Preparation and Interfacial Properties of Hydroxyl-Containing Polyimide Fibers

Abstract

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.

Synthesis of Novel Nonisocyanate Poly(imide-urea)s from CO2-based Polyureas

“…The chemical structure of PIUs was determined by FTIR-ATR (Figure ). For PUa 1k , the ordered hydrogen-bonding urea groups were confirmed by the stretching vibration band of CO at 1614 cm –1 , the stretching and bending vibration band of N–H at 3321 and 1592 cm –1 , and the stretching vibration band of C–H from 2780 to 3000 cm –1 . , For PI, the formation of imide groups was confirmed by the asymmetrical and symmetrical CO stretching vibration at 1768 and 1703 cm –1 , respectively, and the axial, transverse, and out-of-plane vibrations of cyclic imide at 1366, 1078, and 735 cm –1 , respectively. , Furthermore, the characteristic stretching vibration bands of CO of aromatic anhydride at 1855 and 1784 cm –1 disappeared completely, indicating that s-BPDA was fully consumed, and the resulting poly­(amic acid) was completely imidized. For PIU-PUa 1k , with increasing PUa 1k content (Figure a), the absorption bands of the C–H stretching vibration (2780–3000 cm –1 ), the N–H stretching vibration (3321–3353 cm –1 ), and the N–H bending vibration (1551 cm –1 ) became gradually stronger.…”

“…20,21 For PI, the formation of imide groups was confirmed by the asymmetrical and symmetrical C�O stretching vibration at 1768 and 1703 cm −1 , respectively, and the axial, transverse, and out-of-plane vibrations of cyclic imide at 1366, 1078, and 735 cm −1 , respectively. 48,51 Furthermore, the characteristic stretching vibration bands of C�O of aromatic anhydride at 1855 and 1784 cm −1 disappeared Scheme 1. Processes for Poly(imide-urea) (PIU) Synthesized from CO 2 -based PUa, 3,3′,4,4′-Biphenyltetracarboxylic Dianhydride (s-BPDA), and 4,4′-Diaminodiphenyl Ether (ODA) appeared.…”

Preparation of MoS2@PDA-Modified Polyimide Films with High Mechanical Performance and Improved Electrical Insulation

“…Furthermore, the excellent thermal conductivity of MoS 2 assists in dissipating heat generated during friction. This dissipation prevents heat accumulation that could cause local softening and deformation of the material, thereby enhancing tribological performance [ 36 ].…”