Zisman s critical surface tension

Despite the approximation, Zisman s critical surface tension (39, 40) still provides the most convenient means of expressing the surface tension of a solid. Later Gardon (6) suggested a possible linear relationship between the critical surface tension yc and the solubility parameter for liquid-like polymers. He also proposed the following relation between solid surface tension and critical surface tension ... 

Very recently, Good [17] has extended the theory of interfacial energies [16] to include an explicit accoxmt of the different types of inter molecular forces dispersion, dipole induction, and dipole orientation. In the present paper, we will use the theory, as extended [17], to show how the actual surface free energies of certain solids can be calculated from contact angle data, including Fox and Zisman s critical surface tensions. 

Table 59.1 is arranged, like all the tables in this compilation, in order of increasing surface tension so the familiar effect of polar cmistituent groups raising the surface tensimi is readily apparent. Most polymer chemists are familiar with Zisman s critical surface tension of the wetting [4] constituent effect (see Table 59.3) where the order of increasing surface tension is... 

Lee [6] classifies rubbers by wettability, ranking them according to Zisman s critical surface tension (mj/m ), see Table 12.1. 

It is often stated that Zisman s critical surface tension is numerically close to the surface tension of the solid Under some simplifying assumptions and more specifically ... 

In a recent case study (see Svendsen et al, 2007 and also Problem 6.1), in collaboration with a paint company, the adhesion of six different epoxies-silicon systems has been studied. These paints are used in marine coating systems. Some epoxies showed adhesion problems in practice while others did not. The purpose of the study was to understand the origin of these problems and whether adhesion could be described/ correlated to surface characteristics, e.g. surface tensions. An extensive experimental study has been carried out including both surface analysis (contact angle measurements on the six epoxies, surface tension of silicon at various temperatures, atomic force microscopy (AFM) studies of the epoxies), as well as measurements of bulk properties (pull-off adhesion tests and modulus of elasticity). Theoretical analysis included both estimation of Zisman s critical surface tensions and surface characterization using the van Oss-Good theory. 

The liquids used for contact angle measurements must be carefully selected depending on the type of information which is required. For the measurement of Zisman s critical surface tension of wetting for polymers (see Section 23.2.3.2) a series of pure liquids of similar polarity are required. Liquids may be classified into three series (a) nonpolar liquids such as a homologous series of n-alkanes or... 

Table I. Measured values of Zisman s critical surface tension for spreading, Y , culled from the literature (see references contained in Refs. 4 and 12-16) are compared to the average value of Ygg obtained from Equation 5 in the text. To calculate the average Ysb the measured contact angle and the surface tension of each test liquid were used in Equation 5 to obtain a value of SB the values obtained with several liquids on one solid were then averaged. The indicated ranges above are standard deviation.

Zisman s plot cos 6 varies linearly with yi,. Zzisman = Predicts critical surface tension linearity does not hold universally y depends on probe liquids. [73-76]... 

An empirical method to estimate the surface tension of a solid is Zisman s plot (cos 9 as a function of yl), which obtains the critical surface tension of wetting. In the absence of specific interaction between the surface and the liquids used for the measurement of contact angles, the critical contact angle of wetting can be accurately estimated and its value used as the surface tension of the surface. However, if a surface interacts with liquids used as the sessile droplet for the contact angle measurement, to the extent that the surface tension is altered, Zisman s plots deviate from the ideal linear relationship. In a strict sense, the plot is applicable only to imperturbable surfaces with which liquid contact does not alter surface configuration, i.e., no surface dynamics applies. 

Critical surface tension of solids (Zisman s method)... 

The critical surface tension yc as deduced by using Zisman s approach, is also usually considered as an approximation of the surface free energy of solids. Thus, yc values of 30.8 mN m 1 [63] and 39.0 mN m- 1 [62] have been reported for MC and CA, respectively. However, these values are quite different from those reported by Rowe [59,60], which makes questionable the comparison of values obtained by different techniques. 

PVeC copolymer surface are in good agreement, generally within the limits of experimental error. These values of 6 are very similar to those reported previously by Ellison and Zisman[S] on a poly(vinylidene chloride) surface, which for comparison are plotted in Figure 3 along with the present results. The plot of cos 6 vs. in Figure 3 shows the critical surface tension of the additive-free PVeC copolymer surface to lie between 38 and 44 dynes per cm. 

Chen et al. (1999) treated polyester films with plasma in six kinds of gases (O, Nj, He, Ar, H, and CH ). Results in terms of surface tension and three components, and and the critical surface tension of the polyester film are summarized in Table 3.9 (Chen et al., 1999). It is evident that the value of the surface tension of polyester film obtained by the extended Fowkes s equation (Fowkes, 1964) corresponds highly to y of Zisman s plots (Zisman, 1964), which coincides with the theory of (Kitazaki and Hata (1972). Surface tensions of polyester films treated with O, ... 

Fox and Zisman first proposed the concept of critical surface tension in the early 1950s. In Zisman s method, the relationship between the contact angle of various liquids on a solid and the surface tension of the liquids are investigated. Specifically, cos 9 is plotted against yLv (known as Zisman plot) in which a straight line is often obtained when a homologous series of liquids are used to wet the solid s surface (non-linear for non-homologous liquids). 

Zisman s Rule. Having treated a surface, wettability can be characterised by measuring the contact angle for each member of the alkane series. The curve cos E = /(7n) (see Fig. 1.7) is used to define a critical surface tension qc ... 

Our studies showed that the inner surface of the cardiovascular System was hydrophobic surface with Yc(Zis.)=29 dyne/cm. We could easily select polytetrafluoroethylene as the material with a smaller critical surface tension than 29 dyne/cm to make test materials. Figure-3 shows the surface properties of the inner surface of the cardiovascular system and polytetrafluoroethylene in relation to wetting properties viewed from Zisman s plots. How should we treat polytetrafluoroethylene to minimize the difference in wetting properties between the surface of polytetrafluoroethylene and the inner surface of the cardiovascular system. We tried to improve the surface properties of polytetrafluoroethylene by using the graft copolymerization method and expansion method. 

If this quantity is measured for a series of dilferent test liquids, the surface tension of the solid (fiber bundle, powder, or porous solid) can be determined. Because [m lt][rilp ] equals C-yiv cos 9 according to Eq. (53), C-yiv cos 9 can be plotted vs. the liquid-surface tension yiv of the test liquids used. This plot (see Fig. 23) will show a maximum that is analogous to Zisman s critical solid-vapor surface tension y of the investigated material [108,113]. 

The critical Zisman surface tension is anticipated to be only slightly dependent on temperature between room and LH2 temperatures. Tbe temperature dependent coefficient for the surface tension of the liquid and solid materials is negative so that the surface tension increases as the temperature is cooled below the critical temperature (Adamson and Cast, 1997). This property is difficult to measure in solids but is most probable tbat tbe S/V surface tension of SS is at most somewhat larger at LH2 temperatures than at room temperatures. 

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