In-situ composites based on self-reinforcing blends of engineering thermoplastics and
thermotropic liquid crystalline polymers (TLCPs) are recently developed, innovative
polymeric materials, which have been reported to exhibit outstanding property profiles.
These profiles include superior mechanical properties, excellent thermal and dimensional
stabilities at high temperatures, and improved melt processabilities. Such characteristics
make in-situ composites very attractive as performance polymer-based materials for
tribological applications. To date, a thorough investigation of the tribology of in-situ
composites has not yet been undertaken and, thus, the potential of these composites as
performance tribomaterials has not been effectively assessed. The present research
addresses this issue. An investigation is carried into the elevated temperature tribology of
in-situ composite systems based on binary blends of Polyetheretherketone (PEEK) and
HX-1000, a commercially available TLCP, as well as on ternary blends of PEEK,
Polyetherimide (PEI) and HX -1000. The specific tribological phenomenon investigated is
unlubricated sliding. Friction and wear measurements are performed at selected
temperatures in the range from 20°C to 250 °C using a pin-on-disk tribometer. Dynamic
mechanical thermal analysis and morphological studies are carried out in conjunction with
the tribological evaluation. The impact of operating temperature on tribological
performance as well as active friction and wear mechanisms are discussed in terms of
thermally activated molecular relaxation processes and the solid state morphology of the
composite systems investigated. Basic knowledge of the way in which the structure,
mechanical properties and tribological behavior of in-situ composites are interrelated is
gained. Results from this research point to the validity of the concept of TLCP in-situ
reinforcement as a means to produce thermoplastic-based performance tribomaterials.
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