Generation of nylon copolymer reinforced with carbon nanotubes and thermotropic liquid crystalline polymers for use in fused filament fabrication

Abstract Multiscale thermoplastic composites consisting of nylon copolymer (PAc) reinforced with thermotropic liquid crystalline polymer (TLCP) and carbon nanotubes (CNTs) were generated in the form of strands and then processed via fused filament fabrication (FFF). The tensile modulus and strength of the laid‐up strands were found to be similar to those reported for polymer reinforced with nearly continuous carbon fibers. In this paper, 1 wt% CNTs were discovered to significantly enhance tensile properties of a nylon copolymer (PAc) reinforced with 20, 30, and 40 wt% TLCP wholly thermoplastic composite (WTC). The WTC filaments were then laid down via fused filament fabrication (FFF). Based on the previous work carried out in our lab, 1 wt% CNTs were the crucial concentration to efficiently enhance carbon fiber (CF) reinforced multiscale composites. The deagglomerated CNT dispersion in the WTCs was accomplished by using supercritical carbon dioxide (scCO 2 ). The effects of TLCP concentration and printing patterns in the lay‐down processes were explored. The most improvement in tensile properties due to the 1 wt% addition of CNTs was observed to be for the 20 wt% TLCP/1 wt% CNTs/PAc samples. The resulting composite filaments exhibited 225% and 80% improvement in the tensile modulus and strength, respectively, compared to the wholly thermoplastic composites (WTCs) without CNTs. In addition, 40 wt% TLCP/1 wt% CNT/PAc 3D printed specimens with filaments laid parallel to the printing direction exhibited excellent tensile modulus and strength of 38.92 GPa and 127.16 MPa, respectively. The measured tensile modulus of 40 wt% TLCP reinforced WTC is even higher than the reported 69 wt% long glass fiber (LGF) or 26 wt% long carbon fiber (LCF) reinforced nylon in fused filament fabrication with the same printing pattern.