Cannon Instrument miniPV-X - Manual (Page 8)

CANNON ® miniPV-Series Automatic Viscometer with VISCPRO ® Instruction & Operation Manual
Version 1.a— January, 2011; CANNON ® Instrument Company
2139 High Tech Road • State College, PA 16803 • USA
2
Measuring Viscosity
Relative viscosity ( Þ r), a primary 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 result-
ing 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, Þ, to the
viscosity of the solvent, Þs, that is, Юr = Ю/Юs .”
Units of measure As a ratio, relative viscosity is a unitless measurement.
Methodology ASTM Method D2857 describes the appropraite 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 determina-
tion 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 (Þinh) 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: Þinh = ln Þr/c.
Reduced viscosity Calculation of reduced viscosity is accomplished by first obtaining the
relative viscosity increment, Þi, (the ratio of the difference between the
viscosities of solution and solvent to the viscosity of the solvent alone, as
determined by the formula Юi = (Ю- Юs)/ Юs) and then relating that value
to the mass concentration of the polymer (c) using the formula Þ = Þi/c.
Instrinic viscosity Intrinsic viscosity is the limiting value of the reduced viscosity or the
inherent viscosity at infinite dilution of the polymer. This value is calcu-
lated per ASTM D 2857 by extrapolation of viscosity versus concentra-
tion 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.
Adjusted Relative viscosity The adjusted relative viscosity (ARV) is only applicable to Solution
Relative Viscosity samples. The ARV Factor is simply a constant that is
stipulated in the viscosity action window.