Simple Synthesis of Hydroxyl and Ethylene Functionalized Aromatic Polyamides as Sizing Agents to Improve Adhesion Properties of Aramid Fiber/Vinyl Epoxy Composites.

To improve interfacial adhesion between aramid fibers and vinyl epoxy resins, a series of hydroxyl and ethylene-functional aromatic polyamides ((ClPPTA)m-R') with different chain segments were successfully synthesized via a one-pot low-temperature polycondensation. The hydroxyl and ethylene-functional aromatic polyamides were characterized by Fourier transform infrared spectroscopy (FT-IR), solid-state 13C CP/MAS nuclear magnetic resonance spectroscopy (13C CP/MAS NMR), thermal gravimetric analysis (TGA), and wide-angle X-ray diffraction (WXRD). The contact angle of the hydroxyl and ethylene-functional aromatic polyamides films were measured. The hydroxyl and ethylene-functional aromatic polyamides were used as the sizing agents for aramid fiber/vinyl epoxy composites. The surface chemical composition and morphology of the unsized and sized fibers were identified using X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). The interfacial adhesion between aramid fibers and vinyl epoxy composites was investigated by the micro-debond tests. The results showed that the interfacial shear strength between the sized aramid fibers and vinyl epoxy composites was greatly improved.