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Polyetheretherketone (PEEK) composites exhibit high stiffness, chemical stability, and heat resistance and they are therefore employed in applications under severe operating environments. This work aims to provide insight into the effect of the size, concentration, and type of fillers on the thermal and mechanical properties of PEEK. A total of 32 composites are used to highlight the influence of nature (lamellae, such as boron nitride and graphite and silicon carbide and alumina), size (nano and micrometric), and content (2.5, 5, 7.5, and 10 vol%) of fillers. The melting temperature and lamellar thickness did not change regardless of the nature of the filler. The thermomechanical analysis demonstrates that lamellar fillers form a percolating network and contribute significantly to the enhancement of the storage modulus. The increase in the storage modulus is proportional to the filler content, and it is more pronounced for micro composites. As expected, the percolating network is formed at lower concentrations for lamellar fillers than for spherical ones. The highest conductivity is achieved with graphite at 0.823 W m−1 K−1, which is twice that of PEEK for 10 vol%. Moreover, the use of micrometric fillers results in thermal conductivity enhancement attributed to the higher amount of efficient hot zones for heat transfer. [ABSTRACT FROM AUTHOR]

We report the synthesis and characterization of PEEK‐MAX (Ti3SiC2, Ti3AlC2, and Cr2AlC), and PEEK‐MoAlB composites by hot‐pressing. Detailed microstructure analysis by scanning electron microscopy showed that Ti3SiC2 particles are well dispersed in the PEEK matrix after the addition of 5 vol% Ti3SiC2 but at higher concentration (≥10 vol%), the Ti3SiC2 particles segregated at the phase boundaries and formed interpenetrating micro‐networks. PEEK‐Ti3AlC2 and PEEK‐MoAlB composites also showed similar structuring at the microstructural level. PEEK‐Cr2AlC composites showed a different behavior where Cr2AlC particles were well dispersed in the PEEK matrix. All the three PEEK‐MAX composites have lower hardness than PEEK‐MoAlB composites as MoAlB particulates are appreciably harder than MAX phases but were harder than PEEK. Due to heterogenous nucleation, the addition of MAX phases or MoAlB reduced the crystallization temperature (Tc) by a few oC. The formation of imperfect crystals also resulted in the lowering of melting point (Tm) of these composites. PEEK reinforced with 10 vol% Ti3SiC2, Ti3AlC2 and MoAlB showed plastic failure, and had higher strength than PEEK. Comparatively, PEEK reinforced with 10 vol% Cr2AlC did not show any enhancement. All the PEEK‐MAX and PEEK‐MoAlB composites showed triboactive behavior and enhanced wear resistance. [ABSTRACT FROM AUTHOR]