水+油+界面活性劑系統逼近三臨界點界面行為之研究

A Study of Interfacial Behavior Near the Tricritical Point of the System‘Water + Oil + Surfactant’

林炳昌(Ping-Chang Lin)

指導教授 ： 陳立仁

國立臺灣大學/工學院/化學工程學研究所/碩士(2004年)

https://doi.org/10.6342/NTU.2004.00216

摘要

在一個三相共存的平衡系統中，極少量的中間相可能以非濕透、部分濕透或是完全濕透的形式存在於上、下兩相之間。而由部分濕透與非濕透（或是完全濕透）之間的互相轉變，稱為濕透轉變。現今我們所關心的是三臨界點附近的濕透行為，以及是否有濕透轉變的發生。我們可藉由系統參數的改變，如溫度、壓力、鹽類濃度及成分組成等，來逼近三臨界點。在多成分的溶液中，三臨界點定義為三共存的液相同時轉變為相同的一相之臨界點。因此，本實驗乃是利用水＋油＋界面活性劑系統中油類的改變來逼近三臨界點。結果發現：隨著油類碳鏈的減少，可成旦G近三臨界點。

本實驗主要研究的兩大系統為“H2O +Alkane( k=7,8 ) +C4E1” 以及 “H2O +Alkylbenzene( k=11,12,13 ) +C6E2”。我們乃是利用懸附液滴張力儀所測得界面張力值來判斷系統的濕透行為。當系統由下臨界溫度升至上臨界溫度時，我們可觀察到此兩系統皆存在兩個濕透轉變（完全濕透→部分濕透→完全濕透）。另外，我們還多研究了一個系統：“H2O +Octylbenzene +C4E1”。發現到於整個三相區間皆呈現完全濕透現象。由於此系統之三相區間相當小，因而符合Kahlweit et al.(1991) 所提的三臨界點附近皆為完全濕透之論述。

此外，我們所研究的六個系統，於上、下臨界溫度附近皆呈現完全濕透現象。此行為符合Cahn（1977）的臨界濕透理論：針對一個三相共存的系統，當溫度相當接近其中兩相的臨界溫度時，必能觀察到完全濕透行為。

關鍵字

濕透轉變 ； 三臨界點 ； 濕透行為

並列摘要

In a three-phase coexisting equilibrium system, the middle phase may exist in the form of nonwetting, partial wetting, or complete wetting. The transition from a partial wetting regime to a nonwetting (or a complete wetting) regime, or vice versa, is called a wetting transition. What we are concerned about is the wetting behavior near the tricritical point and if the wetting transition exists. By adjusting the system parameters, such as temperature, pressure, salt concentration and compositions, we can make the system come close to its tricritical point. In a multicomponent liquid mixture, a tricritical point (tcp) is defined as a point at which three coexisting liquid phases become simultaneously identical single phase. In this study, we try to search the tricritical point by changing the oil of the system “water +oil +surfactant”. With the decrease of the oil chain length, we can successfully approach the tricritical point.

There are two main systems: “H2O +Alkane( k=7,8 ) +C4E1” and “H2O +Alkylbenzene( k=11,12,13 ) +C6E2” carefully examined in this study. Pendant drop/bubble tensiometry was applied to measure interfacial tensions to judge the wetting behavior of the systems. When rising temperature from the lower critical point to upper critical point, we can find both the two systems exist two wetting transitions: complete wetting→partial wetting→complete wetting. Besides, we also performed an experiment on the system “H2O +Octylbenzene +C4E1”. It is found that complete wetting behavior is observed over the whole three-phase region, consistent with Kahlweit’s finding: only complete wetting would be observed near the tricritical point. Cahn’s theory addresses that for a three-phase coexisting system, complete wetting should be observed near the critical temperature. All the systems examined in this study always exhibit complete wetting behavior near the critical temperature, in accord with Cahn’s theory.

並列關鍵字

wetting behavior ； tricritical point ； wetting transition

參考文獻

Yeh, M.-C., L.-J. Chen, S.-Y. Lin, and C.-T. Hsu, “A Modified Calibration Technique for Pendant Drop/Bubble Tensiometry,” J. Chin. Inst. Chem. Engrs. 32, 109, 2001.

Andreas, J. M., E. A. Hauser, and W. R. Tucker, “Boundary Tension by Pendant Drops,” J. Phys. Chem. 42, 1001, 1938.

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Buff, F. P. and H. Saltsburg, “Curved Fluid Interfaces.Ⅱ.The Generalized Neumann Formula,” J. Chem. Phys. 26, 23, 1957.

Cahn, J. W., “Critical Point Wetting,” J. Chem. Phys. 66, 3667, 1977.