Applicability of Washburn capillary rise for determining contact angles of powders/porous materials
Applicability of Washburn capillary rise for determining contact angles of powders/porous materials
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DOI：
10.1016/j.jcis.2013.01.033
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发表时间：
2013-05-01
影响因子：
9.9
通讯作者：
Newby, Bi-min Zhang
中科院分区：
文献类型：
--
作者：
Kirdponpattara, Suchata;Phisalaphong, Muenduen;Newby, Bi-min Zhang
Washburn毛细管上升（WCR）技术已被广泛用于测定粉末或多孔材料的接触角;然而，存在关于粉末尺寸和粉末填充的问题，特别是对于表现出大接触角滞后的材料。本文讨论了其中一些关切问题。由于尼龙616平板膜具有较大的水接触角滞后，将其粉碎成不同粒度的粉末，然后用作模型填料。将粉末填充在玻璃管中以产生影响测试液体的渗透（即前进）速率的各种填充结构。虽然发现从WCR获得的所有前进接触角被高估，但当使用相对大的粉末（例如500-2000 μ m）来填充管时，得到更合理的值。对于较大的粉末，填料包含较大的空隙，因此导致液体的渗透速率较慢，因此前进接触角相对较小。通过使用座滴法也观察到由较慢的推进速率获得的较小的推进接触角。为了验证使用大粉末（500-2000 μ m）通过使用WCR进行接触角测定的适用性，测量了具有和不具有UV/臭氧处理的细菌纤维素/藻酸盐复合海绵（BCA）的前进水接触角。结果表明，采用相对较大的粉末，WCR可以获得合理的前进接触角，并评估复杂多孔材料的润湿性变化。(C)2013 Elsevier Inc. All rights reserved.
The Washburn capillary rise (WCR) technique has been widely utilized for determining contact angles of powders or porous materials; however, there are concerns regarding powder size and powder packing, especially for materials that exhibit large contact angle hysteresis. In this paper, some of these concerns were addressed. Due to the large water contact angle hysteresis on flat nylon 616 films, these films were ground into powders of different sizes and then used as model packing materials. The powders were packed in glass tubes to result in various packing structures that affected the penetration (i.e. advancing) rate of the test liquids. While all advancing contact angles obtained from WCR were found to be overestimated, more reasonable values were resulted when relatively large powders (e.g. 500-2000 mu m) were used to pack the tubes. With larger powders, the packing contained bigger voids and consequently lead to slower penetration rates of the liquids, hence a relatively smaller advancing contact angle. The smaller advancing contact angle obtained from the slower advancing rate was also observed by using the sessile drop method. To verify the applicability of using large powders (500-2000 mu m) for contact angle determination by using WCR, the advancing water contact angles of a bacterial cellulose/alginate composite sponge (BCA) with and without UV/ozone treatment were measured. The results showed that by using relatively large powders, WCR could be applied to obtain a reasonable advancing contact angle and assess the wettability change of complex porous materials. (C) 2013 Elsevier Inc. All rights reserved.