Surface-tension test

Surface Tension. Testing for surface tension is sometimes referred to as the contact-angle test (see Fig. 13.6). Surface free energy is defined by surface tension which is directly related to surface cleanliness. If an adsorbate (dirt) is present on a surface, the free energy-surface tension is reduced as energy is spent in bonding the adsorbate to the surface. In other words, the surface has become less clean... 

We also ran some samples with the same ratio of S-block- S-stat-MAA) to amine-PDMS copolymers at room temperature, but after IR, acid (water) extraction, TGA, DSC, and surface tension tests, we did not notice significant product... 

Fig. 2. Survey of (electron and scanning force) microscopic methods for investigating micromechanical processes in polymers, a indicates the applied tension stress and the arrows indicate area and direction of investigation in the microscope (see text for full details), (a) fracture surfaces— tension test, impact test, broken pieces (b) surfaces of deformed (loaded) bulk samples (c) in situ deformation of thin samples.

Surface-tension Test —The tombstoning performance of solder pastes has been speculated to be related to the surface tension of respective solder alloys. In this study, a wetting balance was used to measure the surface tension of solder alloys following established conditions. A piece of alumina coupon with a dimension of 2.5 X 0.4 X 0.062 cm was used for the testing. The solder pot was maintained at 245°C for the SnPb alloy and 260°C for SnAgCu alloys. The measured force with respect to time was translated to a graph of force vs. dip depth based on dip speed. When the alumina piece immersed into the solder for a certain depth where the meniscus became stable, the measured force was proportional to the displaced volume of solder. This force may be described as follows ... 

In order to evaluate the rotomoldability of the selected resins rheological, thermal characterization, sintering and surface tension tests were conducted. The material characterization was followed by a series of rotational molding experiments. The molded parts were evaluated in tensile tests. 

General hydrodynamic theory for liquid penetrant testing (PT) has been worked out in [1], Basic principles of the theory were described in details in [2,3], This theory enables, for example, to calculate the minimum crack s width that can be detected by prescribed product family (penetrant, excess penetrant remover and developer), when dry powder is used as the developer. One needs for that such characteristics as surface tension of penetrant a and some characteristics of developer s layer, thickness h, effective radius of pores and porosity TI. One more characteristic is the residual depth of defect s filling with penetrant before the application of a developer. The methods for experimental determination of these characteristics were worked out in [4]. 

Neumann and co-workers have used the term engulfrnent to describe what can happen when a foreign particle is overtaken by an advancing interface such as that between a freezing solid and its melt. This effect arises in floatation processes described in Section Xni-4A. Experiments studying engulfrnent have been useful to test semiempirical theories for interfacial tensions [25-27] and have been used to estimate the surface tension of cells [28] and the interfacial tension between ice and water [29]. 

The extensive use of the Young equation (Eq. X-18) reflects its general acceptance. Curiously, however, the equation has never been verified experimentally since surface tensions of solids are rather difficult to measure. While Fowkes and Sawyer [140] claimed verification for liquids on a fluorocarbon polymer, it is not clear that their assumptions are valid. Nucleation studies indicate that the interfacial tension between a solid and its liquid is appreciable (see Section K-3) and may not be ignored. Indirect experimental tests involve comparing the variation of the contact angle with solute concentration with separate adsorption studies [173]. 

Good, van Oss, and Caudhury [208-210] generalized this approach to include three different surface tension components from Lifshitz-van der Waals (dispersion) and electron-donor/electron-acceptor polar interactions. They have tested this model on several materials to find these surface tension components [29, 138, 211, 212]. These approaches have recently been disputed on thermodynamic grounds [213] and based on experimental measurements [214, 215]. 

It would clearly be desirable to extend the scope of the Kelvin method to include a range of adsorptives having varied physical properties, especially surface tension, molar volume, molecular shape and size. This would enable the validity of the method and its attendant assumptions to be tested more adequately, and would also allow a variation in experimental technique, for example by permitting measurements at 298 K rather than 77 K. 

