Processing Fiber-Reinforced Polymers: Specific Wear Phenomena Caused by Filler Materials

Fiber-reinforced polymers allow for the implementation of
plastic materials in structural components. However,
increasing incorporation of fibers up to 50 wt% causes
accelerated component wear in injection molding
machines. In particular, the barrel and screw in the compression
zone suffer from increased wear. The abrasive
fibers of the compacted polymer pellets in the solid bed
protrude from the surfaces of the resin having an abrasive,
brush-like behavior. A modified pin-on-disk testing system
with specially designed polymer pins was used to emulate
the described tribological system in laboratory scale.
Through varying contact pressure, temperature, and surface
modifications of the counterparts (blank or coated
powder-metallurgical steel), abrasive wear as observed in
industrial-sized extruder screws could be successfully simulated
on a laboratory-scale testing system. Detailed investigations
of the pins and disks highlighted that the glass fibers
plow and cut the surface leading to abrasion as observed in
the real field application. Temperature has been proven to be
the most decisive driving force. Surface modifications such
as protective physical vapor-deposited CrN coatings are
effective against abrasive wear, clearly outperforming
untreated steels. The presented pin-on-disk-test setup will
improve screening of materials for extruders, thus enhancing
the durability of injection molding machines.