Selective sintering of polymer-based composite materials

A powder mixture for use as a building material for manufacturing a three-dimensional object by solidifying the building material layer by layer at positions corresponding to a cross-section of the three-dimensional object in a respective layer by exposure to radiation, wherein the powder mixture comprises:

• a first powder comprising powder particles of a first thermoplastic polymer material and a reinforcement material, wherein the reinforcement material is at least partially embedded in the powder particles of the first powder and/or adhered to a surface of the powder particles of the first powder, the first powder comprising 50-90% of a total volume of the powder mixture;
• and
• a second powder comprising powder particles of a second thermoplastic polymer material which is the same as or different from the first thermoplastic polymer material and excluding the reinforcement material, the second powder comprising 10-50% of the total volume of the powder mixture,
• wherein the reinforcement material is particulate, platelet-like and/or fibrous;
• wherein the reinforcement material is selected from the group consisting of:
• (a) the reinforcement material comprises or consists of fibers, wherein the fibers are selected from the group consisting of carbon fibers, organic fibers, inorganic fibers, and combinations thereof;
• (b) the reinforcement material comprises or consists of nanotubes;
• (c) the reinforcement material comprises or consists of graphite nanoplatelets and/or fullerenes;
• (d) the reinforcement material comprises or consists of platelet-shaped reinforcement materials;
• (e) the reinforcement material comprises or consists of spherical fillers or irregularly shaped low aspect ratio fillers, selected from inorganic and mineral fillers, ceramic particles, aluminium oxide, zirconium oxide, silicon dioxide, zirconium (IV) oxide, titanium (IV) oxide, aluminium titanate, barium titanate, silicon carbide (SiC) and boron carbide (B4C), metals, dye pigments, carbon black, and organic fillers;
• and
• (f) the reinforcement material comprises or consists of flame retardants;
• and wherein the powder mixture has a bulk density of 0.35 to 0.70 g/cm3.