TABLE OF CONTENTS In the rotational moulding industry, the particle size of powders is usually quantified in terms of the mesh size. This relates to the number of mesh openings per inch in the sieve used to grade the powder. Table 4.5 gives some of the mesh sizes defined in the British and American standards.
| Tyler size (x 0.001 inch) | Sieve opening (x 0.001 inch) | Wire diameter (x 0.001 inch) | Particle size (microns) |
|---|---|---|---|
| 35 | 16.5 | 11.4 | 420 |
| 60 | 9.8 | 7.1 | 250 |
| 80 | 7.0 | 5.2 | 177 |
| 100 | 5.9 | 4.3 | 149 |
| 115 | 4.9 | 3.6 | 125 |
| 150 | 4.1 | 3.0 | 105 |
| 170 | 3.5 | 2.5 | 88 |
| 200 | 2.9 | 2.1 | 74 |
| 250 | 2.5 | 1.7 | 63 |
| 325 | 1.7 | 1.2 | 44 |
| 400 | 1.5 | 1.0 | 37 |
A 35 mesh (500 ?m) sieved powder has the typical particle size distribution that is suitable for rotational moulding. Although there have been few studies on the ideal particle size distribution, it is generally accepted that powders having a narrow size distribution under 500 microns offer the best compromise between grinding costs and the fusion characteristics of the plastic.
The preferred particle size distribution will provide good packing of the different particle sizes. This helps to reduce voids between particles,...
