洗浄作用の基礎研究 (第3報)

脂肪酸及び脂肪アルコールの表面張力並びにその分散力成分と極性成分

抄録

Surface tension of fatty acids (C₄C₁₃) and fatty alcohols (C₄C₁₈) was estimated by contact angle measurements. Geometric mean approximation method (extended Fowkes' Equation) was applied to estimate the dispersion force component (γ^d) and the polar force component (γ^p) to the total surface tension (γ) from contact angle data.
Surface tension of liquid oils, i.e., fatty acids (C₄C₈) and fatty alcohols (C₄C₁₁), increases with increasing carbon number between 24.428.9 dyn/cm. The contribution of dispersion force component to surface tension of these oils, γ₁^d/γ₁, is 90% or more and the rest part is the polar force component.
Surface tension of solid fatts, i.e., fatty acids (C₁₂C₁₈) and fatty alcohols (C₁₄C₁₈), decreases with the carbon number increase between 62.424.1 dyn/cm. The contribution of polar force component to surface tension of fatty alcohol is rather high, especially in C₁₄ and C₁₆, however, that of fatty acids is lower and nearly constant ratio (about 10%).
Surface tension of decanoic acid (C₁₀), 1-dodecanol (C₁₂), and 1-tetradecanol (C₁₄) at 10°C (solid state) and 40°C (liquid state) was compared in these two states of materials. It was proved that solid fatty substrates have higher surface tension than liquid ones.
The work of adhesion (W_a) between these model oily soils and the polymer substrates in liquid media may offer the clue to clarify the mechanism of oily soil removal.