Capillary Dynamics of Water/Ethanol Mixtures

Surface tension and contact angle play important roles in capillary dynamics during washing commission of spray-dried detergent powder where interaction between surface chemistry and liquid is concerned. An experimental study for the dynamics of water/ethanol mixtures in both hydrophilic and hydrophobic capillary tubes has been investigated. The combination of water/ethanol mixtures and trimethylchlorosilane coating on capillaries provides a variety of liquid surface tension and contact angle for the penetrating system. Significant differences of penetrating speed on hydrophilic and hydrophobic tubes indicate that dynamic contact angle dominates the hydrophobic surface while liquid surface tension plays a more important role on the hydrophilic surface. The speed gradient of different liquids on hydrophilic surface is greater than the hydrophobic surface, mainly due to the domination between hydrogen bonding structures and water polarity while liquid moves on surfaces covered with different chemistry, physically absorbed water on silica capillaries or silanol group covered capillaries.