A process is disclosed to recycle and/or formulate expandable plastic materials using a system (1) comprising: an extruder unit (10), a mixer-heat exchanger unit (20), said process comprising the steps of: melting in the extruder unit (10), cooling in the mixer-heat exchanger unit (20), and controlling the melt pressure by means of a melt pump unit (50), followed by granulation, extrusion, or injection molding, wherein a first expansion agent (81) is not degassed during a melt processing in the system (1) such that it is substantially contained in the granulated expandable plastic material (130) or used to form either the extruded, formed and expanded plastic material (140) or the molded expanded plastic article (150). The present invention also relates to a granulated expandable plastic material (130), an extruded, formed and expanded plastic material (140), and a molded expanded plastic article (150) obtainable by said process.