A composition for a thermoplastic composite material, said thermoplastic composite material comprising reinforcing fibers or a fibrous reinforcement, and a thermoplastic matrix which impregnates said reinforcing fibers or said fibrous reinforcement,
- said composition comprises:
- reinforcing fibers or a fibrous reinforcement;
- and
- a reactive composition comprising one or more reactive polyamide prepolymers, said composition being a composition which is a precursor of a polyamide polymer of said thermoplastic matrix,
- wherein said one or more reactive polyamide prepolymers comprise different amide units A and B and, optionally, amide units C and D, selected as follows:
- A:
- is a major amide unit present at a molar content ranging from 55% to 95%, chosen from x.T units, where x is a C9 to C18, linear aliphatic diamine, and where T is terephthalic acid,
- B:
- is an amide unit different than A, said unit B being present at a molar content ranging from 5% to 45%, according to the Tm of the polyamide based on unit A and said amide unit B being chosen from x′.T units, where x′ is chosen from:
- B1) a branched aliphatic diamine bearing a single methyl or ethyl branching and having a main chain length which is different by at least two carbon atoms compared with the main chain length of the diamine x of said associated unit A,
- B2) m-xylylenediamine (MXD) or
- B3) a C4 to C18 linear aliphatic diamine when, in the unit A, said diamine x is a C11 to C18 linear aliphatic diamine and x′ is a C9 to C18 diamine when, in the unit A, said diamine x is a C9 or C10 diamine,
- C:
- optional amide unit different than A and than B, chosen from amide units based on a cycloaliphatic and/or aromatic structure or based on x′T as defined above for B but with x′ being different than x′ for the unit B, and
- D:
- optional amide unit different than A, than B and than C when C is present, and chosen from the aliphatic amide units derived from:
- amino acids or lactams which are C6 to C12, r mixtures thereof, the reaction of a C6 to C18 linear aliphatic diacid and of a C6 to C18 linear aliphatic diamine, or mixtures thereof,
- and under the condition that the sum of the molar contents of A+B+C+D is equal to 100%,
- wherein one or more reactive polyamide prepolymers is a precursor of a semi-crystalline polyamide polymer with a glass transition temperature Tg of at least 90° C. and with a melting temperature Tm below or equal to 280° C.,
- and
- wherein said reactive composition further comprises:
- a1) at least one reactive polyamide prepolymer of said thermoplastic composite material, bearing n end reactive functions X, chosen from:
- —NH2, —CO2H and —OH, with n being 2;
- and
- a2) at least one chain extender Y-A′-Y, with A′ being a hydrocarbon-based diradical of nonpolymeric structure, bearing 2 identical end reactive functions Y, which are reactive, by polyaddition, with at least one function X of said reactive polyamide prepolymer a1), a2) having a molecular weight of less than 500, wherein Y is selected from the group consisting of maleimide, optionally blocked isocyanate, oxazinone and oxazolinone.