ASTM D5018 Standard Test Method for Shear Viscosity of Coal-Tar and Petroleum Pitches
3. Summary of Test Method
3.1 The viscosity of a pitch, over the temperature range of about 40 °C to 100 °C above the SP of the material, is determined using a rotational viscometer.
3.2 The recommended specifications herein are for measuring the apparent shear viscosity of binder pitches 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. A concentric cylinder viscometer is useful for measuring the apparent shear viscosity, provided the sample temperature is adequately controlled, the "end-effects" are negligible, and the gap between rotor/cup is small and remains constant during the test. The extrapolated value of apparent shear viscosity at "zero" shear rate is called shear viscosity.
4. Significance and Use
4.1 This test method is useful as one element in establishing the uniformity of shipments.
4.2 Viscosity is also 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 for assessing mix consistency and for evaluating the ease of mix extrusion or molding into artifacts.
