Quimica

Universidad Autonoma de Tlaxcala
Facultad de Ciencias Básicas Ingeniería y Tecnología Ingeniería química Fenómenos de transporte M.C. Elsa Hynmar Fernández Martínez

Presenta: Alan Arodi Gómez Pérez Carolina Julieta González González Cesar Rodríguez Méndez Proyecto “Viscosidades” 6° SEMESTRE Apizaco Tlax., a 22 de febrero de 2012

I.

DATE ABOUT THE ARTICLE

Instrumentation Journal ofPhysics 35 No. 2 (1989) 274-281 Concentric cylinder viscometer extremely low shear stress. R. T. Rodriguez, Raul Montiel C. and A. Romo U. Department of Physics, Universidad Autonoma Metropolitana - Iztapalapa, PO Box 55-534, 09340 Mexico, DF (Received August 2, 1988; accepted January 13, 1989) Summary. This paper describes the design and construction of a Zimm-type viscometer Crothers, whichallows measurement of accurate viscosity values several extremely shear using only a small rotor. 1. Introduction One of the oldest techniques and used in the characterization of materials in solution is plyometrics viscometry. This is based on the fact that the presence of large particles dissolved or suspended in a liquid produced a radical change in the flow property of the system. A very importantadvantage of this technique is that the amount is determined experimentally, either viscous or the torque flow time is directly proportional to viscosity. It may happen, however, that the viscosity of the polymer solution is dependent on the flow conditions of the instrument used: in these cases it is said that the nonNewtonian viscosity. This type of behavior is found mainly in solutions ofhighly asymmetric molecules rigid or flexible molecules in solutions of very high molecular weight. The capillary viscometer has proven to be a versatile and inexpensive, however, due to progress in the study of biological macromolecules, has been found that many of these molecules are degraded under the action of even small shear forces found in the viscometers capillaries. Furthermore, somebiological and synthetic molecules have non-Newtonian behavior when subjected to shear stresses experienced in regular sized capillaries.

In view of this, there is need for a viscosity comparable to convenience and availability of a capillary viscometer, but operating at high shear rates of several

orders of

magnitude

lower than

the

capillary.

The instrument described herein is cheap,puts the solution in contact with only glass, runs at different shear stresses and has been used in cutting forces from 0.003 to 0.0008 dynes/cm2, which are several orders of magnitude less than commonly, used capillary viscometers.

FIGURE 1. The diagram shows the position of the rotor in the stator.

2. Design and construction The viscometer of Zimm-Crothers type [1], is a concentriccylinder viscometer, which is made entirely of glass, this feature provides the facility to work with almost any solvent. The outer cylinder (called the stator) remains fixed, while the inner cylinder (called the rotor) is rotating (Fig.1). At the bottom of the stator was placed a tube for introducing the sample is from the bottom of the viscometer. This device also facilitate filling, very accuratelyadjusts the height of the rotor on the stator core to be reproducible in the viscosity measurements, in general, the relative viscosity measurements have an accuracy of no more than 0.2% . All the viscometer is introduced into a heating jacket (Fig. 2) which allows the device to operate at different temperatures. As temperature control was used brand Haake recirculating bath with platinumresistance control, which controls with accuracy of ±0.05°C. The viscometer should be mounted rigidly to preserve the geometry of the system. For this is supported with a nylon ring which is mounted on a bracket that allows five movements: first, the position of the viscosity on the external magnetic field is carried out through three platforms that move in the x - y z; second, the orientation thereof...