Wilhelmy force loops

Figure 26.9 A typical Wilhelmy force loop of a relatively hydrophobic surface the force loop is composed of three cycles each consisting of one immersion (advancing) and one emersion (receding) process. The sample plate is polycarbonate (PC) modified with TMS plasma.

WILHELMY FORCE LOOPS AND FLUID HOLDING TIME... 

Figure 26.22 Wetting stages of Wilhelmy force loops on a polymeric plate the gray and black lines depict the absence and presence of a continuous water film, respectively the consecutive wetting stages of a Wilhelmy force loop are as follows (A) first immersion (Adv.l), B) first emersion (Rec.l), (C) second immersion (Adv.2), and D) second emersion (Rec.2).

Figure 26.24 Wilhelmy force loops of (CH4 + air) plasma treated glass plates in (W) DDI water and (T) artificial tear fluid at varying second immersion velocities (1) 2mm/min, (2) 5mm/min, (3) lOmm/min, and (4) 20mm/min. Plasma discharge conditions were 38W, SOmTorr, 1 seem CH4, 2 seem air, 20 min first and second emersion and first immersion velocities were fixed at 20mm/min, the use of water and tear fluid 4elded advancing contact angles, 0D,a,i means, and standard deviations of 47° 1 and 48° 3, respectively.

Figure 26.30 Wilhelmy force loops of (A) nylon-6, (B) PMMA, and (C) PTFE plates in artificial tear solution. At the end of the first emersion, the plates were held out of the solution for (1) Omin, (2) 5 min, and (3) 40 min at a depth of 5 mm the use of tear fluid on nylon-6, PMMA, and PTFE, yielded advancing contact angles, 0D,a,i. means, and standard deviations of 68° 3, 91° 3, and 130° 1, respectively.

Figure 26.31 Wilhelmy force loops of (A) untreated, (B) (CH4 + air) plasma treated, and (C) (CH4 + air) plasma then O2 plasma treated contact lens material using artificial tear fluid the emersion/immersion velocities were all fixed at 5 mm/min.

Figure 30.1 Comparison of Wilhelmy force loops (a) LDPE, (b) O2 plasma-treated LDPE.

Figure 30.2 Correlation between the overshooting in Wilhelmy force loop and the plasma susceptibility expressed by the weight loss rates.

Figure 30.3 The effects of O2 flow rate and the treatment time on Wilhelmy force loop Column A 1 seem, B 10 seem, Row from top (1) 0.2 min, (2) 1 min, (3) 2 min, (4) 4 min. System pressure and input power were fixed at SOmtorr and 36 W respectively. The dynamic advancing contact angle of water and fluid holding time, FHT, are shown on each plot.

Figure 30.5 The effects of input power (A) 8 W, (B) 30 W, (C) 63 W, and system pressure (1) 25mtorr, (2) 50mtorr, (3) lOOmtorr, on Wilhelmy force loops of O2 plasma-treated LDPE oxygen flow rate and plasma treatment time were fixed at 10 seem and 0.2 min, respectively, dark-colored force loops were taken just after samples were removed from the reactor, and gray-colored force loops were taken two weeks later after equilibrating with ambient air.

Wilhelmy plate wetting parameters, such as plate velocity during immersion or emersion and halting the motion of the plate after immersion or emersion, have been shown to alfect the intrinsic hysteresis, which consequently affects the overall shape of the force loop [3]. These wetting parameters were found to affect FHT differently depending on whether pure water or an aqueous artificial tear solution was employed as the wetting medium. 

Ring method — Method to determine the - interfacial tension in liquid-gas systems introduced by Lecomte du Noiiy [i]. It is based on measuring the force to detach a ring or loop of a wire from the surface of a liquid. The method is similar to the -> Wilhelmyplate method when used in the detachment mode [ii]. See also -> electrocapillarity, -r electrocapillary curve, -> Gibbs-Lippmann equation, - Wilhelmy plate (slide) method, - drop weight method, - Lippmann capillary electrometer. 

The most common methods used to measure surface tension of surfactant solutions using commercial instruments are the du Noiiy ring and Wilhelmy plate techniques (Fig. 4.7c and d). In the former, the force necessary to detach a ring or wire loop from a liquid surface is measured (for example using... 

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