Properties of Starve-Fed Extrusion on a Material Containing a VHMWPE Fraction
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Single-screw extruders are usually operated with the screw fully filled (flood-fed mode)
and not partially filled (starve-fed mode). These modes result in completely different processing
characteristics, and although starve-fed mode has been shown to have significant advantages, such
as improved mixing and melting performance, it is rarely used, and experimental studies are scarce.
Here, we present extensive experimental research into starve-fed extrusion at feeding rates as low
as 25%. We compared various operating parameters (e.g., residence time, pressure build-up, and
melting performance) at various feeding rates and screw speeds. The results show a first insight into
the performance of starve-fed extruders compared to flood-fed extruders. We explored starve-fed
extrusion of a polyethylene material which contains a Very High Molecular Weight Polyethylene
fraction (VHMWPE). VHMWPE offers several advantages in terms of mechanical properties, but
its high viscosity renders common continuous melt processes, such as compression molding, ram
extrusion and sintering, ineffective. This work shows that operating single-screw extruders in
extreme starve-fed mode significantly increases residence time, melt temperature, and improves
melting and that-in combination?this results in significant elongation of VHMWPE particles.