Filled polymers seem very promising materials for production. Polymers can be filled with a variety of diverse materials, be it polycaprolactam fiber, glass fiber, or steel wire. Compared to their non-filled counterparts, filled composites have a number of advantages. Production of filled polymers can be challenging due to the processing equipment (the rubber mixer, rollers, and extruders) mixing the fiber with the polymer matrix. In their purest form, polymers mostly don’t have the desired properties, which is why special additives (fillers, plasticizers, dyes, stabilizers, etc.) must be added to obtain the desired functional properties. This is why composites account for an ever greater share of polymers.