溫度與壓力對水+聚氧乙烯醇類二成份混合物濕透行為之影響

Temperature and Pressure Effects on Wetting Behavior in Water + Polyoxyethylene Alcohol Binary Mixtures

吳志剛(Chih-Kang Wu)

指導教授 ： 陳立仁

國立臺灣大學/工學院/化學工程學研究所/博士(2005年)

https://doi.org/10.6342/NTU.2005.01624

摘要

在本研究中，我們自行組裝一套實驗設備能應用於多成份(相)系統在較大温度、壓力範圍條件之平衡狀態下，同時進行其平衡組成、密度，及各平衡相間界/表面張力的量測。根據所量測到的實驗數據來瞭解其系統之相行為及濕透行為；另外，可藉由界/表面張力的變化關係來更進一步地探討其系統濕透轉變的存在。
對於一個三相（a, b, r）平衡系統中，各平衡相的密度大小關係：r > b > a。少量的中間（b）相於上（a）下（r）兩相之間所呈現的濕透行為，可分為：非濕透行為（nonwetting）、部份濕透行為（partial wetting）及完全濕透行為（complete wetting）。而部份濕透行為與非濕透行為（或完全濕透行為）之間的相互轉變，我們稱之為濕透轉變（wetting transition）。濕透轉變通常發生在藉由系統條件改變，包含溫度、壓力、鹽度、烷類的碳鏈長度，及界面活性劑的親疏水性等，使系統逼近其臨界點的過程中。
在此，我們選用水+聚氧乙烯醇類兩成份系統，仔細地探討聚氧乙烯醇類分子構型、溫度及壓力條件對濕透行為之影響。從量測到的界/表面張力演算出其對應的濕透係數（wetting coefficient），來判斷其濕透行為與濕透轉變的發生。在水+丁醇類同分異構物系統中，我們發現當分子形狀由直鏈的一級醇->具側鏈的二級醇時，富醇相會發生部份濕透->完全濕透的濕透轉變。而在水+丁基氧乙烯醇類同分異構物系統中，我們發現當分子形狀由具側鏈->直鏈的聚氧乙烯醇時，富醇相則會發生由部份濕透->非濕透的濕透轉變。此外，我們彙整本實驗室先前的成果發現：對於水+聚氧乙烯醇類系統中，使系統逼近其上臨界溫度，醇類的碳鏈越短，富醇相的濕透行為越傾向完全濕透；反之，若使系統逼近其下臨界溫度，醇類的碳鏈越短，則富醇相越傾向非濕透。
接著，對於水+丁基氧乙烯醇類同分異構物系統，我們在其不互溶的液-液兩相區中，都發現到隨著溫度增加，其富醇相的濕透行為會產生：非濕透->部份濕透->完全濕透，這樣一個順序的濕透轉變。配合濕透行為的觀察，我們同時量測到的平衡組成應用UNIQUAC模式來加以處理，將所得到的作用參數以五次多項式來作迴歸。最後，在水+異丁基氧乙烯醇系統中，隨著壓力的增加，在靠近系統下臨界溫度的附近，我們成功地觀察到富醇相發生部份濕透->非濕透的濕透轉變。

關鍵字

濕透行為 ； 濕透轉變 ； 界/表面張力

並列摘要

A new integrated apparatus was assembled to obtain the experimental data of thermodynamic properties: equilibrium phase densities, compositions, and surface/interfacial tensions over a wide temperature and pressure range. The experimental results are important for understanding the phase behavior and wetting behavior of the phase equilibrium system.
Consider three fluid phases, a, b, and r, in equilibrium under gravity and the densities of these three phases are in the order ρr > ρb > ρa. A small amount of the middle b phase at the a-r interface exhibits the wetting behavior, such as nonwetting, partial wetting, and complete wetting. A transition from a partial wetting regime to a complete wetting (or nonwetting) regime, or vice versa, is called a wetting transition.
In this work, the effects of molecular structure, temperature, and pressure on wetting behavior were investigated by a series of the binary aqueous systems including the homologues of non-ionic polyoxyethylene alcohols. The wetting behavior and the location of a wetting transition could be deduced by the wetting coefficient derived from the surface/interfacial tensions. It was found that for the water + isomeric butanol systems, a wetting transition from partial wetting to complete wetting occurs with increasing temperature and the changes of molecular structure from a primary linear butanol to a secondary one. For the two water + isomeric 2-butoxy-ethanol systems, a wetting transition from partial wetting to nonwetting takes place with decreasing temperature and the changes of molecular structure from a branched alcohol to a linear one. Additional results were codified from this work and our previous study.
Otherwise, the influence of temperature on wetting behavior was observed completely in the two water + isomeric 2-butoxy-ethanol systems. It was found that the alcohol-rich phase exhibits a sequence of wetting transitions, nonwetting->partial wetting->complete wetting, at the gas-aqueous interface along with increasing temperature over the temperature range of its closed-loop miscibility gap. Furthermore, the equilibrium phase densities and compositions were obtained to study the phase behavior of the systems simultaneously. The equilibrium phase compositions were then correlated with universal quasi-chemical (UNIQUAC) model by fitting the UNIQUAC interaction parameters as a function of temperature. Finally, the effect of pressure on wetting behavior was first observed experimentally in the simple water + 2-isobutoxy-ehtanol system. A wetting transition from partial wetting to nonwetting happens with increasing pressure at a fixed temperature near its LCST. However, the closed-loop miscibility gap of the system shrinks slightly with a pressure increase up to 100 bar. The wetting transition induced by a pressure change was successfully obtained.

並列關鍵字

wetting behavior ； wetting transition ； surface/interfacial tensions

參考文獻

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