Contact angle measurement hysteresis

While direct, this method is the most difficult experimentally due to the diminutive nature of fiber diameters and the uncertainty involved with contact angle measurements and hysteresis. The value i ) can also be measured on flat sheets of the fiber material but due to fabric finishes and different surface properties incurred during manufacture, the surface energetics of the sheet and fiber may be very dissimilar. Therefore, the value of co8i i was determined in the following manner from detergency data. The Kubelka-Munk Equation (12-13),... 

The meaning of the contact angle a has been illustrated In fig. 1.1.1. Experimentally the procedure is not easy because, in addition to the requirements of surface purity and homogeneity, contact angle measurements may show hysteresis, but in a number of simple systems where such problems did not arise, the Identity of from [1.3.361 and from calorimetry has been ascertained ... 

Contact Angle Measurements. The angle of contact of 93° for poly(L-norleucine) has been reported previously. Problems of preparing uniform adherent films of poly(L-methionine) and hysteresis effects combined to make measurements of 0 very imprecise it is estimated at 55° 10°. No measurements at all were possible with poly(L-leucine) for similar reasons. 

There are two main causes of contact angle hysteresis (i) the penetrahon of wetting hquid into pores during advancing contact angle measurements and (ii)... 

Dettre, R.H., Johnson, R.E.J., 1964. Contact angle hysteresis n. Contact angle measurements on rough surfaces Contact SI32. The dream of sta3ing clean lotus and biomi-metic surfaces. In Fowkes, F.M. (Ed.), Angle, Wettability, and Adhesion. American Chemical Society, Washington, DC, pp. 136—144. 

These values show the remarkably sensitive changes in adhesion levels brought about by the changing chemical groups at the surface. The work of adhesion of the fluorinated surface was only half that of a typical hydrocarbon rubber. Moreover, the hysteresis exhibited by these surfaces was very small, indicating that the systems were near equilibrium, with little frictional energy loss. In addition, the results were consistent with contact angle measurements. 

Dettre, RH. and Johnson, RE., Jr., Contact angle hysteresis. IV. Contact angle measurements on heterogeneous surfaces, J. Phys. Chem., 69, 1507, 1965. 

Dettre, R. H., and Johnson, R. E. Jr. 1963. Contact Angle Hysteresis II. Contact Angle Measurements on Rough Surfaces. Adv. Chem. Ser. 43 136. 

Figure 10.10 Scanning electron microscope images (a) and (b), showing morphology of cellulose nitrate biopolymer spray cast from cellulose nitrate/solvent/biolubricant ternary system (c) measured static water contact angle and hysteresis on the biopolymer coating as a function of biolubricant/solvent weight ratio [18].

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