NOVELTY - Producing an expandable pelletized polymeric material, comprises: (a) providing a polymer component (P1); (b) heating (P1) to form a polymer melt; (c) introducing from 1-5 wt.% of a blowing agent component (T) into the polymer melt to form a foamable melt; (d) homogenizing the mixture; (e) optionally adding additives to (P1); (f) extruding the blowing agent-containing polymer melt through a die plate; and (g) pelletizing the blowing agent-containing melt in a liquid-filled chamber under a pressure of 1.5-15 bar to form a pelletized material.    USE - The process is useful for producing expandable pelletized polymeric materials, which are useful for producing moldings, where the moldings are useful for producing a molded composite body used for an insulation material or body for technical applications or the building sector or as structural foam element for lightweight and composite applications (all claimed) in building construction industry, wind power plants, in automotive industry, boat and/or ship building, furniture making and the exposition industry.    ADVANTAGE - The process: reduces residence time and thermal stress of the material by adding the blowing agent in the extruder during its production and thus avoids the decomposition of the material; and produces the expandable pelletized polymeric materials with improved solvent resistance, heat resistance, mechanical stiffness and blowing agent holding capacity and low water inhibition properties.    DETAILED DESCRIPTION - Producing an expandable pelletized polymeric material comprises: (a) providing a polymer component (P1) comprising (PS) 90-100 wt.% of a styrene polymer component having a glass transition temperature of greater than or equal to 130 degrees C, and (PT) 0-10 wt.% of one or more thermoplastic polymers comprising aromatic polyethers, polyolefins, polyacrylates, polycarbonates, polyesters, polyamides, polyether sulfones, polyether ketones or polyether sulfides; (b) heating (P1) to form a polymer melt; (c) introducing 1-5 wt.% of a blowing agent component (T) into the polymer melt to form a foamable melt; (d) homogenizing the mixture; (e) optionally adding additives to (P1) in one or more steps; (f) extruding the blowing agent-containing polymer melt through a die plate; and (g) pelletizing the blowing agent-containing melt in a liquid-filled chamber under a pressure of 1.5-15 bar to form a pelletized material, where (PS) is formed from (PS1) 30-100 wt.% of one or more styrene polymers comprising (PS11) 60-85 wt.% of polymerized styrene and/or (PS12) alpha -methylstyrene and (PS13) 15-40 wt.% of one or more polymerized monomer comprising maleic anhydride and maleimides, and (PS2) 0-70 wt.% of one or more styrene polymers other than (PS1), comprising (PS21) 60-82 wt.% of (PS11) and/or (PS12), and (PS22) 18-40 wt.% of polymerized acrylonitrile. INDEPENDENT CLAIMS are included for:    (1) the expandable pelletized polymeric material by the process, where the pellets contains greater than or equal to 10 cavities having a size of 1-200 mu m per mm3; and    (2) a molding obtainable from the expandable pelletized material characterized by a density of 15-300 g/l and a maximum dimensional change of not more than 3% on being subjected to a thermal stress of at least 130 degrees C.