Collaboration of Fenton reaction with a tannin acid-based hyperbranched waterborne polyurethane sizing agent for synergistic enhancement of the CF/PA6 composite interfacial properties

The adhesive strength between the sizing agent and carbon fiber (CF) plays a pivotal role in determining the interfacial properties of composites. Unfortunately, this critical aspect has been consistently overlooked. In this study, a hyperbranched waterborne polyurethane (HWPU) sizing agent was prepared by biogenetic derived raw materials including gallic acid as well as tannic acid. Meanwhile, iron ion was introduced onto the surface of CF by Fenton reaction, forming a heterogeneous structure to elevate the mechanical interlocking between the CF and resin. Chelation of TA with iron ion on the fiber surface effectively enhanced the adhesion between sizing agent and CF. The mechanical properties of the newly designed composites were systematically investigated. The results showcase a significant enhancement in both flexural strength and interlaminar shear strength (ILSS) compared to untreated CF, marking improvements of 54.3% and 60.0%, respectively. Furthermore, the interfacial shear strength (IFSS) test exhibited a 71.2% augment. In conclusion, this approach presented a highly promising concept aimed at improving the interfacial performance of CF composite materials.