Surfa.ce Energy. The surface energies of Parylenes N, C, and D were measured by observing the contact angles for several standard probe hquids. AH three have surface energies of approximately 45 mj/m (= dyn/cm), ie, all test Hquids having less than 45 mj/m surface tension completely wet the as-deposited parylene surfaces (43). 

Critical surface tension of wettiag, alkane test Hquids only, unless otherwise iadicated. 

Measurement of Surface Activity. Each surface-active property can be measured in a variety of ways and the method of choice depends on the characteristics of the substance to be tested. The most frequendy determined properties are surface tension (Y5q, Ylg) i t if cial tension (Yll> Tlg) contact angle (9), and CMC. 

OU repeUency is measured by observing a fabric s resistance to wetting by a selected series of numbered test Uquid hydrocarbons with a range of surface tensions. The fabric rating is based on the Uquid that does not wet the fabric surface in a specified time (AATCC Test Method 118 and INDA... 

In OU RepeUency (AATCC Test Method 118), drops of oUs of various surface tensions are placed on the leather and monitored to absorption (14). 

There are many laboratory methods for testing the relative merits of one defoamer against another. It is a simple matter to measure foam height as a function of time to compare the performance of various foam surfactants and defoamers. Unfortunately, this simplicity has led to a wide variety of methods and conditions used with no standard procedure that would make the measurement of foaminess as characteristic of a solution as its surface tension or viscosity. It has been suggested that the time an average bubble remains entrapped ia the foam is such a quantity (49), but very few workers ia the defoamer iadustry have adopted this proposal. Ia practice, a wide variety of methods are used that geaerally fall iato oae of five maia categories ... 

Fig. 10. A schemalic Zisman plot for a given solid specimen. When the cosine of the static advancing contact angle is plotted against the surface tension for a series of apolar liquids against a test solid, a straight line results. Its extrapolation to cost = 1 yields the critical surface tension of the solid.

Fig. 16. The results of Dyckerhoff and Sell for inlerfacial strengths measured hy butt-tensile tests for various lacquers (adhesives) against various plastics as a function of the surface energy, ys of the plastics. Arrows indicate the surface tensions of the adhesive, y, used in the generation of each curve, showing rough agreement with the requirement that a maximum in adhesion is achieved when yt ys (I kp/cm- 0.1 MPa). Redrawn from ref. [71. ...

To check the efficacy of grease removal, the alkali solution is rinsed away or neutralised by dipping in dilute acid. If, after removal from the acid, the draining metal surface remains wetted evenly all over for 30-60 s (or until it dries by evaporation), hydrophobic soils have been removed. Traces of grease cause the surface to de-wet, and surface tension draws the water into separate droplets. This is the water-break test. Traces of grease which remain when the work is plated do not prevent electrodeposition, but are detrimental to adhesion and corrosion resistance. 

Other effects. In addition to the compound formation and ionisation effects which have been considered, it is also necessary to take account of so-called matrix effects. These are predominantly physical factors which will influence the amount of sample reaching the flame, and are related in particular to factors such as the viscosity, the density, the surface tension and the volatility of the solvent used to prepare the test solution. If we wish to compare a series of solutions, e.g. a series of standards to be compared with a test solution, it is clearly essential that the same solvent be used for each, and the solutions should not differ too widely in their bulk composition. This procedure is commonly termed matrix matching. 

Dynamic similarity requires geometric and kinematic similarity in addition lo force ratios at corresponding points being equal, involving properties of gravitation, surface tension, viscosity and inertia [8, 21]. With proper and careful application of this principle scale-up from test model lo large scale systems is often feasible and quite successful. Tables 5-... 

AOS at this proportion the micelle promotion tendency of AOS in the mixture is clearly optimal. At this composition, the authors have also observed a minimum in the surface tension vs. composition plot, and maximum performance benefits in detergency tests (see below). 

---