Cannon Instrument miniPV Addendum - Manual (Page 2)

Measuring Viscosity:
Relative viscosity (ήr), a prήimary concern in the polymer industry,
is determined from kinematic viscosity by factoring in the density
of the solvent and materials in solution and comparing the
resulting absolute viscosity of the solution with the absolute
viscosity of pure solvent. ASTM D 2857 states that relative
viscosity is “the ratio of the viscosity of the solution, ή, to the
viscosity of the solvent, ήs, that is, ήr = ή/ήs .”
Units of measure
As a ratio, relative viscosity is a unitless measurement.
Methodology
ASTM Method D 2857 describes the appropriate test methodology
for determination of relative viscosity.
NOTES
ASTM D 2857 states that “the kinetic energy correction constant is
negligible for the recommended viscometers and efflux times.” For
this reason, a default value of zero is assigned for E if the MiniPV
viscometer tube/bulb has not been calibrated.
Calibration is strongly recommended to ensure the highest precision when
measuring relative viscosity. Calibration is required for accurate determination
of absolute viscosity. However, it is not necessary to calibrate if measuring
dilute solutions in the same bulb in which the solvent “blank” has been
analyzed.
Inherent viscosity
Inherent viscosity (ήinh) is the ratio of the natural logarithm (ln) of
the relative viscosity (hr) to the mass concentration of the polymer
(c) in g/cm3, g/dl or g/ml , as expressed by the equation: ήinh = ln
ήr/c.
Reduced viscosity
Calculation of reduced viscosity is accomplished by first obtaining
the relative viscosity increment, ήi, (the ratio of the difference
between the viscosities of solution and solvent to the viscosity of
the solvent alone, as determined by the formula ήi = (ή- ήs)/ ήs)
and then relating that value to the mass concentration of the
polymer (c) using the formula ή = ήi/c.
Inherent viscosity
Intrinsic viscosity is the limiting value of the reduced viscosity or
the inherent viscosity at infinite dilution of the polymer. This value
is calculated per ASTM D 2857 by extrapolation of viscosity
versus concentration for several solution concentrations. Intrinsic
viscosity calculations performed by VISCPRO yield a value in dl/g
(deciliters per gram). The Billmeyer and Solomon-Ciuta equations
for single-point intrinsic viscosity calculation may also be used.