VISCOSITY, SHEAR OF COAL-TAR AND PETROLEUM PITCHES: ASTM D5018
EXPLANATION
This test method is useful as one element in establishing the uniformity of shipments. Viscosity is valuable for rheological characterization of binder pitches. Binder pitch imparts consistency to carbonaceous mixes and affects their resistance to deformation. Binder pitch viscosity is important in assessing mix consistency and for evaluating the ease of mix extrusion or molding into artifacts. This test method determines the apparent shear viscosity of coal-tar and petroleum based pitches having a Mettler softening point range of approximately 95 to 120° C. This test method is applicable only for rotational viscometers. Strict adherence to details of the procedure are necessary to comply with the theoretical requirements of this test.
TEST SUMMARY
The apparent shear viscosity is measured via a concentric cylinder viscometer. Apparent shear viscosity is the ratio of shear stress to shear rate in a unidirectional simple shear flow field at steady state conditions. The extrapolated value of apparent shear viscosity at zero shear rate is called shear viscosity.
TEST PRECISION
Repeatability: 12 % of mean
Reproducibility: 36 % of mean
There is no bias.
