4.1 The particulate size distribution of vulcanizate particulate rubber is used for the purpose of assigning a product mesh or average particle size designation.

4.2 The product designation for mesh size for the Ro-tap method (Method A, as follows) is based on the size designation screen which allows a range for the upper limit retained of maximum 5 % for up to 850 μm (20 mesh) particles, maximum 10 % for 600 to 150 μm (30 to 100 mesh), and maximum 15 % for 128 to 75 μm (120 to 200 mesh). No rubber particles shall be retained on the zero screen (see Table 1, Classification D5603).

4.3 For Method A, the weight percent retained on a specific screen is noted whereas in Method B (ultrasonic technique), the number of particles at a particular size is counted.

4.4 Method B addresses problems that may be caused by tackiness and static electrical forces that recycled rubber particles exert on each other to form agglomerates, especially for 80 mesh or finer particles. This method eliminates agglomerate formation by ultrasonically dispersing the particles.

4.5 Both methods can be used as a quality control tool.