Thermally expandable composition, comprising a) at least one chemical blowing agent, b) at least one thermoplastic material, c) optionally at least one stabilizer S, wherein the at least one chemical blowing agent comprises at least one carbamate CA according to formula, wherein R 1 and R 2 independently represent linear or branched monovalent hydrocarbon radicals having 1 to 10 carbon atoms, preferably 1 to 5 carbon atoms, which optionally contain one or more heteroatoms, and/or C-C multiple bonds, and/or cycloaliphatic, and/or aromatic moieties, or together represent a divalent hydrocarbon radical having 4 to 10 carbon atoms, preferably 4 to 6 carbon atoms; R 3 represents a linear or branched monovalent hydrocarbon radical having 1 to 20 carbon atoms, preferably 1 to 10 carbon atoms, and optionally contains one or more heteroatoms, in particular one or more optionally substituted tertiary alkyl carbamates, and/or C-C multiple bonds, and/or cycloaliphatic, and/or aromatic moieties; R 4 represents a hydrogen radical or a linear or branched monovalent hydrocarbon radical having 1 to 10 carbon atoms, preferably 1 to 5 carbon atoms, which optionally contain one or more heteroatoms, and/or C-C multiple bonds, and/or cycloaliphatic, and/or aromatic moieties, or together with A represents an (n+1)-valent hydrocarbon radical having 4 to 40 carbon atoms, preferably 4 to 20 carbon atoms, which optionally contains one or more heteroatoms, and/or cycloaliphatic moieties; A represents a linear or branched n-valent hydrocarbon radical having 1 to 20 carbon atoms, which optionally contains one or more heteroatoms, in particular in the form of ether oxygen or amine nitrogen, and optionally one or more C-C multiple bonds, and/or cycloaliphatic, and/or aromatic moieties, or together with R 4 represents an (n+1)-valent hydrocarbon radical having 4 to 40 carbon atoms, preferably 4 to 20 carbon atoms, which optionally contains one or more heteroatoms, and/or cycloaliphatic moieties; index n stands for a value of 1 or 2 or 3 or 4, preferably 2 or 3. a) at least one chemical blowing agent, b) at least one thermoplastic material, c) optionally at least one stabilizer S, R 1 and R 2 independently represent linear or branched monovalent hydrocarbon radicals having 1 to 10 carbon atoms, preferably 1 to 5 carbon atoms, which optionally contain one or more heteroatoms, and/or C-C multiple bonds, and/or cycloaliphatic, and/or aromatic moieties, or together represent a divalent hydrocarbon radical having 4 to 10 carbon atoms, preferably 4 to 6 carbon atoms; R 3 represents a linear or branched monovalent hydrocarbon radical having 1 to 20 carbon atoms, preferably 1 to 10 carbon atoms, and optionally contains one or more heteroatoms, in particular one or more optionally substituted tertiary alkyl carbamates, and/or C-C multiple bonds, and/or cycloaliphatic, and/or aromatic moieties; R 4 represents a hydrogen radical or a linear or branched monovalent hydrocarbon radical having 1 to 10 carbon atoms, preferably 1 to 5 carbon atoms, which optionally contain one or more heteroatoms, and/or C-C multiple bonds, and/or cycloaliphatic, and/or aromatic moieties, or together with A represents an (n+1)-valent hydrocarbon radical having 4 to 40 carbon atoms, preferably 4 to 20 carbon atoms, which optionally contains one or more heteroatoms, and/or cycloaliphatic moieties; A represents a linear or branched n-valent hydrocarbon radical having 1 to 20 carbon atoms, which optionally contains one or more heteroatoms, in particular in the form of ether oxygen or amine nitrogen, and optionally one or more C-C multiple bonds, and/or cycloaliphatic, and/or aromatic moieties, or together with R 4 represents an (n+1)-valent hydrocarbon radical having 4 to 40 carbon atoms, preferably 4 to 20 carbon atoms, which optionally contains one or more heteroatoms, and/or cycloaliphatic moieties; index n stands for a value of 1 or 2 or 3 or 4, preferably 2 or 3.