9 and R 10 are independently selected from alkyl, alkenyl, branched chain alkyl, aryl, phenyl, provided that at least one of R 9 or R 10 is a branched chain alkyl or aryl, or phenyl. I. NHR 2 R 3, wherein R 2 and R 3 are alkyl, alkenyl, branched-chain alkyl, C R 12, aryl, phenyl, or together form a heterocycle. R 12 is alkyl, alkenyl, branched chain alkyl aryl, phenyl, or R 2 and R 3 together form a lactam. II. O-N=CR 9 R 10 wherein R 9 and R 10 are independently selected from alkyl, alkenyl, branched chain alkyl, aryl, phenyl, provided that at least one of R 9 or R 10 is a branched chain alkyl or aryl, or phenyl.