The properties of coloured pigments are primarily affected by the particle size as well as the size distribution. As both are influenced by the production process, the pigment synthesis of Yellow 12 was investigated using a micromixer apparatus. The micromixer ensures fast mixing by multilamination of thin lamellae and thereby a faster complete mixing of the reactants compared to batch processes. It was found that the micromixerbased process leads to a smaller pigment size distribution. This results in an improvement of the pigment properties. Compared to a commercially available Yellow 12 standard the glossiness was increased by 73% and the transparency by 66% with unchanged tinctorial power.
Poly-α-olefin (PAO) is an important synthetic fluid in the field of industry lubricants. To improve the tribological properties of PAO, a Schiff base copper complex was added to the lubricants. The tribological properties of steel and steel lubricated with PAO and PAOs containing a Schiff base copper complex were studied. The friction and wear properties of steel and steel lubricated with PAO and PAOs containing a Schiff base copper complex were evaluated using a SST-ST pin-disc tester. The sliding friction was measured using lubricants with or without a Schiff base copper complex and analyzed using surface analysis techniques including scanning electron microscopy, Fourier transform infrared spectroscopy, and confocal white light microscopy. A UMT-2 universal tribometer was also used to study the tribological properties of modifying PAO containing the Schiff base copper complex. The Schiff base copper complex structure was found to assist in the formation of a stronger tribofilm; more than the tribofilm prepared by lubricating only with PAO and this is crucial in obtaining a low and stable coefficient of friction. A lower stable friction coefficient and wear was found for the steel/steel surface contact when using the PAOs containing the Schiff base copper complex compared to the samples lubricated with the PAO without additives. The excellent tribological performance of the PAOs containing the Schiff base copper complex is attributed to the formation of a useful tribofilm with organic and inorganic groups on the sliding surface.
Reciprocating friction and wear performances of pure ultrahigh-molecular-weight polyethylenes (UHMWPEs) with molecular weights (MWs) of 2, 3, 5, and 9 million and their modified UHMWPEs with 15 wt.% Cu(II) chelate of bissalicylaldehyde-ethylenediamine (add1) against titanium alloy (Ti6Al4V) were investigated under boundary lubrication with 25 vol.% calf serum deionized water solution. Differential scanning calorimetry (DSC) of purchased UHMWPE powders was performed. The enthalpy changed with an increase in MW. UH300 had the lowest temperature of an extrapolated peak and the best peak symmetry in DSC analysis. The friction coefficient curves of molded pure and modified UHMWPEs/Ti6Al4V were compared, and the volume loss by the wear of polymers was measured. 3D topographies of the worn surfaces of polymers and images of the worn surfaces of polymers and titanium alloy against polymers were analyzed by confocal white light microscopy and scanning electron microscopy, respectively. Results showed that the influence of MW of UHMWPE was obvious on the friction and wear characteristics of pure UHMWPEs and 15% add1 UHMWPEs. An MW of 3 million was the best to reduce the friction of rubbing pairs, enhance the wear resistance of pure UHMWPEs and 15% add1-UHMWPEs, and improve the mating properties of Ti6Al4V.
We have investigated the lubrication alignment behavior of point—plane contact and plane—plane contact between the GCr15 steel and polyimide (PI) friction pair using nematic liquid crystals (LCs) as the lubricant. In this system, rubbing orients the macromolecular PI molecules, and the oriented PI molecules induce alignment of the LC molecules in contact with or close to the oriented PI molecules. The LC molecules are aligned in the wear scar grooves of the PI film, and alignment extends to the GCr15-steel counterpart. Alignment of the LC molecules is correlated with the strong interaction force between the PI and LC molecules, the stable coordination structure of the LCs and GCr15 steel, and the weak interaction between the LC molecules. We performed simulations of the pretilt angle of PI and LCs and discussed the relationship between the pretilt angle and the friction properties. Owing to the small pretilt angle between PI and the LCs, the LC molecules orient almost parallel to the PI material, which is beneficial for superlubricity of this type of friction system.
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