Multilayer tubular structure having better resistance to extraction in biofuel and use thereof

The present invention relates to a multilayer tubular structure (MLT) intended for the transport of fluids, in particular of petrol, especially alcohol-containing petrol, comprising, from the outside inwards, at least one barrier layer (1) and at least one inner layer (2) located below the barrier layer,said inner layer (2), or all the layers (2) and the other optional layers located below the barrier layer, containing on average from 0 to 1.5% by weight of plasticizer relative to the total weight of the composition of the layer (2) or to the total weight of all the compositions of the layers (2) and the other optional layers located below the barrier layer, respectively,said inner layer (2) predominantly comprising at least one polyamide of aliphatic type or consisting of more than 75% of aliphatic units, said aliphatic polyamide being chosen from:a polyamide denoted A, having a mean number of carbon atoms per nitrogen atom, denoted CA, of from 4 to 8.5, advantageously from 4 to 7;a polyamide denoted B, having a mean number of carbon atoms per nitrogen atom, denoted CB, of from 7 to 10, advantageously from 7.5 to 9.5;a polyamide denoted C, having a mean number of carbon atoms per nitrogen atom, denoted CC, of from 9 to 18, advantageously from 10 to 18;with the proviso that when said inner layer (2) comprises at least three polyamides, at least one of said polyamides A, B and C is excluded.