Contact angles of polymethyl methacrylate(PMMA), polyvinyl chlorde(PVC), polyvinylidene fluorde(PVdF), and auminum powders were measured by wicking method based on Washburn equation for the organic liquids, methanol and ethanol. sodium dodecyl sulfate(SDS), and cetyltrimethylammonium bromide(CTABr)aqueous solutions. It was observed that the values of contact angle became different depending on chemical structures and physical characteristics of liquids and solids. The critical surface tensions were estimated by Zisman plot using the values of experimentally measured contact angles. From the results, it was clearly observed that the surface characteristics considerably changed with adding surfactants. The surface free energy and its components (dispersive, polar) for PMMA and PVC, of which surfaces were adsorbed from SDS aqueous solution with several different concentrations, were also determined. The dispersive component decreased as the nondispersive component increased significantly, which was caused by the increase of the amount of the adsorption of hydrophilic hydroxyl groups on the hydrophobic solid surface.

분체 PMMA, PVC, PVdF와 aluminum에 대해 유기액체, 몰분율에 따른 메탄올, 에탄올 수용액, 농도에 따른 음이온 계면활성제 SDS와 양이온 계면활성제 CTABrtndyddor과의 접촉각을 Washburnt식을 기본으로 한 wicking법을 사용하여 측정하였다. 이로부터, 접촉각은 고체와 액체의 화학적 구조와 물리적 성질에 따라 다른 값을 가짐을 알 수 있었다. 측정된 접촉각으로부터 고체의 표면 특서을 결정짓는 임계표면장력을 Zisman plot으로부터 예측하였으며, 이로부터 고체의 표면 특성은 계면활성제의 첨가에 의해 상당한 변화가 야기됨을 알 수 있었다. 계면활성제 SDS 수용액을 흡착시킨 분체 PMMA/SDS와 PVC/SDS의 SDS 농도에 따른 표면자유에너지와 그 성분 값을 결정하였는데, 그 결과 고체 표면에 계면활성제 분자의 흡착으로 인해 소수성 고체 표면에 친수성의 수산기가 흡착됨으로써 분산 성분이 감소하는 반면, 극성 성분은 급격히 증가함을 알 수 있었다.

Keywords: contact angle; wicking method; critical surface tension; surface free energy