|DC.description||National Central University||en_US|
水包油凝膠（O/W gel）根據成膠時是否添加膠凝劑，可分為凝膠誘導型與無凝膠型兩種。在此研究中，成功製造出水性界面活性劑添加量低至1wt％的無凝膠型水包油凝膠。本實驗方法分為兩種，第一種方法是藉由凝膠核的生長所誘發，機制類似於晶體生長；第二種則是通過凝膠仍在乳液狀時，逐次添加少量油來稀釋，最終達成乳液到凝膠的轉化。兩種方法皆經歷過渡相轉換，且透過連續攪拌而達成。此外，我們的膠經由流變學的分析，膠呈現類似固體的性質，具有 彈性模數和降伏強度，且發現透過降低水含量可增強機械性質。
以界面活性劑穩定超過五個月之水包油乳液和乳液凝膠已透過簡易以重力為驅動力的攪拌裝置分離成功。此裝置包含了旋轉攪拌磁石和具有超疏水性/超親油性質的柔軟銅網，並摺疊而成所需尺寸的三維形狀。乳液的製備為混合不同比例的烷烴和水(1 % to 99 %)並透過水溶性界面活性劑的穩定而成。當乳液中水的分率較低時，界面活性劑的含量較高，因此得到類固體的乳液型態。研究結果發現，以應力為驅動力的方式能夠有效分離穩定的乳液，其效率高達98%，而分離乳液凝膠的效率也達到96%。以應力為驅動力將油從穩定的乳液中回收的機制，主要是基於銅網水層(超疏水性)的瞬間破裂和增加與油網的接觸所導致油的滲透行為(超親油性)。對於乳液凝膠而言，應力的施加功用主要為誘導乳液短暫的由固體型態轉換為液體型態。該方法可用於有效分離通常由工業過程產生的高度穩定的水包油乳液和乳液凝膠。
|dc.description.abstract||Part I - The Oil-in-Water Gels with Scanty-Water
The oil-in-water (O/W) gel can be classified into two types, gelator-induced and gelator-free, based on the requirement of gelator addition. In this work, the O/W gel with scanty-water belonging to the gelator-free type was successfully produced even when the content of aqueous surfactant solution was as low as 1 wt%. In an attempt to develop this scanty-water O/W gel, two purposely designed approaches with continuous mechanical agitation were proposed. The first approach of gel formation was induced by the growth of gel nuclei, which is similar to the mechanism of crystal growth. Distinct from the first approach, the water content in the emulsion was diluted by oil addition, leading to the transformation from emulsion to gel eventually. Both approaches undergo a phase change associated with the jamming transition. According to rheological measurements, our gels possess solid-like behaviors such as elastic modulus and yield stress. Moreover, the O/W gels with scanty-water can be strengthened by reducing the water content.
Part II - Stress-Driven Separation of Surfactant Stabilized Emulsions and Emulsion Gels by Superhydrophobic/Superoleophilic Meshes
Oil-in-water emulsions and emulsion gels which are stabilized by surfactants for more than five months have been successfully separated by a simple gravity-driven agitation-assisted device. The device contains a rotating magnetic stir-bar and a flexible superhydrophobic/superoleophilic Cu mesh which has been folded into the desired three-dimensional shape. The emulsions were prepared by mixing various fractions of alkane and water (1 % to 99 %) stabilized by a water-soluble surfactant. For low water fractions which contained higher concentrations of surfactant, solid-like emulsion gels were obtained. The stress-driven process was found to effectively separate stable emulsions with a separation efficiency 98 % and emulsion gels with separation efficiency as high as 96 %. The mechanism for oil recovery from stable emulsions by the stress-driven device is based on momentary breakage of the water barrier layer (superhydrophobicity) and enhancement of the oil-mesh contact leading to oil permeation (superoleophilicity). For emulsion gels, the additional function of the stress is to induce a temporary transformation from the solid-like gel into a liquid-like stage. This methodology can be employed for efficient separation of highly stable oil-in-water emulsions and emulsion gels that are often produced by industrial processes.
|DC.title||The Oil in Water Emulsions and Gels and Their Separation||en_US|
|DC.publisher||National Central University||en_US|