Preparation and performance of long carbon fiber reinforced polyamide 6 composites injection-molded from core/shell structured pellets

•Long carbon fiber reinforced PA6 composites were injection-molded from pellets.•Novel core/shell structured pellets were produced by a scalable process.•Carbon fibers were treated with sizing agent to enhance interfacial bonding.•Concentration of sizing agent had an important impact on fiber–matrix adhesion.•The composites had improved performance in comparison to short fiber composites.

In this work, long carbon fiber reinforced polyamide 6 (LCF/PA6) composites were prepared by injection-molding a novel kind of core/shell pellets that were mass produced by a convenient and scalable process of melt impregnation assisted by a single screw extruder. The effect of fiber sizing treatment on fiber distribution, melt flowability, and mechanical properties of the LCF/PA6 composites was investigated. It was demonstrated that the melt flowability exhibited a continuous increase with the increase of sizing concentration while the mechanical properties showed peak values at a sizing concentration of 22 wt.%. In addition, the mechanical properties of the LCF/PA6 composites at the optimal sizing concentration were examined as a function of the content of carbon fibers. These findings may provide guidance for the studies aimed at developing long carbon fiber reinforced thermoplastic composites with desirable mechanical properties.