접촉각 측정에 의한 분체 PMMA에 대한 수용액의 흡착 특성과 임계표면장력 예측

노승백; 안원술; 임미애

Polymer(Korea), Vol.21, No.1, 103-111, January, 1997

Estimation of Critical Surface Tension and Adsorption Characteristics of Aqueous Solution on PMMA Powder by Measuring Contact Angle

노승백, 안원술, 임미애

초록

고분자 고체의 표면 특성을 결정짓는 임계표면장력 (γ_c)을 고체와 여러 유기액체들과의 접촉각 측정으로부터 예측하였다. 분체 PMMA와 표면장력 값이 다른 유기액체들과의 접촉각을 Washburn식을 기본으로 한 wicking법으로 측정하였으며, 필름형태의 PMMA에 대한 유기액체와의 접촉각과 일치하는 결과를 얻었다. 측정된 접촉각으로부터 분체 PMMA의 γ_c는 Gibbs 흡착등온식과 Zismann plot으로 예측하였다. γ_c는 몰분율에 따른 메탄올 수용액, 에탄올 수용액에 대해서는 각각 23.7, 26.3mN·m^-1를 얻었으며, 분산액체들에 대해서는 43.6mN·m^-1의 결과를 얻었다. 사용된 액체의 분자구조와 성질에 따라 각기 다른 γ_c값들을 얻었으며, 이로부터 메탄올, 에탄올 분자의 알킬기가 소수성의 PMMA 표면에 흡착 배열하고 친수성기가 고체 표면 바깥쪽으로 배열하게 되어 물과의 상호작용을 일으킴으로써 접촉각과 γ_c가 감소됨을 유추할 수 있었다. 또한, 분체 PMMA에 대한 메탄올 수용액, 에탄올 수용액 및 분산액체들의 접촉각으로부터 고체의 표면 성질인 상호작용 매개변수(Φ_G)와 점착일 (W_A)을 결정하였다.

Critical surface tension (γ_c) is one of the important surface characteristics of solid polymers. The contact angle on powder polymehylmethacrylate (PMMA) was measured by wicking method on the base of Washburn equation for several liquids with different surface tensions. The measured values were comparable that of the film type contact angle measurement. The values of γ_c of powder PMMA estimated by Gibbs adsorption isotherm and Zismann plot were 23.7 mN·m^-1 for methanol aqueous solution, 26.3 mN·m^-1 for ethanol aqueous solution, and 43.6 mN·m^-1for dispersion liquids, respectively, showing different values depending on molecular structures and characteristics of liquids used for contact angle measurement. From the results of γ_c values, It was considered thats adsorption of organic molecules occurred at the solid polymer surface, leading to decrease in contact angle and γ_c because of increase of interaction with water. The interaction parameter (Φ_G) and work of adhesion (W_A) were also determined for powder PMMA.

Keywords:contact angle;wicking method;Zismann plot;critical surface tension;adsorption

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[3] Gutowski W, J. Adhes., 19, 29 (1985)

[4] Murphy WJ, Roberts MW, Ross JRH, J. Chem. Soc.-Faraday Trans., 68, 1190 (1972)

[5] VanOss CJ, "Interfacial Forces in Aqueous Media," p. 96, Dekker, New York (1992)

[6] "K-12 User Manual," ch. 7, KRUSS GmbH, Hamburg (1993)

[7] Lucassen-Reynders EH, J. Phys. Chem., 67, 969 (1963)

[8] Connor KA, Wright JL, Anal. Chem., 61, 194 (1989)

[9] Vazquez G, Alvarez E, Navaza JM, J. Chem. Eng. Data, 40(3), 611 (1995)

[10] Hoke BC, Chen JC, J. Chem. Eng. Data, 36, 322 (1991)

[11] McNally EJ, J. Adhes. Sci. Technol., 6(4), 445 (1992)

[12] Luner PE, Babu SR, Mebta SC, Int. J. Pharm., 128, 29 (1996)

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[16] Smith GW, Finch JA, J. Chem. Soc.-Faraday Trans., 85(1), 91 (1989)

[17] Kano Y, Akiyama S, J. Adhes. Sci. Technol., 6(11), 1251 (1992)