Empirical study and prediction of liquids retention on structured polymer surfaces

Abstract

Liquids' contact angle hysteresis and critical retention volumes on five commonly used plastics with surface structures were studied. The chevron‐like groove structures, which are orthogonally arranged, make the liquid–solid contact line elongated while the droplet found staying in the Wenzel state. Various dimensions of surface structures were represented by contact length ratio σ. Advancing and receding contact angles of liquids on polymer surfaces with various conditions were reported. Reduced hysteresis H, which links between advancing and receding contact angles, was also studied and found to extend its availability on structured surfaces. The research found that surface structures have linear effects on liquids' advancing contact angles in the range of σ = 1.0 to 1.42. Linear regression analysis was hence proposed to predict advancing contact angles, and the results indicate that approximate 80% of data points have less than 6% error. An empirical model, which adopts liquid–solid surface tension as the source of liquids' retention force, was proposed to estimate liquids' critical retention volumes on inclined surfaces. The proposed model found good agreements with existing experiment data and demonstrated its superiority over previous ones. The present model provides an approach to predict liquids' storage/repellency on structured surfaces when the advancing contact angles are predictable. Copyright © 2016 John Wiley & Sons, Ltd.