Rolling agglomeration

The RDX thus coated and presumed to be 3% waxed RDX or a 97/3 RDX/wax mixt, is hand rolled to crush agglomerates and hand blended before use... 

The Amm perchlorate is coated by dissolving the appropriate wts of RDX TNT in hot ale. After adding the Amm perchlorate, the slurry is stirred until most of the Solv is evapd. The treated material is spread on a tray to dry overnight. Agglomerates formed during the process are crushed by hand rolling and blending the mixt before use... 

In the early days of the rubber industry all mixing was carried out on two-roll mills. Now this situation only occurs occasionally, or when small or expensive batches of material are required, e.g., silicones or fluorocarbons. Mill mixing is an efficient method for breaking down agglomerates and, over a period of time, with good operatives, good homogeneity can be achieved. One batch, however, can take some 30-40 minutes to mix. 

Processes which melt mix polymer and filler are capable of generating the high shear stresses necessary to cause agglomerate break up, together with re-distribution of the primary filler particles. Since its conception in 1835, the two-roll mill has proved to be an effective means of mixing additives into plastics and rubber and is still in widespread use today, principally for laboratory purposes, but to some extent in large-scale industrial applications. 

Two-roll mills have been analyzed in terms of the pressure distribution and velocity profiles created between the rolls [95], the shear imposed on fluid elements exposed to these conditions in the nip region [129] and their resulting efficiency as dispersive mixing devices [130,131]. An earlier mathematical model was proposed to describe the dispersive mixing process of carbon black in rubber on roll mills, through consideration of agglomerate size distribution and... 

Newitt and Conway-Jones defined (2) pelletization as the process of transforming a wet, solid mass of finely divided particles into dry, spherical bodies by a continuous rolling or tumbling motion. In a broader sense, pelletization is an agglomeration event used in many powder processes, either for ease of handling or to add value to the product. It spans a range of industries that process solid particles into some suitable form, such as metallurgical, chemical, plastics, fertilizer, rubber, food, and pharmaceuticals (3-6). Since spheres have the lowest surface to volume ratio and exhibit... 

Figure 12.14. Common shapes and sizes of pellets made by some agglomeration techniques, (a) Sizes and shapes of briquets made on roll-type machines, (b) Catalyst pellets made primarily by extrusion and cutting (Imperial Chemical Industries), (c) Some of the shapes made with tabletting machines.

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