A masterbatch for use in a process of preparing a composite material may contain a blend of a first amorphous polymer with carbon nanotubes. At least 5% by weight of carbon nanotubes may be present in the masterbatch, based on a total weight of the masterbatch. The masterbatch may exhibit a high load melt flow index HLMI1 of less than 40 g/10 min determined at 200° C. under a load of 21.6 kg according to ISO1133. The first amorphous polymer may have a melt flow index MFI1 of at least 10 g/10 min determined at 200° C. under a load of 5 kg according to ISO1133H.