Effects of Two Types of Multi‐Walled Carbon Nanotubes Used for Carbon Fiber Surface Modification on Tensile Properties of Polycarbonate Composites

In this study, carbon fibers (CFs) coated with two types of multi‐walled carbon nanotubes (MWCNTs), manufactured by Nanocyl SA (MWCNT‐a) or TPR Co. Ltd. (MWCNT‐b), were prepared using a reactive polymer, and the effects of the coated MWCNTs on the tensile properties of polycarbonate (PC) composites were investigated. The MWCNT‐coated CFs were prepared through a simple three‐step process. First, a reactive layer of poly(2‐isopropenyl‐2‐oxazoline) (Pipozo) was formed on the CF surface as the first layer. Next, the two MWCNT dispersions were coated onto the Pipozo‐coated CFs to form the second layer. An additional Pipozo layer was then formed as the third layer. Scanning electron microscopy (SEM) observations revealed qualitative differences in coating morphology between the two systems. A quantitative analysis showed that the coating amounts of MWCNT‐a and MWCNT‐b were 0.16 ± 0.017 wt.% and 0.12 ± 0.007 wt.%, respectively. The MWCNT‐b system exhibited the highest mean values among the CF‐containing composites. Fracture‐surface SEM revealed PC resin residue on the treated CF surfaces, indicating partial fracture within the adjacent PC matrix. These results suggest that both the Pipozo‐derived interphase and retained MWCNT coating morphology may be important in the interfacial design of CF‐reinforced thermoplastic composites.