A capillary viscometer designed for evaluating lowhyphen;viscosity (0.2ndash;10 cp) solutions at elevated temperatures lsqb;20ndash;150thinsp;deg;C (68ndash;302thinsp;deg;F)rsqb; has been built and extensively tested. This viscometer is automated, so that minimum operator effort is needed to obtain the viscosity as a function of temperature for a given solution. This viscometer is normally operated at a constant back pressure of 90 psi to avoid bubble formation. While the viscosities are routinely measured at a shear rate of about 38 sminus;1, viscosity measurement at other shear rates (10ndash;250 sminus;1) can also be achieved by changing the set point on the flow controller.
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