TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Method: The supercritical gas, preferably supercritical carbon dioxide is injected into the extrusion head. The supercritical gas, preferably supercritical carbon dioxide is mixed with the impregnating molten polymer in a static mixer. Preferred Components: The neutral gas in the supercritical state is a supercritical neutral gas or its mixture, where the neutral gas in the supercritical state is supercritical carbon dioxide gas, and the mixture of neutral gas in the supercritical state comprises carbon dioxide and a fluorine-containing gas or a mixture of carbon dioxide and nitrogen.    TECHNOLOGY FOCUS - INSTRUMENTATION AND TESTING - Preferred Components: The heating calenders in step (a2) comprise an integrated heating system by an induction coupled to carbonaceous fillers in the presence of thermoplastic polymer or its blend, where each heating calender is associated with a rapid heater. The prepreg material in the form of ribbon has a width and a thickness suitable for removal by a robot in the manufacturing of three-dimensional parts without the need for slitting, where the width is at least 5 mm and up to 100 mm, preferably 5-10 mm.    TECHNOLOGY FOCUS - POLYMERS - Preferred Method: The method further comprises: (a2) shaping the wick or wicks of the parallel impregnated fibrous material, by calendering at least one heating calender, in the form of single unidirectional ribbon or multiple parallel unidirectional ribbons, within a latter case, where the heating calender has multiple calendering grooves, preferably up to 200 calendering grooves, in accordance with the number of the ribbons and with a pressure and/or a spacing between rollers (601) of the calender controlled by a servo control system; and (a3) winding the ribbon or ribbons on at least one coil, where the number of coils is equal to the number of ribbons, and each coil is associated with each ribbon. The step (a1) is completed by covering the single wick or the multiple parallel wicks after impregnation by the polymer melt, by a molten polymer which may be the same or different from the impregnating polymer prior to the calendering step (a2), where the molten polymer is preferably identical to the impregnating polymer, and the covering is performed by crosshead extrusion with respect to the single wick or with respect to the multiple parallel wicks. The calendering step (a2) is performed using many heating calenders. The impregnating step (a1) is performed using an extrusion technique. The impregnation technique is by extrusion crosshead with respect to the single or multiple parallel wicks. Preferred Components: The polymer is a thermoplastic polymer or its blend. The thermoplastic polymer or its blend further comprises: carbonaceous fillers, comprising carbon black or carbon nanofillers, preferably graphenes, carbon nanotubes and/or carbon nanofibrils; and an additive comprising liquid crystal polymer and/or cyclized poly(butylene terephthalate). The polymer or blend of thermoplastic polymers is amorphous polymer whose glass transition temperature is greater than or equal to 80 degrees C, and/or semicrystalline polymers whose melting point is greater than or equal to 150 degrees C. The thermoplastic polymer or its blend is polyaryl ether ketones (preferably polyether ether ketone), polyaryl ether ketone ketone (preferably polyetherketoneketone), polyetherimides, polyaryl aromatic sulfones (preferably polyphenylene sulfones), polyaryl sulfides (preferably polyphenylene sulfides), polyamides, preferably aromatic polyamides optionally modified with urea units (comprising polymethyl methacrylate), or fluoropolymers, preferably polyvinylidene fluoride. The fibrous material comprises continuous fibers comprising carbon fibers (preferred), glass fibers, silicon carbide fibers, basalt fibers, natural fibers (preferably flax or hemp fibers), sisal fibers, silk fibers, cellulose fibers (preferably viscose fibers), thermoplastic fibers (having higher glass transition temperature than the glass transition temperature of thermoplastic polymer or its blend used in step (a1), amorphous thermoplastic fibers having higher melting point than the melting point of thermoplastic polymer or its blend used in step (a1), and/or semi-crystalline thermoplastic fibers. The ratio by volume of the polymer or its blend relative to the fibrous material is: 40-250%, preferably 45-80%; or 0.2-15%, preferably 0.2-5%. EXAMPLE - No suitable example given.