Block expandable polymeric compositions

An expandable polymeric composition comprising:

• a. from 60% to 88% by weight of a vinyl aromatic polymer and/or vinyl aromatic copolymer, calculated with respect to (a)+(b);
• b. from 12% to 40% by weight of a block copolymer, containing at least one vinyl aromatic polymer and/or vinyl aromatic copolymer and at least one hydrogenated diene polymer, calculated with respect to (a)+(b);
• c. from 3 parts to 10 parts by weight of a blowing agent, calculated on 100 parts of (a)+(b);
• wherein all of the polymer and/or (co)polymer of the composition consists of components a) and b);
• wherein the vinyl aromatic polymer and/or vinyl aromatic copolymer (a) is obtained from a vinyl aromatic monomer of formula (I):
• alone, or from a mixture of said vinyl aromatic monomers of formula (I), or from a mixture containing said vinyl aromatic monomers of formula (I) and copolymerizable vinyl monomers;
• in which R is a hydrogen or a methyl group;
• n is zero or an integer that ranges from 1 to 3;
• Y is selected from a halogen;
• a chloromethyl;
• an alkyl group or an alkoxy group having from 1 to 3 carbon atoms;
• wherein said copolymerizable vinyl monomers are selected from (meth)acrylic acid, maleic anhydride, alkyl esters of (meth)acrylic acid having 1 to 18 carbon atoms, or amides and nitriles of (meth)acrylic acid.