Hydrophobicity of fluorocarbon-finished electrospun poly (acrylonitrile) nanofibrous webs

This article reports the hydrophobicity of fluorocarbon-finished nanofibrous webs composed of electrospun poly (acrylonitrile) nanofibers with fiber diameter in the range of about 100-3000nm. The results obtained from sliding angle and contact angle measurements tests are reported. It was found that the contact angle of unfinished samples with average fiber diameters of about 700, 980, and 3050nm lies between 132 degrees and 134 degrees, indicating a rather high and at the same time not much different hydrophobicity for the webs. However, after finishing the electrospun nano- and microfibrous webs, the contact angle increased by a considerable amount to 138 degrees-157 degrees for the webs with average fiber diameter in the range of about 100-3050nm, respectively. Sliding angle test of the finished nanofibrous webs showed a minimum angle of about 3 degrees for the web with average fiber diameter of 3055nm. To the best of authors' knowledge, the rolling angle of 3 degrees is the smallest rolling angle ever reported in the literature. The result of this work showed also that sliding angle test may be more sensitive than contact angle test. It was also ascertained that none of the Wenzel model and Cassie-Baxter model can represent the superhydrophobicity of the fluorocarbon-finished nano- and microfibrous webs.