A method of injection molding or extruding a polymer composition having a
predetermined bulk density associated with particles, granules or pellets
of the polymer composition and a predetermined melt density when the
polymer composition is fully melted and compressed. The method of the
invention employs a screw having a volume compression ratio that is
greater than or equal to the ratio of the predetermined melt density to
the predetermined bulk density of the polymer composition and up to 1.25
.times. the ratio of the predetermined melt density to the predetermined
bulk density of the polymer composition.