This paper used poly (aryl ether ketone) (PAEK) resin with a low melting temperature to prepare laminate via the compression-molding process for continuous-carbon-fiber-reinforced composites (CCF-PAEK). Then, poly (ether ether ketone) (PEEK), or a short-carbon-fiber-reinforced poly (ether ether ketone) (SCF-PEEK) with a high melting temperature, was injected to prepare the overmolding composites. The shear strength of short beams was used to characterize the interface bonding strength of composites. The results showed that the interface properties of the composite were affected by the interface temperature, which was adjusted by mold temperature. PAEK and PEEK formed a better interfacial bonding at higher interface temperatures. The shear strength of the SCF-PEEK/CCF-PAEK short beam was 77 MPa when the mold temperature was 220 °C and 85 MPa when the mold temperature was raised to 260 °C. The melting temperature did not significantly affect the shear strength of SCF-PEEK/CCF-PAEK short beams. For the melting temperature increasing from 380 °C to 420 °C, the shear strength of the SCF-PEEK/CCF-PAEK short beam ranged from 83 MPa to 87 MPa. The microstructure and failure morphology of the composite was observed using an optical microscope. A molecular dynamics model was established to simulate the adhesion of PAEK and PEEK at different mold temperatures. The interfacial bonding energy and diffusion coefficient agreed with the experimental results.

The ablation mechanism and performance of carbon fiber (CF)-reinforced poly aryl ether ketone (PAEK) thermoplastic composites were studied in this paper. The results show that the ablation damaged area is controlled by the irradiation energy, while the mass loss rate is controlled by the irradiation power density. In the ablation center, the PAEK resin and CFs underwent decomposition and sublimation in an anaerobic environment. In the transition zone, the resin experienced decomposition and remelting in an aerobic environment, and massive char leaves were present in the cross section. In the heat-affected zone, only remelting of the resin was observed. The fusion and decomposition of the resin caused delamination and pores in the composites. Moreover, oxygen appeared crucial to the ablation morphology of CFs. In an aerobic environment, a regular cross section formed, while in an anaerobic environment, a cortex–core structure formed. The cortex–core structure of CF inside the ablation pit was caused by the inhomogeneity of fibers along the radial direction and the residual carbon layer generated by resin decomposition in an anoxic environment. The description of the ablation mechanism presented in this study broadens our understanding of damage evolution in thermoplastic composites subjected to high-energy CW laser irradiation.

To achieve polyimide-metal complexes with enhanced properties, 5-amine-2-(5-aminopyridin-2-yl)-1-methyl-benzimidazole (PyMePABZ) that contains stiff 2-(2′-pyridyl)benzimidazole (PyBI) was synthesized and exploited to construct the Cu(ΙΙ)-crosslinked polyimides (Cu-PIs). These Cu-PIs exhibited higher dielectric, thermal, and mechanical properties with an increase in Cu²⁺ content. Among them, their dielectric constants (ε_rS) were up to 43% superior to that of the neat PI, glass transition temperatures (T_gs) were all over 400 °C, and 5% weight loss temperature (T_5%) maintained beyond 500 °C. These data indicate that the metal coordination crosslinking provided a useful guide to develop high performance PIs which possess potential application as useful high temperature capacitors.

PEEK is being used increasingly often in seals, bushings, bearings, and other moving parts due to its excellent mechanical and tribological properties. Herein, PEEK-based composites were prepared using PI as the organic filler and h-BN and nano-SiO₂ particles as the inorganic fillers. There was significant improvement in the tribological properties of PEEK at conditions above the glass transition temperature; the coefficient of friction of +20P/4B/4Si was stabilized at 0.06 at 200 °C and the wear rate was reduced by 60% compared to PEEK. The role played by the thermal conductivity of h-BN and the promotion of friction transfer film by nano-SiO₂ in improving the tribological properties of PEEK is illustrated. The modified composites exhibited stable mechanical and tribological properties over a wide temperature range, which is instructive for instrumentation and testing applications in harsh environments.

Spirobichroman-based polymers with high gas permeability and selectivity are promising for their applications as membranes in gas separation. In this study, three spirobichroman-based polyimides (PIs; 6FDA-FH, 6FDA-DH, and 6FDA-MH) were synthesised by the polyreaction between diamines containing different substituents (benzene ring, pyridine ring, and methyl group) and 4,4′-(hexafluoroisopropylidene)-diphthalic anhydride (6FDA). The physical properties, gas transport behaviour, d-spacing, dihedral angle of molecules, and fractional free volume of the PIs were investigated through experiments and molecular simulations. The PIs exhibited excellent thermal stability and good solubility in common organic solvents. The gas permeability of the PIs was investigated; the results highlighted the critical role of the substituents in the enhancement of the gas separation performance of polymer membranes. Detailed analysis of the PIs showed that 6FDA-FH exhibits the highest gas permeability. This can be ascribed to the loose packing of the polymer chain owing to the increased dihedral angle between the two planes. However, the methyl substituent in 6FDA-MH disrupts the polymer chain packing rather than changing the dihedral angle between the two planes, thus enhancing the gas permeability of 6FDA-MH. Furthermore, 6FDA-DH exhibited the highest CO₂/CH₄ selectivity, which is attributed to the CO₂ affinity of the polymer containing the pyridine unit.

As the adhesive for composites, the resin matrix directly impacts the molding process and product performance of thermoplastic composites (TPCs). Carbon fiber-reinforced polyetherimide (CF/PEI) and polyaryletherketone (CF/PAEK) composites were prepared by a compression molding process. The interface, interlaminar, and low-speed impact properties of TPCs were studied. The results show that the interfacial shear strength of the CF/PEI composite is ~116 MPa, while the CF/PAEK composite is ~78 MPa. However, the interlaminar and low-speed impact performance of CF/PAEK is better than CF/PEI. Type I fracture toughness () and type II fracture toughness () of CF/PEI are ~1051 MPa and ~1060 MPa. But those of CF/PAEK are ~1786 MPa and ~2584 MPa, respectively. The compressive strength after the impact of CF/PAEK (~321 MPa) is 40% higher than CF/PEI (~230 MPa).