Viscometer, Cannon-Fenske capillary

Figure 3.2-1 Diagrams of (A) Ostwald and (B) Cannon-Fenske capillary viscometers.

Assays. Nitrogen assays to determine 1-amidoethylene unit content were done by Kjeldahl method. Limiting viscosity numbers were determined from 4 or more viscosity measurements made on a Cannon-Fenske capillary viscometer at 30°C. Data was extrapolated to 0 g/dL polymer concentration using the Huggins equation(44) for nonionic polymers and the Fuoss equation(45) for polyelectrolytes. Equipment. Viscosities were measured using Cannon-Fenske capillary viscometers and a Brookfield LV Microvis, cone and plate viscometer with a CP-40, 0.8° cone. Capillary viscometers received 10 mL of a sample for testing while the cone and plate viscometer received 0.50 mL. 

Two replicates from each of the experimental treatments were evaluated for changes in viscosity. Dilute solutions (0.10, 0.20, 0.30, 0.40 and 0.50 g/lOOml) of nylon 6,6 dissolved in 90% formic acid were made. Viscosities of the dilute polymer solutions were determined at 25 + O.l C using a size 75 Cannon-Fenske capillary viscometer. Flow time measurements were repeated for each solution and for the pure solvent until three consecutive readings within 0.2 seconds or 0.1% of the mean were obtained (24). The average of the three consecutive flow times was used to determine the relative viscosity for each solution. 

C) ASTM D445 Cannon-Fenske capillary viscometer tube j... 

The viscosities of polymer-surfactant solutions as well as those of the surfactant and of the polymer alone have been measured at 25 using a Cannon-Fenske capillary viscometer. Two high molecular weight nonionic polymers and anionic, cationic and nonionic surfactants have been used in this study (Table I). 

Viscosities of liquid resins are typically determined with a Cannon-Fenske capillary viscometer at 25°C, or a Brookfield viscometer. The viscosity depends on the temperature, as illustrated in Figure 2. Viscosities of soUd epoxy resins are determined in butyl carbitol (diethylene glycol monobutyl ether) solutions (40% solids content) and by comparison with standard bubble tubes (Gardner-Holdt bubble viscosity). The Gardner color of the same resin solution is determined by comparison with a standard color disk. Recently, data have been reported for solid epoxy resins using the ICI Cone and Plate viscometers, which are much more time-efficient because they do not require sample dissolution. 

Ullmann, et al. report the viscosity (Figure 12.10) of aqueous solutions of 7.5, 18.5,100, and 300 kDa polyethylene oxides(35). Polymer concentrations reached 300 g/1. Solution viscosities ri/rio approached 100, as determined with Cannon-Fenske capillary viscometers. Over these ranges, stretched-exponential concentration dependences as seen in Figure 12.10 account weU for the concentration dependence of rj. 

This unit describes a method for measuring the viscosity (r ) of Newtonian fluids. For a Newtonian fluid, viscosity is a constant at a given temperature and pressure, as defined in unit hi. i common liquids under ordinary circumstances behave in this way. Examples include pure fluids and solutions. Liquids which have suspended matter of sufficient size and concentration may deviate from Newtonian behavior. Examples of liquids exhibiting non-Newtonian behavior (unit hi. i) include polymer suspensions, emulsions, and fruit juices. Glass capillary viscometers are useful for the measurement of fluids, with the appropriate choice of capillary dimensions, for Newtonian fluids of viscosity up to 10 Pascals (Newtons m/sec 2) or 100 Poise (dynes cm/sec 2). Traditionally, these viscometers have been used in the oil industry. However, they have been adapted for use in the food industry and are commonly used for molecular weight prediction of food polymers in very dilute solutions (Daubert and Foegeding, 1998). There are three common types of capillary viscometers including Ubelohde, Ostwald, and Cannon-Fenske. These viscometers are often referred to as U-tube viscometers because they resemble the letter U (see Fig. HI.3.1). 

Many modifications of the basic Ostwald geometry are employed in different situations. One example is the Cannon-Fenske routine viscometer (Fig. 6.37b) which is used in the oil industry for measuring kinematic viscosities of 0.02 m2/s and less(4<). As viscosity is sensitive to variations in temperature, these types of viscometer are always immersed in a constant temperature bath. They are not normally suitable for non-Newtonian fluids although FAROOQI and Richardson(47) have employed a capillary viscometer to characterise a power-law fluid. 

Fig. 24. (a) Ostwald glass capillary viscometer, (b) Cannon-Fenske viscometer, and (c) Ubbelohde viscometer. 

The Cannon-Fenske viscometer (Fig. 24b) is excellent for general use. A long capillary and small upper reservoir result in a small kinetic energy correction the large diameter of the lower reservoir minimises head errors. Because the upper and lower bulbs He on the same vertical axis, variations in the head are minimal even if the viscometer is used in positions that are not perfecdy vertical. A reverse-flow Cannon-Fen ske viscometer is used for opaque hquids. In this type of viscometer the Hquid flows upward past the timing marks, rather than downward as in the normal direct-flow instmment. Thus the position of the meniscus is not obscured by the film of Hquid on the glass wall. 

