Molecular Weight Distribution and Molecular Weight Averages of Polyolefins ASTM D6474-20

Scope:

The molecular weight distribution and molecular weight averages of polyethylene (excluding LDPE) and polypropylene resins are measured using the ASTM D6474-20 test procedure. Polyethylenes (excluding high-pressure low-density polyethylene – LDPE) and polypropylenes soluble in 1,2,4 trichlorobenzene (TCB) at 140 °C can be tested using this approach.

The physical qualities of these resins, such as morphology, strength, melt flow, and so on, are greatly affected by differences in molecular weight and molecular weight distribution, and as a result, the final properties of products created from these resins.

Procedure:

A polyolefin sample is dissolved in a solvent and injected onto the chromatographic column(s)  packed with a solid substrate in this ASTM D6474-20 test technique, which separates the molecules in solution based on their size. As the separated molecules elute from the column in concentration order, they are detected and recorded. Receipt timings are transformed to molecular weights by calibration. Molecular weight concentration data are used to calculate average molecular weight parameters and molecular weight distribution. 

Specimen size:

For the ASTM D6474-20 test process, a finely ground polymer is employed as a test specimen. 

Data:

As the α-olefin comonomer content in linear low-density polyethylene increases, the accuracy of the molecular weight results declines, i.e., they become increasingly underrated, according to the ASTM D6474-20 test technique.