ASTM D5018 Standard Test Method for Shear Viscosity of Coal-Tar and Petroleum Pitches
14. Report
14.1 Report viscosity, for each test temperature, to the nearest mPa·s (cP).
14.2 The data can be reported in simple tabular form or plotted on suitable graph paper. (Usually a plot of log viscosity versus 1/T (Celsius) gives a straight-line relationship.)
15. Precision and Bias
15.1 The precision was determined by an interlaboratory study conducted in accordance with Practice E691. Fourteen laboratories tested four materials (three coal-tar pitches and one petroleum pitch) in the temperature range of 150 °C to 210 °C (150 °C to 230 °C for the petroleum pitch); the viscosities ranged from 12 000 mPa·s (cP) to 50 mPa·s (cP). Based on this study, the criteria in 15.1.1 and 15.1.2 shall be used for judging the acceptability of results (95 % probability) obtained in the aforementioned temperature ranges and in the viscosity range of 50 mPa·s (cP) to 12 000 mPa·s (cP):
15.1.1 Repeatability Limits - Duplicate values (cps) by the same operator shall not be considered suspect unless the determined viscosities, at a given temperature, differ by more than 12 % of the average of the duplicate determinations.
15.1.2 Reproducibility Limits - The values reported by each of two laboratories, representing the arithmetic average of duplicate determinations at a given temperature, shall not be considered suspect unless the reported values differ by more than 36 % of the average of the four values.
15.2 Bias - This test method has no bias with any other standard.
16. Keywords
16.1 coal tar pitch; petroleum pitch; pitch; viscosity
