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.