Around direct extrusion, raw ingredients for example polymers, fillers, and additives are generally mixed, reacted, and devolatilized within a high-speed, twin-screw extruder and directly made proper final product, bypassing pelletizing. Though high-speed, twin-screw extruders have been used for quite a while to produce sheet, film, profile, and fibers, only recently five years has right now there been a concerted effort make use of them to perform direct extrusion.

Direct extrusion making use of twin-screw technology was initially mandated, in desperation, because of the need to produce formulations that have been adversely affected by the 2nd heat and shear history inherent while in the single-screw extrusion step. One time the technical viability associated with direct extrusion was demonstrated, it became apparent for the marketplace that substantial reducing spending were also possible using this technology.

Additional benefits add ability to adjust formulations inline to accelerate improvement efforts, and to sustain a proprietary in-house production process. Materials that reap the benefits of direct extrusion include filled olefins, TPE/TPO/TPVs, polyesters, PVB, wood-fiber composites, adhesives, foamed polymers, nylons, as well as degradable polymers.

Corotating twin-screw extruders allow screw rotation approximately 1200 rpm, and command the high-speed, twin-screw marketplace for applications that call for intensive mass transfer. Counter-rotating intermeshing and nonintermeshing twin-screw extruders can also be being used for direct extrusion applications. Typical processes performed inside the twin-screw extruder, regardless from the mode of operation, include reactive processing, devolatilization, alloying, and also compounding particulates into plastics.

High-speed, twin-screw extruders are starve-fed devices in which the output rate is dependant upon the feeder(s), and screw rpm is employed to optimize compounding efficiencies. Feeders maintain consistency on the formulation, introduce ingredients in appropriate order along along the process section, as well as regulate the extent of mixing. For direct extrusion, the feeding and materials handling system for the twin-screw extruder is critical not to lose front-end pressure stability.

Loss-in-weight feeders can even be specified for direct extrusion where the auger speed is modulated up or into maintain a consistent mass flow towards extruder, based on velocity of weight changes inside the hopper situated on a load cell. Twin-screw systems might use up to eight or over feed streams.
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