EXPLANATION
The determination of carbon number distribution of petroleum waxes and the normal and nonnormal hydrocarbons in each can be used for controlling the production processes as well as a guide to performance in many end users, particularly in rubber formulations. This test method determines n-C17 through n-C44 by gas chromatography with internal standardization. Material with a carbon number above n-C44 is determined by difference from 100 mass % and is reported as C45+. This test method is applicable to petroleum derived waxes and wax blends. It is, however, not applicable to oxygenated waxes such as synthetic polyethylene glycols, or natural products such as beeswax or carnauba. This test method is not directly applicable to waxes with an oil content greater than 10 % as determined by Test Method ASTM D721.
TEST SUMMARY
A sample of petroleum wax and an internal standard are completely dissolved in an appropriate solvent and injected into a gas chromatographic column that separates the hydrocarbons by increasing carbon number. The column temperature is linearly increased at a reproducible rate until the sample is completely eluted from the column. The eluted components are detected by a flame ionization detector. The individual carbon numbers are identified by comparing the retention times obtained from a qualitative standard with the retention times of the wax sample. The percentage of carbon number through 44 is calculated via internal standard calculations after applying response factors.
TEST PRECISION
See the precision estimates in the following table.
Where X is the mass % of the component.
The bias of this method has not been determined.