Hard-particle methods lubricants

The presence of other materials in primary explosives (additives) also influences the resulting sensitivity values. In some cases, hard particles (e.g., glass dust) are added to increase the sensitivity of a primary explosive which would otherwise be too insensitive for the desired method of initiation. A typical example is addition of glass dust to the LA which increases the sensitivity of the mixture to a level desired for application in stab and ftictiOTi detonators. The opposite effect is observed after addition of waxes or oils which lubricate the resulting mixture. This desensitizing effect is often utilized when it would be too risky to transport the substance in its pure form. 

If the extrusion is performing well the particles formed are very regular, hard and uniform. The extruder can produce great quantities of variously shaped products and, as a consequence, the extrusion process is relatively cheap in comparison with the pelletization method of making catalyst shapes. The mechanical strength is less than that of the pellets so the extrudates are less resistant to abrasion, but they do have better characteristics from the standpoint of porosity and freedom from lubricant. Furthermore, many different shapes and sizes are possible. 

Ebube and coworkers reported a NIR method that can distinguish between three Avicel products owing to the varying particle sizes. The method was also designed to predict tablet hardness and lubricant concentration. Regardless of the small sample sizes used, good results were obtained. 

There are a few studies that have investigated the effect of filler properties on wear [17, 30]. One simple method is to extrude through a plate of soft metal and measure weight loss from the perforated plate at regular intervals. It was concluded that hard, large irregular particles cause most wear. Surface treatment with a lubricating additive such as stearic acid helps alleviate wear because the additive forms a protective layer around the particles. 

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