The method of moulding plastics articles comprises propelling a solid plastics feed material by screw feed means (10) through a melting zone, the screw feed means (10) propelling the resultant molten plastics material to shaping means, shaping the molten plastics material in the shaping means and allowing the material to solidify to retain the shape, and is characterised by varying the composition of the plastics material cyclically before or along the length of the screw feed means (10) so that the molten material (1, 2) emerging from the screw feed means (10) varies in composition with time, whereby at least one part of each moulded article (50) is of different composition from the remainder of the article (50).