A method for forming a graphene-reinforced polymer matrix composite is disclosed. The method includes distributing graphite microparticles into a molten thermoplastic polymer phase; and applying a succession of shear strain events to the molten polymer phase so that the molten polymer phase exfoliates the graphite successively with each event until at least 50% of the graphite is exfoliated to form a distribution in the molten polymer phase of single- and multi-layer graphene nanoparticles less than 50 nanometers thick along the c-axis direction.

Embodiments of an extruder comprise an extruder housing having an internal wall and a single screw coaxially disposed within the extruder housing, the single screw comprising a shank, wherein the shank and/or a region of the internal wall proximate the shank comprises helical channels. The extruder further comprises a feed channel downstream of the shank, and a visco-seal comprising the helical channels and the annular gap between the shank and the internal wall, wherein the annular gap is variable across its length.

A method for forming a graphene-reinforced polymer matrix composite is disclosed. The method includes distributing graphite microparticles into a molten thermoplastic polymer phase; and applying a succession of shear strain events to the molten polymer phase so that the molten polymer phase exfoliates the graphite successively with each event until at least 50% of the graphite is exfoliated to form a distribution in the molten polymer phase of single- and multi-layer graphene nanoparticles less than 50 nanometers thick along the c-axis direction.

A method for forming a graphene-reinforced polymer matrix composite is disclosed. The method includes distributing graphite microparticles into a molten thermoplastic polymer phase; and applying a succession of shear strain events to the molten polymer phase so that the molten polymer phase exfoliates the graphite successively with each event until at least 50% of the graphite is exfoliated to form a distribution in the molten polymer phase of single- and multi-layer graphene nanoparticles less than 50 nanometers thick along the c-axis direction.

An extruder screw having a worm shaft and a plurality of screw elements that are releasably plugged or pluggable thereon, wherein each screw element has a defined axial minimum length or a length that corresponds to a multiple of the minimum length. The worm shaft has an external toothing and the screw elements have an internal toothing engaging therewith. The external toothing has, forming individual gear rings extending around the circumference, a plurality of recesses extending around the circumference in an offset manner along its axial length, which are spaced apart from one another by the minimum length, such that the internal toothing of each screw element extends, at both axial ends, into the region of the recess, and the ends of the internal toothing are not engaged with the external toothing.

An extruder screw having a worm shaft and a plurality of screw elements that are releasably plugged or pluggable thereon, wherein each screw element has a defined axial minimum length or a length that corresponds to a multiple of the minimum length. The worm shaft has an external toothing and the screw elements have an internal toothing engaging therewith. The external toothing has, forming individual gear rings extending around the circumference, a plurality of recesses extending around the circumference in an offset manner along its axial length, which are spaced apart from one another by the minimum length, such that the internal toothing of each screw element extends, at both axial ends, into the region of the recess, and the ends of the internal toothing are not engaged with the external toothing.