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Effects of thermal aging on the blend phase morphology of polyimide/ultrahigh molecular weight polyethylene (PI/UHMWPE) blend composites were studied by using Raman Mapping. Friction and wear tests were conducted to study the influence of thermal aging on the tribological properties of the blend composites. The results indicate that the phase morphology of PI/UHMWPE blend composites could be controlled by thermal aging. At relatively low thermal aging temperatures (100 °C, 120 °C), the blend with high PI/UHMWPE ratio tended to form continuous layered structures. As a consequence, the tribological performance was significantly improved. While for the blend with low PI/UHMWPE ratio, the improvement of tribological performance was not significant. For the blends thermal aged at relatively high temperature (150 °C), the tribological performance was poor due to significant phase separation that occurred after thermal aging. • Thermal oxidation resistance of UHMWPE could be significantly improved by blending PI to the UHMWPE matrix. • The phase morphology of PI/UHMWPE blend composites could be controlled by thermal aging. • The wear resistance of PI/UHMWPE blend was improved after thermal aging at the temperature below melting point. [ABSTRACT FROM AUTHOR]

Polyimide/ultrahigh molecular weight polyethylene (PI/UHMWPE) blends with different mass ratio were produced. A ratio-image method was adopted by plotting the ratio of Raman peak intensity of a typical band of PI with that of UHMWPE as a function of position, Raman Mapping images with a relatively high accuracy and enhanced visualization were obtained. Two-phase distribution morphologies of the blends were studied using Raman Mapping. Effects of blend phase morphology and phase distribution on the tribological properties of blend composites were investigated. The results indicated that both the phase structures and their distribution are obviously different for the PI/UHMWPE blends with different mass ratios, which significantly influence the tribological properties of the blends. PI phase disperses in an island form in the UHMWPE matrix phase when the mass ratio of PI/UHMWPE is relatively small (10/90). The scattered PI dispersed phase effectively reduces the friction coefficient of the blend and improves the wear resistance. For the PI/UHMWPE blend composite with the mass ratio of 30/70, layered PI phase forms and distributes in the UHMWPE matrix phase, improving bearing capacity and wear resistance of the blends. Large continuous area structure and phase separation occurs in the blend when the mass ratio of PI/UHMWPE increases to 50/50, resulting in a significant reduction in the wear resistance of the blend composite. Image 1 • A ratio-image method was adopted by plotting the ratio of Raman peak intensity of a typical band of PI with that of UHMWPE as a function of position. • Different phase morphologies and their distribution are formed for the PI/UHMWPE blends with different mass ratios. • PI/UHMWPE blend with island or layered morphology of PI improves the tribological properties of UHMWPE. [ABSTRACT FROM AUTHOR]

Herein, the internal lubrication of polyether ether ketone (PEEK) with added whiskered carbon nanotubes (Wh-CNTs) was investigated under point-contact dry sliding conditions with various loads and velocities. The wear rate of the composite was reduced by 86.99% at a maximum Hertzian contact pressure of 344.69 MPa, which was attributed to the addition of additives with excellent mechanical properties and high-temperature stability. Wh-CNTs could be uniformly distributed in the PEEK to form a three-dimensional (3D) network structure with load-bearing capacity, thus the load could be effectively borne to prevent crack propagation on the PEEK surface. Besides, the filler was induced to form a micron-sized 3D spherical structure with a ball bearing effect, which promotes lubrication more effectively than the fragment structure. [ABSTRACT FROM AUTHOR]

In this work, the causes of failure of electroplating silver coatings on aero-engine nuts were explored. And the microhardness of low temperature pulsed DC magnetron sputtering silver coatings was increased by 25%, and the bonding force was increased by about 1.2 times. At high temperature, the friction coefficients of magnetron sputtering silver coatings was about 20% lower than that of electroplating silver coatings, and the wear volume was about 90% lower than that of it at maximum. The wear mechanism of magnetron sputtering silver coatings was mainly abrasive wear, while that of electroplating silver coatings was mainly adhesive wear. Besides, the results of molecular dynamics showed that silver coatings would move and aggregate in layers during the friction. • Adhesive wear and abrasive wear cause failure of silver coatings on aero-engine nuts. • Low hardness, poor bonding, and thickness uniformity are defect of silver coatings. • Magnetron sputtering silver coatings better perform at high temperature. • Silver coatings transfers and aggregates during friction. [ABSTRACT FROM AUTHOR]

PI/UHMWPE blends are going to be used as the bush material of sliding bearings under high speed dry condition in one project. Prior to the fabrication of these bearings, the tribological properties PI/UHMWPE blends with various component ratio under the specific service condition was investigated by using a pin-on-disk tribometer. The results revealed that the compression modulus of PI/UHMWPE blends increases with the increase in PI content. Furthermore, the coefficient of friction and wear rate decrease firstly and then increase slightly with the increase in PI content, both of which reach the minimum value when PI content is 70%. The analyses of transfer membrane indicate that both of UHMWPE and PI can transfer to the metal counterface, while the increase of PI content is more conducive to the increase of transfer membrane. • The coefficient of friction and wear rate of PI/UHMWPE blends decrease firstly and then increases slightly with the increase in PI content, both of which reach the minimum value when PI content is 70%. • The analyses of transfer membrane indicate that both UHMWPE and PI can transfer to the metal counterface, while the increase of PI content is more conducive to the increase of transfer membrane. [ABSTRACT FROM AUTHOR]