Effect of Temperature on Surface Tension

An important variable of surface tension is temperature, which has practical value during the adhesion bonding of plastics. Surface tension of both adhesive and polymer is affected by temperature. Guggenheim s equation (Eqn (3.24)) is apphcable to liquids that have small molecules. It has also been found to be applicable to polymers. In this equation, 70 is surface tension at F = 0 K and Tc is the critical temperature (K) of the liquid. The values of 70 and 

---

Effect of Temperature on Surface Tension According to the kinetic theory, molecular kinetic energy is proportional to absolute temperature. The rise in temperature of a liquid, therefore, is accompanied by increase in energy of its molecules. Since intermolecular forces decrease with increase in the energy of molecules, the intermolecular forces of attraction decrease with rise of temperature. 

Fig. 2.4 Effect of temperature on surface tension and dynamic viscosity of water, data from [14]...

Effects of anion on surface tension. Surface tension measurements by the du Nouy ring method kept the type of cation constant while the anions were varied to include [BMIM][Bp4], [BMlM][PFg], BMlM][Tf2 N], and [BMIMJpFjSO ] and four additional cation-anion pairs. The dry ionic liquids showed the expected decreasing trends in surface tension with increasing temperature for each ionic liquid cation-anion series [5]. Increasing anion size appeared to correlate with a decrease in surface tension of the ionic liquid - as noted in reference [34]. 

Solubility, causes modifying, 319 and chemical potential, 359 curve, 307 equation, 306 of gases in liquids, 275, 371 effect of pressure on, 316 effect of surface tension on, 447 effect of temperature on, 302, 372... 

The effect of temperature on viscosity may be linked with its effect on other properties, such as density, surface tension, and vapour pressure. 

For both mechanisms the effect of temperature on deposition can be attributed to change in viscosity, as surface tension does not vary much with temperature. Investigation of the effect of viscosity with ash particles is difficult, because little is known about the viscosities of iron aluminosilicates and ferrous sulfide at temperatures from 850° to 1050°C and, in any case, the ash particles vary in composition and presence of high melting phases. Therefore, we have chosen to use glass spheres as a homogeneous model material of known viscosity in tests for a study of deposition. We assume that the two materials are sufficiently alike in relevant properties that their borderlines for deposition occur at the same viscosity although their temperatures there may be different. We report here a few results of a preliminary nature. 

Based on surface tension measurements using the rise height of water in narrow capillaries and then obtaining the entropy term by numerical differentiation of the data, Drost-Hansen (1965) found a large peak in entropy of surface formation near 30 C. This is taken to mean that vicinal water is disorganized at 30°C (see also Drost-Hansen, 1973). Another example is provided by the data of Wershun (1967), who studied the effects of temperature on chromosome aberration rate in the broad-leaf bean Viciafaba. As shown in Figure 7, a notable peak occurs at 30°C. 

The effect of temperature on the surface tension of mixtures of n-propanol/ -heptane has been investigated. The variation of surface tension by temperature (K) for pure components was... 

To obtain any thermodynamic information of such systems it is useful to consider the effect of temperature on the interfacial tension. The aUcane-water interfacial tension data have been analyzed (Eigure 3.10). These data show that the interfacial tension is lower for Cg (50.7 mN/m) than for the other higher chain length alkanes. The slopes (interfacial entropy -djIdT) are all almost the same, 0.09 mN/m per CH2 group. This means that water dominates the temperature effect, or that the surface entropy of the interfacial tension is determined predominantly by the water molecules. Eurther, as described earlier, the variation of surface tension of alkanes varies with chain length. This characteristic is not present in interfacial tension data however, it is worth noting that the slopes in the interfacial tension data are lower than those of both pure alkanes and water. The molecular description must be analyzed. 

Despite these many advances, certain aspects of the subject of this paper have been neglected and further investigation is much needed. No reliable data are available on the effect of temperature on the equilibrium contact angles of any systems all of the measurements reported here were made at 20°C. and 50% relative humidity. However, several general effects of variations in the temperature and humidity on the contact angle can be outlined. It is well known that the surface tensions, 7lv > organic liquids decrease linearly with rising... 

In the method employed in obtaining these data any effect of temperature on the solid-liquid interfacial tension is ignored. For the n-alkanes [66] the amount of xmdercooling was only 12° to 13°C. Hence, applying any reasonable temperature coefficient-e.g., -0.05 dyne per cm. per degree-would not have a significant effect. It is therefore suggested that a satisfactory estimate of the solid-liquid tension for n-decane on solid hydrocarbon surfaces would be 10 dynes per cm. 

In view of the uncertainty regarding the effect of temperature on the benzene result and because the hydrocarbon surfaces of interest are paraffinic rather than aromatic, any estimate for the solid-liquid tension for solid-benzene pairs is less satisfactory than the n-decane value. Nevertheless, it is of interest to make such estimates for several other hydrocarbon liquids as well as for benzene. The increase in solid-liquid interfacial tension for aromatic compoxmds, which is indicated by the undercooling experiments, can at least be reflected in such estimates. Since both one-liquid and two-liquid adhesion tension data are available for isopropylbiphenyl, an estimate for this liquid is desirable. For comparison, and because one-liquid adhesion data exist, tert-butylnaphthalene has been chosen as another case for which an estimate of the solid-liquid interfacial tension has been made. 

Effect of temperature on the surface tension of surfactant solutions... 

One can obtain a relationship (Eq. (2.11)) between the critical surface tension and the solid-vapor surface tension by setting the contact angle to 0 in Young s equation (Eq. (2.6)). Therefore, critical surface tension is smaller than solid-vapor surface tension. Figure 2.7 shows the effect of temperature on the critical surface tension of two plastics. The surface energy of plastics decreases with temperature. 

Figure 2.7 Effect of temperature on critical surface tension of two plastics.t ...

The effects of temperature on filter performance are complex in so far as physical properties which influence all parts of the cycle are affected. Temperature affects the rates of liquid flow through fluid viscosities and moisture contents during deUquoring through surface tensions (the effects of fluid densities being relatively insignificant). The important fluid property... 

The effect of temperature on adsorption equilibrium Is worth mentioning. Rise of temperature decreases the extent of adsorption. This is in spite of the fact that surface tension decreases with a rise in temperature. The reason behind this observation is that molecular cohesion, a fundamental cause of adsorption, is disrupted by thermal agitation. For example, when iodine is added to starch solution, a blue colour appears due to formation of starch iodide. However, upon heating, the blue colour disappears due to the failure of iodine to remain adsorbed on the starch particles at higher temperatures. 

---