Effect of polyetherimide sizing on surface properties of carbon fiber and interfacial strength of carbon fiber/polyetheretherketone composites

The sizing process is almost invariably performed after the manufacture of carbon fiber (CF) and the sizing agent takes the effect of protecting CF surface. However, the traditional sizing agent is not suitable for processing continuous CF reinforced thermoplastic composites (CFRTPs) with high processing temperature. In this work, polyetherimide (PEI) is chosen as the sizing agent for CF reinforced polyetheretherketone (CF/PEEK) composites, and the sizing content as well as the type of sizing agent (including solvent-based and emulsion type) were systematically researched. After a series of characterization of CF surface properties and interfacial strength of CF/PEEK, the improvement of interfacial shear strength (IFSS) and mechanical performances of sized CF/PEEK proves the enhancement of interfacial adhesion after sizing. CF/PEEK composites which contain CF handled by emulsion type sizing agent have good mechanical properties, indicating that it has the potential to replace solvent-based sizing agent. Besides, the miscible feature of PEEK with PEI, the raise of CF surface roughness and surface energy might cause the reinforcement of interfacial mechanical properties. This research may create a potential way for CF production field, aiming at improving the interfacial performance of CFRTPs.

Automated summary

The sizing process is crucial for protecting carbon fiber surface and improving interfacial adhesion. In this study, polyetherimide (PEI) was chosen as the sizing agent for CF reinforced polyetheretherketone (CF/PEEK) composites, leading to enhanced mechanical properties and interfacial shear strength. The use of emulsion type sizing agent showed promising potential to replace solvent-based sizing agent in processing high temperature continuous CF reinforced thermoplastic composites.