Contact Angle of Water on Polymer Surfaces
Contact Angle of Water on Polymer Surfaces
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DOI：
10.1021/la00019a068
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发表时间：
1994-07
期刊：
影响因子：
3.9
通讯作者：
T. Yasuda;T. Okuno;H. Yasuda
中科院分区：
文献类型：
--
作者：
T. Yasuda;T. Okuno;H. Yasuda
固着滴(前进和后退)接触角表面上的水凝胶凝胶固体(15%),琼脂凝胶固体(2%),研究了聚四氟乙烯(PTFE)薄膜在20 c水的前进接触角与凝胶的postcoagulation时间增加,达到一个固定值(平衡接触角)在大约1 h。水前进接触角的价值大约是75和25明胶凝胶和琼脂凝胶,分别聚四氟乙烯为100。接触角的推进取决于空气的相对湿度，相对湿度越低，接触角越大。明胶凝胶表现出明显的接触角滞后（前进和后退的接触角之间的差异），而琼脂凝胶表现出前进和后退的接触角之间的差异很小，部分原因是前进角小。在前进和后退过程中，ptfsurface的前进和后退接触角几乎相同，液滴下的表面积也相同。对于明胶水凝胶，在后退过程中，接触面积不会随着液滴体积的减小而减小（只是使无根液滴的轮廓变平），而与明胶的接触面积会随着轻微的滞后效应而减小。通过液滴接触角测量在聚合物膜上观察到的滞后效应主要是由于水和聚合物分子之间产生了吸引力，这是由于液态水和接触聚合物固体的表面状态之间建立新的平衡而引起的表面构型的改变。
Sessile droplet (advancing and receding) contact angles of water on surfaces of gelatin gel (15% solid), agar gel (2% solid), and polytetrafluoroethylene (PTFE) film were investigated at 20 C. The advancing contact angle of water increases with the postcoagulation time of the gels and reaches a stationary value (the equilibrium contact angle) in approximately 1 h. Thevalue of the advancing contact angle of water is around 75 and 25 for the gelatin gel andthe agar gel, respectively, and 100 for PTFE. The advancing contact angle is dependent on the relativehumidity of air, andthe lower the relative humidity, the higher is the contact angle. The gelatin gel shows a pronounced hysteresis of contact angle (discrepancy between advancing and receding contact angles), while the agar gel shows very little difference between the advancing and receding contact angles, partly due to the low advancing angle. Advancing and receding contact angles are nearly identical for the PTFEsurface, and also the surface area under the droplet in the advancing and receding processes are identical. With gelatin hydrogels, the contact area does not decrease according to the decrease of drop volume during the receding process (merely flattens down the profileof the sessile droplet), whereas the contact area with the agargel decreases with a slight hysteresis effect. The hysteresis effect observed with a polymeric film by thesessile droplet contact angle measurement is largely attributable to the creation of an attractive force between the water and polymer molecules, which results from the change of the surface configuration to establish a new equilibrium between liquid water and the surface state of the contacting polymer solid.