Crosslinkable compositions comprising 100 parts by weight of compounds of the formula Y-[(CR 1 2) b -SiR a (OR 2) 3-a] x, where Y denotes an x-valent polymer radical bonded via nitrogen, oxygen, sulfur or carbon, R may be identical or different and represents a monovalent, optionally substituted hydrocarbyl radical, R 1 may be identical or different and represents hydrogen atom or a monovalent, optionally substituted hydrocarbyl radical which may be attached to the carbon atom via nitrogen, phosphorus, oxygen, sulfur or carbonyl group, R 2 may be identical or different and represents hydrogen atom or a monovalent, optionally substituted hydrocarbyl radical, x is an integer from 1 to 10, a may be identical or different and is 0, 1 or 2, and b may be identical or different and is an integer from 1 to 10, at least 5 parts by weight of silicone resins comprising units of the formula R 3 c (R 4 O) d R 5 e SiO (4-c-d-e)/2, where R 3 may be identical or different and denotes hydrogen atom, a monovalent, SiC-bonded, optionally substituted aliphatic hydrocarbyl radical or a divalent, optionally substituted, aliphatic hydrocarbyl radical which bridges two units of the formula, R 4 may be identical or different and represents hydrogen atom or a monovalent, optionally substituted hydrocarbyl radical, R 5 may be identical or different and represents a monovalent, SiC-bonded, optionally substituted aromatic hydrocarbyl radical, c is 0, 1, 2 or 3, d is 0, 1, 2 or 3, and e is 0, 1 or 2, with the proviso that the sum of c+d+e is less than or equal to 3 and in at least 40% of the units of the formula the sum c+e is 0 or 1, and at least 10 parts by weight of carbon black. 100 parts by weight of compounds of the formula Y-[(CR 1 2) b -SiR a (OR 2) 3-a] x, where Y denotes an x-valent polymer radical bonded via nitrogen, oxygen, sulfur or carbon, R may be identical or different and represents a monovalent, optionally substituted hydrocarbyl radical, R 1 may be identical or different and represents hydrogen atom or a monovalent, optionally substituted hydrocarbyl radical which may be attached to the carbon atom via nitrogen, phosphorus, oxygen, sulfur or carbonyl group, R 2 may be identical or different and represents hydrogen atom or a monovalent, optionally substituted hydrocarbyl radical, x is an integer from 1 to 10, a may be identical or different and is 0, 1 or 2, and b may be identical or different and is an integer from 1 to 10, Y denotes an x-valent polymer radical bonded via nitrogen, oxygen, sulfur or carbon, R may be identical or different and represents a monovalent, optionally substituted hydrocarbyl radical, R 1 may be identical or different and represents hydrogen atom or a monovalent, optionally substituted hydrocarbyl radical which may be attached to the carbon atom via nitrogen, phosphorus, oxygen, sulfur or carbonyl group, R 2 may be identical or different and represents hydrogen atom or a monovalent, optionally substituted hydrocarbyl radical, x is an integer from 1 to 10, a may be identical or different and is 0, 1 or 2, and b may be identical or different and is an integer from 1 to 10, at least 5 parts by weight of silicone resins comprising units of the formula R 3 c (R 4 O) d R 5 e SiO (4-c-d-e)/2, where R 3 may be identical or different and denotes hydrogen atom, a monovalent, SiC-bonded, optionally substituted aliphatic hydrocarbyl radical or a divalent, optionally substituted, aliphatic hydrocarbyl radical which bridges two units of the formula, R 4 may be identical or different and represents hydrogen atom or a monovalent, optionally substituted hydrocarbyl radical, R 5 may be identical or different and represents a monovalent, SiC-bonded, optionally substituted aromatic hydrocarbyl radical, c is 0, 1, 2 or 3, d is 0, 1, 2 or 3, and e is 0, 1 or 2, with the proviso that the sum of c+d+e is less than or equal to 3 and in at least 40% of the units of the formula the sum c+e is 0 or 1, and R 3 may be identical or different and denotes hydrogen atom, a monovalent, SiC-bonded, optionally substituted aliphatic hydrocarbyl radical or a divalent, optionally substituted, aliphatic hydrocarbyl radical which bridges two units of the formula, R 4 may be identical or different and represents hydrogen atom or a monovalent, optionally substituted hydrocarbyl radical, R 5 may be identical or different and represents a monovalent, SiC-bonded, optionally substituted aromatic hydrocarbyl radical, c is 0, 1, 2 or 3, d is 0, 1, 2 or 3, and e is 0, 1 or 2, with the proviso that the sum of c+d+e is less than or equal to 3 and in at least 40% of the units of the formula the sum c+e is 0 or 1, and at least 10 parts by weight of carbon black.