Contact angle measurement procedure

Section 4.1 briefly describes some of the commonly employed experimental tools and procedures. Chaudhury et al., Israelachvili et al. and Tirrell et al. employed contact mechanics based approach to estimate surface energies of different self-assembled monolayers and polymers. In these studies, the results of these measurements were compared to the results of contact angle measurements. These measurements are reviewed in Section 4.2. The JKR type measurements are discussed in Section 4.2.1, and the measurements done using the surface forces apparatus (SFA) are reviewed in Section 4.2.2. 

Procedures for infrared and ultraviolet absorption and contact angle measurements are reported in the previous publication (11). 

Procedure. With the exception of poly (ethylene terephthalate), 20/ films of each polymer were prepared by the evaporation or approximately 4% solutions in quartz or glass dishes of 50 cm.2 area for extraction experiments. For contact angle measurements, films were evaporated on acid-cleaned microscope slides by a dipping technique. Tetrahydrofuran was used with poly (vinyl chloride), methylene chloride with the other polymers. 

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 ... 

Surface free energies of hydroxylapatite and fluorapatite were determined by Busscher et al. (1987) from contact angle measurements. They found that in vacuum y ranges between 72 and 95 mJ/m. In the presence of a saturated vapor, y was found to be between 28 and 48 mJ/m. The difference in y obtained by the two methods was explained as resulting from the presence of an adsorbed film originating from the liquid droplets employed in the measuring procedure. Face-specific measurements revealed for the 001 crystal face y = 28 3 mJ/m, and y = 48 7 mJ/m on 100 for fluorapatite, and for hydroxylapatite the 001 crystal face y = 39 11 mJ/m, and y = 30 3 mJ/m on... 

The foregoing method can also be employed to determine the adhesion properties of other filled polymer systems. The procedures involved in this analytical method are summar ized as follows (1) Use proper experiments to obtain the contact angle measurements for both the filler and the polymer, (2) Plot the contact angle measurements as cos 9 versus An y and determine the critical surface... 

Now we analyze the trends in Fig. 5 in two steps (1) the silanization procedure in toluene solution and (2) contact angle measurement in an aqueous environment and their surface energies. In the n = I case, silane molecules can bind to reactive sites on the surfaces in a densely packed state but probably patchy style, due to the three bulky methyl groups per silane molecule. 

Powder contact angle This procedure allows the measurement of average contact angle and sorption speeds of powders and other porous species. The change in the weight as a function of time is measured. 

Many of the techniques listed above have been used in our past and current work, but in this charter we report mainly results relating to a subset of these, particularly XPS, contact angle measurements, and various "functional" tests. Regarding XPS, our surface analytical instrument (VG - ESCALAB 3 Mk II) and spectral deconvolution procedures have been described in detail elsewhere [21,27], and wiU not be repeated here. 

Figure-1. Zisman s plot procedure and liquids used for contact angle measurements...

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