Interfacial strengthening of carbon fiber/epoxy composites through a sulfonated high-epoxy-value sizing agent

In order to improve the wettability of epoxy resin to carbon fibers (CFs) and enhance the interfacial adhesion of carbon fiber reinforced epoxy composites (CFREs), the epoxy resin was chemically modified with polyethylene glycol (PEG) and maleic anhydride (MAH) to prepare a sulfonated high-epoxy-value waterborne epoxy sizing agent. Both ends of the sizing molecule are epoxy groups, which could greatly improve the wettability between the CFs and the resin matrix. The sulfonic acid groups introduced in the middle chain could heighten the hydrophilicity and shorten the molecular weight of the sizing agent. Thereby we prepared a sizing agent with smaller particle size and higher storage stability. Use various methods to characterize the performance of the emulsion. Experimental results showed that, the sizing agent prepared by PEG800 could achieve the best performance of the composite, where the tensile strength of the single filament and the interfacial shear strength of the CFREs increased by 2.73% and 11.18%, respectively. This study shows that the use of a high-epoxy-value sizing agent is one of the alternative methods to strengthen the mechanical properties of the fiber-matrix interface and enhance the mechanical properties of CF/epoxy composites.