The Measurements of Contact Angles of Nylon 12 powder and the Consideration of the Dependency of Tablet Porosity for the Wetting

In present study, the author proposed a comparatively simple method for the evaluation of contact angles of liquid on polyamide powder by measuring adhesional and immersional wetting. Furthermore, the author evaluated the porosity dependency of wetting of pressed tablet and examined versatility of corrected equation derived from Young equation. First, change of the advancing contact angles of a liquid drop with time for the systems composed of the powder pressed into tablet, sodium dodecyl sulphate solutions, and the air, were measured at suitable time intervals. Secondly, similar measurements were done with several tablets having various porosities. The results obtained showed that plot of the advancing contact angle against time gave a straight line. Accordingly, the contact angle (θ0*) was determined by extrapolated the line to time zero and regarded as the apparent contact angle on nylon 12 plate with rough-surface. Since the extrapolated contact angle (θ0*) changed linearly with increasing tablet porosity, the true contact angle (θ) could be calculated from the proposed equation, cosθ0*=cosθ± (1±cosθ) εfχ.