NOVELTY - Preparing a composite material containing nanotubes (10-50 wt.%) comprises: introducing a polymeric composition containing at least one thermoplastic polymer and nanotubes, in a mixer; melting the thermoplastic polymer; and mixing the molten thermoplastic polymer and nanotubes, where the process further comprises adding at least one plasticizer in a mixer, in a ratio of 10-400 wt.% with respect to the nanotubes and plasticizer (at least 50 wt.%) is introduced upstream or in the polymer melting area.    USE - The composite material is useful for: preparing composite product and/or providing electrical, mechanical and thermal property to the polymer matrix; fabricating conductive fibers or mono layer conductive films or multi layer conductive films; and viscosifying and/or thickening a liquid formulation, including an ink composition, varnish, paint, putty, asphalt or concrete product containing at least one thermoplastic polymer solvent (all claimed). The composite product is useful for: manufacturing transport or storage of fluids, such as pipes, tanks, offshore pipe or hoses, e.g. to prevent accumulation of electrostatic charge; and for manufacturing compact or porous electrodes, preferably supercapacitors or fuel cells.    ADVANTAGE - The process is simple and inexpensive to prepare composite materials without significantly degrading the nanotubes or the matrix, and without polluting the equipment. The process: allows controlling the temperature of the polymer matrix and thus ensuring the stability of process by maintaining stable energy consumption; provides composite material, which is easy to granulate without causing breakage of the string.    DETAILED DESCRIPTION - Preparing a composite material containing nanotubes (10-50 wt.%) comprises: introducing a polymeric composition containing at least one thermoplastic polymer and nanotubes, in a mixer; melting the thermoplastic polymer; and mixing the molten thermoplastic polymer and nanotubes, where: the process further comprises adding at least one plasticizer in a mixer, in a ratio of 10-400 wt.% with respect to the nanotubes, the plasticizer (at least 50 wt.%) is introduced upstream or in the polymer melting area; the plasticizer, the thermoplastic polymer and nanotubes are introduced simultaneously or successively in the same feed hopper of mixer; and the polymer is present in the form of a powder/granules from 10:90 to 100:0, preferably in the powder form. INDEPENDENT CLAIMS are included for:    (1) the composite material obtained by the process; and    (2) preparing composite product comprising preparing the composite material and introducing the composite material in a polymer matrix.