Scope:

The ASTM D5296 test method uses high-performance size-exclusion chromatography to measure the molecular weight averages and molecular weight distribution of polystyrene. The  ASTM D5296 test method is appropriate for samples having molecular weight components with elution volumes within the polystyrene standards’ elution volume range (that is, molecular weights generally from 2000 to 2 000 000 g.mol^-1). The molecular weight (MW) and molecular weight distribution (MWD) of a polymer sample are important properties that are utilized in a  number of relationships for fundamental study, processing, and commercial applications.

Procedure:

For ASTM D5296 test, a dilute polystyrene sample is injected into a liquid mobile phase containing the same solvent used to produce the polymer solution. The polymer is transported into and through a chromatographic column that is filled with a solid or semi rigid, porous substrate that separates the polymer molecules in the solution according to their size. A detector constantly monitors the eluate as a function of elution volume beginning with injection (or time).  The size-separated molecules are identified and recorded according to their concentration after emerging from the column(s). The elution volumes (or times) are converted to molecular weights by calibration, and the molecular weight/concentration data is used to determine various molecular weight characteristics for the sample.

Specimen size:

For the ASTM D5296 test procedure, polystyrene is used as a test specimen.

Data :

MW and MWD are reported in the SI unit and are considered standard.

The ASTM D5296 test method is only valid for polystyrene and non-exclusion effects are to be avoided due to the need for particular calibration of the polymer type.

Conclusion:

The ASTM D5296 test method uses high-performance size-exclusion chromatography to measure the molecular weight averages and molecular weight distribution of polystyrene.