Question

describe the advantage and disadvantage of pendant drop method to determine the contact angle/surface tension.

Answer 1

The pendant dtop method offers several advantages. Both advancing and receding contact angles can be established by slowly pulling the surface away from the liquid or pushing back toward the liquid; thus, the dynamic contact angles can be studied. Due to its high sensitivity, the technique can be used to characterize surfaces with low contact angle hysteresis (on the order of 1°). The technique has shown great potential in discriminating low friction surface coatings. However, evaporation of the test liquid can cause uncertainty of the measured distance h, which will induce a small deviation in the experimental A(h) curve. Moreover, to measure the wetted area, the method requires transparent films to be coated on a transparent spherical surface, which can cause serious limitation and inconvenience in sample preparing. This problem might be solved by introducing a new and better means to measure the wetted area.