Capillary viscometers are simple and inexpensive. They are normally constructed from glass and resemble a U-tube with a capillary section between two bulbs. The initial design originated with Ostwald and is shown as part A in Figure 3.2-1. The Cannon-Fenske type, a popular modification of the Ostwald design that moves the bulbs into the same vertical axis, is shown as part B in Figure 3.2-1. 

The [ n] values of all polymers were measured with a Cannon Fenske type capillary viscometer. 

Viscosity measurements were carried out using Cannon-Fenske viscometers of appropriate capillary diameter so as to keep the efflux time between 200-300 seconds. Approximate shear rate at the wall was calculated using the equation... 

Capillary viscometers that have this design are called Ostwald viscometers. There are many specific designs of Ostwald viscometers. The most frequently used are the Cannon-Fenske viscometer... 

Is a Cannon-Fenske viscometer a capillary type or a rotational type Explain. 

A Cannon-Fenske viscometer is a capillary type of viscometer. It utilizes the flow through a capillary tube as a means of measuring viscosity. 

Batch flow times are generally used in other words, the time required for a fixed amount of sample to flow from a reservoir through a capillary is the datum actually observed. Any features of technique that contribute to longer flow times are usually desirable. Some of the principal capillary viscometers in use are those of Cannon-Fenske, Ubbelohde, Fitzsimmons, and Zeitfuchs. 

Viscometers Devices for measuring viscosity are called viscometers. The most common viscometer consists of a Cannon-Fenske tube, which is a U-shaped glass tube (see Figure 5.6), one arm of which consists of a capillary tube through which liquids flow slowly. The more viscous the liquid, the longer it takes for a given volume to flow through the capillary. This time is related to the viscosity of the liquid in poise or centipoise, which can be calculated from the measured time, a calibration constant, and the liquid s... 

The Ubbelohde viscometer is shown in Figure 24c. It is particularly useful for measurements at several different concentrations, as flow times are not a function of volume, and therefore dilutions can be made in the viscometer. Modifications include the Cannon-Ubbelohde, semimicro, and dilution viscometers. The Ubbelohde viscometer is also called a suspended-level viscometer because the liquid emerging from the lower end of the capillary flows down only the walls of the reservoir directly below it. Therefore, the lower liquid level always coincides with the lower end of the capillary, and the volume initially added to the instrument need not be precisely measured. This also eliminates the temperature correction for glass expansion necessary for Cannon-Fenske viscometers. 

Fig. 17.1 Two types of viscometers Ubbelohde (left) and Cannon-Fenske (right). The Ubbelodhe viscometer has the following components (1) fill tube, (2) capillary outlet, (3) pressure relief tube, (4) solution bulb, (5) suspended volume bulb, (6) lower flow bulb, (7) upper flow bulb, (8) upper timing mark, and (9) lower timing mark. The Cannon-Fenske Viscometer has the following components (1) fill tube, (2) capillary outlet tube, (3) solution bulb, (4) lower flow bulb, (5) upper flow bulb, (6) upper timing mark, and (7) lower timing mark.

This protocol describes a method for measuring the viscosity of pure liquids and solutions by capillary viscometry. The sample is loaded into a Cannon-Fenske viscometer. The time required for the sample to flow between two time points on the viscometer is used to calculate the kinematic viscosity or viscosity. 

This method is an adaptation of the Basic Protocol for measuring the viscosity of pure liquids and solutions. The °brix (unithi.4) of the sample is adjusted to a desired value by dilution. In many protocols, a nominal value of 5 °brix is the accepted target value for dilution. The sample is then filtered to remove particles that would plug the capillary tube of the viscometer, and the serum viscosity is measured in a Cannon-Fenske viscometer. 

Fig. 6.37. Common capillary viscometers (a) simple Ostwald type (b) Cannon-Fenske type...

Measuring Viscosity Several common methods are available for measuring viscosity. Two very common ones are the use of capillary tubes such as Ubbelohde, Ostwald, or Cannon-Fenske viscometer tubes and the use of a rotating spindle such as the Brookfield viscometer. 

As an example of a simple modern capillary viscometer let us examine the Cannon-Fenske modification of the Ostwald viscometer, illustrated in Fig. 4-6. A specified volume of liquid is charged into the viscometer in the bottom reservoir A, and the liquid is then carefully drawn up through the capillary into the bulb B. The volume between the markers I and II is known precisely. The upper bulb T serves as a reservoir for the amount of liquid required to get the viscometer into steady-state operation. 

Table 4-1 shows some of the dimensions and operating characteristics of Cannon-Fenske viscometers. These particular instruments are designed for flow times in the range 200-1000 seconds. Capillary viscometer outflow time is governed partly by the acuity with which the transit of the... 

TABLE 4-1. DIMENSIONS AND VISCOSITY RANGES FOR CANNON-FENSKE GLASS CAPILLARY VISCOMETERS... 

After releasing the suction, one measures the time required for the liquid meniscus to fall between points A and B. The long, narrow capillary helps approximate steady, laminar flow, while the bulb reservoirs help approximate a constant hydrostatic pressure. In addition to the Ostwald-style viscometer shown in Figure 6.3a, a number of other styles are available to accommodate transparent or opaque fluids and different viscosity ranges, many of them having their own names such as Ubbelohde and Cannon-Fenske, see References [i] and [16], for examples. 

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