Surface Modification of Carbon Fibers With Multi‐Walled or Single‐Walled Carbon Nanotubes and the Mechanical Strength of Their Polystyrene Composites

ABSTRACT This study investigated the effect of the morphology of carbon nanotubes (CNTs) on the mechanical properties of polystyrene (PS) composites by surface modification of carbon fibers (CFs) through the coating of large amounts of multi‐walled carbon nanotubes (MWCNTs) or single‐walled carbon nanotubes (SWCNTs) using a reactive polymer. A simple two‐step procedure was used: a reactive monomolecular coating of poly(2‐isopropenyl‐2‐oxazoline) (Pipozo) was first coated onto the CF surface, followed by grafting either MWCNTs or SWCNTs from their respective dispersions. Quantitative analysis revealed CNT coating amounts of 0.10 wt% for MWCNTs and 0.37 wt% for SWCNTs. These coated CNTs provided a physical anchoring effect at the fiber–matrix interface, thereby improving the mechanical properties of the PS composites. The SWCNT‐coated CFs showed particularly strong effects. Scanning electron microscopy confirmed that MWCNTs and SWCNTs remained adhered to the CF surface after melt mixing, further enhancing interfacial adhesion.