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Crosslinked fluorinated polyimides (CFPI) were successfully synthesized to study and explore the effect of cross-linkage on the migration of fluorinated segments and on the adhesion strength. Characterization by dynamic thermomechanical analysis (DMA) and thermo gravimetric analysis (TGA) confirmed good thermal properties of CFPI. X-ray photoelectron spectroscopy (XPS) results showed that the ratio of fluorinated component (6FDA-ODA) concentration of the surface to the bulk decreased with the crosslink density. The water contact angle of CFPI was lower than that of non-crosslinked fluorinated polyimide, indicating that the migration of fluorinated groups to the surface was reduced by the presence of cross-linkage. Therefore, CFPI, with no fluorine segregation on the surface, exhibited excellent wetting of adherent surfaces and adhesion strength, which was proved by lap shear strength (LSS) measurements and scanning electron microscopy.

Carbon fabric reinforced polytetrafluoroethylene (PTFE) composites with different PTFE content, viz. 30, 40, 50, 60, and 70 vol%, were fabricated by a dispersion impregnation technique followed by a hot-press process. The composites were evaluated for their mechanical and tribological properties. The tribological tests were conducted on a friction and wear tester with a ring-on-block arrangement. The mechanical properties were also tested and their relationship with tribological properties was analyzed. The worn surface and wear debris were analyzed by a scanning electron microscope (SEM) to study the wear mechanism. It was found that the resin content had a great influence on both the mechanical properties and the tribological properties, and the tribological properties were correlated with the mechanical properties. The composite with 50 vol% PTFE showed promising tribological behaviors under the selected test conditions.

Reinforced phenolic resin (PF) was prepared by in situ polymerization of different fractions of carbon nanotubes (CNTs) that had undergone oxidation. The compressive strength and hardness of the material, according to mechanical property testing, was improved by the modified CNTs. The tribological properties of PF composites were investigated by a block-on-ring friction and wear tester. The results indicated that CNTs reinforced PF showed lower friction coefficient and higher wear resistance, compared with pure PF. The morphologies of the worn surfaces, debris, and transfer films were observed by scanning electron microscopy (SEM) and optical microscopy (OM). A continuous and thinner transfer film formed during the friction test of the composites led to the significant improvement of the tribological properties.

Untreated and air-plasma-treated hybrid polytetrafluoroethylene (PTFE)/poly(p-phenylene terephthalamide) (Kevlar) fabrics were used to prepare hybrid fabric–polyphenylene sulfide (PPS) composites b...

Hybrid fabric/polyphenylene sulfide (PPS) composites filled with the particulates of PPS were prepared by dip coating the polytetrafluoroethylene (PTFE)/poly(p-phenylene terephthalamide) (Kevlar) hybrid fabric in a PPS suspension solution containing the particulates to be incorporated. The friction coefficient and wear rate of the hybrid fabric/PPS composites were evaluated on a MPX-2000A friction and wear tester with an end-face contact mode in a dry sliding condition. The results showed the hybrid PTFE/Kevlar fabric composites filled with 40 wt% PPS had the best tribological behavior. The friction coefficient and wear rate decreased with an increase in sliding speed, and they reached the lowest value when the load was 1000 N. The Rockwell hardness affected the wear rate to some degree. Scanning electron microscopy (SEM) micrographs revealed that even, smooth, and coherent transfer films, formed on the counterface, played an important role in the friction process. They were effective in improving the tri...

The tribological properties of polyoxymethylene (POM) modified by nano-polytetrafluorethylene (nano-PTFE) were investigated by a block-on-ring wear tester. For comparison, modified POM with micro-polytetrafluoroethylene (micro-PTFE) was also studied. The modified POM with a much lower concentration of nano-PTFE showed the similar tribological properties compared with POM modified by micro-PTFE. The friction coefficient decreased with the increase of nano-PTFE, while the wear rate showed the lowest value when the concentration of nano-PTFE was 2%. Scanning electron microscope (SEM) micrographs revealed that transfer films played an important role in the friction process. The transfer films decreased and stabilized the friction coefficient. Comparing to POM/2%nano-PTFE, when the concentration of nano-PTFE reached 4%, the mechanical properties decreased significantly, possibly due to poor dispersion of nano-PTFE.

4,4′-(hexafluoroisopropylidene) diphthalic anhydride (6FDA)-based copolyimides were synthesized and the tribological properties of the copolyimides with different heat histories were studied at different temperatures. Fluoride-containing polyimide (PI) showed better thermal stability, decreased friction coefficients, and postponed the consequence of friction variation, which depended on temperature, than nonfluorinated PI. Thermal treatments seemed to increase the friction coefficients of copolyimides, and reduced the tensile strengths of the materials. The effects of applied load (P) and sliding speed (V) on tribological behaviors of thermally treated copolyimides were also examined and the variations of friction coefficient depending on PV values were investigated for clear understanding of its relationship between PV value and friction coefficient with different thermal treating time. Distortions of net structures of the chains and molecular motion contributed to variations of tribological properties o...

The 4,4′-(hexafluoroisopropylidene) diphthalic anhydride (6FDA) was used to synthesize polyimide to introduce different amounts of fluoride to the main chain of polyimide. The infrared spectra indicate that the imidizing process was almost complete and fluorinated monomer was formed in the structure. Fluoride-containing polyimide showed better thermal stability, higher tensile strength, and lower surface energy than neat polyimide. The increase of the fluoride monomer ratio contributed to the tribological properties of polyimide. The friction coefficient decreased with the increase of the fluoride monomer ratio. Surface-free energy and friction heat can alter the physical state of polymer sliding surfaces, and had a great effect on the tribological behaviors. Abrasive wear was designed and executed in this work. The wear rate decreased with the increase of the fluoride monomer ratio.