DuNouy tensiometer

Measurement of Pituitousness Value (2). The pituitousness (stringiness) values were obtained with a conventional duNouy tensiometer. The wire ring was lowered into the solution and then raised above the surface. The time required for the solution to break all contact with the ring was recorded as the pituitousness value, thus giving an empirical measure of the stringiness of the solutions. 

In principle, by measuring the force needed to extend the film, the wire frame shown in Fig. 18.1 could be used to measure the surface tension. In practice, other devices are more convenient. The ring-pull device (called the duNouy tensiometer) shown in Fig. 18.2 is one of the simplest of these. We can calibrate the torsion wire by adding tiny masses to the end of the beam and determining the setting of the torsion scale required to keep the beam level. To make the measurement, we place the ring on the beam and raise the liquid to be... 

In the duNouy tensiometer, the force required to pull up a ring of fine wire lying in the surface of the liquid is measured. If the diameter of the ring is 1.0 cm and the force needed to pull the ring up (with the surface of the liquid attached to the inner and outer periphery of the ring) is 6.77 mN, what is the surface tension of the liquid ... 

For confirmation of the experimental data, the work of adhesion was calculated aeeording to the Young-Dupre equation. The surface tension was observed on the duNouy tensiometer. The eontact angles of wetting were defined using a goniomet-ric method. 

Aqueous viscosity was measured at room temperature with a Brookfield and Ubbelohde viscometer. Intrinsic viscosities were measured by a five-point dilution method no shear-rate corrections were made for the data. Interfacial tension was measured with a DuNouy ring tensiometer against toluene at various polymer concentrations. The formulations used to evaluate the HMHECs for latex paints have been described elsewhere (5). 

The surface tension of the samples was determined by a DuNouy ring method using a KSV Sigma 70 tensiometer (Braumann, Germany). The equipment is useful for determination the dynamic surface tension of liquids, the wetting contact angle and the water uptake or swelling of solid samples. 

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