ASTM D1921 test method deals with the particle size of plastic materials in the powdered, granular, or pelletized forms. It utilizes a dry sieving, with a lower limit of measurement to be 38 µm. Multiple and specific sieves are selected for test methods A and B, and the distribution of particle diameter and size are determined. SI units are considered to be standard.
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.
Test Procedure:
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 on the bottom. Weigh the sample and shake it on a mechanical sieve shaker. Next, weigh each sieve with the material separately. 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 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.
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