Tensiometers, automated

The LAUDA measuring instruments program covers systems for measuring the surface and inteifacial tension of liquids. Available devices include ring plate tensiometers (automated and nonautornated), drop volume tensiometers, bubble pressure tensiometers, and film balances. 

For instance. G. Faour et al. (J. Colloid Interface Set 181 (1996) 385) developed an automated pendent drop tensiometer allowing 3-5 measurements per second, so dynamic processes slower than that could be studied. 

Automated Droplet Tensiometer. Surface tension and surface dilational moduli were measured by an automated droplet tensiometer (ADT) (IT concept, France) as a function of ageing time of the droplet.22 Surface tension was determined by drop shape analysis of a gas bubble formed in a cuvette containing the protein solution. The bubble was illuminated by a uniform light source and its profile imaged and digitised by a CCD camera and a computer. The profile was used to calculate the surface tension using Laplace s equation. The... 

Nasr-El-Din and coworkers [57, 5S] conducted detailed studies on the effect of acids and stimulation additives on surface tension, using an automated Kriiss (Model K-12) Tensiometer. The measurements were carried out at 25 °C using the Wilhelmy plate method. All aqueous solutions were prepared using Millipore Milli-Q water. 

This chapter covers some of the methods and instruments used to determine the mechanical properties of polymers. Examples of instrument designs and typical data generated in these measurements will be introduced. In particular, automated axial tensiometers (to find elastic modulus, yield stress, and ultimate stress), dynamic mechanical analyzers (to determine storage and loss moduli), and rheometers (to measure flow viscosity) will be introduced. This chapter considers the principles behind the devices used to establish and measure the properties of viscometric flows. One of the common techniques used to determine viscous flow properties, PoisueiUe (laminar) flow in cylindrical tubes, is also important in technical applications, as polymer melts and solutions are often transported and processed in this manner. The time-temperature superposition principle is also covered as a way to predict polymer behavior over long timescales by testing materials across a range of temperatures. 

The cmc of sodium oleate was lO M at 25 C using surface tension/concentration plots where there is an intersection between a rapidly decreasing nearly linear part and the slightly decreasing linear part. The ring method was used for the measurements. Modem Tensiometers are automated to measure surface or interfacial tension as well as the cmc. See also NSRDS, NBS.36, National Bureau of Standards, U.S. Government Office, Washington, 1971. 

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