Abstract: A process is provided for forming plastic into a predetermined shape from a plastic particulate material, and a heat-activated expandable foam plastic filler material, comprising the steps of: (i) providing first and second complementary mould parts; (ii) heating said first and second mould parts at least on their face portions such that the mould parts are at a temperature to make the plastic particulate material molten or sinterable; (iii) contacting the first and second mould parts with plastic particulate material; (iv) contacting the heat-activated expandable foam plastic filler material to the plastic particulate material; (v) melting or sintering at least a portion of the plastic particulate material on each mould part into a moulded skin; (vi) bringing together the complementary face portions of the heated first and second mould parts to form a composite sandwich.