Poly(arylene ether nitrile ketone) Resin-Modified PA66 Filaments for FFF Printing: Mechanical Reinforcement and Improved Printability

Polyamide 66 (PA66) is a widely used engineering plastic, which is applied in diverse fields due to its high mechanical strength, excellent wear resistance, and outstanding chemical stability. However, in fused filament fabrication (FFF) 3D printing, PA66 suffers from two critical challenges that restrict its printability and applications: low melt viscosity leads to reduced printing precision and difficulties in filament fabrication, while significant crystalline shrinkage during cooling causes warpage. Herein, an amorphous poly(arylene ether nitrile ketone) resin (PPHENKK) with a glass transition temperature of 225 °C (below the melting point of PA66) and a high melt viscosity is synthesized, and polyethyleneimine (PEI) is subsequently incorporated as a compatibilizer. The crystallinity of the PA66/PPHENKK/PEI blend decreased by 27%, and the coefficient of thermal expansion was reduced by 20%, enabling the successful preparation of filaments suitable for FFF 3D printing with high dimensional accuracy and negligible warpage. Furthermore, with the introduction of PPHENKK, the tensile strength reaches 62.6 MPa (an increase of 25.5%), while the elongation at break remains at a relatively high level of 13.1%. Meanwhile, the heat resistance was improved, with the glass transition temperature increased by 11 °C. Overall, the developed PPHENKK/PA66 blend exhibits a balanced combination of mechanical strength, thermal stability, and dimensional accuracy, making it an effective material for advanced FFF 3D printing applications.