The invention relates to a thermoplastic structure comprising at least one layer consisting of a composition comprising a copolyamide of formula X/10.T/Y, wherein: X represents either the residues of an aliphatic amino acid comprising between 8 and 18 carbon atoms, or a lactam, or the unit X1.X2 representing the residues resulting from the condensation of an aliphatic diamine comprising between 6 and 18 carbon atoms and a (cyclo)aliphatic diacid comprising between 6 and 18 carbon atoms; 10.T represents the residues resulting from the condensation of a decanediamine and terephthalic acid; and Y represents the residues resulting from the condensation of an aliphatic diamine comprising between 9 and 14 carbon atoms and an aromatic diacid, Y being different from the unit 10.T; the molar proportion of 10.T units in the copolyamide being higher than 0%; the molar proportion of Y units in relation to the group of 10.T and Y units being between 0 and 30%; and the proportion of X units being between 0.4 and 0.8 mole for a mole of semi-aromatic units 10.T and Y.