Scope:

ASTM D1921 test method measures particle size distribution which is important in lot-to-lot uniformity. The handling and processing characteristics are determined and dealt with. Based on the calculations, the daily application of plastic materials is decided.

Procedure:

In ASTM D1921, the sieves should be sufficient to cover the particle sizes and should be coated such that the coarsest sieve is on top and the pan is at the bottom. The net weight of the material retained on the sieves can be measured by subtracting it from the total weight before. 

Specimen size:

The specimen size should be concerning the requirements such as 100 ±0.1 g.

Data:

Mean particle size can be calculated for ASTM D1921 testing as:

Dₘ ꞊ Pᵢ Dᵢ/100
Where:
Dₘ = mean particle diameter, µm
Pi = material retained on sieve (or pan) , %
Di = average particle size of material on a sieve, µm.

Conclusion:

ASTM D1921 test method measures particle size distribution which is important in lot-to-lot uniformity.