Phase Behavior Of Ternary System Benzene-Water-Ethanol And The Cross-linking Mechanism Of W/O Emulsion Cross-linking Agent

This article studied the related properties of oil-water dispersions, divided into two parts:first, the phase behavior of ternary system benzene-water-ethanol; second, the cross-linking mechanism of W/O emulsion cross-linking agent.1. Phase behavior of ternary system benzene-water-ethanolGenerally, a microemulsion consists of oil, water, surfactant and sometimes cosurfactant, and it is believed that the surfactant is the important component in stabilizing these systems. However, Smith et al. reported an oil-continuous (or W/O) microemulsion composed of hexane,2-propanol and water, and this ternary system was considered as surfactant-free (or detergentless) microemulsion (denoted as SFME) because no traditional surfactant involved in the system. Subsequently, the SFMEs have attracted much attention, their many physical properties were measured, and it was found that the phase behavior of the systems were similar to those observed with surfactant-based microemulsion systems. So far, all SFMEs reported in literatures are water-in-oil (W/O) systems, and the understanding for SFMEs is very shallow. It is necessary to conduct systematic research to enhance scientific understanding of microemulsion and provide the basis for a wide range of applications.The ternary system composed of benzene, water, and ethanol was selected as a model system to study the phase behavior. Ternary phase diagram was constructed by visual titration, finding that there were a single-phase region and a two-phase region in ternary phase diagram. The electrical conductivity measurement was employed to investigate the sub-phase regions of the single-phase region, and a water-in-benzene (W/O) microemulsion, a bicontinuous (BC) microemulsion, a benzene-in-water (O/W) microemulsion, a water-ethanol hydrogen bond aggregates and a conventional ternary solution microregions were identified, which was confirmed by freeze-fracture transmission electron microscopy (FF-TEM) observations. The sizes of the microemulsion droplets are in the range of 20-50 nm. The results show that SFME may have the same type as conventional microemulsion, and the oil-water-short chain alcohol systems without surfactants may have a rich phase behavior.2. The cross-linking mechanism of W/O emulsion cross-linking agent The cross-linking mechanism of a emulsion cross-linking agent for PHPA solution, developed by Shengli Oilfield, China, was investigated. First, the cross-linking agent sample was characterized, proving to be the W/O emulsion with crosslinking agent aqueous solution as water phase; then, the phase changes of the W/O emulsion in water were studied, and it was found that a W/O/W multiple emulsion was formed, the inner water phase was crosslinking agent aqueous solution, the intermediate oil phase was a mineral oil and the external phase was water (or PHPA solution). Based on these results, a cross-linking mechanism was proposed. Aggregation, fusion and film rupture will gradually occur amonge the droplets of the multiple emulsion, and the cross-linking agents were slowly released, which could delay the crosslinking process.