Purpose -The purpose of this paper is to develop a new oil-in-water (O/W) emulsion used for alpha phase brass, which can increase the antiwear and anti-galling abilities of the rollers, and improve the surface quality of the rolled brass sheet. The aim is to evaluate the tribological performance of new kind of O/W emulsion for the hot rolling of alpha brass, which provides the fundamental information for the selecting of new chemical group, and to understand the lubrication mechanism of the used rolling emulsion and to correlate the laboratory findings with those of industrial rolling of alpha phase brass. Design/methodology/approach -According to the hydrophile-lipophile balance theory and the evaluation results of friction, wear and lubrication using a four-ball tribometer, a novel O/W emulsion was developed for the hot rolling process of CuZn 32 (ASTM C26200) and CuZn 30 (ASTM C26000) alloys by controlling the composition of the emulsion, such as emulsifying, antiwear, extreme pressure, antirust and so on. By scanning electron microscope (SEM), energy-dispersive X-ray (EDX), and roughness profile the tribological mechanism were studied. Findings -The production result proved that it was easy to control the accuracy and size of the brass sheet because of the emulsion-jet to the roller surface directly and in succession. Polyol with hydroxyl group is found to provide better lubrication and lower coefficient of friction. The actual hot rolling results proved that it was easy to control the accuracy and size of the brass sheet with the emulsion jet. The morphologies and roughness profile of the copper sheet surface were observed and measured by SEM and topographic meter under different lubricant conditions. The in situ results supported the selection of compositions of O/W emulsion. The suitable temperature of feed emulsion is over 208C.Research limitations/implications -The tribological mechanism of friction modified emulsion is not still clear. The thermal mechanical properties of rollers under this kind of emulsion are also worth studying in the future. Practical implications -Understanding the tribological behaviour of O/W emulsion, will be useful for emulsion chemists, tribologists and rolling mill users. Originality/value -The current study shows new compositions of O/W emulsion used for hot rolling of alpha phase brass.

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As a critical stage which severely affects the final coalescence of droplets, film drainage in the collision process of two simple droplets has been deeply studied for many years. However, the collision of multiple emulsions which contain other phases (like daughter droplets or particles) has never been studied although multiple emulsions are very important in emulsion industries nowadays. In this paper, the head-on collision of two core-shell double emulsions with equal sizes is investigated through a boundary integral method to disclose the effects of the inner droplet on the film drainage. When capillary number Ca is relatively high, due to the effect of the inner droplet on the inner circulation of mother droplets, the film drainage of double emulsions includes three stages: drainage, drainage halt, and second drainage, instead of two stages for that of simple droplets: drainage and drainage halt.

This paper summarizes the tribological properties of MoS2 nano-particles with about 30 nm under different frictional conditions. By four-ball tribometer, the results showed that as the nano-MoS2 content is over 0.5 wt% the extreme pressure of lubricating oil is higher than to 30% than that of lubricating oil with same content of common MoS2. The nano-MoS2 particles can decrease the friction coefficient of lubricating oil obviously. However the results showed that their friction reductions have not obvious difference by the ring-on-block tribometer. The analyses of surface composition conducted by XPS and SEM images showed that the nanoparticles form a protective film (WO3) allowing an increase in the load capacity of rubbed pairs. The main advantage of the nanoparticles is ascribed to the release and furnishing of the nanoparticles from the valley onto the rubbing metal surface and their confinement at the interface.