a process for bonding a semi - crystalline or crystalline thermoplastic polymer to a thermosetting polymer component , the process including selecting compatible semi - crystalline thermoplastic polymer and uncured thermosetting polymer components wherein the curing temperature of the uncured thermosetting polymer components is above the melting temperature of the semi - crystalline thermoplastic polymer . the process includes locating the thermoplastic polymer in contact with the uncured thermosetting polymer component and heating the thermoplastic polymer and uncured thermosetting polymer or thermosetting polymer composite component to the curing temperature of the thermosetting polymer components and the thermoplastic polymer are able to at least partly interpenetrate before the thermosetting polymer cures . the thermoplastic polymer and cured thermosetting polymer component are then cooled such that the thermoplastic polymer is very strongly bonded to the cured thermosetting polymer component .