The phlegmatization of fusible mixtures

Even by the end of the nineteenth century it had become clear that some explosives safe to handle in principle (e.g. picric add), are nevertheless too sensitive to the impact that occurs when the projectile containing them strikes against heavy armour plate. Attempts were made therefore to decrease this sensitiveness by desensitization, or phlegmatization of the explosive. 

Montan wax, widely used in Germany, is a better phlegmatizing agent than paraffin. Hence before and during World War I German naval armour-piercing shells were filled with TNT, desensitized by 6% of montan wax. 

During World War II PETN, desensitized by 10% (sometimes 5 or 15%) of montan wax was employed for small shells (e.g. 20 mm) in Germany. 

The inclusion of wax-type phlegmatizing substances in the mixture facilitates the pressing of the explosive as it decreases the friction between the crystals. Thus a mixture with a higher density can be obtained by applying a lower pressure. 

Non-explosive substances which, when molten, act as solvents for explosives, are another type of desensitizing agents. For instance, pentaerythritol tetra-acetate was suggested by Bombrini-Parodi Delfino [43] as a phlegmatizer of PETN. 

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