Preparation and Interfacial Properties of Hydroxyl-Containing Polyimide Fibers

Developing polyimide (PI) fibers with excellent interfacial adhesion and high mechanical properties for the PI fiber-reinforced polymer matrix composites (PFRPs) industry has been challenging. In this work, 4,4 '-diamino-(1,1 '-biphenyl)-3,3 '-diol (HAB) diamine was introduced into the rigid molecular chains, and the high-performance PI fibers, presenting an interfacial shear strength (IFSS) value of 46.33 MPa, tensile strength of 2.62 GPa, and modulus of 100.15 GPa, were successfully manufactured when the content of HAB in mixed diamines was 30 mol %. Fourier transform infrared (FTIR) spectroscopy identified the presence of intermolecular H-bonding interactions, and 2D small-angle X-ray scattering indicated that the introduction of HAB moiety contributed to reducing the radii of microvoids in the fibers, which were considered to be the key factors leading to a significant enhancement in the mechanical properties of the fibers. X-ray photoelectron spectroscopy (XPS) and the static contact angle intuitively illustrated that the synthetic fiber surface contained active hydroxyl groups. The IFSS value of PI fiber/epoxy resin composites (PI/EPs) was 56.47 MPa when the content of HAB reached 70 mol %. Failure morphologies confirmed that the interfacial adhesion of PI/EPs was enhanced owing to the surface activity of PI fibers. Consequently, this study provides an effective strategy to the long-standing problems of high mechanical performances and poor surface activity for traditional PI fibers used in the PFRPs industry.

Automated summary

In this study, high-performance polyimide (PI) fibers with excellent interfacial adhesion and mechanical properties were successfully developed by introducing 4,4'-diamino-(1,1'-biphenyl)-3,3'-diol (HAB) diamine into the molecular chains. The fibers exhibited an interfacial shear strength (IFSS) value of 46.33 MPa, tensile strength of 2.62 GPa, and modulus of 100.15 GPa. The introduction of HAB moiety contributed to the reduction of microvoid radii in the fibers, leading to significant enhancement in their mechanical properties. The surface activity of the synthetic fibers was confirmed by X-ray photoelectron spectroscopy and static contact angle measurements, and the enhanced interfacial adhesion in PI fiber/epoxy resin composites was demonstrated. This study provides an effective strategy to address the long-standing challenges in the PI fiber-reinforced polymer matrix composites industry.