Enhancing the processability of high-performance composite blends for injection molding and extrusion

Polyether ether ketone (PEEK) is a semi-crystalline polymer known for its high mechanical strength, excellent chemical resistance, and thermal stability up to 250 °C. Still, it requires high processing temperatures and exhibits relatively low impact toughness. Moreover, due to its high melt viscosity and thermal sensitivity, it requires several precautions to be suitably processed. These drawbacks are more critical for PEEK-matrix composites, such as carbon fiber-reinforced PEEK (C-PEEK). Conversely, polyetherimide (PEI) is an amorphous thermoplastic with superior ductility, lower melt viscosity, and good dimensional stability. The blending of polymers, PEEK (or C-PEEK) and PEI, is a promising strategy to enhance processability and tune high-performance mechanical and thermal properties for demanding applications. In this paper, two blends made of C-PEEK and PEI, with two different fractions (i.e., 20 and 30 wt%) of PEI, were mixed and analyzed. Results show that the processability by injection molding of the blends is improved in comparison with the C-PEEK, due to the presence of PEI, which, however, reduces (< -26%) the mechanical properties. The processability by extrusion molding of 3D-printing filaments was also successfully tested with filaments having tolerance dimensions and good surface quality.