Influence of Internal Lubricants (PTFE and Silicon Oil) in Short Carbon Fibre-Reinforced Polyimide Composites on Performance Properties

Abstract

Short carbon fibre-reinforced thermoplastic polyimides (30 wt%) often show high and unstable coefficients of friction. In this study, the effects of internal lubrication by polytetrafluoroethylene (PTFE) (15 wt%) or silicon oil (15 wt%) have been investigated using a reciprocating cylinder-on-plate test under 50-100 N normal loads and 0.3-1.2 m/s sliding velocities. The sliding mechanisms are discussed by considering mechanical and thermochemical modifications. The PTFE additives provide lowest coefficients of friction completely stabilising after a transition from mechanically into thermally controlled sliding at 120°C. The sliding mechanisms and homogeneous transfer films are mainly controlled by plasticisation rather than easy-shear of its lamellar structure that is hindered by fibre reinforcement. Thermoplastic lubricants decrease the mechanical strength and therefore cause deformation and highest wear rates under 200 N. Internal oil lubricants do not reduce coefficients of friction at mild to intermediate normal loads and sliding velocities, while they become most efficient at severe sliding conditions, augmenting the pv-limit. While coefficients of friction match uniquely to the pv-conditions, the wear rates are mainly influenced by the load level: the lowest wear rates are provided by PTFE at low to intermediate pv-conditions and by oil lubricants under high normal loads.

Selectively enhanced oil retention of porous polyimide bearing materials by direct chemical modification

“…Figure 5 shows the FTIR spectra, XPS survey spectra and TGA curves of Si-TPI. In Figure 5(a), it seemed that there were no obvious differences between PI and Si-TPI, except the characteristic vibration of saturated CAH at 2963 cm 21 in ACH 3 which are only present in UMIDA. At the same time, in Figure 5(b), Si element was not found on the surface of PI0 but appeared on Si-TPI.…”

Tribological behaviors of polyurethane composites containing self‐lubricating microcapsules and reinforced by short carbon fibers

“…The thermal stability of the microcapsules containing methyl silicone oil decreases, which directly leads to the poor heat resistance of binary composites compared to pure polyurethane, as shown in Figure . The curve showed that the large mass loss was at 300 to 450 °C because of the fact that the crosslinked structure of melamine‐formaldehyde resin was destroyed and the mass loss at 500 °C was due to the thermal decomposition of the methyl silicone oil . After SCFs added, the initial decomposition temperature of the ternary composites increased with the increase of SCFs content.…”

“…The curve showed that the large mass loss was at 300 to 450 8C because of the fact that the crosslinked structure of melamineformaldehyde resin was destroyed and the mass loss at 500 8C was due to the thermal decomposition of the methyl silicone oil. 19 After SCFs added, the initial decomposition temperature of the ternary composites increased with the increase of SCFs content. For the comparison of carbon residue rate, the residual carbon rate of the ternary composites increase, it was mainly due to the fact that the high heat resistance of the carbon fiber contribute to the good heat resistance of composites.…”

An investigation on the mechanical and tribological properties of carbon fiber/polyimide composites at elevated temperatures

“…Generally speaking, the carbon fiber additives can improve the wear resistance of polymeric matrix through increasing the loading capacity , while their lubricity is ambiguous under different conditions. When perpendicular to the sliding plane and sliding direction, the carbon fiber leads to high coefficient of friction, while it may result in low friction coefficient in parallel to orientation . According to Li et al , the incorporation of a certain amount of carbon fiber can greatly enhance the wear resistance but either increase or reduce the friction coefficient of CF/PI composites at room temperature (RT).…”